In recent years, many studies have been devoted to quantifying and mapping terrestrial CO₂ degassing. Besides climate effects, another reason to study the natural degassing of endogenous CO₂ concerns its role in tectonics, and here I will focus primarily on this aspect, referring to the results obtained in central and southern Italy. In central and southern Italy, non-volcanic CO₂ of deep origin is released from numerous vents and diffuse emission zones, and from groundwater with high CO₂ content. Groundwater degassing was estimated coupling hydrogeochemical and hydrogeological data and using the mass balance of the carbon dissolved in the springs of high flow rate (hundreds to thousands kg/s). This approach allowed us both to quantify the emission (2.1 × 10¹¹ mol yr⁻¹) and to create a detailed map of the process. The map shows two large degassing structures: TRDS (Tuscan Roman degassing structure) and CDS (Campanian degassing structure). The same CO₂-rich groundwater are “slightly thermal” having a temperature of few degree C higher than that expected for normal groundwater. These anomalous temperatures are due to high geothermal heat fluxes (up to 350 mW/m²). This coincidence, combined with the presence at depths > 10 km of a large zone of low-velocity of the seismic waves, suggested that the hot CO₂-rich fluids are probably emitted from a large magmatic intrusion located in the root of the central Apennines. The Apennine belt is characterized by seismicity that recently peaked with strong earthquakes in 2009 (L'Aquila earthquake, M = 6.3) and 2016 (Amatrice-Norcia earthquakes, M = 6.0 and 6.5). We observed that CO₂ emissions correlate with seismicity both geographically and over time: Apennine seismicity affects in fact the eastern edges of the TRDS and the CDS, and CO₂ emissions increased during, and likely before, the 2009 and 2016 events.

How to cite: Chiodini, G.: Carbon dioxide earth degassing, heat flux and earthquakes in central and southern Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5052, https://doi.org/10.5194/egusphere-egu26-5052, 2026.

North-central Chile is a highly seismically active region. While the last megathrust earthquake occurred in 1730, the area has also experienced large events in recent decades, such as the 2015 Illapel earthquake (Mw 8.3), as well as numerous seismic sequences and persistent swarms. Although these phenomena are widespread along the Chilean subduction margin, their dynamics and potential connection to major earthquakes remain poorly understood. 

Within this framework, the ABYSS project has deployed Distributed Acoustic Sensing (DAS) interrogators along offshore telecommunication fiber-optic cables, complemented by temporary and permanent onshore seismic stations. This configuration offers a unique opportunity to monitor and investigate the offshore microseismicity in a region characterized by sparse permanent instrumentation and the absence of previous offshore sensors.

In this study, we develop a workflow to precisely relocate the seismicity recorded by the ABYSS network. We combine the probabilistic, non-linear hypocentral inversion using NonLinLoc with double-difference relocation using HypoDD, incorporating a 3D P- and S-wave velocity model and differential times derived from waveform cross-correlation on both DAS and onshore stations. Through this integrated approach, we identify and analyze clusters of seismicity associated with swarm activity and short-term seismic sequences. In particular, we apply the workflow to episodes such as the Tongoy swarm initiated on 30 December 2024, whose largest event reached Ml 5.3, and the offshore Ovalle sequence that occurred between October and November 2025.

Our goal is to precisely characterize these sequences by improving constraints on the geometry and spatio-temporal evolution, gaining insights into the processes driving this activity, and shedding light on how present-day swarm dynamics may relate to the occurrence of larger earthquakes along the Chilean subduction margin.

How to cite: Peralta, T., Flores, M. C., Rivet, D., Potin, B., Baillet, M., and Ruiz, S.: High-resolution relocation of seismic swarms using offshore DAS and onshore seismic data in north-central Chile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-887, https://doi.org/10.5194/egusphere-egu26-887, 2026.

Numerical simulations of earthquake cycles provide essential insights into fault mechanics and the physical interpretation of frictional parameters. Here, we utilize a spring-block system governed by rate-and-state friction to systematically compare earthquake cycle behaviors under quasi-dynamic and fully dynamic conditions. Our simulations demonstrate that for both approaches, the static stress drop, dynamic stress drop, and peak stress scale linearly with the logarithm of the loading rate [ln(Vpl/V0)]; however, the scaling coefficients are distinct and are modulated by both frictional parameters and the system stiffness. Specifically, we observe stress overshoot during the coseismic phase in dynamic models, contrasting with the undershoot observed in quasi-dynamic simulations. Additionally, parameter sweeps reveal that stress drops decrease as the stiffness ratio kc/k increases. This study highlights the importance of the inertial term effect in interpreting earthquake cycle behaviors.

How to cite: Chai, L. and Hu, F.: Scaling of Stress Drop with Rate-and-State Frictional Parameters in Spring-Block Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6568, https://doi.org/10.5194/egusphere-egu26-6568, 2026.

Collision and relentless underthrusting of India beneath Eurasia resulted in large-scale deformation of the Indian lithosphere. Anisotropic parameters serve as a good proxies to decipher deformation in such complex orogenic collision zones. In this study, we present anisotropy characteristics of the crust beneath Sikkim Himalaya using harmonic decomposition of P-to-S converted phases identified in P-wave receiver functions (P-RFs). Analysis of azimuthal variation of these phases enabled parameterizing the crustal anisotropic properties, with depth. Initially, 11,087 high quality P-RFs were computed using waveforms of teleseismic earthquakes having magnitude  ≥ 5.5 and signal to noise ratio  ≥ 2.5 within an epicentral distance range of 30° - 100°, recorded at a network of 38 seismic stations deployed in Sikkim Himalaya and the adjoining foreland basin. Analysis of the first three harmonic degrees (i.e. k= 0, 1 and 2) reveals that the upper crustal anisotropy is oriented WSW-ENE to E-W, coinciding well with the trends of crustal microcracks and fractures. The mid to lower crustal anisotropy aligns predominantly with the dipping decollement layer along which the Indian plate is underthrusting Tibet. An orthogonal reorientation is observed within the extent of the Dhubri-Chungthang Fault Zone authenticating its role in segmenting the orogen. The lower crustal anisotropy is highly perturbed signifying a highly heterogeneous nature of the Moho.  Existence of multiple layers of anisotropy possessing distinct geometries varying with depth could be an indication of a highly complex deformational regime resulting from active crustal shortening.

How to cite: Kumar, G., Singh, A., Singh, C., Saikia, D., and Kumar, M. R.: Crustal Seismic anisotropy in Sikkim Himalaya: Implications for deformation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10972, https://doi.org/10.5194/egusphere-egu26-10972, 2026.

Regular monitoring of small to moderate sources of continuous earthquake events in the complex tectonics of Himalayan region helps in clearly defining the ongoing seismotectonic process. The study of moment tensor inversion to decipher the fault planes responsible for current seismic activity in the Kishtwar region of Northwest part of Himalaya has been undertaken by establishing a six-station network in 2022 and among them 15 events of shallow origin with magnitude ranging from M_L ~ 3.0 to 4.0 occurred in the local region of seismic network are used for the moment tensor inversion. A few number of studies didn’t able to clearly demarcate the actual scenario of seismotectonics in the northwest part of Himalaya due to its difficult terrain and complex geology. This area has been studied for fault plane solution by a software package ISOLA based on MATLAB programming environment. The source inversion is performed via iterative deconvolution method and synthetic seismogram is generated through green’s function computation via discrete wavenumber method using the regional crustal velocity model. However, the inversion is performed at several trial source position and at various frequency bands based on the epicenter distance and the magnitude of earthquake to find the best solution resulting from the maximum correlation between the recorded and synthetically generated waveforms. A 2D space-time grid search is performed for determining the optimal time and positon of earthquake generation. Perhaps calculating source parameters such as moment magnitude, centroid depth and fault parameters equally with describing uncertainty quantities such as variance reduction factor and condition number will deliver the reliability and stability to the solution. A strong follow-up uncertainty quantification can justify the best estimated fault plane solution. Quality of earthquake event can be calculated through their DC and CLVD percentage and maximum & minimum compression stress direction. Focal mechanism solution of these events following thrust with strike-slip focal mechanism and represents the compressional regime in north-northeastern direction. The centroid depth obtained by moment tensor inversion of all events falls within the depth zone of Main Himalayan Thrust (MHT) suggesting seismicity is concentrated along the major detachment in the region.

How to cite: Tiwari, S. and Gupta, S. C.: Moment tensor analysis and uncertainty quantification of local earthquake events: tectonic implication in the northwestern Himalayan region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13656, https://doi.org/10.5194/egusphere-egu26-13656, 2026.

With the popularization of dense seismic array observations, tomographic imaging of subsurface velocity structures using surface wave dispersion data extracted via subarray partitioning has emerged as a new trend. The primary advantages of subarray-based dispersion data extraction lie in its reduced susceptibility to the inhomogeneous distribution of noise sources, which yields more stable and reliable dispersion measurements. Additionally, this approach enhances the energy of higher-order modes, thereby providing tighter constraints on subsurface velocity structures. Compared with the higher-order modes of Rayleigh waves, both the fundamental and higher-order modes of Love waves exhibit simpler dispersion characteristics with fewer mode crossings and overlaps, making them more favorable for joint inversion to constrain subsurface SH-wave velocity structures.

Traditional subarray surface wave imaging methods (e.g., SSWI) typically perform 1D velocity structure inversion at individual locations first, followed by stitching all 1D models to generate pseudo-2D or 3D velocity models. Despite its simplicity and computational efficiency, this direct stitching strategy is highly vulnerable to uneven station distributions, and the resultant velocity models may suffer from artificial velocity jumps. To address these limitations, Luo & Yao (2025) proposed a direct subarray surface wave imaging method (SSWDI), which eliminates the stitching step inherent in traditional methods and incorporates spatial smoothness constraints on velocity structures, thus enabling more robust inversion of subarray-derived dispersion data for subsurface imaging. However, the SSWDI method originally focused exclusively on the fundamental mode of Rayleigh waves. In this study, we further extend the SSWDI framework to accommodate both fundamental and higher-order modes of Love waves, and validate the improved method using both numerical synthetic data and field observational data.

Reference

Luo, S., and H. Yao (2025), Direct Tomography of S-wave Structure Using Subarray Surface Wave Dispersion Data: Methodology and Validation, Geophysics, 1–60, doi:10.1190/geo-2024-0515.

How to cite: Luo, S.: 3D SH-wave Velocity Tomography via Direct Inversion of Multimode Love Wave Dispersion Curves from Seismic Subarrays, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16937, https://doi.org/10.5194/egusphere-egu26-16937, 2026.

Seismic hazard assessment is crucial for the design of critical facilities, whose damage could lead to severe consequences. The design of such facilities typically requires the definition of seismic actions associated with recurrence periods on the order of 5,000-10,000 years. Earthquakes with such low frequencies are well documented in highly deforming regions, where paleoseismic records commonly encompass several seismic cycles of active faults. In contrast, in slow-deforming regions or areas of low seismicity, the scarcity of seismic data hinders the definition of seismogenic zones. In this context, geological studies of active seismogenic faults are essential, as they allow the characterisation of seismic behaviour over time spans far exceeding those covered by instrumental or historical records. These data can contribute to constraining fault’s seismic cycles and estimating earthquake magnitude–frequency distributions at the fault scale.

Despite their importance, the incorporation of faults into seismic hazard models remains challenging, particularly in low strain regions such as the western margin of the Valencia Trough. This region of the NE of Iberia (from the Vallès-Penedès Graben to the Valencia Depression) corresponds to a passive margin characterised by a basin-and-range structure, bounded by multiple NNE–SSW-oriented normal faults formed during the Neogene rifting episode. Those faults are usually associated with mountain fronts, although our recent studies have found some new faults crosscutting Pleistocene alluvial fans. These newly discovered faults are being studied by means of geomorphology, geophysics, paleoseismology and geochronology in order to estimate their seismic parameters. Several challenges arise when analysing these faults, including fault identification, incomplete geological records, and the need for complex dating techniques.

Moreover, in regions characterised by fault systems, fault interactions may play a significant role. In regions such as the studied area, these interactions may result in long quiescent periods followed by phases of increased activity or even cascading events. Under such conditions, distinguishing between quiescent and active phases is especially difficult, as recurrence intervals are expected to span several thousands of years in both cases.

In this work, we explore existing methodologies for the computation of seismic hazard incorporating geological data from faults and fault systems in slow-deforming regions, using the western margin of the Valencia Trough as a case study. To this end, a detailed geometric characterization of the fault system is carried out to establish the geometric relationships among faults. Recent morphotectonic analyses and newly acquired geological data are then used to constrain the seismic parameters of the studied faults and to estimate their earthquake frequency distributions. Finally, several alternative seismic source models are proposed, forming the basis for the construction of a logic tree for subsequent seismic hazard calculations. These
models, although in progress, provide a framework for improving seismic hazard assessments in slow-deforming regions, contributing to safer design of critical infrastructure.

How to cite: Ollé-López, M., García-Mayordomo, J., Scotti, O., and Masana, E.: A seismogenic modelling approach for rift-basin fault systems in slow-deforming regions: application to the western margin of the Valencia Trough, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20741, https://doi.org/10.5194/egusphere-egu26-20741, 2026.

The 2015 Mw 7.8 Gorkha earthquake was followed by numerous aftershocks that provided important information on active faulting in central Nepal. Accurate moment tensor estimations are essential for determining the source parameters of these seismic events. In this study, we determine double-couple and full moment tensor solutions for selected aftershocks of the 2015 Nepal earthquake sequence using a regional 1D velocity model.

The waveform data recorded by the temporary broadband network (NAMASTE) are used to analyse 51 aftershocks with M > 3.5. A library of Green’s functions is computed using the frequency–wavenumber method based on a 1D velocity model of the Nepal region. Synthetic waveforms derived from the Green’s functions are used to invert the waveform data for moment tensor estimation. Both body waves and surface waves are used in the inversion, and they contribute separately to the moment tensor solutions. The analysis focuses on regional waveforms in relatively higher frequency ranges.

Both double-couple–constrained and full moment tensor inversions are performed, and the resulting source parameters are examined in terms of waveform fit, centroid depth, and fault-plane orientation. This work presents a set of moment tensor solutions for the 2015 Nepal aftershocks using a 1D regional velocity model and provides a reference for future studies using more complex velocity structures.

How to cite: Lahon, P., Silwal, V., and Mahanta, R.: Double-Couple and Full Moment Tensor Solutions of the 2015 Nepal Aftershocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21099, https://doi.org/10.5194/egusphere-egu26-21099, 2026.

The alternative proxy parameters for seismic site amplification beyond the conventional time-averaged shear wave velocity of the upper 30 m (V_S,30) are investigated in this study with a focus on quantities that can be derived or constrained from surface wave-based measurements such as Spectral Analysis of Surface Waves (SASW) and Continuous Surface Wave System (CSWS) testing. Surface wave methods provide dispersion curves that are inverted to obtain near-surface shear wave velocity profiles, which are then used to construct synthetic one-dimensional layered models for ground response analysis. For each profile, two different candidate site parameters are evaluated, including V_S,30 and the impedance ratio between the surface layer and the underlying half-space. These parameters are chosen to reflect what can realistically be inferred from SASW/CSWS-derived velocity profiles, particularly the shallow stiffness and impedance contrasts that strongly influence amplification. Correlation analyses are carried out to quantify how well each parameter explains the variability in amplification across the synthetic suite. The results are used to assess whether the impedance ratio provides stronger or more consistent correlation with amplification than V_S,30, thereby offering guidance on how surface wave–based site characterization can be better integrated into proxy-based amplification and site classification schemes in seismic design practice.

How to cite: Singh, V. and Baidya, D. K.: Evaluating SASW/CSWS-Derived Proxies for Seismic Site Amplification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21425, https://doi.org/10.5194/egusphere-egu26-21425, 2026.

The Rif’s belt is characterized by low to moderate seismic activity resulting from the continental collision between the African and Eurasian plates. This seismic activity, which involves devastation and human losses, requires an in-depth study of its origins and mechanisms. This study aims to identify the geological structures responsible for seismic activity in the eastern Rif by adopting an integrated methodological approach. The methodology relies on the use of a Geographic Information System (GIS) to process and analyze multiple geological, seismological, and geophysical datasets. Various filters were applied to magnetic and gravimetric data (vertical derivatives) to characterize the subsurface. The analysis of earthquake focal mechanisms helped identify active faults. The results show that the seismicity, with a NW-SE orientation, is localized within a fragile depression south of the city of Selouane. The final geological model highlights a system of faults and strike-slips oriented NE-SW and NW-SE. A significant spatial correlation is observed between epicenters and Messinian-aged NW-SE strike-slips, suggesting their reactivation. The analysis indicates that a system of dextral strike-slips is likely the source of this seismic activity. The proposed geodynamic model represents a major advancement in understanding local seismic activities and serves as an essential reference for future studies. These results significantly contribute to the assessment and management of seismic risks, thereby enhancing the safety and resilience of populations in this high-risk area.

KEYWORDS: Geodynamic model; Seismotectonic; Focal mechanism; Magnetic; Gravimetric; ·
Eastern Rif. 

How to cite: Iken, H., Nouayti, A., Nouayti, N., and Khattach, D.: An integrated geodynamic analysis of seismic sources in the Eastern Rif: Insights from geological, seismological, gravimetric, and aeromagnetic data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22669, https://doi.org/10.5194/egusphere-egu26-22669, 2026.

Current demand for critical metals including Cu is outstripping current supply and will further escalate in the future. A significant source of Cu comes from porphyry deposits, which contribute to >60% of global Cu ore production. Many of these porphyry Cu deposits are found along convergent margins such as the Andes and the Sunda-Banda arc in Indonesia and these same arcs also host highly active volcanoes. Understanding the magmatic and geodynamic factors that contribute towards priming magmas for Cu fertility as opposed to volcanic eruptions can aid in identification of prospective targets for exploration.

Here we present analyses of apatite populations from known porphyry Cu deposits and active volcanoes along the Sunda-Banda arc in Indonesia. To gain a complete overview of the mineral associations and their information, we incorporate textural information to analyze both apatite inclusions and their mineral hosts, such as pyroxenes and amphiboles, as well as groundmass apatite. These mineral compositions will serve as input for thermodynamic models to constrain the volatile chemistry and budget, as well as the volatile saturation depths. The information gathered will be combined to test our working hypotheses that the magmas with high Cu fertility store at distinct depths, have geochemical signatures that suggest deep fractionation of garnet and amphibole, and are associated with anomalous geodynamic features such as slab tears.

Our ongoing work advances current understanding on magma storage and transfer along and across fertile magmatic arcs, aiming to better understand magmatic pre-conditioning for porphyry copper deposit formation to complement exploration efforts to find copper deposits in the geological records.

How to cite: Utami, S. B., Ubide, T., Rosenbaum, G., Li, W., Handini, E., Wood, S., Handley, H., and Goode, L.: Insights into the copper accumulation potential of magmas along the Sunda-Banda arc, Indonesia from apatite and its mineral hosts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-938, https://doi.org/10.5194/egusphere-egu26-938, 2026.

Abstract:

Strike-slip basement faults and their related segments are crucial for oil and gas exploration. These faults are considered favorable channels for hydrocarbon migration. The multistage activities of these faults influence the development of hydrocarbon-bearing structures. They can also produce fracture systems that enhance reservoir properties and boost oil and gas production. Understanding how strike-slip fault segments and their associated structures affect hydrocarbon accumulation is essential for geological research and exploration planning. This study aims to characterize the geometry and structural evolution of the strike-slip basement fault with Pan-African or Arabian trends, investigate the relationship between fault segments, and assess their impact on the distribution of hydrocarbon traps. This research focuses on the structural and tectono-sedimentary analyses of the Kazerun fault system based on processing and interpretation of the surface data (e.g., satellite images and aeromagnetic data) and the subsurface data (e.g., 2D and 3D seismic and well data) in the Zagros orogenic belt, SW Iran. The relationship between the segmented strike-slip fault zone and hydrocarbon reservoirs is analyzed through map view patterns and profile features. Results reveal that the Arabian-trending Kazerun fault system comprises segmented dextral strike-slip faults and is considered a transform and wrench fault. These faults display various planar configurations, including linear, en-echelon, horsetail splays, and irregular geometries in the map view. Based on the seismic data interpretation, three structural styles develop along the Kazerun strike-slip fault zone, including vertical or oblique, pull-apart (negative flower structure), and push-up (positive flower structure) segments. Releasing and restraining bends and oversteps formed at the tail end of the Kazerun strike-slip fault segments. In the study area, salt diapirism occurred along the pull-apart segment and the releasing bend. Hydrocarbon traps are developed in the push-up segment and the restraining bend. Fractures are less prominent in the vertical segments but more developed in push-up and pull-apart segments, which act as pathways for fluid migration and improving reservoir quality. The push-up segment and restraining bend exhibit a higher degree of branching fractures, making them the most significant for reservoir development. This research shows that strike-slip fault segmentation (in the form of fault overlapping or stepping) and their lateral linkage control the reservoir distribution and connectivity. Recognizing the growth and lateral connections of strike-slip fault segments is crucial for structural analysis and predicting fault-controlled reservoirs. These findings offer valuable insights into the structural characteristics of strike-slip fault zones and can enhance oil and gas exploration in the Zagros fold-and-thrust belt and other similar regions.

Keywords:

Strike-slip basement fault, Segmentation pattern, Oil/Gas fields, Zagros orogenic belt, SW Iran

How to cite: Soleimany, B., Tajmir Riahi, Z., Payrovian, G. R., and Sepahvand, S.: Impact of segmentation pattern of the Pan-African trending strike-slip basement fault on the spatial distribution of hydrocarbon traps in SW Iran, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1377, https://doi.org/10.5194/egusphere-egu26-1377, 2026.

Skarn-type Cu–Fe–Au mineralization in the Middle–Lower Yangtze River Metallogenic Belt (MLYRB) is closely associated with Early Cretaceous intermediate to felsic magmatism; however, the links between magmatic evolution and ore-forming efficiency remain poorly constrained. In the Tonglushan ore field, one of the largest Cu–Fe–Au skarn systems in eastern China, multiple intrusive phases are spatially distributed, providing an ideal opportunity to investigate how magmatic processes control metallogenic potential. Here we present new geochronological and geochemical constraints on quartz monzodiorite porphyry, quartz monzodiorite, quartz diorite, and their mafic microgranular enclaves (MMEs) from different sectors of the Tonglushan ore field.

Zircon U–Pb ages indicate synchronous emplacement of all intrusive phases and MMEs at ca. 142–140 Ma. Whole-rock geochemistry and Sr–Nd–Hf isotopes indicate that these intrusive rocks belong to a high-K calc-alkaline to weakly adakitic series and were derived from an enriched lithospheric mantle source modified by slab-derived components, followed by extensive fractional crystallization. The MMEs record efficient mixing between mafic and felsic magmas, highlighting the role of mafic recharge in supplying heat and metal components to the evolving system. Estimates of magmatic water contents and oxygen fugacity from zircon compositions reveal systematic variations among different intrusions. The Jiguanzui and Tonglushan quartz monzodiorite porphyries are characterized by high water contents and elevated oxidation states, consistent with intense Cu–Au and Cu–Fe–Au mineralization, whereas the weakly mineralized Zhengjiawan quartz diorite exhibits lower values. These observations suggest that, beyond structural controls, the metallogenic fertility of intrusions in the Tonglushan ore field was primarily governed by fractional crystallization, mafic magma input, and the development of highly hydrous and oxidized magmatic systems.

Our study demonstrates that integrated whole-rock and zircon geochemical indicators provide effective tools for evaluating the ore-forming potential of skarn-type Cu–Fe–Au mineralization related intrusions in the MLYRB.

How to cite: Zhang, M. and Tan, J.: Magmatic controls on skarn-type Cu–Fe–Au mineralization in the Tonglushan ore field, Middle–Lower Yangtze River Metallogenic Belt, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2162, https://doi.org/10.5194/egusphere-egu26-2162, 2026.

Low-temperature thermochronology provides key constraints on the post-mineralization exhumation and preservation of orogenic gold deposits. In this study, we investigate the exhumation histories of the Anjiayingzi and Jinchanggouliang gold deposits, located respectively in the Kalaqin metamorphic core complex (MCC) and the Nuluerhu magmatic dome within the Chifeng–Chaoyang metallogenic belt on the northern margin of the North China Craton.

Both deposits formed in the Early Cretaceous (~130 Ma), but at significantly different depths (5.6–7.1 km for Anjiayingzi and 1.0–2.6 km for Jinchanggouliang), and are currently exposed at the surface, implying differential post-mineralization exhumation. Zircon and apatite (U–Th)/He and fission-track analyses were conducted on ore-hosting rocks to reconstruct cooling and exhumation histories. Combined age–elevation relationships and thermal history modeling reveal that the Anjiayingzi deposit experienced multi-stage, rapid exhumation totaling ~6.75 km since mineralization, with the most intense exhumation occurring between 130 and 80 Ma. In contrast, the Jinchanggouliang deposit underwent slower and more limited exhumation, with a total exhumation of ~2.50 km over the same period.

The contrasting exhumation histories coincide with an Early Cretaceous regional extensional regime affecting the northern margin of the North China Craton. We suggest that tectonic setting plays a first-order role in controlling post-mineralization exhumation. Deposits hosted within MCCs are characterized by rapid extensional denudation related to detachment faulting, whereas deposits hosted in magmatic domes are mainly exhumed through regional uplift and surface erosion. These results emphasize the importance of structural architecture in governing the exhumation, preservation, and exposure of gold deposits in extensional orogenic systems.

How to cite: Li, A. and Fu, L.: Post-mineralization exhumation of gold deposits on the northern margin of the North China Craton: constraints from low-temperature thermochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2243, https://doi.org/10.5194/egusphere-egu26-2243, 2026.

The Southeast Anatolian Suture Belt hosts the oceanic and continental remnants of the southern Neotethyan realm. During the Late Cretaceous, the southern Neotethyan domain experienced an Andean-type magmatism on its northern continental margin (the Tauride-Anatolide Platform), characterized by the Baskil Magmatics. The plutonic part of this unit is intruded by numerous dikes, which are the primary focus of this study. The U-Pb zircon dating of the dikes and their granodioritic host rocks indicates that their emplacement occurred within a narrow interval, between 81-79 Ma. The dikes vary chemically from basalt to dacite, while the host rocks range from andesitic to dacitic. On the normal mid-ocean ridge (N-MORB)-normalized plots, all samples exhibit negative Nb anomalies. Trace element systematics reveals that this dike system is chemically heterogeneous, consisting of five distinct chemical types. The elemental and isotope ratios indicate varying contributions from depleted and enriched components. All chemical types, with relative Nb depletion, suggest incorporation of slab-derived and/or crustal additions. This interpretation is further supported by the EM-2-like Pb isotopic ratios. Based on the variability in elemental and isotopic composition, this intrusive system appears highly heterogeneous, likely due to the combined effects of mantle source, crustal contamination, and fractional crystallization. The bulk geochemical characteristics of the studied dikes and their host rocks suggest that these intrusives formed at a continental arc. Considering the available paleontological and geochronological age data, it appears that the intraoceanic subduction and continental arc magmatism in the Southern Neotethys occurred simultaneously; the former created the Yüksekova arc-basin system, whereas the latter formed the Baskil Arc.

Note: This study was supported by project Fübap-MF.15.12.

How to cite: Ural, M., Sayit, K., Koralay, E., and Göncüoglu, M. C.: Geochemical and Geochronological approaches of Baskil Dikes (Elazığ, Eastern Turkey): Discrimination between the Late Cretaceous Continental and Oceanic Arc-related Magmatism in the Southern Neotethys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2274, https://doi.org/10.5194/egusphere-egu26-2274, 2026.

The Kaladgi Basin, an E–W trending intracratonic basin in the northern part of the Dharwar Craton, preserves favourable structural and stratigraphic conditions for sandstone-hosted and unconformity-related U–REE mineralization. In the study area, the Neoproterozoic Cave Temple Arenite (CTA) of the Badami Group unconformably overlies deformed Mesoproterozoic rocks of the Bagalkot Group. The crystalline basement of the Kaladgi Supergroup comprises Meso- to Neoarchaean Peninsular Gneiss and the Chitradurga Greenstone Belt. This association of cratonic basement, schist belt, and basin-margin fault and fold systems provides an excellent structural framework for hydrothermal fluid circulation and mineralization.

Detailed thematic mapping at 1:25,000 scale in the Ramdurg–Suriban sector reveals that NNW–SSE–oriented Dharwarian stress generated a series of anticlines and synclines involving the Saundatti Quartzite, Malaprabha Phyllite, and Yaragatti Argillite, as constrained by conjugate fracture analysis and S–C fabric development. An E–W trending tectonic fault defines the contact between the Peninsular Gneissic Complex and Saundatti Quartzite, with comparable faulted contacts also developed within the Bagalkot Group. Intense faulting resulted in silicification, chalcedonic brecciation, and pervasive hydrothermal alteration along these contact zones. Transverse normal faults with associated brecciation accommodate strain related to the main E–W structure and indicate episodic reactivation of the basin architecture.

Fusion ICP–MS analysis of 20 bedrock samples collected proximal to these fault zones shows U₂₃₈ concentrations exceeding twice the threshold values of National Geochemical Mapping (NGCM) stream sediment sample. Uranium enrichment is spatially associated with Malaprabha Phyllite, first-cycle CTA, and silicified banded hematite quartzite veins of the Hiriyur Formation. Chondrite-normalized (La/Yb)_n versus (Eu/Eu*)_n systematics indicates a dominantly low-temperature basinal brine hydrothermal system characterized by low (La/Yb)_n <25 and negative Eu anomalies. Redox-sensitive (Ce/Ce*)_n versus (Eu/Eu*)_n plots further indicate reducing fluid conditions. In contrast, quartz–chlorite veins developed within sheared Malaprabha Phyllite and younger dolerite record comparatively higher-temperature fluids, marked by Eu²⁺ mobilization ((Eu/Eu*)_n > 0.8) and negative Ce anomalies. These results suggest that reactivated, structure-controlled tectonites acted as effective fluid pathways, with the TTG-dominated Peninsular Gneissic Complex serving as a likely uranium source and contributing to localized U–REE mineralization along the basin margin.

How to cite: Mahanandia, A., Lal, M. M., Singh, T. G., Nandhagopal, N., and Singh, S.: Structure-controlled Uranium + REE mineralization in low temperature basinal brine hydrothermal system at the contact of Kaladgi Basin and Peninsular Gneissic Complex, South India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2923, https://doi.org/10.5194/egusphere-egu26-2923, 2026.

Gravity observations are widely used in volcanic monitoring to infer subsurface mass redistributions, commonly interpreted in terms of magma intrusion. However, gravity changes may also arise from thermo-poro-elastic (TPE) processes associated with temperature and pore-pressure variations in fluid-saturated reservoirs. Neglecting these effects can lead to ambiguous or misleading interpretations of gravity signals during volcanic unrest.

The recent development of TPE inclusion models allows us to describe the mechanical fields induced by fluid-saturated rock volumes undergoing pore-pressure and temperature variations. These sources can coexist with magmatic sources within volcanic systems and are typically located at shallower depths than the deep magmatic reservoir, which acts as the primary engine by releasing hot fluids. These exsolved fluids rise from depth and either accumulate in, or migrate through, overlying brittle rock volumes, which respond to thermal and pore-pressure perturbations and therefore act as secondary sources of deformation and gravity change. In this work, we consider a disk-shaped TPE inclusion, a geometry that has been successfully applied in previous studies to represent deformation fields that are predominantly radial and associated with axisymmetric sources.

The results show that gravity variations induced by a TPE inclusion depend strongly on the fluid phase. Both liquid water and gaseous fluids can produce the same significant ground uplift, but lead to different gravity residuals: negative for liquid water and minor but positive for gaseous fluids. In contrast, condensation or vaporization of a thin layer near the surface can generate large gravity changes without notable deformation. As a result, heating and pressurization of a TPE inclusion can mask or weaken the gravitational signature of magma ascent, complicating the interpretation of gravity data and highlighting the need to account for hydrothermal effects when estimating magma volumes during unrest.

Gravity data collected over the past decades at the Campi Flegrei caldera (Italy) provide an ideal test site for applying our model and offer intriguing insights into both past and current unrest phases, although our results are applicable to any volcanic system with an active hydrothermal system. These findings highlight the importance of incorporating TPE effects into gravity data interpretation and integrated volcano monitoring strategies. Accounting for them improves our ability to distinguish between magmatic and hydrothermal contributions, leading to more robust assessments of subsurface dynamics and volcanic hazards.

How to cite: Nespoli, M., Bonafede, M., and Belardinelli, M. E.: Thermo-Poro-Elastic effects as hidden drivers of gravity signals in volcanic systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3001, https://doi.org/10.5194/egusphere-egu26-3001, 2026.

Abstract: Unlike ionosphere, troposphere is nondispersive and delays cannot be determined from observations of signals at different radio frequencies. In GNSS data processing, station height, receiver clock error and tropospheric delay are highly correlated to each other, especially in kinematic situations. Although zenith hydrostatic delay can be provided with sufficient accuracy, zenith wet delay, which is more spatially and temporally varying than hydrostatic component, has to be carefully processed. Usually, temporal dependence of tropospheric delays at zenith is modeled as a random walk process with a solely given process noise rate σ_rw in GNSS processing. The usually used σ_rw is a constant throughout whole process session and is in range of 3~10 mm per sqrt hour. This setting is generally appropriate for desirable GNSS positioning estimation in normal conditions. However, modeling zenith tropospheric delay by using a constant σ_rw in whole session will be unsatisfactory in cases of special weather conditions, e.g., the shower case. The σ_rw is a measure of magnitude of typical variation of zenith path delay or its residual after calibration in a given time. Values of σ_rw that are too large could weaken strength for geodetic estimation, while values that are too small may introduce systematic errors, since a strong constraint for tropospheric unknowns is imposed to stabilize the system. The random walk model for wet delay must be constrained approximately to "correct" value to obtain optimum parameters estimates. Assuming temporal change of tropospheric delay at an arbitrary station can be described by random walk model, the process noise levels were calculated by some scholars. They employed water vapor radiometric, surface meteorological measurements and numerical weather model data set for optimum selection of σ_rw. In general, although a lot of efforts have made to optimize post-processing and/or real-time GNSS tropospheric delay estimation, stochastic modeling of zenith wet delay remains insufficiently investigated, especially for kinematic applications. Since temporal variation of zenith wet delay depends on water vapor content in atmosphere, it seems to be reasonable that constraints should be geographically and/or time dependent. In this work, we first investigate sensitivity of both station coordinates and zenith wet delay estimators on different σ_rw values, and then try to propose to take benefit from post-processed static or kinematic estimated tropospheric delay to obtain the optimum σ_rw. The general objective is that if zenith tropospheric delays are of different variation characteristic, e.g., relatively stable or rapid changing, then a varying σ_rw, e.g., small or large value, could be employed, which should be more theoretically feasible compared with a invariant σ_rw. The initial results show that the new method can efficiently obtain epoch-wise σ_rw values at different stations. Compared to results from conventional constant σ_rw value, time-varying noise rate can improve precision of PPP solutions. We note that this first results represent performance view at several selected stations, more works should be done to draw global or even long-term conclusions.

This work is supported by National Natural Science Foundation of China (42304010), Youth Foundation of Changzhou Institute of Technology (YN21046).

How to cite: Wang, M., Lu, B., and Zhong, Q.: The initial results about optimum the random walk process noise rate for GNSS tropospheric delay estimation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4327, https://doi.org/10.5194/egusphere-egu26-4327, 2026.

The Yanshan-Liaoning metallogenic belt (YLMB), the second-largest molybdenum deposit cluster in China, hosts over twenty porphyry molybdenum deposits, including the large-scale Caosiyao, Sadaigoumen, and Dasuji deposits, as well as the newly discovered medium- to large-scale Qiandongdamiao, Zhujiawa, and Taipingcun deposits. Geochronological data indicate that the duration of molybdenum mineralization spanned ca. 100 Myrs, from the Triassic to Early Cretaceous (240–140 Ma). However, the reasons for such a prolonged or multi-period metallogenic event, and the magmatic and geodynamic processes controlling the spatial–temporal distribution of these deposits, remain poorly understood.

Here we summarize the geological, chronological and geochemical data from selected molybdenum deposit to reconstruct the temporal–spatial distribution and tectonic setting of ore- metallogenic history in the YLMB. The formation of molybdenum deposit in the YLMB can be divided into three periods of 240–220 Ma, 185–180 Ma and 160–140 Ma. The ore-forming intrusions among these three periods illustrate an overall characteristic that metaluminous to peraluminous, high-K calc-alkalic to shoshonite series acidic rocks, and the source of intrusions is the Archaean–Paleoproterozoic lower crust. Through in-depth analysis of Sr-Nd-Hf isotopic data, we find that the magma source that during the 185-180 Ma stage is relatively younger, mainly reflecting the partial melting of Paleoproterozoic crust, whereas the magma source that during the 240–220 Ma and 160–140 Ma stages likely are contained both from the Paleoproterozoic and Neoarchean crust. Further calculations using trace element content ratios reveal a shallower magma source along the magma evolution during the 240–220 Ma period, which supported by the gradual decrease trend in crustal thickness. In contrast, the calculation of crustal thickness during the 185–180 Ma and 160–140 Ma stages show an increase trend, suggested an thicken process in the depth of the magma source.

Spatially, the porphyry molybdenum deposits formed during these three periods exhibit distinct geographic distributions. Deposits formed at 240–220 Ma are mainly located in the northern part of the YLMB, including the Chengde-Zhangbei-Fengning district. Those formed at 185–180 Ma are primarily located in the Liaoxi district, eastern part of the YLMB while deposits formed at 160–140 Ma are located in the southern part of the YLMB, particularly in the Xinghe-Zhangjiakou-Xinglong district. We propose that the variations of the spatial–temporal distribution and geochemical characteristics of the molybdenum deposit formed during different periods in the YLMB are controlled by variations of their geodynamic settings. The porphyry molybdenum deposits formed in 240–220 Ma are under the post-collision or post-orogenic extension environment between the North China Plate and the Siberian Plate in the Middle Triassic. Deposits formed in 185–180 Ma are under the extension environment in the early stage of the Yanshanian movement, and porphyry molybdenum deposits formed in 160–140 Ma are in the strong extrusion environment in the main stage of the Yanshanian movement.

Our findings demonstrate the multi-period metallogenic history of the YLMB, highlighting the critical role of magma source, storage depth, and geodynamic setting in controlling the formation of porphyry molybdenum deposits.

How to cite: Jiang, C., Liu, Q., Cao, L., Li, A., and Fu, L.: Magmatic and geodynamic processes control on the formation of porphyry molybdenum deposits: Insights from the Yanshan-Liaoning metallogenic belt, northern margin of North China Craton, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4396, https://doi.org/10.5194/egusphere-egu26-4396, 2026.

Microcontinents are isolated fragments of continental crust surrounded by oceanic lithosphere. They commonly occur in modern ocean and are also recognized in orogenic system. They can be accreted onto continental margins through collision and subduction during ocean-continent subduction process, and lead to migration of subduction zone toward the oceanic side. However, it is not well understood whether and how this process can be recorded by metamorphism. In this study, a high grade metamorphic-magmatic terrane is recognized along the previously defined Qilian block. The Datong-Mengyuan terrane (DMT) is separated from the low-medium grade metamorphic basement of the Qilian block (QLB) by dextral strike-slip ductile shear zone and ophiolite mélange. The petrology and texturally-controlled U-Pb multi-mineral geochronology reveal that the mafic and felsic granulites from the DMT record two significance events of metamorphism. The earlier event experienced a pressure and temperature conditions of 11.4–13.7 kbar and 735–805°C at ca. 500 Ma, and later stage records a pressure and temperature conditions of 5.5–9.6 kbar and 790–840°C at ca. 460 Ma. We suggest that the earlier Cambrian high pressure granulite facies metamorphism is resulted from collision and thickening related to the accretion of the DMT to the Qilian block, and the later low-medium pressure granulite facies overprinting formed by decompression heating, which happened in continental arc setting and is associated with shift of subduction zone toward the ocean. These findings provide a critical example of metamorphic record on the microcontinent accretion and convergent plate boundary dynamics.

How to cite: Mao, X. and Zhang, J.: Metamorphism records microcontinent accretion and subduction relocation: an example from early Paleozoic Qilian Orogenic Belt, NW China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4872, https://doi.org/10.5194/egusphere-egu26-4872, 2026.

The distribution of rare gases within the Earth’s interior has caught the attention of scientists for the past few years. The inertness and volatility of noble gases make them excellent tracers for understanding the chemical evolution of Earth’s mantle and atmosphere. Previous studies indicate that noble gases can be found associated with clathrates, form their own oxides, or, in some cases, noble gases such as helium and xenon can even bond with Fe under extreme pressure (p) - temperature (T) conditions like those in Earth’s core. However, the ability of lower mantle mineral phases to house rare gases remains poorly understood, leaving important gaps in knowledge. Helium and argon are noble gases of interest in this study. The isotopes ⁴He and ⁴⁰Ar are produced from the radioactive decay of ²³⁸U and ⁴⁰K within the Earth’s interior, while ³He and ³⁶Ar are regarded as primordial, introduced during the accretion of Earth. Dong et al. (2022) revealed that noble gases can become reactive under mantle pressure conditions. Still, their ability to be incorporated into mantle minerals via adsorption needs to be thoroughly studied, as there are many limitations in the experiments conducted to measure the solubility of noble gases in minerals under mantle p-T conditions. In this study, we investigated the adsorption behavior of helium and argon on the (001) plane of periclase (MgO) by employing first-principles density functional theory (DFT) calculations.

Adsorption energies were estimated across pressures ranging from 0 to 125 GPa, representative of conditions throughout Earth’s interior, i.e., approximately up to the Core Mantle Boundary (CMB). At ambient pressure, both helium and argon showed negative adsorption energies, indicating stable adsorption relative to isolated species (MgO, Ar, He). These energies became increasingly negative with pressure, becoming notably negative beyond 75 GPa which corresponds to lower mantle pressures. This may be due to the accelerated reactivity of noble gases at extreme pressure conditions, as reported in previous studies. Additionally, under all pressure conditions argon exhibited stronger adsorption than helium, indicating enhanced argon retention in lower mantle conditions. However, further investigations into the mechanical and dynamical stability of these adsorbed structures are required to completely understand the mechanisms governing noble gas occurrence in the Earth’s lower mantle.

How to cite: Karangara, A. and Kumar Das, P.: Adsorption of Helium and Argon on the (001) Surface of Periclase: A First-Principles Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4988, https://doi.org/10.5194/egusphere-egu26-4988, 2026.

Soil CO₂ emission is a key proxy for investigating fluid migration processes associated with volcanic and tectonic activity. In particular, the analysis of the spatial distribution of geochemical anomalies represents an effective tool for identifying active structures and zones of ongoing deformation. Numerous studies have shown that faults and fracture systems play a fundamental role in controlling the localization and evolution of surface geochemical anomalies.

Vulcano Island (Aeolian Archipelago, Italy) is characterized by intense hydrothermal activity and persistent soil CO₂ emissions, providing a natural laboratory to investigate the relationships between fluid circulation and active tectonic structures. In this study, we present an integrated analysis of soil CO₂ fluxes based on results obtained from periodic surveys and continuous soil CO₂ flux records acquired at key sites across the island.

Periodic measurements are performed on fixed spatial grids, allowing the production of soil CO₂ flux maps and the identification of areas characterized by elevated degassing rates. At selected sites, the carbon isotopic composition of gases is analyzed to constrain gas sources.

These spatial datasets provide insights into the structural control exerted by the main tectonic lineaments on gas release at the surface. Continuous CO₂ flux monitoring enables the investigation of temporal variations and transient degassing signals potentially related to seismic and tectonic processes. In particular, the recent volcanic crisis at Vulcano Island, started on 2021, characterized by a marked increase in soil CO₂ flux, allowed a more detailed identification of preferential CO₂ emission pathways, highlighting zones of enhanced permeability associated with fault and fracture systems.

This work is carried out within the framework of the CAVEAT project (Central-southern Aeolian islands: Volcanism and tEArIng in the Tyrrhenian subduction system), which aims to provide a comprehensive understanding of the current geodynamics of the southern Tyrrhenian region.

How to cite: De Gregorio, S., Camarda, M., Capasso, G., Di Martino, R. M. R., Pisciotta, A., and Prano, V.: Soil CO₂ Emissions as Indicators of Fluid Pathways in Volcanic–Tectonic Environments: Insights from Vulcano Island, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5147, https://doi.org/10.5194/egusphere-egu26-5147, 2026.

Mg-bearing minerals, including brucite [Mg(OH)₂], lizardite [Mg₃(Si₂O₅)(OH)₄] and iowaite [Mg₆Fe³⁺₂(OH)₁₆Cl₂·4H₂O] are variably reactive with carbon dioxide (CO₂) at Earth’s surface conditions and can be used to mineralize and sequester this greenhouse gas. Here, we assess the impact of temperature (5, 20 and 40 °C) on the rate of CO₂ mineralization of these minerals. At each temperature, mineral powders (~100 mg ) were placed in a 7.5-litre flow-through reactor that was supplied with humidified laboratory air (0.042% CO₂; 100% RH) at ~200 mL/min. Subsamples (n = 54) of each mineral were collected over 3 months and analyzed (XRD, TIC, BET) to ascertain the amount and rate of carbonation as a function of time, temperature, and mineral feedstock.

Preliminary X-ray diffraction (XRD) results show the formation of dypingite [Mg₅(CO₃)₄(OH)₂·5H₂O] and a decrease in the abundance of brucite over time. The 003 peak of iowaite shifted to smaller d-spacings, indicating replacement of chloride by carbonate ions and a transition to a more pyroaurite-rich [Mg₆Fe³⁺₂(CO₃)(OH)₁₆·4H₂O] composition. Total Inorganic Carbon (TIC) measurements were used to determine the amount and rate of carbonation as a function of time, temperature, and mineralogy.

The results of this study will help us estimate the carbonation kinetics of these minerals in ultramafic ores and mine tailings under different temperature conditions relevant to large-scale deployment of CO₂ mineralization at mines across the globe.

How to cite: Sulemana, S. Z., Wilson, S., Moyo, A., Akhtar, S., Power, I. M., and Sleep, S.: Temperature-dependence of CO2 drawdown into Mg-bearing minerals., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6294, https://doi.org/10.5194/egusphere-egu26-6294, 2026.

The main focus of the study is to calibrate Sentinel-1 InSAR Line-of-Sight (LOS) velocities along a ~700 km North-South transect extending from the Black Sea coast (Kastamonu-Samsun) to the Mediterranean (Mersin-Gaziantep). This transect encompasses diverse tectonic regimes, including the North Anatolian Fault Zone, the Central Anatolian Block, and the junction of the East Anatolian Fault Zone. This complex structure of the transect requires detailed analysis of the GNSS-InSAR calibration procedure including validation. 

Across the study region, processed LiCSAR products are integrated with 3D velocities derived from the continuous local CORS network (21 stations) and an extensive campaign-based GNSS network (200 stations). For calibration, GNSS velocities are first projected into the satellite LOS geometry using LOS vectors derived from coherent InSAR pixels within a 1-km radius. The velocity bias (ΔVlos) is calculated at continuous GNSS locations. This correction surface is propagated using various conventional and Machine Learning techniques independently, including Kriging, Weighted Least Squares (WLS) based Quadratic Surface fitting, Thin Plate Spline (TPS) and Radial Basis Functions (Gaussian, Multiquadric, and Inverse Multiquadric). To address specific error sources, the contributions of topography-correlated atmospheric delays and local spatial trends are also analyzed by Geographically Weighted Regression (GWR) and Random Forest regression. Cross-validation is applied to assess the quality of each model individually where spatial random sampling and plate boundaries are also considered. This study presents preliminary results for obtaining a validated basis for generating up-to-date velocity fields over Türkiye.

How to cite: Elvanlı, M. and Durmaz, M.: Comparative Analysis of Machine Learning and Geostatistical Approaches for GNSS-InSAR Integration: A Case Study in Anatolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7178, https://doi.org/10.5194/egusphere-egu26-7178, 2026.

Geomagnetic storms (GS) significantly perturb the near-Earth environment, leading to enhanced thermosphere density, increased non-conservative forces, and degraded satellite orbit determination, particularly for Doppler-based techniques such as DORIS. In this study, we investigate and improve DORIS orbit determination performance during GS conditions by developing storm-adapted processing strategies. Storm days were classified using geomagnetic indices and categorized into moderate to severe storm levels (G3-G5).

Four distinct processing strategies were implemented and evaluated: a standard operational solution and three experimental storm-adapted solutions, designed through systematic modifications of drag constraints and observation-elimination criteria. These strategies were tested through targeted daily and weekly experiments conducted across multiple DORIS-equipped satellites, with a particular emphasis on periods of intense storms.

The storm-adapted strategies demonstrate clear performance improvements relative to the standard solution during geomagnetic storms. The modified strategies reduce orbit residual RMS in all orbital components, improve Length-of-Day (LOD) variance by approximately 40-80%, and decrease LOD mean biases by nearly 60%. Additionally, Earth Rotation Parameters (ERP) exhibit notable improvements, with reductions of approximately 22–25% in both bias and variability for the polar motion components (X/Y pole). Among the tested configurations, the combined strategy, particularly when applied with zero-rotation constraints, consistently delivers the best performance during intense storm conditions (Kp ≥ 8+). These results demonstrate that storm-adapted DORIS processing strategies significantly enhance orbit and geophysical parameter estimation during disturbed space-weather conditions.

How to cite: Kumar, V., Stepanek, P., Filler, V., Balasubramanian, N., and Dikshit, O.: Impact of Storm-Adapted DORIS Processing on Orbit Quality and Earth Rotation Parameters During Geomagnetic Storms , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7764, https://doi.org/10.5194/egusphere-egu26-7764, 2026.

Abstract: The study of fluid inclusions and sulfur isotope characteristics of barite deposits is crucial for tracing the source of ore-forming materials and predicting prospecting targets. Current research indicate that the Sangmuchang barite deposit in northern Guizhou is primarily hosted within the joint fractures of dolomites in the Sinian Dengying Formation and Cambrian Qingxudong Formation. The contact between ore bodies and surrounding rocks is distinct, with the orebodies occurring as veins and lenticular. The ore textures are mainly veinlets, stockworks, massive, and banded, while the ore structures consist of inequigranular tabular-columnar blastic, fine-crystalline, and arenaceous texture.  Fluid inclusion studies reveal that  the inclusions are single-phase aqueous inclusions. Microthermometric measurements of 33 inclusions show that their homogenization temperatures range from 81°C to 182°C, with an average of 132°C; Salinity values vary from 9.61 wt.% NaCl eqv to 20.63 wt.% NaCl eqv, with an average of 17.53 wt.% NaCl eqv. Ten sulfur isotope analyses from the deposit show that the δ³⁴SV-CDT values range from 40.89‰ to 46.95‰, with a mean of +44.51‰.The characteristics of fluid inclusion salinity, temperature and sulfur isotopes suggest that the ore-forming fluids of this barite deposit are characterized by moderate-low temperature and moderate-high salinity. These ore-forming fluids were mainly derived from basin brines, with contributions from meteoric water. The significant enrichment of heavy sulfur isotopes and homogeneous sulfur isotope composition reveal that the sulfur source of ore-forming materials in this barite deposit is a relatively singular source for the sulfur in the ore-forming materials, which is similar to the δ³⁴S characteristics of Sinian marine evaporites, suggesting a close genetic relationship between the sulfur source and evaporites. Therefore, the Sangmuchang barite deposit is interpreted as a moderate-low temperature hydrothermal deposit.  It was formed by the migration of moderate -low temperature hydrothermal fluids in the sedimentary basin, which leached ore-forming materials from underlying and surrounding barium-rich evaporite sequences, followed by precipitation within structural fracture zones under the mixing of meteoric water. The structural fracture zones and areas indicative of fluid migration pathways along the basin margin are important targets for exploration prediction. Keywords: ore-forming fluid; fluid inclusion; sulfur isotope; barite; northern Guizhou

How to cite: Chen, Y., Wang, J., and Liu, Z.: Study on the Source of Ore-Forming Materials of the Sangmuchang Barite Deposit in Northern Guizhou, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8505, https://doi.org/10.5194/egusphere-egu26-8505, 2026.

Uranium is a strategically important metal with applications in nuclear energy, medicine, radiometric dating, food processing, industrial radiography, material sciences, and catalysis. This study presents a detailed microtextural and geochemical investigation of uranium mineralization from the Bodal uranium mine, Mohla-Manpur-Chowki, Central India. Uranium occurs as both crystalline and colloidal precipitates, with coffinite [U(SiO₄)_1-x(OH)_4x] and gummite representing the dominant uranium-bearing phases. The mineralization is spatially and genetically associated with altered metabasalts. Petrographic and geochemical evidence indicates that late-stage hydrothermal alteration played a crucial role in uranium remobilization and ore enrichment. Sulphide minerals, including cobaltite (CoAsS), galena (PbS), arsenopyrite (FeAsS), and chalcopyrite (CuFeS₂), are intimately associated with uranium phases and likely acted as effective reductants and sorption substrates, facilitating uranium precipitation under reducing conditions. The ore assemblage is accompanied by abundant accessory minerals such as zircon, allanite, and apatite. Substitution of U⁴⁺ for Zr⁴⁺ in zircon locally records uranium-rich hydrothermal fluids and contributes to zirconium enrichment. Collectively, these observations suggest that hydrothermal fluid–rock interaction and redox-controlled precipitation were the dominant processes responsible for uranium enrichment at the Bodal mine.

Keywords: Uranium mineralization; Hydrothermal alteration; Redox-controlled precipitation; Bodal mine; Central India

How to cite: Ganveer, S., Mallick, S. P., and Pruseth, K. L.: Hydrothermal remobilization and redox trapping of uranium in metabasalts of the Bodal mine, Central India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11094, https://doi.org/10.5194/egusphere-egu26-11094, 2026.

The Kirazlı porphyry and high-sulfidation (HS) epithermal system is situated in the central Biga Peninsula of northwestern Türkiye, a region characterized by the protracted closure of the Tethyan oceanic branches and the subsequent collision of Gondwana-derived continental fragments with the Sakarya Zone. This geodynamic framework facilitated the development of diverse tectono-magmatic environments, leading to the formation of porphyry and associated hydrothermal mineralization during the Cenozoic. Based on established geochronological data, magmatism in the Biga Peninsula occurred in five discrete chronostratigraphic episodes: Paleocene to Early Eocene (65–49 Ma), Middle–Late Eocene (49–35 Ma), Late Eocene to Early Oligocene (35–23 Ma), Late Oligocene to Middle Miocene (~23–14 Ma), and Late Miocene to Pliocene (14–5 Ma). Mineralization within the Kirazlı district is temporally constrained to two primary intervals—Late Eocene to Early Oligocene and Oligocene to Early Miocene corresponding to specific magmatic pulses and structurally mediated by major regional shear zones.

Integration of the ages of fault-hosting lithologies, structural styles, fault geometries, and paleostress reconstructions indicates three distinct tectonic phases consistent with the regional Cenozoic evolution: (1) NW–SE extension (Phase-1), (2) NNE–SSW extension (Phase-2), and (3) NE–SW extension (Phase-3). Detailed field observations, petrographic analysis, and microstructural investigations of oriented samples demonstrate that the porphyry and HS-epithermal stages were governed by these shifting stress regimes. B- and D-veins associated with the porphyry stage exhibit preferred orientations along an ENE–WSW strike, consistent with the NW–SE extensional regime of Phase-1. In contrast, late-stage quartz veins within the HS-epithermal overprint formed under a NNE–SSW extensional stress field, aligning with the Phase-2 tectonic pulse.

Analysis of fault planes for both Phase-2 and Phase-3 indicates that ENE–WSW and NE–SW strike directions are common to both phases. Phase-3 displays kinematic and geometric features characteristic of the modern transtensional NE–SW and strike-slip regime currently active in the Biga Peninsula. Correlation of these structural data with magmatism–mineralization age constraints indicates that the porphyry and HS-epithermal components of the Kirazlı system were emplaced during distinct tectonic periods. This evolution reflects the transition from a post-collisional setting to the current extensional and strike-slip dominated regime of western Anatolia.

How to cite: Çam, M., Kuşcu, İ., and Kaymakcı, N.: Tectono-Magmatic Evolution and Structural Controls on the Kirazlı Porphyry-High Sulfidation Epithermal System, Biga Peninsula, NW Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11195, https://doi.org/10.5194/egusphere-egu26-11195, 2026.

El Chichón is an active volcano in Chiapas, Mexico, that features a hydrothermal system characterized by thermal springs, fumaroles and an acid crater lake. Many studies have focused on tracking the geochemical evolution of its fluids since its last eruption in 1982 and some have specifically aimed to evaluate the geothermal potential.  This work assesses the evolution of the geothermal potential through time using published geochemical data (1983-2025). We use geochemical diagrams, temperatures estimated with geothermometers and water-rock interaction analysis to identify the main system changes that influence the geothermal potential estimations. Given that El Chichón has been considered  a geothermal prospect since the 1980s, we discuss the possible uses of this resource in terms of its recent active seismicity, the risk scenarios and the local socio-cultural context. 

How to cite: Salas Ferman, J. L., Jácome Paz, M. P., Campion, R., Armienta, M. A., and Inguaggiato, S.:  Temporal evaluation of El Chichon´s geothermal potential in the period of 1983-2025. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15407, https://doi.org/10.5194/egusphere-egu26-15407, 2026.

Traditional methods for determining geopotential and height require successive transfers of leveling and gravity measurements, which are prone to error accumulation, face challenges in transoceanic applications, and are generally time-consuming, labor-intensive, and inefficient. Based on the principles of general relativity, an alternative approach using high-precision time-frequency signals to determine geopotential can overcome these limitations. In this study, simulation experiments were conducted to determine geopotential differences using BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer technology. The simulations employed clocks with different performance characteristics, utilizing precise clock offsets and multi-frequency observation data from both systems. The results show that the frequency stability achieved by BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer can reach approximately 3×10⁻¹⁷. The root mean square of the determined geopotential differences corresponds to centimeter-level equivalent height accuracy, and the convergence accuracy of the geopotential difference by the final epoch can reach better than 3.0 m²·s⁻². Given the rapid development of GNSS multi-frequency signals and ongoing improvements in the precision of products such as code and phase biases, geopotential determination based on Galileo and BDS multi-frequency signals is expected to have broader application prospects in the future. This study was supported by the National Natural Science Foundation of China project (No. 42304095), the Key Project of Natural Science Research in Universities of Anhui Province (No. 2023AH051634), the Chuzhou University Research Initiation Fund Project (No. 2023qd07).

How to cite: Xu, W. and Song, J.: Geopotential Difference Determination via BDS and Galileo Multi-Frequency Time-Frequency Signals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15725, https://doi.org/10.5194/egusphere-egu26-15725, 2026.

How well mixed is Earth's mantle? Are there primordial reservoirs? What fraction of the mantle feeds surface volcanism? We attempt to address these questions using large-scale Lagrangian particle tracking in time-reversed and forward convection models. We track particles backward in time using a Back-and-Forth Nudging (BFN) method applied to time-reversed thermal convection, initialized with a present-day seismic–geodynamic–mineral physics model (Glisovic & Forte, 2016, 2025). We likewise carried out long-term (multi-hundred-million-year) forward-in-time mantle convection simulations initialized with present-day mantle structure inferred from tomography. In all cases, we employ mantle viscosity structure that has been independently constrained and verified against a wide suite of present-day geodynamic observables that include free-air gravity anomalies, dynamic surface topography, horizontal divergence of plate velocities, excess core-mantle boundary ellipticity, and glacial isostatic adjustment data. A voxel-based analysis quantifies sampling density, residence time, and flux throughout the mantle.

We use different particle starting conditions, each designed to address a specific aspect of mantle mixing. To identify long-lived isolated regions, we track uniformly distributed particles both forward and backward in time, calculating residence times to locate candidate reservoirs. To estimate the sampling of lower mantle material in the upper mantle, we initialize particles in the D" layer and track them forward to determine what fraction reaches the upper mantle. To address plume dynamics and sampling, we place cylindrical arrays of particles beneath present-day hotspots and track them backward, using the statistical evolution of their standard deviation to quantify mixing along transport pathways, with transit time, and voxel analysis. To measure upper-to-lower mantle exchange, we initialize particles uniformly in the upper mantle. By combining these approaches, we systematically identify regions of low flux and high residence time, candidates for reservoirs. We further take a statistical approach based on voxel density sampling to quantify mixing across the volume of the mantle.

How to cite: Johnston, G., Anderson, M., Forte, A., and Glišović, P.: How Well Is the Mantle Sampled? A Global Voxel-Based Analysis of Residence Time and Flux from Forward- and Reverse-Time Mantle Convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15990, https://doi.org/10.5194/egusphere-egu26-15990, 2026.

Accurate geoid models are essential for converting GNSS-derived heights into physically meaningful elevations and for ensuring consistency in modern height reference systems. This study presents a unified geodetic framework for refining gravimetric geoids using GNSS/leveling residuals through physically interpretable fitting models. Five correction representations are evaluated, ranging from local Cartesian planar surfaces to geodetically consistent spherical formulations of increasing degree. The analysis demonstrates that low-order models effectively remove regional bias and tilt but show limited predictive stability. To enhance robustness, iteratively reweighted least squares is applied to mitigate the influence of outliers while preserving deterministic structure. Higher-order geodetic models are stabilized using ridge regularization, with the regularization strength selected objectively through leave-one-out cross-validation. This strategy ensures numerical conditioning while directly optimizing predictive performance. Results show that the full degree-2 geodetic model offers the best balance among accuracy, stability, and physical interpretability. It reduces long-wavelength distortions while maintaining consistent in-sample and cross-validated performance. The proposed approach supports reliable GNSS-based height determination in modern vertical datum realization and height modernization efforts.

How to cite: Abdalla, A. and Dwira, C.: Geodetic degree-based Models for Robust Regional Geoid Refinement, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16148, https://doi.org/10.5194/egusphere-egu26-16148, 2026.

Sulfur released by magmatic activity strongly impacts the climate and is essential for ore mineralisation. Many porphyry systems contain up to billions of tons of sulfur, far exceeding the sulfur capacity of silicate melt and therefore requiring an additional, efficient S‑transfer mechanism.

We present a unique mafic rock (SiO₂ = 53–59 wt.%, MgO = 5.3–7.3 wt.%) containing ~15–20 vol.% anhydrite, ~30–40 vol.% biotite and ~40–50 vol.% plagioclase from the largest porphyry–epithermal system in China. Magmatic anhydrite, indicated by textural relations and LREE‑rich compositions, yields bulk‑rock S contents of ~2–3 wt.%, far above experimental S solubilities.

Plagioclase shows sharp core–rim decreases from An₅₀–₇₀ to An₂₅–₄₅, recording strong CaO depletion caused by sulfate saturation. Extensive sulfate saturation also suppressed amphibole/orthopyroxene and removed a large proportion of LREEs from the melt, producing flat REE patterns in co-crystallised apatite. Biotite exhibits pronounced Ba depletion from core to rim. Because Ba partitions strongly into sulfate melt, not into anhydrite, this Ba zoning is best explained by the formation of a sulfate melt, rather than by crystallisation of anhydrite from a silicate melt.

Nd isotopic compositions (ԑNd(t) ≈ -1.0) indicate that the magma was derived from partial melting of the mantle wedge. We suggest that ascent of this oxidised, sulfur‑rich mafic magma led to decompression-driven oxidation of S²⁻ to S⁶⁺, sulfate saturation, and exsolution of an immiscible sulfate melt. This discrete sulfate‑melt migrated upward and provided an efficient pathway for long‑distance transfer of large amounts of sulfur to porphyry systems. This sulfate‑melt exsolution process is a previously unrecognised mechanism that relaxes the constraint imposed by the sulfur capacity of silicate melt, and LREE‑depleted apatite associated with abundant magmatic sulfate phases may serve as an indicator of sulfate‑melt exsolution and a proxy for porphyry mineralisation potential in the upper crust.

How to cite: Huang, W., Humphreys, M., and Liang, H.: Magmatic sulfate‑melt exsolution as a mechanism for excess sulfur in porphyry systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22040, https://doi.org/10.5194/egusphere-egu26-22040, 2026.

Diamond is an extraordinary material of the Earth’s deep interior, characterized by remarkable thermo-elastic properties and chemical stability. However, pure diamond itself does not provide definitive information about the pressure and temperature at which it forms but in principle, these conditions can be determined by measuring the stress state of minerals trapped as inclusions at the time of diamond growth (Angel et al. 2022). Indeed, inclusions and defects in diamond have the potential to provide fundamental constraints on the mechanisms of plate tectonics and carbon and volatile cycles in the Earth if the depth and temperature of diamond growth are known. Olivine is one of the most common mineral phases found within diamonds. However, most olivine inclusions entrapped in diamonds are surrounded by cracks, show evidence of fluid rims (Nimis et al. 2016) and the calculated residual pressures are so low that they indicate diamond growth and olivine entrapment outside the diamond stability field (Angel et al. 2022). This is clearly unrealistic and indicates the need to investigate the mechanisms responsible for the release of residual inclusion pressure, which are not accounted for by the simple elastic geobarometry model that has been successfully applied to inclusions in garnets from ultra-high-pressure metamorphic rocks (Murri et al. 2018, 2022).

In this work we will therefore (i) review what is currently known about the effects of cracking and plastic deformation in diamond, as well as other factors that may contribute to the reduction in inclusion pressures; and (ii) discuss possible approaches to identify and quantify the key mechanisms responsible for low inclusion pressures that will then allow the entrapment conditions of the majority of inclusions in diamond to be determined. 

References:

Angel, R. J., Alvaro, M., & Nestola, F. (2022). Crystallographic methods for non-destructive characterization of mineral inclusions in diamonds. Reviews in Mineralogy and Geochemistry, 88(1), 257-305.

Murri, M., Mazzucchelli, M. L., Campomenosi, N., Korsakov, A. V., Prencipe, M., Mihailova, B. D., ... & Alvaro, M. (2018). Raman elastic geobarometry for anisotropic mineral inclusions. American Mineralogist, 103(11), 1869-1872.

Murri, M., Gonzalez, J. P., Mazzucchelli, M. L., Prencipe, M., Mihailova, B., Angel, R. J., & Alvaro, M. (2022). The role of symmetry-breaking strains on quartz inclusions in anisotropic hosts: Implications for Raman elastic geobarometry. Lithos, 422, 106716.

Nimis, P., Alvaro, M., Nestola, F., Angel, R. J., Marquardt, K., Rustioni, G., ... & Marone, F. (2016). First evidence of hydrous silicic fluid films around solid inclusions in gem-quality diamonds. Lithos, 260, 384-389.

Acknowledgments

This work has been supported by the InROAD+ 2025 - Fostering ERC talents @UNIPV assigned to M. Murri and by the Fondazione Cariplo grant agreement #2023-2431 assigned to M. Alvaro.

How to cite: Murri, M., Gilio, M., Nestola, F., and Duretz, T.: Olivine inclusions in diamond: towards real entrapment conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1628, https://doi.org/10.5194/egusphere-egu26-1628, 2026.

Abstract: The Permian–Triassic in the Shawan Sag, Junggar Basin, serves as a key reserve replacement area of the basin; however, its hydrocarbon charging history is complex due to multi-source and multi-stage charging. This study integrates inclusion analysis (including petrographic analysis, fluorescence spectroscopy, microthermometry, and gas-liquid ratio measurements) with source rock thermal evolution to systematically reconstruct the hydrocarbon charging history of the Permian–Triassic reservoirs in the Shawan Sag. Results demonstrate that two stages of hydrocarbon inclusions were developed in quartz grains and calcite cements of the Triassic Karamay Formation, with the fluorescence spectral maximum-intensity wavelength (λ_max) of 473.69–500.33 nm and 436.67–470.51 nm, respectively, and homogenization temperature (T_h) peaks of the coexisting aqueous inclusions at 90–100 ℃ and 120–130 ℃. These correspond to hydrocarbon charging events in the Early–Middle Jurassic and Early–Late Cretaceous. The hydrocarbon inclusions formed during the Cretaceous charging have a gas-liquid ratio (F_v) of approximately 4.43%–6.67%, and the paleo-pressure coefficient during accumulation, which is calculated via inclusion paleo-pressure analysis is about 1.25–1.40, indicating an overpressured environment. Three stages of hydrocarbon inclusions were identified in quartz grains, siliceous cements, and calcite cements of the Permian Upper Wuerhe Formation, with λ_max of 477.33–496.88 nm, 458.68–473.33 nm, and 436.67–455.38 nm, respectively. The T_h peaks of the coexisting aqueous inclusions are respectively 80–90 ℃, 110–120 ℃, and 140–150 ℃, corresponding to Late Triassic–Early Jurassic, Early Cretaceous, and Paleocene–Eocenecharging events, respectively. The hydrocarbon inclusions formed during the Early Cretaceous charging have a F_v of 3.08%–4.45% and the calculated reservoir pressure coefficient is 1.35–1.60. Hydrocarbon inclusions formed since the Paleogene have a F_v of 6.32% and a reservoir pressure coefficient of 1.74, indicating a strongly overpressured environment. Integrated analysis reveals three phases of hydrocarbon charging in the study area: ① Late Triassic–Jurassic: The source rocks of the Lower Wuerhe Formation entered the hydrocarbon generation window. Early hydrocarbons migrated along active faults and were initially trapped, forming inclusions within quartz grains. ② Cretaceous–early Paleogene: Source rocks reached the oil generation peak, the formation overpressure reactivated faults, enabling large-scale hydrocarbon charging, with hydrocarbon inclusions mainly trapped within quartz and calcite cementation. ③ Paleogene–present: Source rocks have entered the high- to over-mature stage, intense overpressure reactivated the faults again, high mature oil and natural gas charged into the reservoirs, with hydrocarbon inclusions predominantly trapped in calcite cements.

Keywords: Junggar Basin; Shawan Sag; Permian–Triassic; fluid inclusions; paleo-pressure; hydrocarbon charging history

How to cite: Zhao, Z., Liu, H., and Cheng, B.: Characteristics of Fluid Inclusions and Analysis of Hydrocarbon Charging History in the Permian–Triassic Reservoir of the Shawan Sag, Junggar Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2440, https://doi.org/10.5194/egusphere-egu26-2440, 2026.

The Au-rich sulfide saturation during deep magmatic evolution of hydrothermal ore-forming systems has emerged as a frontier in recent research. However, the underlying formation mechanisms and their coupling with shallow mineralization remain controversial. The North China Craton (NCC), one of the most significant gold province globally, exhibits characteristics of short-term and explosive mineralization, providing an ideal natural laboratory to investigate gold enrichment processes. Here, we present an LA–ICP–MS study of sulfide inclusions (SIs) and CO2-bearing compound droplets from mantle xenoliths in Fangcheng basalts and intermediate-mafic dikes in Guocheng gold deposit.
We discovered SIs in both mantle xenoliths and dikes from different depths within the same magmatic system. The SIs in mantle xenoliths contain Au contents (0.01–0.98 ppm, mean 0.15 ppm, n=102) that are 2-5 orders of magnitude higher than whole-rock mantle peridotites from the eastern NCC, indicating significant Au pre-enrichment during the sulfide saturation stage. Furthermore, the prevalent occurrence of SIs in phenocrysts at the Mg-rich and Fe-rich zones of hornblende phenocrysts exhibit higher Au contents (0.03–1.90 ppm, mean 0.36 ppm, n=49), suggesting that multi-stage crust-mantle mixing triggered sulfide melting and further promoted gold enrichment. Element ratios of the SIs largely correspond to those of unaltered bulk ore, indicating that the dikes and ore share a common origin, with the magmatic sulfides having served as a key transport medium of Au and ore-forming elements. In addition, by simulating the diffusion of olivine to record the constraints on the rapid ascent of magma, we suggest that CO2-bearing compound droplets inhibited sulfide precipitation and redissolution, allowing Au-rich SIs to retain their metal enrichment during ascent.
We propose a continuous metal-enrichment model for deep magmatic systems, providing new insight into the efficient transfer of metals from the mantle and lower crust to shallow hydrothermal systems.

How to cite: Yan, Z. and Tan, J.: Sulfide inclusions reveal deep Au pre-enrichment and efficient metal transfer to hydrothermal systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2561, https://doi.org/10.5194/egusphere-egu26-2561, 2026.

The fluid diapir is formed through the upward intrusion of fluids along pre-existing fracture zones, with hydraulic fracturing and fluid charge occurring at the uplift point of the overpressure interface. The DF1-1 diapir is the most typical fluid diapir in the Yinggehai Basin, characterized by multi-layer gas accumulation. In this study, petrography observation, laser Raman spectroscopy analysis, micro-thermometry, approximate calculation of fluid inclusion capture pressure and natural gas characteristics have been integrated to delineate the natural gas dynamic accumulation process and summarize the accumulation model of DF1-1 diapir. Results suggest that four-episode natural gas with different composition have been documented in the DF1-1 diapir. The first and second episode of hydrocarbon gas-dominated charging occurred at 3.4-2.9Ma and 1.8-0.4Ma, respectively. The third and fourth episode were dry gas and inorganic CO₂, which occurred at 0.4-0Ma. The paleo-pressure evolution of HL₁ Formation was reconstructed following a model of “pressurization-release--pressurization”. And the coupling relationship between the Formation paleo-pressure evolution and the natural gas charge history was elucidated. Based on these analyses, this conformed to an overpressure-controlled episodic gas accumulation model, and the accumulation process of the DF1-1 diapir can be summarized as follows: initially, gas accumulated in deep reservoirs, with formation pressure increasing to fracture pressure, leading to diapir opening and subsequent gas loss or adjustment to shallower reservoirs along diapir faults for further accumulation. Simultaneously, gas filled the reservoirs and episodic diapir activity in the later stages resulted in rapid gas charging. This process is the primary factor contributing to the heterogeneity of gas distribution.

How to cite: He, Z.: Hydrocarbon Accumulation Processes and Model Controlled by Overpressure Evolution of the DF1-1 diapir in the Yinggehai Basin, South China Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3867, https://doi.org/10.5194/egusphere-egu26-3867, 2026.

Diamonds provide unique snapshots of otherwise inaccessible regions of Earth’s mantle, preserving mineral, melt, and fluid inclusions that record pressure, temperature, and redox conditions at the time of entrapment. Redox conditions are a key control on mantle mineralogy, carbon speciation, and melt generation, yet natural constraints at depths greater than ~250 km remain scarce.

Here we report diamond-hosted inclusions that document an active redox-driven metasomatic process in the deep upper mantle. Two diamonds from the Voorspoed mine (Kaapvaal craton, South Africa) contain coexisting nickel-rich metallic and carbonate inclusions, accompanied by silicate and oxide phases. Integrated infrared and Raman spectroscopy, electron microprobe analysis, transmission electron microscopy, and synchrotron micro-diffraction reveal the presence of a metallic Ni–Fe alloy with Ni# = 100 × Ni/(Ni + Fe) ≈ 85 and a Ni-rich carbonate with Ni# ≈ 89 within the same growth zones of the host diamonds. The extreme Ni enrichment of both phases indicates a genetic link and disequilibrium conditions during diamond formation.

Pressure-sensitive Raman and infrared signatures of coesite, N₂ and CO₂, together with the presence of high-pressure silicates including a K-rich NAL phase and Na–Al–rich pyroxene, constrain diamond formation to depths of ~280–470 km. These depths overlap with conditions where subducted carbonated oceanic crust is expected to intersect its melting curve.

We interpret the inclusion assemblage as a direct record of interaction between an oxidized carbonatitic–silicic melt derived from subducted material and a reduced, metal-bearing peridotitic mantle. Infiltration of this melt into reduced mantle lithologies triggered oxidation reactions, the redistribution of Ni between the alloy, olivine, and carbonate, and the growth of diamonds. Rather than recording equilibrium conditions, the high Ni# values of the alloy and carbonate reflect transient chemical exchange during metasomatism.

These observations provide rare natural evidence for deep mantle redox reactions involving carbonatitic–silicic melts and demonstrate the power of diamond-hosted inclusions to capture dynamic mantle processes. Such metasomatism may represent an important mechanism for mantle oxidation and enrichment, with implications for the generation of enriched alkalic magmas, including kimberlites and some ocean island basalts.

How to cite: Weiss, Y., Kempe, Y., Remmenik, S., Tschauner, O., Navon, O., and Holland, T.: Nickel-rich metallic and carbonate inclusions in diamonds: snapshots of redox-driven metasomatism in the deep upper mantle, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4096, https://doi.org/10.5194/egusphere-egu26-4096, 2026.

Atmospheric nitrogen (N₂) is the dominant constituent of Earth’s atmosphere and exerts a first-order control on surface pressure, climate sensitivity(1), and long-term habitability(2). Despite its importance, quantitative constraints on past atmospheric nitrogen partial pressure (pN₂) remain limited(3). Fluid inclusions in hydrothermal quartz record the composition of crustal fluids as well as the composition of Earth’s ancient atmosphere (4, 5), but reconstructing atmospheric pN₂ from inclusions is complicated by radiogenic overprints and fluid evolution(6). We present a new method using N₂-Ne-Ar elemental and isotopic systematics applied to fluid inclusions in ~20 Ma quartz veins from the Alps and Himalaya mountains ranges in order to evaluate the preservation of atmospheric nitrogen signals. Mixing relationships between N₂/²²Ne and ²¹Ne/²²Ne are used to distinguish atmospheric components from crustal contributions, with nucleogenic ²¹Ne tracing crustal inputs. Linear trends allow extrapolation to air-saturated water endmembers and reconstruction of atmospheric pN₂. Samples from low-grade geological contexts yield pN₂ estimates consistent with the modern atmosphere, indicating closed-system behavior after entrapment. In contrast, samples influenced by syn-tectonic metamorphism show excesses in N₂ (elevated apparent pN₂), reflecting addition of crustal nitrogen. These results demonstrate the potential of combining fluid inclusions and noble gas geochemistry to link crustal fluid processes with atmospheric evolution.

1.    R. Wordsworth, R. Pierrehumbert, Hydrogen-nitrogen greenhouse warming in Earth's early atmosphere. Science 339, 64-67 (2013).
2.    E. E. Stüeken et al., Marine biogeochemical nitrogen cycling through Earth’s history. Nature Reviews Earth & Environment 5, 732-747 (2024).
3.    D. C. Catling, K. J. Zahnle, The archean atmosphere. Sci Adv 6, eaax1420 (2020).
4.    B. Marty, L. Zimmermann, M. Pujol, R. Burgess, P. Philippot, Nitrogen isotopic composition and density of the Archean atmosphere. Science 342, 101-104 (2013).
5.    G. Avice et al., Evolution of atmospheric xenon and other noble gases inferred from Archean to Paleoproterozoic rocks. Geochim Cosmochim Ac 232, 82-100 (2018).
6.    D. V. Bekaert, G. Avice, B. Marty, Fluid inclusions: tiny windows into global paleo-environments. Commun Earth Environ 6, 820 (2025).

This work received funding from the European Research Council (ERC) under the European Union's Horizon Europe Research and Innovation Program (Grant Agreement 101041122 to Guillaume Avice).

How to cite: Su, G., Avice, G., Vayrac, F., and Melis, R.: Reconstructing atmospheric nitrogen pressure from N2-Ne-Ar systematics in quartz-hosted fluid inclusions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5575, https://doi.org/10.5194/egusphere-egu26-5575, 2026.

Natural hydrogen is considered to be of utmost importance for the transition towards a low carbon energy system. As natural hydrogen systems can be hosted by a variety of geological settings, they are extremely versatile so that generation, migration, and accumulation processes are often insufficiently understood. This contribution presents the results of a case study that was carried out to determine the origin and evolution of CH₄- and H₂-rich fluids trapped in faulted, felsic granulite from the Bohemian Massif (Lower Austria). Samples were taken in an active quarry, where the granulite occurs spatially associated with tectonically incorporated, partly serpentinized, ultramafic lenses.

Fluid inclusions are found in quartz and garnet. While the inclusions in quartz are clearly of secondary origin, the ones in garnet are primary and therefore related to the high-grade granulite facies metamorphism. Raman spectroscopy measurements revealed a complex polyphase composition. The primary inclusions contain CH₄ and H₂ as well as several (hydrous) mineral phases. Three mineral parageneses can be distinguished: (i) granitic, (ii) Al-silicates, and (iii) hydrous Mg-silicates. The secondary inclusions generally contain no solid phases and mainly consist of CH₄, H₂, N₂, and H₂S (± H₂O). Based on microthermometry measurements combined with thermodynamic calculations, the secondary inclusions in quartz can be attributed to fluid migration during the latest stage of exhumation at conditions of approximately 200 °C and 60 MPa corresponding to a depth of 2 to 2.5 km. Serpentinization at low temperature is further evidenced by lizardite being the predominant serpentine polymorph. Whereas H₂, CH₄, and H₂S in secondary inclusions are related to low temperature serpentinization and accompanying carbon hydrogenation (Fischer-Tropsch type) reactions, the gas species in the primary inclusions are of deep-crustal or mantle origin. Observations during Raman spectroscopy measurements, however, may also indicate an impact of photocatalytic reactions triggered by the laser on fluid composition in the primary inclusions.

How to cite: Pengg, A., Bakker, R. J., and Misch, D.: Methane and hydrogen in fluid inclusions of metamorphic and hydrothermal origin: Implications for natural hydrogen system analysis and exploration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6278, https://doi.org/10.5194/egusphere-egu26-6278, 2026.

Abstract: The Tahe Oilfield in the northern Tarim Basin contains one of China's largest Ordovician carbonate reservoirs. Influenced by multi-phase tectonic uplift and subsidence, significant differences exist in hydrocarbon accumulation between the Tahe area and its periphery. This study focuses on the Ordovician Yingshan (O₁₋₂y) and Yijianfang (O₂yj) formations in the Tahe and surrounding areas. Integrating systematic analysis of source rocks, structure, reservoirs and fluid inclusion, the diagenetic processes and evolutionary sequences of the target strata were clarified, the phases and timing of hydrocarbon charging were determined, and a hydrocarbon accumulation model was established to identify the controlling factors behind differential accumulation. The key findings are as follows:

(1) Hydrocarbon properties and reservoir types vary across the study area. Crude oil density increases—and oil becomes heavier—from south to north, whereas the dryness coefficient and maturity of natural gas gradually increase from northwest to southeast. Reservoir types transition concentrically from south to north in the following sequence: dry/wet gas reservoirs → condensate gas reservoirs → volatile oil reservoirs → light oil reservoirs → medium oil reservoirs → heavy oil reservoirs.

(2) Fluid inclusions exhibit distinct characteristics in different wells. In the Yingshan Formation, blue inclusions dominate in Well YQ8 (East Yuqi) and Well TS3 (Deep Tahe), indicating high-maturity hydrocarbons. Well YQX1 (West Yuqi) contains a mixture of blue, yellow, and orange inclusions, reflecting the coexistence of high- and low-maturity hydrocarbons. Well TP18 (Tuoputai) is dominated by yellow~green inclusions, corresponding to medium~low maturity hydrocarbons. In the Yijianfang Formation, Well YJ1X (Yuejin) contains both blue and yellow~green inclusions, representing high and medium~low maturity levels.

(3) Multiphase hydrocarbon accumulation is evident, with significant variation in charging timing among wells. In the Yingshan Formation, Well YQ8 experienced three accumulation phases: Middle Hercynian (338~305 Ma), Middle Yanshanian (130~111 Ma), and Late Himalayan (22~16 Ma). Well YQX1 underwent a single phase during the Middle~Late Himalayan (31~6 Ma). Well TS3 recorded three phases: Late Caledonian (458~454 Ma), Early Yanshanian (191~173 Ma), and Late Himalayan (22~18 Ma). In the Yijianfang Formation, Well TP18 had three accumulation phases: Indosinian (233~210 Ma), Middle Yanshanian (138~123 Ma), and Late Himalayan (21~13 Ma); Well YJ1X experienced two phases: Middle Yanshanian (134~117 Ma) and Late Himalayan (22~12 Ma).

(4) Differential hydrocarbon accumulation is jointly controlled by multiple factors. Variations in hydrocarbon generation and evolution of source rocks determine the fundamental reservoir types and fluid properties. Differences in tectonic evolution directly influence the phases and timing of hydrocarbon accumulation, with multiphase tectonic activity serving as the primary driver of the complex hydrocarbon distribution patterns observed in the study area.

These results provide a theoretical foundation and technical reference for further exploration of hydrocarbon accumulation in deep to ultra-deep strata.

Keywords: Fluid inclusions; Differential hydrocarbon accumulation; Ordovician; Tahe area; Tarim Basin

How to cite: Feng, T. and Chen, Z.: Hydrocarbon Accumulation Differences in the Deep Ordovician Reservoirs of the Tahe Oilfield and Its Peripheral Regions, Tarim Basin, Western China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6438, https://doi.org/10.5194/egusphere-egu26-6438, 2026.

The abnormally high pore pressure is developed in the Huangliu Formation reservoirs of the Ledong X structure on the slope of the Yinggehai Basin. The present maximum pressure coefficient reaches 2.3, indicating a strongly overpressured system. The development and evolution of reservoir overpressure are closely associated with multi-stage natural gas charging. Based on fluid inclusion petrography and laser Raman spectroscopic analysis of gas inclusions, the pressure evolution of the Huangliu Formation reservoirs was reconstructed.

The results show that three types of gas inclusions occur in the Ledong X area: N₂–CH₄, CH₄–CO₂, and CO₂ inclusions. Three episodes of fluid charging were identified. The first stage was dominated by hydrocarbon gas charging at approximately 2.3 Ma. The second and third stages involved mixed CO₂–CH₄ charging, initiating at ~1.8 Ma and ~0.5 Ma, respectively.

The pressure evolution of the Huangliu Formation reservoirs can be divided into two main stages: (1) an early pressure build-up stage and (2) a re-pressurization stage following formation fracturing and pressure release. During 2.3–0.8 Ma, combined hydrocarbon gas and CH₄–CO₂ charging caused a rapid increase in reservoir pressure, with pressure coefficients exceeding 2.3. Subsequent formation fracturing led to pressure dissipation and partial loss of early-charged gas. Since approximately 0.4 Ma, renewed large-scale natural gas charging during the third stage has caused reservoir pressure to rise again, ultimately reaching the present overpressured state.

These results demonstrate that gas charging plays a key role in overpressure development and pressure evolution in deep, overpressured gas reservoirs, providing new constraints on gas accumulation and preservation in the Yinggehai Basin.

Keywords：fluid inclusion，Raman spectrum、paleo-pressure restoration、natural gas charging history、Yinggehai Basin

How to cite: Yue, X.: Natural Gas Charging and Pressure Evolution in the Slope of the Yinggehai Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10469, https://doi.org/10.5194/egusphere-egu26-10469, 2026.

Fluid inclusions (FIs) represent an invaluable source of information for investigating hydrothermal systems, as they preserve composition, temperature and pressure of entrapment of the fluids circulating during mineral growth at depth.

In this study, rock cores of two deep wells (Mofete 3 and Mofete 5) from Mofete geothermal field (Campi Flegrei caldera) were selected to investigate the chemical-physical conditions occurring in the hydrothermal system through fluid inclusion study. Three types of fluid inclusions were identified: Type 1 two-phase liquid -rich fluid inclusions; Type 2 multi-phase liquid + vapor bubble + one or more daughter minerals; Type 3 monophase (vapor) fluid inclusion. Type 1 FIs occur in quartz and calcite at 1324m (Mofete 3) and 1750m (Mofete 5) of depth respectively and can be distinguished petrographically in primary and secondary (Type 1a and Type 1b). Type 2 FIs are hosted within quartz, scapolite and anhydrite of Mofete 5 well at 2492, 2607 and 2698 m of depth. They appear primary Type 3 FIs are prevalently secondary. They occur in Mofete 5 well at 2607 and 2698m of depth within quartz and scapolite

Microthermometric experiments were carried out on Type 1 and Type 2 FIs. At 1324m of depth, Type 1a FIs (Mofete 3) show temperature of homogenization (T_h) between 178 °C and 291 °C with a mode around 215 °C, while Type 1b has T_h between 195 °C and 257 °C with a modal value at 240 °C. Salinity of Type 1a FIs ranges between 2.7 and 5.1 wt.% NaCl_equiv. with a mode at 3.5 wt.% NaCl_equiv.. Type 1b FIs show salinity in the range 3.4-6.9 wt.% NaCl_equiv. with mode around 4.5 wt.% NaCl_equiv..

At 1750m of depth (Mofete 5) T_h of Type 1a FIs are between 250 °C and 273 °C with a modal value at ~255 °C. Type 1b FIs have T_h between 271 °C and 299 °C mode around 285 °C. Salinity of these inclusions has been determined in only 3 Type 1b FIs giving consistent results at 2.9 wt.% NaCl_equiv..

Type 2 FIs revealed T_h in the range 317-453 °C with the mode ~380 °C (2698m of depth Mofete 5) and 331-434 °C mode at ~360 °C (2607m of depth Mofete 5). At 2492m of depth we obtained only 3 data, giving a range between 347 and 383 °C. Salinities determined in Type 2 FIs are: 38-58 wt.% NaCl_equiv. (2698m of depth Mofete 5), 40-65 wt.% NaCl_equiv. (2607m of depth Mofete 5). At 2492m of depth we determined only one salinity data which is 44 wt.% NaCl_equiv..

Our data highlights an increase in the temperature of homogenization from Type 1a to Type 1b FIs. We would also remark that although FIs show an increase of temperature in time, Type-2 FIs are hypersaline fluids (~50% NaCl_eq. Wt%) with T_h comparable to present day measured deep well temperatures, and salinities similar to fluids circulating at these depths.

The increase in T_h of FIs in the shallower hydrothermal system points toward an increase in the activity of the system.

How to cite: Masi, M., Marianelli, P., and Fulignati, P.: Fluid inclusion constraints on the Mofete geothermal system, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11407, https://doi.org/10.5194/egusphere-egu26-11407, 2026.

Ultramafic bodies hosted within subducted continental crust can provide unique opportunities to investigate crust-mantle interaction. Crustal-derived melts and fluids can interact with the surrounding mantle and be trapped as primary inclusions in phases crystalized during the process. The study of these inclusions provides direct constraints on crust-mantle interaction during the subduction of the continental crust. In Svartberget (Western Gneiss Region, Norway), a garnet-peridotite body hosted by migmatitic gneiss exhibits a complex network of crosscutting veins with a composition ranging from olivine-garnet-websterite to phlogopite-garnet-websterite and garnetite. Previous studies ascribed the presence of all these different generations of veins to a metasomatic interaction between a crustal-derived fluid (from country rock) and the ultramafic body (Vrijmoed et al., 2013). In order to better investigate this process from the fluid perspective, we present a study of multiphase solid inclusions (MSI) trapped in garnets and clinopyroxenes of phlogopite-garnet-websterite and phlogopite-garnetite veins.

The phlogopite-garnet-websterite is coarse-grained and the major mineral phases are clinopyroxene, orthopyroxene, garnet, phlogopite and amphibole. Two types of MSI, ~ 30 µm in diameter, occur either isolated or in clusters in poikilitic clinopyroxene and skeletal garnet. They frequently exhibit negative crystal shape. These were investigated with micro-Raman spectroscopy to determine the main mineral assemblages. Type I inclusions contain quartz and feldspar polymorphs, i.e., kumdykolite and kochetavite. Type II consists of quartz, cristobalite, pyrophyllite, carbonates, corundum, and CO₂.

Phlogopite-garnetites are dominated by poikilitic garnet and phlogopite with minor clinopyroxene and amphibole. Garnets host primary MSI (~ 30 µm) consisting of quartz, plagioclase, feldspar polymorphs (kumdykolite and bonaccorsite), biotite, muscovite, osumilite, and CO₂ bubbles. Often in these inclusions, zircons occur as accidentally trapped phases.

Type I MSI in phlogopite-garnet-websterite and MSI in the garnetites have a mineral assemblage suggesting a granitoid composition, and thus they represent a trapped granitic melt potentially similar to the original melt that metasomatized the peridotite body. Type II inclusions in phlogopite-garnet-websterite might represent a COH fluid. Further analysis on the geochemistry of these inclusions will help to better constrain crust-mantle interaction, fluid evolution during metasomatism, and incompatible trace elements and volatiles mobility during crustal subduction.

Vrijmoed et al. (2013) Metasomatism in the Ultrahigh-pressure Svartberget Garnet-peridotite (Western Gneiss Region, Norway): Implications for the Transport of Crust-derived Fluids within the Mantle. J Petrol, 54(9), 1815-1848.

How to cite: Polyák, P. Á., Borghini, A., Cuthbert, S., Vrijmoed, J. C., and Majka, J.: Multiphase solid inclusions in Svartberget peridotite body, Western Gneiss Region (Norway): Implications for crust-mantle interaction and mantle metasomatism, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13674, https://doi.org/10.5194/egusphere-egu26-13674, 2026.

For millennia humans have pondered the question "Are we alone in the universe?" In recent decades the search for evidence of life beyond earth has focused on the search for habits in which liquid water is now or has in the past been present, as well as the search for organic molecules in extraterrestrial (ET) samples. These efforts have, in turn, spurred significant technological advances to develop methods to analyze fluid inclusions (FI) in ET materials, including meteorites and more recently ET samples collected and returned to earth by various missions that have visited a variety of planetary bodies.

Some early reports of fluid inclusions in meteorites in the 1970s were later found to be artifacts introduced during sample preparation. As a result, the study of FI in extraterrestrial samples entered a dark period in which any reports of FI in meteorites were dismissed as likely representing fluids introduced after the samples reached earth. The study of FI in ET samples gained renewed interest following the discovery and documentation of aqueous FI in halite in the Monahans (1998) H5 chondrite. The halite and its contained FI were clearly present before the meteorite reached earth, and subsequent studies confirmed that the age of the halite and its contained FI was 4.7 ±0.2 Ga. This discovery spurred new interest to search for FI in meteorites, now using sample preparation methods that avoid introducing water or other fluids into the sample. 

In the last two decades much progress has been made in identifying FI in meteorites and mission returned samples, and there are now dozens of well documented reports of FI in these samples.  The rarity of FI in ET samples, combined with the generally small size of the FI (less than approximately 1-2 microns in many cases), has led to efforts to develop and improve analytical techniques to characterize the FI. To this end, our group has determined the bulk chemical and H & O stable isotopic composition of individual FI in Zag and Monahans (1998) halite and asteroid Ryugu pyrrhotites using cryo-Time of Flight Secondary Ion Mass Spectrometry (cryo-TOF-SIMS). In this presentation we will summarize some of these recent efforts involving careful and sophisticated sample preparation and analysis methods.

How to cite: Bodnar, R., Dolocan, A., Zolensky, M., Han, J., Hanna, R., Gerba, I., Chan, Q., Ireland, T., Le, L., Matsumoto, M., Tsuchiyama, A., Matsumoto, T., and Nakamura, T.: What have we learned about the distribution of water and organic molecules in the solar system from studies of fluid inclusions in meteorites and mission return samples?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14702, https://doi.org/10.5194/egusphere-egu26-14702, 2026.

Over geological timescales, processes such as subduction and convection have generated and distributed geochemical heterogeneities in the Earth’s mantle. Basaltic eruptions at oceanic islands sample the mantle and preserve their diverse geochemical signatures in crystal-hosted melt inclusions (MIs), revealing significant heterogeneity on short lengthscales. While mantle heterogeneity is well documented spatially, its temporal expression during the course of a single eruption, and its influence on magma evolution and volatile budgets, remain poorly constrained. 

The Canary Islands mantle is thought to comprise depleted and enriched lithologies overprinted by metasomatism involving carbonated and hydrous melts [1]. Here, we investigate how this heterogeneous mantle was sampled over the course of the 2021 Tajogaite eruption (La Palma), whose erupted products exhibited time-dependent geochemical variability [2]. We analysed olivine-hosted MIs using electron microprobe (major elements and S), ion microprobe (H₂O, CO₂, Cl, F), LA-ICP-MS (trace elements), and Raman spectroscopy (CO₂ density in bubbles). Since up to 85% of a MI’s volatile budget can be stored within its bubble [2,3], we also analysed experimentally homogenised MIs to reconstruct total volatile contents. We find temporal changes in MI compositions, including increasing MgO contents and decreasing Zr/Y ratios, consistent with progressive tapping of deeper and less fractionated magma batches during the eruption. Although H₂O contents decrease with time from 1.9 to 0.4 wt%, the highest CO₂ concentrations (up to 1.0 wt%) occur in homogenised MIs from Stage 2B of the eruption, suggesting enhanced contributions from CO₂-rich magmas.

We use time-resolved variations in REE ratios to trace changes in melting depth and the relative contributions of depleted and enriched melts; Rb–Ba–Nb–Ta systematics to constrain the role of minor hydrous phases; and Hf–Zr correlations to assess the imprint of carbonatitic metasomatism. By linking temporal variations in magma composition with in situ gas flux measurements and changes in eruptive style, we evaluate how the expression of mantle heterogeneity may have influenced gas emissions and eruption dynamics.

References: 

[1] Gómez-Ulla et al. (2018) Chemical Geology 10.1016/j.chemgeo.2018.07.015 

[2] Scarrow, J. H. et al. (2024) Volcanica 10.30909/vol.07.02.953980 

[3] Schiavi, F. et al. (2020) Geochemical Perspectives Letters 10.7185/geochemlet.2038 

[4] Buso, R. et al. (2025) Communications Earth & Environment 10.1038/s43247-025-02958-y 

How to cite: Buso, R.: Melt inclusion constraints on the temporal evolution of magma and mantle during the 2021 Tajogaite eruption (La Palma) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19370, https://doi.org/10.5194/egusphere-egu26-19370, 2026.

The identification of phosphorus (P) sources is critical for implementing effective eutrophication mitigation strategies. Lake Baldegg (Switzerland) has a history of excessive phosphorus inputs leading to severe eutrophication. Here, we utilise the oxygen isotopic composition of inorganic phosphate (δ¹⁸O(PO₄)) to discriminate soil-bound phosphate sources (orchard, arable, grasslands and forest; effluents from the local wastewater treatment plant and manure).
Previously, source apportionment using δ¹⁸O(PO₄) has been limited by the number of sources exceeding the number of tracers. In attempt to resolve this issue, additional tracers (C, N and geochemical elements) have been incorporated into the mixing models. As these tracers may originate from different sources and/or undergo different biogeochemical cycling than phosphate, their use for phosphate apportionment can potentially lead to erroneous results.
To overcome this issue, we analysed the δ¹⁸O(PO₄) values in multiple inorganic phosphate pools: NaOH-extractable (Fe/Al-bound), HCl-extractable (Ca/Mg-bound) and HNO₃-extractable residual inorganic P (modified Hedley sequence). The pools were purified using a zirconium-loaded resin, precipitated as Ag₃PO₄ and analysed for δ¹⁸O(PO₄) via high-temperature pyrolysis based isotope ratio mass spectrometry (TC/EA-IRMS).
Preliminary results show that δ¹⁸O(PO₄) values discriminate in each pool between land-uses: forest (NaOH: +10.2‰; HCl: +10.6‰), orchards (NaOH: +15.6‰; HCl: +14.7‰), arable fields (NaOH: +16.0‰; HCl: +14.9‰) and grassland soils (NaOH: +17.0‰; HCl: +16.8‰). As such, multiple pools can be potentially used as tracers for phosphate apportionment and remove the need for additional non-phosphate-specific tracers. While this study demonstrates the discrimination between different sources, analysis of the lake sediments is currently ongoing. We aim to reconstruct 130 years of inorganic phosphate sources and identify key moments the catchment’s history.

How to cite: Heinrich, R., Cox, T., Jaisi, D., Tamburini, F., and Alewell, C.: Using δ¹⁸O(PO4) for historical source apportionment of inorganic phosphates in the eutrophic lake Baldegg, Switzerland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1857, https://doi.org/10.5194/egusphere-egu26-1857, 2026.

Oxygen (O), the most abundant element in the Earth's crust, has an underexplored isotope system in plant and soil sciences compared to carbon and nitrogen, despite its strong potential to serve as a robust proxy for climate, ecohydrology and biogeochemical studies. The stable isotope ratio of O (δ¹⁸O) in bulk soil organic matter (SOM) might reflect the isotope composition of soil water during SOM formation. However, this signal is blurred by the presence of O from inorganic minerals and a dynamic exchangeable O fraction that can quickly equilibrate with ambient water. To address these challenges, the O in SOM must be isolated from interfering O-containing inorganic compounds in plant OM and minerals. Moreover, the exchangeable O fraction must be accounted for. Although we hypothesise that the exchangeable O fraction in SOM is smaller than that of H, it can likely not be ignored.

We evaluated two alternative methods to separate organic and inorganic O from the soil: demineralisation (i.e., removal of inorganic compounds using HF and HCl) and removal of the organic compounds by muffling combined with a KCl treatment to remove oxyanions. After isolating the organic fraction, we applied a steam equilibration procedure, in which we equilibrated the samples with different water vapours of known O-isotopic composition to determine the δ¹⁸O value of the nonexchangeable O fraction, as has already been similarly established for H. We used standard materials like ethylene glycol, p-Nitro aniline, and Aldrich humic acid (AHA) for the demineralisation method and two O-containing minerals (Goethite and Apatite), both pure and mixed with AHA as model substances for the organic matter removal method and also ¹⁸O-spiked chemicals to select the procedure with no (or minimal) alterations of the original O isotope ratios. Our preliminary data reveal an exchangeable O fraction of 1-1.5% in AHA and excluding its effect by using mass balance calculation, the resulting δ¹⁸O value of the nonexchangeable fraction of AHA was ~15.2‰, which is significantly depleted relative to the humic acid extracted from natural soil (18.4-24.6‰), a discrepancy attributable to the absence of microbial decomposition and associated isotopic fractionation in our synthetic model compound (AHA). Thus, by quantifying the exchangeable O fraction and assessing the stability of the non-exchangeable O fraction against our treatments, this study provides a methodological prerequisite for the accurate determination of oxygen isotope ratios of the nonexchangeable O fraction in plant and soil science.

How to cite: Ghosh, D., Wilcke, W., and Oelmann, Y.: Decoding the stable isotope signature of the non-exchangeable oxygen fraction of bulk soil organic matter: methodological prerequisites , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1885, https://doi.org/10.5194/egusphere-egu26-1885, 2026.

Winter is a critical yet understudied phase in the annual cycle of Arctic seabirds, largely due to logistical challenges of polar fieldwork. While geolocators have advanced our understanding of migration and overwintering behavior, their cost and technical limitations constrain widespread use. As a complementary and scalable alternative, feather analysis offers integrated insights into both ecology and contaminant exposure at individual and population levels.

In this study, we examined head feathers from thick-billed murres (Uria lomvia) collected at seven colonies spanning West Greenland, the Canadian Arctic, and Svalbard. This species breeds widely across the circumpolar Arctic, but several Atlantic populations are in decline. Because head feathers are grown during the non-breeding season, they reflect mercury exposure at overwintering sites. We measured total mercury concentrations, stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N), and mercury isotope compositions (δ²⁰²Hg, Δ¹⁹⁹Hg) to assess variation in winter foraging habitats and mercury exposure pathways. Our results reveal distinct spatial patterns in δ²⁰²Hg that align with known west-to-east gradients in the Hg isotopic composition of North Atlantic prey fish, suggesting region-specific foraging areas during winter. Intra-colony variation in δ²⁰²Hg further highlights individual-level differences in winter habitat use, consistent with patterns derived from geolocator data. Additionally, the strong positive correlation between total Hg concentration and Δ¹⁹⁹Hg suggests that foraging depth significantly influences mercury uptake. These findings demonstrate that an integrated isotopic-tracking approach advances ecological biogeochemistry by tracing both contaminant pathways and seabird movement using natural isotopic tracers.

How to cite: Li, M.-L., Janssen, S., Tate, M., Choy, E., Elliot, K., and Gousy-Leblanc, M.: Integrating Geolocator Tracking and Isotopic Tools to Reveal Winter Foraging Ecology and Mercury Exposure in Arctic Seabirds, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2458, https://doi.org/10.5194/egusphere-egu26-2458, 2026.

Closed-transient chamber systems are widely used to measure the transport of non-reactive greenhouse gases (GHGs) and their stable isotopes between the soil and atmosphere. Technologies used to measure GHGs in chamber-based systems have advanced since their first introduction. In many early systems, gas analysis was performed off-line using gas chromatography and/or mass spectrometry. The introduction of non-dispersive infrared gas analyzers suitable for field deployment allowed CO₂ to be measured on-line, but for other GHGs on-line analysis was not possible until the more recent introduction of tunable diode laser absorption spectroscopy (TDLAS)- based gas analyzers. The most recent generations of TDLAS analyzers have extended measurement capabilities from reporting total concentration of a given GHG, to separating concentrations of its most abundant stable isotopologues. For CO₂, this advancement makes possible near real-time estimation of isotopic signature (δ¹³C) of the carbon source pool.

Linear mixing model-based approaches are used to separate the isotopic signature of a source pool from background condition observed during soil chamber measurements. The most common, those proposed by Keeling (1958) and Miller and Tans (2003), uses the relationship between the normalized isotopic ratio (δ) and total concentration, or some derivate term of either, to estimate the source pool conditions. Keeling’s methodology is widely cited but requires extrapolation well beyond measured conditions. The Miller-Tans approach is predicated on the same underlying mass balance as Keeling but uses a solution that estimates the source pool only over measured conditions, reducing uncertainty in final estimates. Both approaches require independent measurement of the total concentration and normalized isotopic ratio, which is not possible with TDLAS based analyzers. TDLAS analyzers measure individual isotopologue mole fractions and use the same set of individual measurements to calculate both total concentration and the normalized isotopic ratio, introducing an inherent autocorrelation between them. Additionally, the δ exhibits a bias as a function of total measured CO₂ concentration, introducing an apparent concentration dependence error (CDE) in d reported from TDLAS.

We present an alternative approach to estimating the source pool isotopic composition specific to TDLAS measurements. This alternative approach relies only on measurements of individual isotopologue mole fractions, avoiding autocorrelation, and does not require extrapolation beyond measurement conditions. We include a sensitivity analysis of mixing model approaches and errors common to TDLAS based instruments, using a chamber dataset synthesized from field-based measurements of environmental conditions and physical properties of gas transport.

How to cite: Hupp, J., Belovitch, M., Lynch, D., and Vath, R.: An alternative approach to determine source stable carbon isotope composition for closed-transient chamber measurements using TDLAS analyzers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2823, https://doi.org/10.5194/egusphere-egu26-2823, 2026.

Effective management of river pollution is often limited by low-frequency monitoring approaches that fail to resolve the spatiotemporal dynamics of nutrient sources, hydrodynamic transport, and in-stream biogeochemical processing. To address this, we applied a high-resolution Lagrangian sampling framework to a well-characterised reach of the River Thames, enabling continuous tracking of water parcels downstream of key nutrient inputs. This approach combined nutrient concentration data, optical characterisation, and stable isotope tracers with detailed hydrodynamic measurements to resolve nutrient sources, mixing behaviour, and short-reach processing. Water samples were collected for conventional nutrient analysis, excitation–emission matrix (EEM) fluorescence, and isotopes of nitrate and phosphate. Field measurements were supported by drone-based infrared imaging to characterise surface flow structure and a remote-controlled survey vessel equipped with Acoustic Doppler Current Profiler, Single Beam Echo Sounder, and GPS to resolve hydrodynamics and channel morphology. In situ sondes and large-volume sampling further captured water-quality variability. Phosphate oxygen isotopes (δ¹⁸O_p) were used to directly trace wastewater-derived phosphorus downstream of a wastewater treatment works (WWTW) outfall. Nineteen river samples collected at ~20 m intervals were compared with upstream river and WWTW effluent end members. Effluent phosphate exhibited a distinctly lower δ¹⁸O_p value than background river phosphate, enabling a two-endmember isotope mixing model. Results indicate that WWTW-derived phosphate contributed approximately 20–55% of riverine phosphate across most of the reach, with localized zones of near-complete effluent dominance. A pronounced low-δ¹⁸O_p anomaly coincident with elevated phosphorus concentrations is interpreted as a localized hydrodynamic pulse of wastewater phosphate superimposed on progressive biological reprocessing. Together, these results demonstrate that wastewater phosphorus can exert strong, spatially heterogeneous control on riverine phosphate over very short distances, even under conditions of active mixing and biological cycling. More broadly, this integrated Lagrangian-hydrodynamic-isotopic framework provides a powerful new basis for quantifying nutrient sources, transport, and transformation in rivers, with direct implications for more effective nutrient management strategies.

How to cite: Gooddy, D., O'Brien, A., Bowes, M., Everard, N., Laize, C., Rameshwaran, P., Pesso, C., Harrison, P., Sorensen, J., Smith, A., and Krause, S.: Taking the Pulse: Tracking Wastewater Nutrients Through a River Using Lagrangian Sampling and Isotopic Tracers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3089, https://doi.org/10.5194/egusphere-egu26-3089, 2026.

Rapidly expanding biogeochemical applications based on compound specific isotope ratios require instrumentation versatility to meet different analytical challenges. Here we present features and benefits of using the following GC injection techniques: on-column injection, Large Volume Injection (LVI) Programmed Temperature Vaporization (PTV) technique, Static Headspace Sampling (SHS) injection and conventional Split/Splitless injection. We will demonstrate capability of Thermo Scientific™ GC IsoLink™ II IRMS System to support these injection techniques to properly transfer a representative portion of the sample to the analytical column while avoiding discrimination and isotopic effects.

On-column injection is applied for analysis of thermally labile or unstable compounds, as well as for samples with large analyte-boiling-point differences. It can be advantageous in a wide area of applications, i.e. for investigations of alkenones and alkanes from soils and sediments. We will present an optimized GC-IRMS analytical setup for stable carbon isotope ratios analysis of saturated hydrocarbons.

The LVI PTV is an injection technique which allows the introduction of larger volumes of samples in the GC injector which can be particularly useful for analysis of organic pollutants present in very small quantities. Here we present an optimized methodology for analysis of very small amounts of saturated hydrocarbons.

The SHS injection via split/splitless injector eliminates the need for direct liquid sample injection, reducing column contamination and improving analyte separation and reproducibility of isotope data. Here we demonstrate excellent precision and accuracy for GC-C-IRMS analysis of VOCs by using an optimized method for SHS, including improved sensitivity and lower detection limits.

Finally, we also present an optimized workflow for the analysis of PAHs by GC-IRMS with conventional Splitless injection, including characterization of PAHs standards and data evaluation.

How to cite: Milano, S., de Castro, M., and Tuthorn, M.: GC-IRMS: optimization of injection techniques for analysis of saturated hydrocarbons, VOCs and PAHs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3304, https://doi.org/10.5194/egusphere-egu26-3304, 2026.

Temporal variability of tree-ring cellulose δ²H (δ²H_ring-cel) can be a unique tool for understanding tree physiology and climate. However, we do not fully understand the drivers of temporal variability in δ²H_ring-cel. Investigating seasonal δ²H_ring-cel in boreal forests is particularly challenging. Previous studies on intra-annual tree-ring δ¹⁸Ohave shown that tree-ring isotope variability can result from the combined but opposing effects of source water and leaf assimilates, a dynamic likely relevant for δ²H_ring-cel as well. To be able to use δ²H_ring-cel as a standalone and reliable bioindicator, it is important to understand the variable hydrogen isotope fractionation between source water and tree rings. Our study aimed to provide context to this variability in a natural forest by tracing intra-annual δ²H_ring-cel to the δ²H of its sources (water, sugars & starch), and comparing δ²H_ring-cel to physiological and climatic factors.

The δ²H of source water, leaf water and carbohydrate pools (i.e. water-soluble carbohydrates, starch) were analysed from five pine (Pinus sylvestris) trees during 2019 at Hyytiälä forest, Finland. Their δ²H were used to model continuous δ²H of source water (δ²H_source) and bulk leaf water (δ²H_leaf-water) and photosynthetic water (δ²H_photo-water). Intra-annual δ²H_ring-cel were analysed in 2018 and 2019 at a resolution of 5-10 timepoints per year, and they were allocated to xylogenetic timepoints. They were then compared to time-integrated δ²H_source, δ²H_leaf-water, δ²H_leaf-sug, net assimilation rate, and various other physiological and climatic factors.

Carbohydrate δ²H was significantly different among leaves, branches and stems. δ²H_ring-cel had strong time-integrated relationships to modelled δ²H_source, net leaf assimilation rate and evapotranspiration, but the direction of their relationships was different between years. At monthly resolution, water-soluble carbohydrate δ²H measured from one year-old needles had a strong, positive relationship to δ²H_ring-cel. δ²H_ring-cel also had strong relationships to Standardized Soil Moisture Index (SSMI) in both years.

We show that δ²H_ring-cel has a potential as an indicator of soil drought conditions, and that this signal is likely mediated by the leaf-level response to soil drought. This clearly support the growing body of evidence that δ²H_ring-cel is strongly mediated by physiological processes, while also opening a new avenue for δ²H_ring-cel interpretations. Our results show promise for δ²H_ring-cel functioning as a bioindicator of soil drought related physiological stress signals in long-term tree ring chronologies.

How to cite: Angove, C., Lehmann, M., Saurer, M., Tang, Y., Sahlstedt, E., Young, G., Treydte, K., Leppä, K., Schiestl-Aalto, P., Wiesenberg, G., and Rinne-Garmston, K.: Intra-annual tree-ring cellulose δ2H as an indicator of soil drought, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3928, https://doi.org/10.5194/egusphere-egu26-3928, 2026.

Against the backdrop of climate change, the destructive power of tropical cyclones (TCs) has intensified, highlighting the urgent need for a more comprehensive understanding of tropical cyclone activity beyond the records provided by meteorological observations and historical documents. In this study, we compiled TC events affecting the Hong Kong region of South China since 1980 and investigated their isotopic imprints in precipitation and tree rings. We compared the hydrogen isotopic composition of precipitation (δ²H_ppt) during TC-affected and TC-free months. After accounting for the rainfall amount effect and seasonal influences, we demonstrate that δ²H_ppt consistently captured the anomalously depleted isotopic signals associated with TC rainfall. Furthermore, robust regression analysis indicated that TC-related precipitation isotopic variability explained approximately 30.5% of the variance in lignin methoxy stable hydrogen isotopes (δ²H_LM) of tree-ring latewood in Pinus elliottii Engelm. at the Hong Kong site. Additionally, TC precipitation (TCP) exerted the strongest positive control on TC signals recorded in latewood δ²H_LM, with additional contributions from TC intensity (MaxInte) and a significant negative seasonal effect (SeasonalIdx), while storm duration (Days) and distance (MinDist) showed limited independent influence. Overall, TC signals preserved in latewood δ²H_LM reflect the integrated hydroclimatic effects of multiple storm characteristics at the annual scale, rather than being controlled by any single statistical descriptor of tropical cyclone activity. Our findings demonstrate that tree-ring latewood δ²H_LM in P. elliottii can serve as a robust recorder of tropical cyclone signals. This work broadens the application of tree-ring lignin hydrogen isotopes and provides a novel proxy for improving interpretations of historical TC variability.

How to cite: Wang, Y., Li, W., and Song, X.: Extremely low δ2H signatures in tropical cyclone precipitation recorded by tree-ring lignin methoxy hydrogen isotopes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4359, https://doi.org/10.5194/egusphere-egu26-4359, 2026.

The release of carbon dioxide and reactive nitrogen in various forms by humans disrupts the functioning of ecosystems around the world. In Europe, many valuable habitats, particularly wetlands and dry grasslands, are under threat due to eutrophication. However, contrasting water regimes mean that the uptake of anthropogenic nitrogen by plants in these ecosystems differs, and this is also interrelated with an increase in trophic level in both habitats.

In our study, we measured the δ15N and δ13C values, as well as the total nitrogen content (TN), of 99 pairs of foliar samples collected from seven species of vascular plants in dry grasslands and wetlands in Poland. Each pair consisted of a historical sample, collected from a herbarium voucher dating from before 1939 (i.e. before the widespread use of artificial fertilisers in agriculture), and a contemporary sample, collected in 2024, from the same species in a similar location.

We performed t-tests to determine whether there were significant differences in the means of δ15N, TN, and δ13C between samples from the two habitats. Next, we calculated the differences in δ15N, TN, and δ13C between the contemporary and historical samples for each pair. We then tested whether the difference for each species and habitat type was significantly different from zero using 90% confidence intervals. We analysed the relationships between differences in δ15N and TN over time and the following factors using multiple linear regression: habitat type, the proportion of farmland in the landscape, the consumption of synthetic nitrogen fertiliser and NOx deposition. 

The δ15N and TN values were lower for dry grassland species than for wetland species in both the contemporary and historical subsets. For dry grassland species, the mean δ15N value was lower in contemporary samples than in historical ones. For wetland species, however, the opposite was true. The difference in δ15N values between pairs of samples was positively correlated with the proportion of farmland in the landscape. The mean TN value was higher in contemporary wetland samples than in historical ones, but not in dry grassland plants. The mean δ13C value, corrected for the Suess effect, was lower in contemporary samples than in historical ones. The mean difference was −0.51 ‰ for dry grassland species and −3.85 ‰ for wetland species.

Our study revealed that a century of carbon emissions, increased nitrogen input into the environment and the dominance of artificial fertilisers and combustion-derived nitrogen over biological nitrogen sources has not resulted in consistent responses across habitats and species. While the isotopic composition of nitrogen and carbon in plant tissues in Central Europe has undoubtedly changed, this change is context-dependent. Its magnitude and direction are impacted by the habitat and the identity and/or ecology of the species. As expected, man-made alterations appear to be more pronounced in wetland environments than in dryland habitats. Furthermore, the source of disruption may differ between the habitat types. Specifically, wetlands are exposed to a multitude of anthropogenic nitrogen and carbon sources, whereas dry grasslands seem to be predominantly affected by changes in atmospheric composition.

How to cite: Dembicz, I., Chojnowska, N., Chibowski, P., and Kozub, Ł.: Contrasting isotopic responses of dryland and wetland plants to a century of global anthropogenic changes in nutrient cycling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4432, https://doi.org/10.5194/egusphere-egu26-4432, 2026.

Dissolved inorganic carbon (DIC) - including aqueous CO₂, carbonic acid, bicarbonate, and carbonate - is often the largest pool of carbon in aquatic systems. Biogeochemical processes result in exchanges of carbon between the various DIC components and may act to move carbon into or out of the DIC pool. The isotopic composition of carbon is a product of both its source and mass-dependent fractionation as carbon changes form through the processes acting on it. Consequently, measurement of the stable carbon isotope composition of DIC is a valuable tool for understanding biogeochemical processes in aquatic systems. However, differences in isotopic composition are small, and separating source contributions requires precise measurement.

Measurement of DIC can be done by conversion to CO₂ in the presence of a strong acid and quantification of liberated CO₂ by gas analysis. To determine isotopic composition of the liberated CO₂ (δ¹³C) historical methods used isotope ratio mass spectrometry (IRMS). More recently, tunable diode laser absorption spectrometry (TDLAS) based gas analyzers have been adopted for these measurements but have continued to base methodological considerations on those developed for IRMS. While IRMS and TDLAS can both be used to determine δ¹³C, there are fundamental differences in the technology, which should be considered during application. In particular, this has meant δ¹³C - DIC measurements have been unable to take full advantage of TDLAS performance characteristics.  

Here we describe methodological advancements from integration of a TDLAS (LI-7825 carbon isotope analyzer) with a DIC measurement system (LI-5370A), that include changes to the pneumatic and analytical approach used in the DIC system. Pneumatic modifications allow the TDLAS to operate at an independent flow rate from the DIC system and serve to manipulate the residence time for CO₂ along the flow path. We describe use of a non-CO₂ free carrier gas, which allows the DIC measurement to take full advantage of analyzer precision and minimize errors intrinsic to δ¹³C as determined by TDLAS. We present data demonstrating measurement precision over a range of conditions and show that under similar conditions, these methodological changes result in precision exceeding that published previously for TDLAS-DIC measurements.

How to cite: Griessbaum, F., Hupp, J., Lynch, D., Scaboo, M., Leclerc, A., and Cai, W.-J.: Methodological advancements for stable carbon isotope measurement of dissolved inorganic carbon using tunable diode laser absorption spectrometers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5063, https://doi.org/10.5194/egusphere-egu26-5063, 2026.

This study examines the stable oxygen and hydrogen isotopic composition of gypsum (CaSO₄·2H₂O) hydration water (GHW) preserved in sediments from the Laguna de la Ratosa playa lake (Málaga Province, southern Iberian Peninsula). The objective was to reconstruct the lake water isotopic composition between 18.5 and 7.5 ka, reflecting hydroclimate variability in the southern Iberian Peninsula during the Pleistocene-Holocene transition. The GHW proxy relies on the fact that during crystallization, gypsum incorporates water from the solution, allowing the isotopic composition of the paleo-lake water to be directly inferred from that of GHW. This is possible because the oxygen and hydrogen isotope fractionation factors between aqueous solutions and GHW are well constrained and largely insensitive to temperature and salinity. The reconstructed lake-water isotopic values show a progressive decrease (from mean values of 6 to 0‰ for δ¹⁸O and from 10 to –5‰ for δ²H) between 18.5 and 11 ka, coincident with the deglaciation. This trend indicates a transition toward less evaporative conditions associated with increasingly humid climate. Superimposed on this overall trend, however, are three arid intervals centered at ca. 18 ka, 16 ka, and 12–13 ka, during which both δ¹⁸O and δ²H values increased. These arid phases are interpreted as reflecting the influence of the Last Glacial Maximum, Heinrich Stadial 1 (HS1), and the Younger Dryas on lake hydrology. During the Early-Mid Holocene (11–7.5 ka), isotopic values stabilized at the lowest levels of the record (ca. 0‰ for δ¹⁸O and ca. –5‰ for δ²H), suggesting persistently reduced evaporation and the establishment of a more permanent lacustrine system under sustained wetter conditions. Overall, these results demonstrate that gypsum hydration water preserved in playa-lake sediments constitutes a robust proxy for reconstructing paleohydrological variability and associated climatic changes.

Acknowledgments: This study was funded by the GYPCLIMATE (PID2021-123980OA-I00) and PID2021-125619OB-C21 projects of the Spanish Ministry of Economy and Competitiveness and FEDER European Regional Development Funds. J.C.P. acknowledges the Research Teaching Training contract PRE2022-103493 Ministry of Economy and Competitiveness of Spain. L.M. was funded by the FPU21/06924 grant of the Spanish Ministerio de Educación y Formación Profesional. C.V. was funded by the European Comission (Marie Curie postdoctoral fellowship, grant no. 101063961). F.G acknowledges the Ramón y Cajal contract (RYC2020-029811-I) and the PPIT-UAL grant from the Andalusian Regional Government -FEDER2022-2026 (RyC-PPI2021-01).

How to cite: Cañada-Pasadas, J., Gázquez, F., Martegani, L., Voigt, C., Sánchez-Villanueva, A. I., García-Alix, A., and Jiménez-Moreno, G.: Reconstructing hydroclimate across the Pleistocene–Holocene transition in southern Iberia using stable isotopes of gypsum hydration water, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5528, https://doi.org/10.5194/egusphere-egu26-5528, 2026.

The strontium isotope ratio ⁸⁷Sr/⁸⁶Sr is a key tracer with wide-ranging applications in geochemistry, hydrology, paleoclimatology and migration research. To make sound interpretations of ⁸⁷Sr/⁸⁶Sr isotope ratios in the context of biogeosciences, researchers need high quality data. In this contribution, we critically evaluate the accuracy of two conceptually different analytical protocols for ⁸⁷Sr/⁸⁶Sr determination on the example of a large dataset (n = 135) comprising biogenic and abiogenic materials.  

Water, soil extracts, and hydroxyapatites (tooth enamel) were prepared according to established procedures and analyzed by solution-based multi-collector inductively coupled plasma mass spectrometry (MC ICP-MS). For the calibration we used two protocols: internal normalization (also termed internal mass bias correction or internal calibration) and standard-sample-bracketing (external calibration). Isotope dilution mass spectrometry was not considered suitable, because this calibration approach becomes very time- and cost-intensive when applying to a large sample set.

Analysis of water, soil extracts and hydroxyapatites showed that the majority of ⁸⁷Sr/⁸⁶Sr isotope ratios which were determined by internal normalization shifted towards higher values in comparison to data determined by standard-sample-bracketing. Extensive evaluations ruled out sample preparation or measurement errors. Instead, internal normalization yielded biased data, because it is based on the assumption that all samples have the same ⁸⁸Sr/⁸⁶Sr isotope ratio, which can be used for normalization. However, in 90% of the investigated samples the ⁸⁸Sr/⁸⁶Sr significantly deviated from the assumed invariant value; in particular, the ⁸⁸Sr/⁸⁶Sr that is conventionally expressed as δ(⁸⁸Sr/⁸⁶Sr)_SRM987 ranged from -1.01‰ to 0.20‰. As a consequence, internally normalized ⁸⁷Sr/⁸⁶Sr data biased by up to 0.00043, which was 2-times larger than previously predicted by theoretical calculations. These results demonstrate that the choice of calibration method has a much higher impact on the accuracy of ⁸⁷Sr/⁸⁶Sr isotope ratios than initially expected. The implication of these findings in biogeoscience applications will be discussed.

This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n°856453 ERC-2019-SyG).

How to cite: Tchaikovsky, A., Braeuer, S., Pohl, W., and Hann, S.: Critical evaluation of internal normalization and standard-sample-bracketing for accurate ⁸⁷Sr/⁸⁶Sr analysis , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5954, https://doi.org/10.5194/egusphere-egu26-5954, 2026.

Quantifying labile soil carbon (C) pools and their stable isotope composition (δ¹³C) is fundamental for elucidating microbially mediated C cycling, soil organic matter turnover, and isotope fractionation during biogeochemical transformations. Extractable C and microbial biomass C are commonly obtained using salt solutions (e.g., 0.25–0.5 M K₂SO₄); however, subsequent determination of C concentrations and isotope ratios typically requires labor-intensive sample preparation steps, including freeze-drying, oven-drying, or desalting by dialysis. These procedures are time-consuming and may result in substantial losses of dissolved organic C, potentially biasing isotopic signatures.

Here, we present a novel analytical method that enables the simultaneous determination of C concentrations and stable isotope composition (δ¹³C) directly from liquid 0.5 M K₂SO₄ soil extracts without any prior sample preparation. This approach allows direct quantification of extractable and microbial biomass C, substantially reducing sample handling and associated analytical uncertainty.

Method validation across contrasting soil types demonstrates high precision and reproducibility for both elemental concentrations and isotope ratios, while avoiding C losses associated with dialysis or concentration procedures. The method facilitates rapid, high-throughput analysis and enhances the temporal and mechanistic resolution of studies on microbial turnover, rhizosphere processes, and soil C dynamics.

Overall, this approach provides a robust new tool for biogeoscience research, enabling integrated assessments of labile C pools and their isotopic signatures and supporting improved process-based understanding of soil biogeochemical cycling.

How to cite: Adnew, G. A., de Castro, M., and Ambus, P. L.: A novel method for simultaneous quantification and isotope analysis of labile soil carbon directly from liquid extracts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6598, https://doi.org/10.5194/egusphere-egu26-6598, 2026.

The biogeochemical cycling of sulfur stands as a cornerstone in the regulation of the Earth's surface redox state, acting as a primary buffer for atmospheric oxygen and a critical player in the burial of organic matter. The formation and subsequent preservation of sedimentary pyrite represents the dominant sink of reduced sulfur from the global ocean. For decades, the sulfur-isotopic composition of pyrite has been utilized by geochemists as a proxy to reconstruct the chemical evolution of earth's oceans and atmosphere. However, the reliability of this isotopic archive is linked to the physical and chemical state of the sediment-water interface, a boundary layer that was radically transformed by the evolution and intensification of bioturbation - the mixing and ventilation of sediments by burrowing animals. While it is often assumed that the onset of benthic faunal activity had a profound effect on the preserved S-isotope ratio (e.g., (Canfield and Farquhar 2009), actual studies exploring the impact of bioturbation are scarce. (Riemer et al. 2023) show experimental data that suggests that bioturbation shifts the isotope ratio of dissolved H₂S towards more negative values. This is in contrast to numerical studies that suggest that bioturbation has no effect on the pyrite S-isotope ratio (Mertens, Paradis, and Hemingway 2025). Here we extend the iron-redox shuttle model of (Van de Velde and Meysman 2016) to include iron-monosulfide and pyrite precipitation, dissolution and oxidation reactions. Our model explicitly tracks, O₂, SO₄, OM, S0, S^2-, Fe^3+, Fe²⁺ in liquid and sorbed state, FeS and FeS₂ and their respective S-isotope ratios. Model results suggest that bioturbation has either no, or only a very small, impact. However the current model does not yet include sulfur disproportionation and organic sulfur, so these findings are preliminary.

References

Canfield, Donald E., and James Farquhar. 2009. “Animal Evolution, Bioturbation, and the Sulfate Concentration of the Oceans.” Proceedings of the National Academy of Sciences 106 (20): 8123–27. doi:10.1073/pnas.0902037106.

Mertens, Cornelia, Sarah Paradis, and Jordon D. Hemingway. 2025. “Sedimentary Conditions Drive Modern Pyrite Burial Flux to Exceed Oxidation.” Nature Geoscience. doi:10.1038/s41561-025-01855-5.

Riemer, Sydney, Alexandra V. Turchyn, André Pellerin, and Gilad Antler. 2023. “Digging Deeper: Bioturbation Increases the Preserved Sulfur Isotope Fractionation.” Frontiers in Marine Science 9 : 1039193. doi:10.3389/fmars.2022.1039193.

Velde, Sebastiaan van de, and Filip J. R. Meysman. 2016. “The Influence of Bioturbation on Iron and Sulphur Cycling in Marine Sediments: A Model Analysis.” Aquatic Geochemistry 22 (5-6): 469–504. doi:10.1007/s10498-016-9301-7.

How to cite: Wortmann, U.: The impact of bioturbation on pyrite sulfur isotope ratios: A numerical experiment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8048, https://doi.org/10.5194/egusphere-egu26-8048, 2026.

The biological pump is a fundamental component of the oceanic carbon cycle, in which export production from the euphotic zone and subsequent organic carbon remineralization in the twilight zone jointly regulate carbon sequestration in the ocean interior. However, the magnitude, spatial variability, and tracers of these coupled processes remain incompletely understood. Here, we investigate the linkage between export production, twilight zone remineralization, and particulate barium in the western North Pacific (wNP) and the South China Sea (SCS). Organic carbon remineralization fluxes in the twilight zone (150-600 m) are quantified using a newly developed transfer function relating particulate excess barium (PBa_xs) to oxygen utilization rates, revealing pronounced spatial heterogeneity, with PBa_xs concentrations and remineralization fluxes increasing from the subtropical gyre to the North Pacific transition zone. Satellite-derived net primary production (NPP) and export production (EP) exhibit spatial patterns broadly consistent with the inferred remineralization fluxes, indicating a strong association between upper-ocean productivity and mesopelagic carbon degradation. Estimates of the e-ratio and r-ratio based on NPP, EP, and remineralization fluxes demonstrate contrasting biological pump efficiencies, with low e-ratios and high r-ratios in the subtropical gyre reflecting weak carbon sequestration, and high e-ratios and low r-ratios in the transition zone indicating a more efficient biological pump. We further evaluate the potential of particulate barium isotopes as tracers of EP by establishing a calibration between twilight zone particulate barium isotopic composition and euphotic-zone EP in the modern ocean, which reveals a significant negative relationship. However, this relationship does not persist in sedimentary archives: barium isotopic compositions show no systematic response to glacial-interglacial variations in paleoproductivity, and EP reconstructed using the modern calibration exhibits no correlation with sedimentary total organic carbon fluxes. Overall, this study provides an integrated assessment of the applicability and limitations of barium-based proxies from the water column to sediments, highlighting the tight association between Ba, export production, and twilight zone remineralization while emphasizing the challenges and limitations in extending modern barium-based proxies to reconstruct past biological pump dynamics.

How to cite: Yuan, Y., Zhao, S., Zhang, Z., Frank, M., and Cao, Z.: Tracing twilight zone organic carbon remineralization and paleoproductivity with particulate barium proxies: insights and limitations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9004, https://doi.org/10.5194/egusphere-egu26-9004, 2026.

Carbon use efficiency (CUE), defined as the ratio of net primary production (NPP) to gross primary production (GPP), reflects the efficiency of carbon conversion into plant biomass after accounting for respiratory losses. As a key parameter in plant carbon budgeting and terrestrial carbon sequestration assessments, CUE is difficult to measure directly due to the challenges in quantifying gross CO₂ fixation and total respiration. Thus, many carbon cycle models rely on simplified empirical values (e.g., 0.5). Although climate warming may influence CUE due to the widely observed temperature‐sensitivity of respiration, the responses of CUE to warming remain unclear.

In this study, we grew wheat (T. aestivum) and upland rice (O. sativa) in controlled chambers under two temperatures: 25°C (control) and 29°C (+4°C warming). We took advantage of a gas exchange and ¹³C-labelling facility to estimate the gross photosynthetic rate of individual plants and trace the allocation of fixed carbon to shoot and root growth. A compartment model was fit to the data of tracer dynamic during the chase period to analyze the turnover features of carbon pools.

Both species exhibited physiological acclimation to warming: increased leaf‐level maximum carboxylation rate and specific leaf area, but decreased basal respiration rate. Consequently, whole‐plant CUE did not differ significantly between temperature treatments. ¹³C dynamics further revealed that warming did not alter the turnover rates of carbon pools supporting respiration and growth. These results indicate that +4°C warming did not affect CUE in wheat or upland rice, demonstrating a coordinated acclimation of photosynthesis and respiration to elevated temperature.

How to cite: Gong, X., Yang, Z., Liu, Q., and Li, L.: Plant carbon-use efficiency under warming: insights from a ¹³CO2 pulse-chase experiment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9124, https://doi.org/10.5194/egusphere-egu26-9124, 2026.

How to cite: Perdomo-Sosa, O., C. Coldwell, B., Lodoso Ruíz, E., Cartaya Arteaga, S., Asensio Ramos, M., V. Melián, G., A. Hernández, P., and M. Pérez, N.: Strontium isotopes as geological fingerprints in potatoes cultivated on ocean-island basalts , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10602, https://doi.org/10.5194/egusphere-egu26-10602, 2026.

Lignin is a major component of plant-derived organic matter in soils, and the stable carbon isotopic composition of lignin-derived methoxyl (δ ¹³C LMeO) groups provides a distinct molecular fingerprint for identifying sources and their relative contributions to soil organic matter. This study investigates δ ¹³C LMeO values in soil profiles from surface horizons to bedrock in  a deciduous and coniferous forest in Switzerland, with the aim of estimating the relative contributions of lignin from photosynthetic and non-photosynthetic plant tissues. Analyses were conducted on two particle-size fractions (<63 µm and 63–200 µm), and the influence of ¹³C isotopic fractionation during lignin degradation was evaluated for both size fractions.

Preliminary source apportionment results, not accounting for isotopic fractionation during degradation, indicate that the coarse fraction at the coniferous site is dominated by lignin derived from non-photosynthetic plant tissues, approaching a 100% contribution. In contrast, the fine fraction at the coniferous site and both particle-size fractions at the deciduous site comprise approximately 60% lignin from non-photosynthetic tissues.

In contrast to bulk δ¹³C and other compound-specific stable isotope tracers, δ ¹³C LMeO  values exhibited a systematic isotopic depletion in the fine (<63 µm) fraction. This depletion suggests preferential stabilization of the more easily degradable lignin from photosynthetic tissues. In the coarse (63–200 µm) fraction, δ ¹³C LMeO values showed a clear relationship with the extent of degradation, consistent with isotopic fractionation during lignin loss. In contrast, no systematic degradation-related trend was observed in the fine fraction. Together, these results highlight contrasting controls of degradation and stabilization on lignin across soil particle-size fractions and underscore the importance of accounting for isotopic fractionation when applying δ ¹³C LMeO for soil organic matter source attribution.

How to cite: Cox, T., mharchat, F., and Alewell, C.: Lignin Methoxyl δ¹³C Reveals Particle-Size–Dependent Sources and Degradation  in Forest Soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10623, https://doi.org/10.5194/egusphere-egu26-10623, 2026.

Gross primary production (GPP) describes ecosystem-scale canopy photosynthesis and provides the foundation of the ecosystem carbon budget. It is often derived from eddy covariance data based on models of the component processes. At several sites in Sweden and the Czech Republic, we have quantitatively tested these GPP estimates against independent empirical data based on stem-scale measurements of xylem water flux and intrinsic water-use efficiency (iWUE), where iWUE is estimated from the stable isotope composition of phloem contents. With one exception, these comparisons have agreed well in the middle of the growing season. On the other hand, at several sites, the methods showed distinct discrepancies either at the beginning or the end of the growing season. We discuss possible causes of these seasonal discrepancies ,including the decoupling of phloem contents from gas-exchange, the scaling of sap flux, mesophyll conductance, decoupling of air masses above and below the canopy, and the inference of GPP from eddy covariance data. Quantitative tests of these methods against independent data will be critical as our need to quantify carbon sources and sinks continues to grow.

How to cite: Marshall, J., Tarvainen, L., Vernay, A., Stojanović, M., Stangl, Z. R., and Rütting, T.: Comparing eddy covariance estimates of gross primary production to estimates from stem sap flux and phloem d13C across sites., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10665, https://doi.org/10.5194/egusphere-egu26-10665, 2026.

The Atacama Desert contains the largest natural nitrate accumulations on Earth. Yet, the processes controlling their formation and redistribution remain debated, particularly for nitrate veins hosted in bedrock. In this study, we combine field observations with chemical and stable isotope analyses (δ¹⁸O, Δ¹⁷O, δ¹⁵N) of nitrate from all major deposit types across the Atacama nitrate provinces. All nitrate occurrences display large positive Δ¹⁷O values (+13 to +22‰) and elevated δ¹⁸O (+43 to +65‰), confirming a unanimous atmospheric origin via ozone-driven photochemical oxidation of NO_x.

Vein-hosted nitrates in volcanic and sedimentary rocks show suppressed Δ¹⁷O and δ¹⁸O values trending toward fossil hydrothermal waters, indicating partial oxygen isotope exchange during interaction with hot, saline, acidic fluids. Field relationships, fault-controlled mineralization, rhyolitic exsolution textures, and sulfate sulfur isotopes independently confirm hydrothermal dissolution, transport, and reprecipitation of originally atmospheric nitrate.

These results define a two-stage geological cycle: long-term atmospheric deposition, groundwater transport, and evaporative concentration under hyperaridity, followed by tectonically driven hydrothermal recycling linked to Andean magmatism. This two-mechanism framework reconciles the isotopic, mineralogical, and spatial diversity of nitrate deposits, demonstrating that the Atacama Desert records a coupled atmospheric–hydrothermal cycle linked to the tectonic and magmatic evolution of the central Andean margin, and providing a template for other nitrate-bearing deserts on Earth and potentially on other planets.

Nitrate deposit δ¹⁵N = −8 to +4‰ are slightly higher than in atmospheric nitrate and overlap with the Atacama soil nitrate profile compositions, but in contrast show a positive correlation with δ¹⁸O. This excludes humidity driven microbial denitrification and gaseous N loss as a major driver for local secondary composition contrasts.

How to cite: Riffo Contreras, C., Chong, G., Klipsch, S., E. Böttcher, M., Davies, A., and Staubwasser, M.: The Geologic Super-Cycle of Chilean Nitrate Deposition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11165, https://doi.org/10.5194/egusphere-egu26-11165, 2026.

How to cite: Seed, M., Preece, C., Boocock, T., and De Reuss, M.: Fully integrated TOC and TNb analysis of estuarine and sea water samples with the Elementar iso TOC cube® , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11252, https://doi.org/10.5194/egusphere-egu26-11252, 2026.

Volcanic hydrocarbon reservoirs are distributed across more than 40 basins in 13 countries globally. In recent years, significant exploration prospects have been identified in Mesozoic volcanic strata within China’s offshore basins, including the Bohai Bay, East China Sea, Pearl River Mouth, and Qiongdongnan basins. The study of volcanic reservoirs remains a frontier topic in petroleum geology. Characterized by strong heterogeneity resulting from the superposition of multiple diagenetic processes and subsequent reformation, these reservoirs pose significant challenges for favorable reservoir prediction. Furthermore, the pronounced intra-volcanic heterogeneity leads to significant variations in hydrocarbon properties within single volcanic edifices, complicating the determination of hydrocarbon sources and the reconstruction of accumulation histories.Taking the BZ8S-A area in the Bozhong Sag of the Bohai Bay Basin as a case study, this research addresses these challenges. The study area is currently drilled by four exploration wells, revealing distinct variations in hydrocarbon composition, reservoir temperature and pressure, gas-oil ratios (GOR), and hydrocarbon column heights. Notably, two of these wells have tested high-yield oil and gas flows. To delineate the hydrocarbon accumulation process, a comprehensive multi-disciplinary approach was adopted, integrating geological background analysis, source rock distribution, hydrocarbon generation evolution in adjacent sags, and seismic interpretation.Advanced geochemical analyses were employed, including compound-specific carbon isotope analysis of oil and gas, monomeric hydrocarbon carbon isotopes, and organic matter stable carbon isotopes. These were combined with biomarker analysis (saturated hydrocarbons, aromatics, and adamantanes) and numerical simulation of hydrocarbon migration pathways. By establishing carbon isotopic cross-plots for source rocks at different stratigraphic levels in the hydrocarbon-generating sags and comparing them with typical generated hydrocarbon samples, the study conclusively determines that the hydrocarbons in the BZ8S-A volcanic reservoir are primarily sourced from the Shahejie Formation. Moreover, the geochemical evidence indicates that hydrocarbons in different well locations originated from distinct hydrocarbon-generating sags, revealing a complex, multi-source charging model for this volcanic reservoir.

How to cite: Shiyang, Z. and Qi, W.: Tracing Multi-Source Mixing in Volcanic Reservoirs Using Biomarkers and Carbon Isotopes: A Case Study of the Bozhong Sag, Bohai Bay Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11279, https://doi.org/10.5194/egusphere-egu26-11279, 2026.

The discovery of heterotrophic nitrification has expanded our view of nitrification beyond the canonical chemolithoautotrophs. Yet, the role of heterotrophic bacteria in nitrification across environmental and engineered systems remains unclear, partly due to limited physiological characterization and the absence of robust diagnostic tools. The analysis of nitrogen (N) isotope fractionation effects has been used for tracing biogeochemical N cycle processes and offers the potential to resolve underlying biochemical pathways. While autotrophic nitrification is known to generate substantial N isotope effects during ammonia (NH₃) oxidation to nitrite (NO₂⁻), comparable constraints for heterotrophic nitrifiers are lacking. Here, we report for the first time the N isotope effects associated with heterotrophic nitrification by Alcaligenes faecalis, an organism capable of converting NH₃ into several nitrogenous products. In batch incubations with 2.2 mM ammonium (NH₄⁺) as the sole N source, A. faecalis produced up to 0.67 ± 0.04 mM NH₂OH, 0.11 ± 0.01 mM NO₂⁻, and 12 ± 1.2 µM N₂O, while the remaining NH₄⁺ was assimilated into biomass. Therefore, the main NH₄⁺consumption pathway of A. faecalis is, in fact, best described by ammonium assimilation, which supports previous findings. Total NH₄⁺ consumption showed an isotope effect of 13.8 ± 0.4‰, exceeding that of biomass formation (4.8 ± 0.2‰). Both values fall within the known range for bacterial NH₄⁺ assimilation, but the disparity suggests additional fractionating steps beyond assimilation alone. NH₂OH, NO₂⁻, and N₂O were initially strongly ¹⁵N-depleted relative to the NH₄⁺ source, and became progressively enriched as NH₄⁺ was consumed. N₂O exhibited a variable site preference (24–38‰), indicating contributions from at least two production pathways. Overall, our findings show that heterotrophic nitrification produces N-isotopic signatures fundamentally distinct from canonical ammonia oxidation. These characteristic patterns in both NH₄⁺ and NO₂⁻ pools highlight the diagnostic potential of stable isotopes for identifying heterotrophic nitrification in complex systems.

How to cite: Frey, C., Lenferink, W. B., von Kessel, M. A. H. J., Magyar, P. M., Jetten, M. S. M., Lehmann, M. F., and Lücker, S.: Isotopic fingerprint of heterotrophic nitrification by Alcaligenes faecalis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13059, https://doi.org/10.5194/egusphere-egu26-13059, 2026.

Stable isotope analysis of organic materials is essential in environmental, geochemical, and food authenticity research, offering insights into carbon sources and product origins. Traditional Picarro Combustion Module–Cavity Ring-Down Spectroscopy (CM-CRDS) systems provide reliable, cost-effective δ¹³C analysis; furthermore, enabling simultaneous δ²H measurement greatly expands their utility for many applications.

We present a straightforward extension of the CM-CRDS system, integrating two dedicated analyzers: the Picarro G2201-i for δ¹³C and the Picarro L2130-i for δ²H. Key modifications include removing the water trap, heating the transfer tubing, and adding a heated buffer volume, enabling direct isotopic analysis of water vapor alongside carbon dioxide. This setup maintains the original sample delivery for carbon isotope analysis, while a simple software adjustment allows precise peak integration for hydrogen isotopes.

Performance was validated using a range of international standards representing diverse organic materials: USGS88 (marine collagen), USGS89 (porcine collagen), USGS90 (millet flour), USGS91 (rice flour), and IAEA CH7 (polyethylene foil). The system demonstrated excellent δ²H linearity (with slopes of 1.040, 1.074 and 1.017 on three separate days and R² values exceeding 0.99) while maintaining the high accuracy of δ¹³C measurements. Precision was assessed with hexamethylenetetramine (HMT), yielding a δ²H standard deviation of 0.26‰ and δ¹³C of 0.04‰ over 50 replicates. We chose HMT to determine the precision because it does not exchange hydrogen isotopes during storage and analysis and is used to determine the carbon-bound non-exchangeable hydrogen in fructose and glucose in honey [1]. Calibration procedures and best practices for hydrogen isotope analysis are discussed.

Our findings highlight the potential of combining the G2201-i and L2130-i analyzers with a CM in a coordinated analytical workflow for dual isotope analysis. This methodology opens new opportunities for isotope studies for environmental as well as food authenticity and food origin studies, and is a low-cost, easy to use alternative to IRMS analysis.

Reference

[1] Li et al., 2024, A new approach to detecting sugar syrup addition to honey: Stable isotope analysis of hexamethylenetetramine synthesised from honey monosaccharides (fructose and glucose). Food Chemistry 434.

How to cite: Wozniak, J., Roy, S., Hofmann, M. E. G., Bhattacharya, J., and Hemenway, T.: Simple, Fast, and Highly Precise δ¹³C and δ²H Analysis of Organics via Dual Picarro CRDS Integration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14109, https://doi.org/10.5194/egusphere-egu26-14109, 2026.

The content and stable isotopic (⁹⁸Mo/⁹⁵Mo) composition of bladder wrack (Fucus vesiculosus) were investigated for their potential as a sink for dissolved molybdate in coastal environments. The macrophytes were grown in mesocosms fed with brackish coastal waters from a temperate coastal bay (Kiel Bight) under ambient conditions of simulated environmental stress, e.g., enhanced temperature and/or CO₂ partial pressure. Conditions were set up to simulate possible future climate change scenarios applying a delta-approach. Dissolved molybdate in brackish Baltic seawater was isotopically found to be close to the open North Sea, with a slight trend towards isotopically more negative values with decreasing salinity. This is in-line with a fresh water contribution originating from weathered minerals in the catchment area. It was found that the organic tissue of Fucus vesiculosus was substantially enriched in ⁹⁵Mo compared to dissolved seawater molybdate by up to -1.5 mU. Isotope fractionation was slightly enhanced by increasing temperature but no effect was observed for the other or combined treatments. Seasonal effects in the contents and isotope signatures of the tissue were observed with diminished incorporation of Mo during summer time and an associated lowered isotope signature. No clear trend in the fractionation of the different Mo isotopes can be predicted for different complex climate change scenarios, considering an increase in carbon dioxide partial pressure, in combination with temperature. Mainly temperature seems to impact Mo incorporation and associated isotope signature. A mass balance approach indicates, that the impact of Fucus growth on the total Mo budget in the coastal bight is small due to a continuous water exchange. The results for Mo in seaweed are compared to other trace elements and stable isotope signatures (C, N, S) incorporated into the tissue, too. The results from the present study demonstrate the potential of seaweed to act as an environmental multi-element biomonitor.

How to cite: Böttcher, M. E., Winde, V., Neubert, N., Roeser, P., and Nägler, T. F.: Seaweed is a sink for isotopically light molybdenum in temperate coastal environments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14217, https://doi.org/10.5194/egusphere-egu26-14217, 2026.

Stable silicon isotopes have emerged as powerful tracers of marine biogeochemical processes, yet their application in high-latitude environments remains comparatively underexplored. Here we synthesize silicon isotope observations from the Eurasian Arctic Ocean to show how isotope patterns help disentangle physical transport, including open-ocean circulation, shelf–basin exchange, and river influence, from biological utilization across ice-covered and seasonally ice-free regimes. Using published case studies from the Siberian shelves and the Transpolar Drift, we illustrate how Si isotope signatures resolve coupled physical and biogeochemical controls on nutrient pathways. We then outline key methodological challenges for extending Si isotope work into sea ice, including defining open versus closed brine habitats, linking isotope signals to brine-network connectivity, and avoiding sampling artifacts that integrate unknown source volumes. Finally, we discuss how ongoing Arctic observing efforts, including large international campaigns, open new avenues for applying Si isotope techniques to questions of nutrient availability, ecosystem change, and ice–ocean coupling in a rapidly transforming Arctic system.

How to cite: Laukert, G., Hendry, K., and Horner, T. J.: Stable silicon isotopes as tracers of Arctic sea ice–ocean macronutrient cycling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14259, https://doi.org/10.5194/egusphere-egu26-14259, 2026.

Quantifying the relative contributions of evolutionary mechanisms to tree water-use strategies is critical for predicting species’ responses to climate change and supporting forest management strategies. Common garden experiments can explicitly address the contributions of genetics and plasticity in physiological-related traits. However, these experiments typically focus on young trees, and long-term physiological measurements from common garden experiments are largely lacking. Stable isotope analysis of tree rings bridges this gap by enabling the reconstruction of long-term water-use strategies of mature trees growing in long-term common garden experiments.

In this study, we investigate the evolutionary mechanisms underlying long-term water-use strategies in Quercus petraea across its distribution range by analysing annually-resolved stable isotope ratios (δ¹³C, δ¹⁸O, δ²H) from tree-ring cellulose. We sampled 234 individuals originating from nine provenances grown in four European common gardens (Denmark, France, Poland, and the United Kingdom). For the period 2012–2021, we derived annual carbon isotope discrimination (∆¹³C), intrinsic water-use efficiency (iWUE), and isotopic enrichment relative to precipitation (∆¹⁸O and ∆²H). Linear mixed-effects models were used to quantify the contributions of genetic variation, phenotypic plasticity, and its interaction (i.e. genetically-based plasticity) to variation in iWUE, ∆¹⁸O, and ∆²H. The dual-isotope approach (δ¹³C and ∆¹⁸O) was applied to investigate the provenance-specific adjustments in photosynthetic rate and stomatal conductance across sites.

Our results revealed significant genetic and genetically-based plasticity effects on all isotope ratios whereas phenotypic plasticity had a significant effect only on ∆²H. ∆¹⁸O and ∆²H exhibited distinct patterns related to genetics and phenotypic plasticity effects. Notably, ∆²H variability across sites exceeded provenance-level variation. These results could be indirectly related to the link of ∆²H to primary C metabolism. The dual-isotope analysis (δ¹³C and ∆¹⁸O) further identified adjustments in stomatal conductance as the main plastic response to contrasting environments. The provenance with the least plasticity (originally from the United Kingdom) also showed reductions in photosynthetic rates, indicating a limited capacity to adjust to contrasting environments. Overall, these findings highlight strong genetic and plastic control in water-use traits and demonstrate the potential of stable isotopes in tree rings to unravel evolutionary mechanisms in tree water-use strategies.

How to cite: Martínez-Sancho, E., Vitasse, Y., Treydte, K., Saurer, M., Argelich Ninot, M., Benito-Garzón, M., Bigler, C., Fonti, P., Miranda, J. C., Pålsson, A., Verstege, A., and Rellstab, C.: Stable isotopes in tree rings reveal the role of genetics and phenotypic plasticity in shaping water-use strategies of sessile oak across Europe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14404, https://doi.org/10.5194/egusphere-egu26-14404, 2026.

Non-traditional trace metals are increasingly utilized to evaluate potential microbial processes in the search for evidence of ancient life. Recent investigations of modern terrestrial hot spring silica deposits (sinter), as analogs for early life on Earth or Mars (e.g. Homeplate, Gusev crater), have highlighted unique gallium enrichments associated with silicified microbial filaments and microbially mediated rock textures, such as stromatolites. We used new analytical methodologies for in situ and bulk analysis of gallium isotopes in sinter to better understand the observed Ga enrichment. In situ analysis, by Cameca 1280 ion probe, provides the necessary spatial resolution to target individual microbial filaments with a 10 μm ion beam, but with a lesser precision of ~±3 ‰, compared to the ±0.06 ‰ precision via MC-ICPMS bulk analysis. In situ results indicate heterogeneity of δ⁷¹Ga (>10 ‰ variation overall) with silicified microbial filaments on average isotopically lighter than adjacent silica.  Multiple processes may influence the Ga isotopic ratio in sinter including preferential microbial selection, changes in fluid chemistry, and silicification processes. Ongoing experiments on Ga-Si spiked microbial growth and abiotic silica precipitation may further elucidate the cause of isotopic variability as we continue to refine this in situ isotopic methodology and its utility in planetary biosignature detection.

How to cite: Rowe, M. C., Kunihiro, T., Tanaka, R., Dao, N. V., Ota, T., Campbell, K. A., Ruff, S. W., Nersezova, E. E., Stallard, D., Lyon, B., and Langendam, A.: Gallium isotopes in silicified microbial hot spring deposits: a potential geochemical biosignature, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15347, https://doi.org/10.5194/egusphere-egu26-15347, 2026.

Stable carbon isotope compositions (δ¹³C) in plant materials are an important tool to study variations in the environment that plants live in. δ¹³C in resin has been less explored than in other extensively studied materials, e.g. tree rings, leaves and n-alkanes, with its temporal and spatial variability poorly quantified. Here, we sampled resin from the breast-height stem and leaves at the lower canopy across 80 pine forest plots in Southwestern China (~ 800,000 km²), and examined the climatic signal recorded in δ¹³C in resin and leaves. Our results show a clear humidity signal (e.g. precipitation and aridity index) recorded in resin δ¹³C, much stronger than that preserved in leaf δ¹³C. The climatic signal was strongest when averaged over the previous two growing seasons, suggesting an average turnover time of two years in the stem resin pool. Our results highlight that resin δ¹³C is a promising indicator for spatial variability in climatic signals, so resin can serve as a practical alternative to leaves for δ¹³C-based studies.

How to cite: Tang, Y., Cui, J., Rinne-Garmston, K. T., and Piao, S.: Humidity Signal Recorded in δ¹³C of Pine Resin and Leaves in Southwestern China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15473, https://doi.org/10.5194/egusphere-egu26-15473, 2026.

Carbon isotope ratios of C₃ plants can been used to infer intrinsic water-use efficiency. Several transects have been established across Australia to study the sensitivity of intrinsic-water use efficiency to mean annual precipitation. These investigations showed a surprising divergence in the sensitivity of carbon-isotope discrimination to mean annual precipitation among sub-continental regions. Here, we combine previous observations with measurements along a new transect in northeastern Australia to show that such sub-continental scale sensitivity in the response of intrinsic water-use efficiency to precipitation depends on regional-scale soil phosphorus concentrations. The influence of soil phosphorus appears to operate through modulation of stomatal conductance, rather than, or in addition to, photosynthetic capacity. We hypothesize that Australian woody plant species have evolved to use high transpiration rates to facilitate phosphorus foraging in phosphorus-impoverished, ancient soils. Our analyses suggest that this strategy interacts with the well know strategy of increasing intrinsic water-use efficiency in response to decreasing mean annual precipitation.

How to cite: Cernusak, L., Alam, I., Farquhar, G., Givnish, T., De Kauwe, M., Schulze, E.-D., Westerband, A., Wright, I., and Cheesman, A.: Sub-continental patterns of carbon-isotope discrimination across Australia in relation to precipitation and soil nutrients, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15760, https://doi.org/10.5194/egusphere-egu26-15760, 2026.

Archaeological wood holds value not only as a source of information on how people used to live centuries or millennia ago, it is also a valuable proxy for reconstructing past climatic and environmental changes. When the sample amount available for destructive analytical methods is limited it forces the research team to judiciously prioritize what information to extract and which method to use. When it comes to light stable isotope analyses, the most widely used instrumentation requires rather intensive manual sample preparation and the prepared sample cannot be recuperated after analyses.

The elemental analyzer is currently the go-to sample introduction peripheral for stable isotope analyses of tree rings, but as any analytical method it has its draw-backs and limitations. A key limitation is that each growth ring must be individually separated mechanically and prepared for analysis; this challenge can be managed with sufficient time and manpower. However, very narrow growth rings (<1mm) are a clear limiting factor when each ring needs to be manually removed or when multiple analysis are required for each growth ring. Both issues can easily be circumvented by using a laser ablation (LA) module as sample introduction peripheral. Core segments or wood slices of up to 4.5 cm length can be analyzed in situ (including duplicates and triplicates) without further preparation. For archaeological wood, this method has the added benefits of being minimally invasive, the ablation tracks being practically invisible, and circumventing the need to sacrifice a portion of the artifact for analyses.

Our case study is a fragment of oak wood (Quercus sp.) provided by the National Museum of Denmark. The wood originates from construction timber found during an archaeological excavation of wells located near The Wadden Sea in south-west Denmark. The whole sample contains 199 growth rings and has been dendrochronologically dated to AD 407-605, covering the mid-sixth century where a global climate crisis caused a longer period of cold and wet growth seasons; this is also expressed in archaeological wood by the formation of extremely narrow growth rings. Because of growth ring widths down to 0.49 mm, it is challenging to separate and prepare wood material from each ring for stable isotope analyses using the traditional EA IRMS method.

Our LA IRMS setup comprises the isoScell Δ100 sample chamber (Terra Analitic), LSX 213 G2+ (Teledyne Photon Machines), CryoPrep and HS2022 IRMS (both Sercon). For δ¹³C a spatial resolution of 60μm is easily achievable, with precision on the QC of 0.08 ‰. Mean δ¹³C on the analyzed segment is -24.17 ‰ v. VPDB. The dataset is also in acordance with data from wider rings that could be analyzed via EA IRMS.

How to cite: Ellegaard Larsen, H. M., Stremtan, C. C., Puscas, C. M., and Olsen, J.: In situ δ13C analysis of <1mm thick annual growth rings in archaeological wood samples via LA IRMS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20124, https://doi.org/10.5194/egusphere-egu26-20124, 2026.

Stable isotope approaches are rapidly transforming how we investigate trace-element cycling in living systems, offering information that goes far beyond concentration measurements. Mercury (Hg) stable isotopes, in particular, have proven highly informative across a broad range of environments, and marine studies have highlighted their value for disentangling sources and in vivo processing. Studies on apex marine predators (e.g., seabirds) show that Hg isotopes can track internal processing and trophic transfer. In contrast, selenium (Se) isotopic characterization in biota, more specifically in animals, is still limited and technically challenging, but it opens promising perspectives, especially given Se’s recognized antagonistic role in Hg toxicity.

Key gaps persist in the Brazilian Amazon, where complex Hg (and Se) exposure scenarios call for higher-resolution tracers. Translating Hg and Se isotope approaches to Amazonian freshwater systems, from fish to riverside populations, may clarify bioaccumulation pathways and fate. Recent progress achieved in marine organisms, including compound-specific strategies, will be presented, together with the main analytical challenges and opportunities for extending these approaches to the Amazon.

How to cite: Pedrero Zayas, Z., Marchan Moreno, C., Queipo Abad, S., Neves, G., Barbosa Jr., F., Corns, W., Cherel, Y., Bustamante, P., Amouroux, D., Louvat, P., and Bueno, M.: Mercury and selenium stable isotopes across contrasting food webs: marine insights, amazon priorities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20589, https://doi.org/10.5194/egusphere-egu26-20589, 2026.

Cadmium (Cd) exhibits nutrient-type behaviour in the modern ocean and its isotope system has emerged as a promising tracer of primary productivity and carbon burial. Phytoplankton preferentially assimilate lighter Cd isotopes across a wide range of oceanic conditions, leaving surface waters comparatively enriched in heavier isotopes. This biologically-driven fractionation underlies the application of Cd-isotope ratios as a tracer for nutrient availability and the intensity of primary productivity in both modern marine settings and  palaeo-oceans. However, Cd-isotope systematics are also strongly influenced by redox conditions, specifically through the formation and removal of isotopically light Cd sulphides under euxinic conditions. The extent to which sedimentary Cd-isotope signatures faithfully record overlying water-colum processes under such conditions remains poorly constrained.

Here we present new Cd-isotope data from both the water column and sediments of Framvaren Fjord in Norway, the most intensely reducing modern marine basin. Framvaren Fjord serves as a modern analogue for strongly euxinic marine conditions that prevailed during extreme climate events throughout Earth’s history. Notably, the redoxline separating oxic from anoxic waters is uniquely located within the photic zone, in close proximity to the depth of maximum biological productivity. These data allow us to deconvolve Cd-isotope fractionation associated with biological uptake from that linked to Cd sulphide precipitation, and to shed light on how these processes are transferred to and preserved in the underlying sediment.

How to cite: Gangl, S., Stirling, C., Porcelli, D., Druce, M., and Reid, M.: Cd isotopes under extreme euxinia: Tracing productivity and redox in palaeo-oceans, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20811, https://doi.org/10.5194/egusphere-egu26-20811, 2026.

The increasing demand for reliable food authentication highlights the need for scalable and innovative tools to link geochemical fingerprints in food products with their geographic provenance. Food authentication is not only essential for preventing fraud but also offers a unique opportunity to relate agricultural products to their underlying geochemical signatures. Here we present a unified framework that combines stable isotopes (e.g. ⁸⁷Sr/⁸⁶Sr) and trace-element fingerprints measured in food products with explainable and cost-aware machine learning to support provenance verification.

We first develop a cost-aware binary classification model for French sparkling wines, demonstrating how high-precision ⁸⁷Sr/⁸⁶Sr ratios can be partially substituted by low-cost elemental proxies (e.g. Rb) while maintaining strong discriminative power. To address scalability constraints, we extend this approach to a multiclass setting using cost-sensitive logistic regression to classify wines from multiple Portuguese and Chilean regions, explicitly handling class imbalance and feature redundancy. Finally, we introduce TeaPrint, an unsupervised multimodal clustering framework that jointly integrates isotopic, elemental and volatile organic compound data to uncover coherent regional geochemical patterns in international tea samples without requiring prior labels.

Across these case studies, we show that food products carry integrated geochemical signatures that can be exploited for robust provenance authentication across heterogeneous datasets. By bridging forensic geochemistry and explainable machine learning, our approach offers a cost-efficient and scalable pathway towards robust provenance authentication and transparent food supply chains.

How to cite: Lu, Y., Doerr, C., and Sebilo, M.: From Geochemical Fingerprints to Food Authentication: Integrating Explainable and Cost-Aware Machine Learning for Provenance Analysis , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21380, https://doi.org/10.5194/egusphere-egu26-21380, 2026.

Marine macroalgae are central to coastal carbon cycling and represent a significant portion of global primary production and organic matter export. Giant kelp (Macrocystis pyrifera) forests, in particular, serve as major carbon sinks and influence regional nutrient dynamics. However, the isotopic and biochemical pathways that define these contributions remain poorly constrained. While hydrogen isotope (δ²H) analyses are widely utilised in terrestrial ecology to integrate environmental water signals and metabolic fractionation, their application in marine macroalgae, particularly at the compound-specific level, currently remains underutilised.

Our previous research demonstrated that δ²H values in the soluble sugars of M. pyrifera are highly sensitive to light intensity, which indicates a distinct metabolic imprint tied to photosynthetic carbohydrate supply. We have now expanded this investigation to include lipid biomarkers, specifically focusing on fatty acids (analysed as methyl derivatives) and sterols (analysed as acetate derivatives). Samples were collected across six kelp forest sites in Carmel Bay, California. Preliminary Gas Chromatography-Mass Spectrometry results from three fully processed sites show complex profiles of C12–C26 saturated and unsaturated fatty acids, alongside a range of cholest-, ergost-, and stigmast-based sterols. These molecular distributions vary systematically with site and depth, offering early evidence of biochemical partitioning between photosynthetic and post-photosynthetic pathways under varying natural light regimes.

This presentation will explore new compound-specific δ²H measurements performed on the aforementioned compounds. By doing so, we aim to determine whether δ²H signatures in fatty acids and sterols primarily track photosynthetic fractionation or are shaped by downstream metabolic adjustments. By synthesising isotopic and molecular data, we seek to disentangle external environmental drivers, such as light and water isotopic composition, from intrinsic biochemical controls on compound-specific δ²H values. Refining these relationships is vital for the development of robust δ²H-based paleoenvironmental proxies and for assessing the role of modern and ancient kelp forests as dynamic carbon sinks.

How to cite: Salik, M. A., Cormier, M.-A., Steller, D., Lehmann, M., Al-Sid-Cheikh, M., and Gagnon, P.: Hydrogen Isotope Dynamics in Macrocystis pyrifera: Implications for Compound-Specific Isotope Analyses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21521, https://doi.org/10.5194/egusphere-egu26-21521, 2026.

Isotopic analyses of carbon (δ¹³C) and oxygen (δ¹⁸O) are widely applied in biogeosciences to investigate biogeochemical cycles, ecosystem functioning, and environmental dynamics. Elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) represents one of the most widely applied systems for bulk samples. The laser ablation-IRMS (LA-IRMS) provides the possibility to resolve spatial and temporal variability at high resolution, but also presents some limitations due to gas handling, signal stability, and analytical comparability with conventional approaches.

For this study, we present a methodological comparison between δ¹³C and δ¹⁸O measurements obtained using EA-IRMS and an improved LA-IRMS configuration. In our configuration, the LA is coupled with the IRMS through a greenhouse gas (GHG) analyzer specifically modified to concentrate, purify, and stabilize CO₂ and CO generated during ablation to improve the gas signal for isotope measurements.

Analyses were conducted on hazelnut (Corylus avellana L.) wood slices for EA-IRMS and tree-ring increments for LA-GHG-IRMS. The comparison between the two methods showed main differences related to sampling resolution and analytical configuration. The LA-GHG-IRMS system provided high-resolution isotope measurements that allowed investigations of intra-seasonal patterns.

The application of the LA-GHG-IRMS system extends the analytical utility of laser-based stable isotope measurements in biogeosciences, providing new opportunities for high-resolution studies of ecological processes in terrestrial ecosystems.

How to cite: Tunno, I., Portarena, S., Carlino, P., Stremtan, C., Papale, D., and Calfapietra, C.: Application of EA-IRMS and a LA-GHG-IRMS approach for high-resolution carbon and oxygen isotope analysis in woody biomass, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21817, https://doi.org/10.5194/egusphere-egu26-21817, 2026.

Research on the nitrogen (N) cycle in agricultural ecosystem is key to better understand and manage N nutrition of crops and N losses to the environment. Stable isotope tools have been extensively used to identify and quantify N pathways and processes, but suitable methods typically require sophisticated and expensive instrumentation which is not always available and is rarely suitable for in situ analysis. A quadrupole mass spectrometer (GAM200, InProcess, Bremen) was modified to study ¹⁵N enrichment in N species and N₂ in water and air in the lab and in the field. To establish a membrane inlet mass spectrometer (MIMS) a silicone tubing inlet was added to enable online analysis of dissolved gases. Four applications were established:

• The MIMS was used to analyze N₂ and Ar in groundwater samples to determine excess-N₂ from denitrification. In situ online analysis in the Fuhrberger Feld aquifer was conducted at multilevel groundwater monitoring wells, clearly identifying the steep rise in denitrification upon appearance of sulfides.
• To study N₂ production by denitrification the in situ ¹⁵N push pull method [1] was used, where ¹⁵N labelled NO₃^- solution is injected to groundwater and subsequently samples containing ¹⁵N labelled N₂ are analyzed, in this study by the MIMS. This method was automated and tested in lab mesocosms [2].
• An automated sample preparation unit for inorganic nitrogen (SPIN) was coupled to the MIMS for automated and sensitive determination of the ¹⁵N abundances and concentrations of nitrate, nitrite, and ammonium in aqueous solutions. It was based on the principle of the SPIN-MAS [3] but with the advantage to analyze samples online. It provides a wide dynamic range for all three N species for both isotope abundance and concentration measurements [4, 5]. We propose to use this method in conjunction with online sampling of dissolved N species in soil using dialysis membranes [6] which had not been performed until now to our knowledge.
• The improved ¹⁵N gas flux method to measure N₂ fluxes from soils under N₂ depleted atmosphere has been applied int the field [7] but was complicated by the difficulty to maintain stable background concentrations [8]. A capillary inlet was added to the GAM 200 and used for in situ monitoring of background N₂ concentrations in flux chambers.

We conclude the used quadrupole mass spectrometer has been proven as a versatile, economic and easy to use detector for a wide range of applications in N cycle research and is promising for future applications.

References:

• Well, R. and D.D. Myrold, 1999. doi.org/10.1016/S0038-0717(99)00029-22.
• Eschenbach, W. and R. Well DOI: 10.1002/rcm.5066
• Stange, C.F. et al. ,2007 DOI: Doi 10.1080/10256010701550658
• Eschenbach, W. 2018, DOI: 10.1021/acs.analchem.8b02956
• Eschenbach, W. et al 2017 DOI: 10.1021/acs.analchem.7b00724
• Inselsbacher, E., et al. 2011, doi.org/10.1016/j.soilbio.2011.03.003
• Well, R., et al 2019 doi.org/10.1002/rcm.83638.
• Eckei, J., et al., 2024. DOI: 10.1007/s00374-024-01806-z

How to cite: Dyckmans, J. and Well, R.: Using a quadrupole mass spectrometer as versatile detector to study N transformations and fluxes  in soils and aquatic systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21873, https://doi.org/10.5194/egusphere-egu26-21873, 2026.

Since the robust performance of Long Short-Term Memory (LSTM) networks was established, their physics-awareness and interpretability have become central topics in hydrology. Seminal works (e.g., Lees et al. (2022)) have argued that LSTM internal states spontaneously capture hydrological concepts, and suggested that cell states can represent soil moisture dynamics despite not being explicitly trained on such data. Conversely, more recent studies (e.g., Fuente et al. (2024)) demonstrated that mathematical equifinality causes non-unique LSTM representations with different initialisations.

In this work, we report an arguably more systematic "bug" in the software environment that causes instability in internal states. We initially aimed to investigate how internal states behave differently when trained with or without historical observation data. We encountered this issue while reassembling a computational stack and attempting to replicate the initial results, as the original Docker environment was not preserved. While random seeds have been indicated to lead to different internal state trajectories, we found the computational backend (e.g., changing CUDA versions, PyTorch releases, or dependent libraries) also produces them. These are the findings:

• In gauged catchments: Discharge predictions remained stable (in one catchment, NSE was 0.88 ± 0.01) across computational environments, yet the internal temporal variations (e.g., silhouette, mean, and std of cell states) fluctuated noticeably.
• In pseudo-ungauged scenarios: The prediction performance itself became more reliant on the computational environment (in the same catchment, NSE dropped to 0.31 ± 0.15), yet the internal temporal variations of the cell states fluctuated only as much as they did during the gauged scenario.

These findings suggests that instability in the computational environment poses not only a risk of altering interpretability in training (by altering internal states) but also casts doubt on reliability in extrapolation (by altering outputs).

It is worth mentioning that we confirmed this is not a replicability issue; completely identical cell states and predictions are produced when the computational environment, seeds, and training data are held constant. We argue that such stability must be established as a standard benchmark before assigning physical meaning to deep learning internals.

How to cite: Nagumo, R., Woods, R., and Rico-Ramirez, M.: The Unreliable Narrator: LSTM Internal States Fluctuate with Software Environments Despite Robust Predictions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1897, https://doi.org/10.5194/egusphere-egu26-1897, 2026.

Moments or periods of struggle not only propel scientists forward, but sharing these experiences can also provide valuable lessons for others. Indeed, the current bias towards only publishing ‘positive’ results arguably impedes scientific progress as mistakes that are not learnt from are simply repeated. Here we present a new article type in EGU journals covering LESSONS learnt to help overcome this publishing bias. LESSONS articles describe the Limitations, Errors, Surprises, Shortcomings, and Opportunities for New Science emerging from the scientific process, including non-confirmatory and null results. Unforeseen complications in investigations, plausible methods that failed, and technical issues are also in scope. LESSONS thus fit the content of the BUGS session and can provide an outlet for articles based on session contributions. Importantly, a LESSONS Report will offer a substantial, valuable insight. LESSONS Reports are typically short (1,000-2,000 words) to help lower the barrier to journal publication, whilst LESSONS Posts (not peer-reviewed, but with a DOI on EGUsphere) can be as short as 500 words to allow early-stage reporting. LESSONS aim to destigmatise limitations, errors, surprises and shortcomings and to add these to the published literature as opportunities for new science – we invite you to share your LESSONS learnt.

Finally, a big thank you from this paper’s ‘core’ writing team to the wider group who have helped shape the LESSONS idea since EGU GA in 2025, including PubCom and in particular its Chair Barbara Ervens.

How to cite: Hillier, J., Proske, U., Gaillard, S., Blume, T., and Queiroz Alves, E.: New EGU Manuscript Types: Limitations, Errors, Surprises, and Shortcomings as Opportunities for New Science (LESSONS), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2771, https://doi.org/10.5194/egusphere-egu26-2771, 2026.

Photocatalysis is frequently presented in the literature as a straightforward route toward efficient degradation of pollutants, provided that the “right” material is selected. Layered double hydroxides (LDH) are often highlighted as promising photocatalysts due to their tunable composition and reported activity in dye degradation. Motivated by these claims, this study evaluated LDH as mineral analogs for photocatalytic water treatment, ultimately uncovering a series of unexpected limitations, methodological pitfalls, and productive surprises.

In the first stage, Zn/Cr, Co/Cr, Cu/Cr, and Ni/Cr LDHs were synthesized and tested for photocatalytic degradation of methylene blue (0.02 mM) and Acid Blue Dye 129 (0.3 mM). Contrary to expectations,¹ photocatalytic performance was consistently low. After one hour of irradiation, concentration losses attributable to photocatalysis did not exceed 15%, while most dye removal resulted from adsorption. Despite extensive efforts to optimize synthesis protocols, catalyst composition, and experimental conditions, this discrepancy with previously published studies could not be resolved.

To overcome limitations related to particle dispersion, surface accessibility, and charge-carrier separation, a second strategy was pursued by incorporating clay minerals as supports.² Zn/Cr LDH, identified as the most active composition in preliminary tests, was coprecipitated with kaolinite, halloysite, and montmorillonite. Experiments with methylene blue (0.1 mM) and Acid Blue 129 (0.3 mM) demonstrated enhanced adsorption capacities. However, photocatalytic degradation efficiencies remained poor, typically below 10% after one hour, indicating that apparent performance gains were largely adsorption-driven rather than photochemical.

This failure proved to be a turning point. Instead of abandoning LDH entirely, they were combined with graphitic carbon nitride (GCN) to form a heterostructure.³ This approach resulted in a dramatic improvement: after optimization of the synthesis protocol, 99.5% of 1 ppm estrone was degraded within one hour.⁴ Further modifications were explored by introducing Cu, Fe, and Ag into the LDH/GCN system. While Cu and Fe suppressed photocatalytic activity, silver, at an optimized loading, reduced estrone concentrations below the detection limit within 40 minutes.⁵

This contribution presents a full experimental arc - from promising hypotheses that failed, through misleading adsorption-driven “successes,” to an ultimately effective but non-intuitive solution - highlighting the value of negative results and surprises as drivers of scientific progress.

This research was funded by the AGH University of Krakow, grant number 16.16.140.315.

Literature:

1            N. Baliarsingh, K. M. Parida and G. C. Pradhan, Ind. Eng. Chem. Res., 2014, 53, 3834–3841.

2            A. Í. S. Morais, W. V. Oliveira, V. V. De Oliveira, L. M. C. Honorio, F. P. Araujo, R. D. S. Bezerra, P. B. A. Fechine, B. C. Viana, M. B. Furtini,
              E. C. Silva-Filho and J. A. Osajima, Journal of Environmental Chemical Engineering, 2019, 7, 103431.

3            B. Song, Z. Zeng, G. Zeng, J. Gong, R. Xiao, S. Ye, M. Chen, C. Lai, P. Xu and X. Tang, Advances in Colloid and Interface Science, 2019, 272, 101999.

4            A. Jędras, J. Matusik, E. Dhanaraman, Y.-P. Fu and G. Cempura, Langmuir, 2024, 40, 18163–18175.

5            A. Jędras, J. Matusik, J. Kuncewicz and K. Sobańska, Catal. Sci. Technol., 2025, 15, 6792–6804.

How to cite: Jędras, A. and Matusik, J.: False Starts and Silver Linings: A Photocatalytic Journey with Layered Double Hydroxides, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3077, https://doi.org/10.5194/egusphere-egu26-3077, 2026.

BUGS can arise in individual research projects, but also at the level of communities of researchers, leading to shifts in the scientific consensus.  These community-level BUGS typically arise from observations that are surprising to (or previously overlooked by) substantial fractions of the research community.  In this presentation, we summarize several community-level BUGS in our field: specifically, key surprises that have transformed the hydrological community's understanding of hillslope and catchment processes in recent decades.  

Here are some examples.  (1) Students used to learn (and some still do today) that storm runoff is dominated by overland flow.  But stable isotope tracers have convincingly shown instead that even during storm peaks, streamflow is composed mostly of water that has been stored in the landscape for weeks, months, or years.  (2) Maps, and most hydrological theories, have typically depicted streams as fixed features of the landscape.  But field mapping studies have shown that stream networks are surprisingly dynamic, with up to 80% of stream channels going dry sometime during the year.  (3) Textbooks have traditionally represented catchment storage as a well-mixed box.  But tracer time series show fractal scaling that cannot be generated by well-mixed boxes, forcing a re-think of our conceptualization of subsurface storage and mixing.  (4) Waters stored in aquifers, and the waters that drain from them, have traditionally been assumed to share the same age.  But tracers show that waters draining from aquifers are often much younger than the groundwaters that are left behind, and this was subsequently shown to be an inevitable result of aquifer heterogeneity. 

Several examples like these, and their implications, will be briefly discussed, with an eye to the question: how can we maximize the chances for future instructive surprises?

How to cite: Kirchner, J., Benettin, P., and van Meerveld, I.: Instructive surprises in the hydrological functioning of landscapes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4074, https://doi.org/10.5194/egusphere-egu26-4074, 2026.

Coming from geosciences, we hopefully know what we want to do. Coming from numerics, however, we often know quite well what we are able to do and look for a way to sell it to the community. A few years ago, deep-learning techniques brought new life into the glaciology community. These approaches  allowed for simulations of glacier dynamics at an unprecedented computational performance and motivated several researchers to tackle the numerous open questions about past and present glacier dynamics, particularly in alpine regions. From another point of view, however, it was also tempting to demonstrate that the human brain is still more powerful than artificial intelligence by developing a new classical numerical scheme that can compete with deep-learning techniques concerning its efficiency.

Starting point was, of course, the simplest approximation to the full 3-D Stokes equations, the so-called shallow ice approximation (SIA). Progress was fast and the numerical performance was even better than expected. The new numerical scheme enabled simulations with spatial resolutions of 25 m on a desktop PC, while previous schemes did not reach simulations below a few hundred meters.

However, the enthusiasm pushed the known limitations of the SIA a bit out of sight. Physically, the approximation is quite bad on rugged terrain, particularly in narrow valleys. So the previous computational limitations have been replaced by physical limitations since high resolutions are particularly useful for rugged topographies. In other words, a shabby house has a really good roof now.

What are the options in such a situation?

• Accept that there is no free lunch and avoid contact to the glacialogy community in the future.
• Continue the endless discussion about the reviewers' opinion that a spatial resolution of 1 km is better than 25 m.
• Find a real-world data set that matches the results of the model and helps to talk the problems away.
• Keep the roof and build a new house beneath. Practically, this would be developing a new approximation to the full 3-D Stokes equations that is compatible to the numerical scheme and reaches an accuracy similar to those of the existing approximations.
• Take the roof and put it on one of the existing solid houses. Practically, this would be an extension of the numerical scheme towards more complicated systems of differential equations. Unfortunately, efficient numerical schemes are typically very specific. So the roof will not fit easily and it might leak.

The story is open-ended, but there will be at least a preliminary answer in the presentation.

How to cite: Hergarten, S.: How useful is a new roof on a shabby house? An example from glacier modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4196, https://doi.org/10.5194/egusphere-egu26-4196, 2026.

“Show your working!” – is the universal phrase drilled into science and maths students to show a clear demonstration of the steps and thought processes used to reach a solution (and to be awarded full marks on the exam). 

Beyond the classroom, “show your working” becomes the methods section on every scientific paper, and is critical for the transparency and replicability of the study. However, what happens if parts of the method are considered assumed knowledge, or cut in the interests of a word count? 

An inability to fully replicate the results of a study became the unexpected glitch at the start of my PhD. Eager to familiarise myself with global climate model datasets, I set out to replicate the results of a widely cited paper which calculates the equilibrium climate sensitivity (ECS) across 27 climate models. The ECS is the theoretical global mean temperature response to a doubling of atmospheric CO₂ relative to preindustrial levels. A commonly used method to calculate the ECS is to apply an ordinary least squares regression to global annual mean temperature and radiative flux anomalies. 

Despite the simplicity of a linear regression between two variables, we obtained ECS estimates for some climate models that differed from those reported in the original study, even though we followed the described methodology. However, the methodology provided only limited detail on how the raw climate model output – available at regional and monthly scales – was processed to obtain global annual mean anomalies. Differences in these intermediate processing steps can, in turn, lead to differences in ECS estimates.

Limited reporting of data-processing steps is common in the ECS literature. Whether these steps are considered assumed knowledge or deemed too simple to warrant explicit description, we demonstrate that, for some models, they can materially affect the resulting ECS estimate. While the primary aim of our study is to recommend a standardised data-processing pathway for ECS calculations, a secondary aim is to highlight the lack of transparency in key methodological details across the literature. A central takeaway is the importance of clearly documenting all processing steps – effectively, to “show your working” – and to emphasise the critical role of a detailed methods section.

How to cite: Zehrung, A., King, A., Nicholls, Z., Zelinka, M., and Meinshausen, M.: The importance of describing simple methods in climate sensitivity literature, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4587, https://doi.org/10.5194/egusphere-egu26-4587, 2026.

Observation of atmospheric constituents and processes is not easy. As atmospheric chemists, we use sensitive equipment, for example mass spectrometers, that we often set up in a (remote) location or on a moving platform for a few-weeks campaign to make in-situ observations. All this with the goal of explaining more and more atmospheric processes, and to verify and improve atmospheric models. However, glitches can happen anywhere in an experiment, be it in the experimental design, setup, or instrumental performance. Thus, complete data coverage during such a campaign is not always a given, resulting in gaps in (published) datasets. And the issue with air is that you can never go back and measure the exact same air again. Here, I would like to share some stories behind such gaps, and what we learned from them. This presentation aims to encourage early career researchers who might be struggling with feelings of failure when bugs, blunders and glitches happen in their experiments - you are not alone! I will share what we learned from these setbacks and how each of them improved our experimental approaches.

How to cite: Pfannerstill, E. Y.: Why are there gaps in your measurements? Sharing the stories behind the missing datapoints, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5494, https://doi.org/10.5194/egusphere-egu26-5494, 2026.

Over a 24-year research period, three successive experimental investigations led to three publications, each of which falsified the author’s preceding hypothesis and proposed a revised conceptual framework. Despite an initial confidence in having identified definitive solutions, subsequent experimental evidence consistently demonstrated the limitations and inaccuracies of earlier interpretations. This iterative process ultimately revealed that samples, in particular geological reference materials, sharing identical petrographic or mineralogical descriptions are not necessarily chemically equivalent and can exhibit markedly different behaviors during chemical digestion procedures. These findings underscore the critical importance of continuous hypothesis testing, self-falsification, and experimental verification in scientific research, particularly when working with reference materials assumed to be identical. I will be presenting data on the analysis of platinum group elements (PGE) and osmium isotopes in geological reference materials (chromitites, ultramafic rocks and basalts), which demonstrates the need for challenging matrices for method validation. 

How to cite: Meisel, T. C.: Self-falsification as a driver of scientific progress: Insights from long-term experimental research, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5771, https://doi.org/10.5194/egusphere-egu26-5771, 2026.

In atmospheric sciences, a central tool to test hypotheses are numerical models, which aim to represent (part of) our environment. One such model is the weather and climate model ICON [1], which solves the Navier-Stokes equation for capturing the dynamics and parameterizes subgrid-scale processes, such as radiation, cloud microphysics, and aerosol processes. Specifically, for the latter exists the so-called Hamburg Aerosol Module (HAM [2]), which is coupled to ICON [3] and predicts the evolution of aerosol populations using two moments (mass mixing ratio and number concentration). The high complexity of aerosols is reflected in the number of aerosol species (total of 5), number of modes (total of 4), and their mixing state and solubility. The module calculates aerosol composition and number concentration, their optical properties, their sources and sinks, and their interactions with clouds via microphysical processes. Aerosol emissions are sector-specific and based on global emission inventories or dynamically computed.

Within our work, we stumbled upon an interesting pattern occurrence in our simulations upon changing/turning off single emission sectors. If we, e.g., removed black carbon from aircraft emissions, the strongest changes emerged over the African continent, which is not the region where we were expecting to see the strongest response. Further investigations revealed that this pattern emerges independently of the emission sector as well as species, confirming our suspicion that we are facing a bug within HAM. Here, we want to present how we approached the challenge of identifying and tackling a bug within a complex module with several thousand lines of code.

[1] G. Zängl, D. Reinert, P. Ripodas, and M. Baldauf, “The ICON (ICOsahedral Non-hydrostatic) modelling framework of DWD and MPI-M: Description of the non-hydrostatic dynamical core,” Quarterly Journal of the Royal Meteorological Society, vol. 141, no. 687, pp. 563–579, 2015, ISSN: 1477-870X. DOI: 10.1002/qj.2378

[2] P. Stier, J. Feichter, S. Kinne, S. Kloster, E. Vignati, J. Wilson, L. Ganzeveld, I. Tegen, M. Werner, Y. Balkanski, M. Schulz, O. Boucher, A. Minikin, and A. Petzold, “The aerosol-climate model ECHAM5-HAM,” Atmospheric Chemistry and Physics, 2005. DOI: 10.5194/acp-5-1125-2005

[3] M. Salzmann, S. Ferrachat, C. Tully, S. M¨ unch, D. Watson-Parris, D. Neubauer, C. Siegenthaler-Le Drian, S. Rast, B. Heinold, T. Crueger, R. Brokopf, J. Mülmenstädt, J. Quaas, H. Wan, K. Zhang, U. Lohmann, P. Stier, and I. Tegen, “The Global Atmosphere-aerosol Model ICON-A-HAM2.3–Initial Model Evaluation and Effects of Radiation Balance Tuning on Aerosol Optical Thickness,” Journal of Advances in Modeling Earth Systems, vol. 14, no. 4,e2021MS002699, 2022, ISSN: 1942-2466. DOI: 10.1029/2021MS002699

How to cite: Omanovic, N., Ferrachat, S., and Lohmann, U.: Back to square one (again and again): Finding a bug in a complex global atmospheric model  , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6794, https://doi.org/10.5194/egusphere-egu26-6794, 2026.

In situ cloud measurements are essential for understanding atmospheric processes and establishing a reliable ground truth. Obtaining these data is rarely straightforward. Challenges range from accessing clouds in the first place to ensuring that the instrument or environment does not bias the sample. This contribution explores several blunders and unexpected glitches encountered over fifteen years of field campaigns.

I will share stories of mountain top observations where blowing snow was measured instead of cloud ice crystals and the ambitious but failed attempt to use motorized paragliders for sampling. I also reflect on winter campaigns where the primary obstacles were flooding and mud rather than cold and snow. While these experiences were often frustrating, they frequently yielded useful data or led to new insights. One such example is the realization that drone icing is not just a crash risk but can also serve as a method for measuring liquid water content. By highlighting these setbacks and the successful data that emerged despite them, I aim to foster a discussion on the value of trial and error and persistence in atmospheric physics.

How to cite: Henneberger, J.: How Not to Measure a Cloud: Lessons from Fifteen Years of Fieldwork Failures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8228, https://doi.org/10.5194/egusphere-egu26-8228, 2026.

Forests are powerful climate regulators: Their CO₂ uptake provides a global biogeochemical cooling effect, and in the tropics, this cooling is further strengthened by evapotranspiration. Given that temperature-related mortality is a relevant global health burden, which is expected to increase under climate change, we set out to test what we thought was a promising hypothesis: Can forests reduce human temperature-related mortality from climate change? 

To test this, we used simulated temperature changes to reforestation from six different Earth System Models (ESMs) under a future high-emission scenario, and paired them with age-specific population data and three methodologically different temperature-mortality frameworks (Cromar et al. 2022, Lee et al. 2019, and Carleton et al. 2022). We expected to find a plausible range of temperature-related mortality outcomes attributable to global future forests conservation efforts.

Instead, our idea ran head-first into a messy reality. Firstly, rather than showing a clear consensus, the ESMs produced a wide range of temperature responses to reforestation, varying both in magnitude and sign. This is likely due to the albedo effect, varying climatological tree cover and land use processes implemented by the models, in addition to internal variability which we could not reduce due to the existence of only one ensemble member per model. Consequently, the models disagreed in many regions on whether global forest conservation and reforestation would increase or decrease temperature by the end of the century.

The uncertainties deepened when we incorporated the mortality data. Mortality estimates varied by up to a factor of 10 depending on the ESM and mortality framework used. Therefore, in the end, the models could not even agree on whether forests increased or decreased temperature-related mortality. We found ourselves with a pipeline that amplified uncertainties of both the ESM and mortality datasets.

For now, the question remains wide open: Do trees save us from temperature-related deaths in a warming world, and if so, by how much?

* The first two authors contributed equally to this work.

How to cite: Hohmuth, N., Fahrenbach (presenting), N. L. S., Zou (presenting), Y., Reek, J., Specker, F., Crowther, T., and Zohner, C. M.: Do trees save lives under climate change? It’s complicated , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8359, https://doi.org/10.5194/egusphere-egu26-8359, 2026.

Hydrological modelling has long been shaped by a steady drive toward ever more sophisticated models. In the era of machine learning, this race has turned into a relentless pursuit of complexity: deeper networks and ever more elaborate architectures that often feel outdated by the time the ink on the paper is dry. Motivated by a genuine belief in methodological progress, I, like many others, spent considerable effort exploring this direction, driven by the assumption that finding the “right” architecture or model would inevitably lead to better performance. This talk is a reflection on that journey; you could say my own Leidensweg. Over several years, together with excellent collaborators, I explored a wide range of state-of-the-art deep-learning approaches for rainfall–runoff modelling and other hydrological modelling challenges. Yet, regardless of the architecture or training strategy, I repeatedly encountered the same performance ceiling. In parallel, the literature appeared to tell a different story, with “new” models regularly claiming improvements over established baselines. A closer inspection, however, revealed that rigorous and standardized benchmarking is far from common practice in hydrology, making it difficult to disentangle genuine progress from artefacts of experimental design. What initially felt like a failure to improve my models turned out to be a confrontation with reality. The limiting factor was not the architecture, but the problem itself. We have reached a point where predictive skill is increasingly bounded by the information content of our benchmark datasets and maybe more importantly by the way we frame our modelling challenges, rather than by model design. Like many others, I have come to believe that if we want to move beyond the current performance plateau, the next breakthroughs are unlikely to come from ever more complex models alone. Instead, as a community, we need well-designed model challenges, better benchmarks, and datasets that meaningfully expand the information available to our models to make model comparisons more informative.

How to cite: Loritz, R., Dolich, A., and Heudorfer, B.: The empty mine: Why better tools do not help you find new diamonds, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10401, https://doi.org/10.5194/egusphere-egu26-10401, 2026.

Examining catchment response to precipitation at event scale is useful for understanding how various hydrological systems store and release water. Many of such event scale characteristics, for example event runoff coefficient and event time scale are also important engineering metrics used for design. However, deriving these characteristics requires identification of discrete precipitation-streamflow events from continuous hydrometeorological time series.

Event identification is not at all a trivial task. It becomes even more challenging when working with very large datasets that encompass a wide range of spatial and temporal dynamics. Approaches range from visual expert judgement to baseflow-separation-based methods and objective methods based on the coupled dynamics of precipitation and streamflow. Here, we would like to present our experience in the quest to devise the “ideal” method for large datasets – and trust us, we tried, a lot. We demonstrate that expert-based methods can be seriously flawed simply by changing a few meta parameters, such as the length of displayed periods, baseflow-separation-based methods deliver completely opposite results when different underlying separation methods are selected, and objective methods suddenly fail when dynamics with different temporal scales are simultaneously present.

Ultimately, we realized that finding a one-size-fits-all method was not possible and that compromises had to be made to select sufficiently representative events across large datasets. Therefore, we advocate for pragmatic case-specific evaluation criteria and for transparency in event identification to make study results reproducible and fit for purpose, if not perfect.

How to cite: Tarasova, L. and Astagneau, P.: How NOT to identify streamflow events?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13630, https://doi.org/10.5194/egusphere-egu26-13630, 2026.

A defining attribute of global-storm resolving models is that modelling is replaced by simulation.  In addition to overloading the word “model”  this avails the developer of a much larger variety of tests, and brings about a richer interplay with their intuition.  This has proven helpful in identifying and correcting many mistakes in global-storm resolving models that traditional climate models find difficult to identify, and usually compensate by “tuning.”  It also means that storm-resolving models are built and tested in a fundamentally different way than are traditional climate models. In this talk I will review the development of ICON as a global storm resolving model to illustrate how this feature, of trying to simulate rather than model the climate system, has helped identify a large number of long-standing bugs in code bases inherited from traditional models; how this can support open development; and how sometimes these advantages also prove to be buggy.

How to cite: Stevens, B., Giorgetta, M., and Segura, H.: Buggy benefits of more fundamental climate models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14148, https://doi.org/10.5194/egusphere-egu26-14148, 2026.

Hydrological and water systems modelling has long been driven by the search for better models. We do so by searching for models or at least parameter combinations that provide the best fit to given observations. We ourselves have contributed to this effort by developing new methods and by publishing diverse case studies. However, we repeatedly find that searching for and finding an optimal model is highly fraught in the presence of unclear signal-to-noise ratios in our observations, of incomplete models and of highly imbalanced databases. We present examples of our own work through which we have realized that achieving optimality was possible but futile unless we give equal consideration to issues of consistency, robustness and problem framing. We argue here that the strong focus on optimality continues to be a hindrance for advancing hydrologic science and for transferring research achievements into practice – probably more so than in other areas of the geosciences.

How to cite: Wagener, T. and Pianosi, F.: The dangerous temptation of optimality in hydrological and water resources modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14374, https://doi.org/10.5194/egusphere-egu26-14374, 2026.

Among soil physical analyses, determination of the soil particle-size distribution (PSD) is arguably the most fundamental. The standard methodology combines sieve analysis for sand fractions with sedimentation-based techniques for silt and clay. Established sedimentation methods include the pipette and hydrometer techniques. More recently, the Integral Suspension Pressure (ISP) method has become available, which derives PSD by inverse modeling of the temporal evolution of suspension pressure measured at a fixed depth in a sedimentation cylinder. Since ISP is based on the same physical principles as the pipette and hydrometer methods, their results should, in principle, agree.

The ISP methodology has been implemented in the commercial instrument PARIO (METER Group, Munich). While elegant, the method relies on pressure change measurements with a resolution of 0.1 Pa (equivalent to 0.01 mm of water column). Consequently, the PARIO manual strongly advises avoiding any mechanical disturbance such as thumping, bumping, clapping, vibration, or other shock events. This warning is essentially precautionary, because to date no systematic experimental investigation of such disturbances has been reported.

To explore this issue, we prepared a single 30 g soil sample following standard PSD procedures and subjected it to 26 PARIO repeated measurement runs over a period of five months, each run lasting 12 h. Between runs, the suspension was remixed but otherwise not altered. The first ten runs (over ten days) were conducted without intentional disturbance to establish baseline repeatability. This was followed by eight runs with deliberately imposed and timed disturbances that generated single or repeated vibrations (“rocking and shocking”). After approximately two and five months, we conducted additional sets of five and three undisturbed runs, respectively.

We report how these mechanical disturbances, along with temperature variations during measurement and the time elapsed since sample pre-treatment, affected the derived PSD. The results provide a first quantitative assessment of how fragile—or robust—the ISP method and PARIO system really are when reality refuses to sit perfectly still.

How to cite: Nemes, A. and Durner, W.: Rocking and Shocking the PARIOTM: How Sensitive Is ISP-Based Particle-Size Analysis to Mechanical Disturbance?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14763, https://doi.org/10.5194/egusphere-egu26-14763, 2026.

Predicting soil hydraulic behavior is necessary for the modeling of catchments and agricultural planning, particularly for a country like Norway where only 3% of land is suitable for farming. Soil texture is an important and easily accessible parameter for the prediction of soil hydraulic behavior. However, some Norwegian farmland soils, which formed as glacio-marine sediments and are characterized by a medium texture, have shown the hydraulic behavior of heavy textured soils. Coined by the theory behind well-established sedimentation-enhancing technology used in waste water treatment, we hypothesized that sedimentation under marine conditions may result in specific particle sorting and as a result specific pore system characteristics. To test this, we designed four custom-built devices to produce artificially re-sedimented columns of soil material to help characterize the influence of sedimentation conditions. We successfully produced column samples of the same homogeneous mixture of fine-sand, silt, and clay particles obtained by physically crushing and sieving (< 200 µm) subsoil material collected at the Skuterud catchment in South-East Norway, differing only in sedimentation conditions (deionized water vs 35 g per liter NaCl solution). Then, the inability of standard laboratory methods to measure the saturated hydraulic conductivity of such fine material, led us to “MacGyver” (design and custom-build) two alternative methodologies to measure that property, i.e. i) by adapting a pressure plate extractor for a constant head measurement and ii) by building a 10 m tall pipe-system in a common open area of the office, in order to increase the hydraulic head on the samples. There was a learning curve with both of those methods, but we have found that the salt-water re-sedimented columns were about five times more permeable than the freshwater ones, which was the complete opposite of our expectations. However, an unexpected blunder in the conservation of our samples suggests that our hypothesis should be further explored rather than dismissed. These contributions hint about the mechanisms that may underlie the anomalous hydraulic behaviour of certain Norwegian soils and raise new questions on the formation of marine clays, improving knowledge available for land managers and modellers.

How to cite: Nemes, A., Bazzocchi, P., Weiland, S., and van der Ploeg, M.: Some Norwegian soils behave differently: is it an inheritance from marine sedimentation?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14852, https://doi.org/10.5194/egusphere-egu26-14852, 2026.

“It is in the tentative stage that the affections enter with their blinding influence. Love was long since represented as blind…The moment one has offered an original explanation for a phenomenon which seems satisfactory, that moment affection for his intellectual child springs into existence…To guard against this, the method of multiple working hypotheses is urged. … The effort is to bring up into view every rational explanation of new phenomena, and to develop every tenable hypothesis respecting their cause and history. The investigator thus becomes the parent of a family of hypothesis: and, by his parental relation to all, he is forbidden to fasten his affections unduly upon any one” (Chamberlin, 1890).

The MADE (macro-dispersion) natural-gradient tracer field experiments were conducted more than 35 years ago. It aimed to determine field-scale dispersion parameters based on detailed hydraulic conductivity measurements to support transport simulation. A decade of field experiments produced a 30-year paper trail of modelling studies with no clear resolution of a successful simulation approach for practical use in transport problems.  As a result, accurately simulating contaminant transport in the subsurface remains a formidable challenge in hydrogeology.

What went awry, and why do we often miss the mark?

Herweijer et al. (2026) conducted a ‘back to basics’ review of the original MADE reports and concluded that there are significant inconvenient and unexplored issues that influenced the migration of the tracer plume and or biased observations. These issues include unreliable measurement of hydraulic conductivity, biased tracer concentrations, and underestimation of sedimentological heterogeneity and non-stationarity of the flow field. Many studies simulating the tracer plumes appeared to have ignored, sidestepped, or been unaware of these issues, raising doubts about the validity of the results.

Our analysis shows that there is a persistent drive among researchers to conceptually oversimplify natural complexity to enable testing of single-method modelling, mostly driven by parametric stochastic approaches. Researchers tend to be anchored to a specialised, numerically driven methodology and have difficulty in unearthing highly relevant information from ‘unknown known’ data or applying approaches outside their own specialised scientific sub-discipline. Another important aspect of these ‘unkowns knowns’ is the tendency to accept published data verbatim. Too often, there is no rigorous investigation of the original measurement methods and reporting, and, if need be, additional testing to examine the root cause of data issues.

Following the good old advice of Chamberlin (1890), we used a knowledge framework to systematically assess knowns, unknowns, and associated confidence levels, yielding a set of multi-conceptual models. Based on identified 'unknowns', these multi-models can be tested against reliable 'knowns' such as piezometric data and mass balance calculations.  

Chamberlin, T.C., 1890, The method of multiple working hypotheses. Science 15(366): 92-96. doi:10.1126/science.ns-15.366.92.

Herweijer J.C., S. C Young, P. Hayes, and O. Batelaan, 2026, A multi-conceptual model approach to untangling the MADE experiment, Accepted for Publication in Groundwater.

How to cite: Batelaan, O., Herweijer, J., Young, S., and Hayes, P.: The unknown knowns – the inconvenient knowledge in hydrogeology we do not like to use, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16619, https://doi.org/10.5194/egusphere-egu26-16619, 2026.

Free-slip boundary conditions are routinely used in 3D geodynamic modelling because they reduce computational cost, avoid artificial shear zones at domain edges, and simplify the implementation of large-scale kinematic forcing. However, despite their apparent neutrality, our experiments show that free-slip boundaries systematically generate first-order artefacts that propagate deep into the model interior and can severely distort the interpretation of continental rifting simulations.

Here we present a set of 3D visco-plastic models inspired by the South China Sea (SCS) that were originally designed to study the effect of steady-state thermal inheritance and pluton-controlled crustal weakening. Unexpectedly, in all simulations except those with a very particular inverted rheological profile (POLC), the free-slip boundary on the “Vietnam side” of the domain generated a persistent secondary propagator, producing unrealistic amounts of lithospheric thinning in the southwest corner. This artefact appeared irrespective of crustal rheology, seeding strategy, or the presence of thermal heterogeneities.

We identify three systematic behaviours induced by free-slip boundaries in 3D:
(1) forced rift nucleation at boundary-adjacent thermal gradients,
(2) artificial propagator formation that competes with the intended first-order rifting, and
(3) rotation or shearing of micro-blocks not predicted by tectonic reconstructions.

These artefacts originate from the inability of free-slip boundaries to transmit shear traction, which artificially channels deformation parallel to the boundary when lateral thermal or mechanical contrasts exist. In 3D, unlike in 2D, the combination of oblique extension and boundary-parallel velocity freedom leads to emergent pseudo-transform behaviour that is entirely numerical.

Our results highlight a key negative outcome: free-slip boundaries cannot be assumed neutral in 3D rift models, especially when studying localisation, obliquity, multi-propagator dynamics, or the competition between structural and thermal inheritance. We argue that many published 3D rift models may unknowingly include such artefacts.

How to cite: Le Pourhiet, L.: The Hidden Propagator: How Free-Slip Boundaries Corrupt 3D Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17373, https://doi.org/10.5194/egusphere-egu26-17373, 2026.

How to cite: Williamson, E., Pritchard, M., Iwi, A., Pepler, S., and Parton, G.: Data Disaster to Data Resilience: Lessons from CEDA’s Data Recovery , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18600, https://doi.org/10.5194/egusphere-egu26-18600, 2026.

Aerosol-cloud interactions remain one of the largest uncertainties in global climate modelling. This uncertainty arises because of the dependence of aerosol-cloud interactions on many tightly coupled atmospheric processes; the non-linear response of clouds to aerosol perturbations across different regimes; and the challenge of extracting robust signals from noisy meteorological observations. The problem is particularly acute in the Arctic, where sparse observational coverage limits model constraints, pristine conditions can lead to unexpected behaviour, and key processes remain poorly understood.

A common way to tackle the challenge of uncertainties arising from aerosol-cloud interactions in climate simulations is to conduct sensitivity experiments using cloud and aerosol microphysics schemes based on different assumptions and parameterisations. By comparing these experiments, key results can be constrained by sampling the range of unavoidable structural uncertainties in the models. Here, we apply this approach to a case study of an extreme, polluted warm air mass in the Arctic that was measured during the MOSAiC Arctic expedition in 2020. We simulated the event in the WRF-Chem-Polar regional climate model both with and without the anthropogenic aerosols from the strong pollution event to study the response of clouds and surface radiative balance. To understand the sensitivity of our results to the choice of model configuration, we tested two distinct, widely-used cloud microphysics schemes.

Initial results showed that the two schemes simulated opposite cloud responses: one predicted a surface cooling from the pollution that was reasonably in line with our expectations of the event, while the other predicted the opposite behaviour in the cloud response and an associated surface warming. These opposing effects seemed to suggest that structural uncertainties in the two schemes relating to clean, Arctic conditions was so strong that it even obscured our ability to understand the overall sign of the surface radiative response to the pollution.

However, since significant model development was required to couple these two cloud microphysics schemes to the aerosol fields in our model, there was another explanation that we couldn’t rule out: a bug in the scheme that was producing the more unexpected results. In this talk, we will explore the challenges of simulating the Arctic climate with a state-of-the-art chemistry-climate model and highlight how examples like this underscore the value of our recent efforts to align our collaborative model development with software engineering principles and Open Science best practices.

How to cite: Lapere, R., Price, R., Marelle, L., Bastien, L., and Thomas, J.: Opposite cloud responses to extreme Arctic pollution: sensitivity to cloud microphysics, or a bug?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19755, https://doi.org/10.5194/egusphere-egu26-19755, 2026.

All statistical tools come with assumptions. Yet many scientists treat statistics like a collection of black-box methods without learning the assumptions. Here I illustrate this problem using dozens of studies that claim to show that solar variability is a dominant driver of climate. I find that linear regression approaches are widely misused among these studies. In particular, they often violate the assumption of ‘no autocorrelation’ of the time series used, though it is common for studies to violate several or all of the assumptions of linear regression. The misuse of statistical tools has been a common problem across all fields of science for decades. This presentation serves as an important cautionary tale for the Earth Sciences and highlights the need for better statistical education and for statistical software that automatically checks input data for assumptions.

How to cite: Steiger, N.: Pervasive violation of statistical assumptions in studies linking solar variability to climate, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19776, https://doi.org/10.5194/egusphere-egu26-19776, 2026.

A key reason for the widespread use of peat-based growth media in horticulture is their reliable nutrient availability when supplemented with fertilisers. However, due to environmental concerns over continued peat-extraction and use, peat-alternatives (e.g., coir, wood fibre, composted bark, biochar) are increasingly being used commercially. These alternative media often blend multiple materials, making it crucial to understand elemental composition and nutrient interactions between components. This study evaluates whether benchtop Energy Dispersive X-ray Fluorescence (EDXRF) can provide a rapid method for determining the elemental composition of peat-alternative components.

Representative growing media components (peat, coir, wood fibre, composted bark, biochar, horticultural lime, perlite, slow-release fertilisers, and trace-element fertiliser) were blended in different ratios to generate industry-representative mixes. Individual components and prepared mixes were dried and milled to ≤80 μm. An industry-representative mix (QC-50: 50% peat, 30% wood fibre, 10% composted bark, 10% coir, with fertiliser and lime additions) and 100% peat were analysed by EDXRF (Rigaku NEX-CG) for P, K, Mg, Ca, S, Fe, Mn, Zn, Cu and Mo, and compared against ICP-OES reference measurements. The instrument’s fundamental parameters (FP) method using a plant-based organic materials library showed large discrepancies relative to ICP-OES (relative differences: 268–390 084%) for most elements in both QC-50 and peat, with the exception of Ca in QC-50 (11%). These results confirm that the FP approach combined with loose-powder preparation is unsuitable for accurate elemental analysis of organic growing media.

An empirical calibration was subsequently developed using 18 matrix-matched standards (CRMs, in-house growing media and individual component standards). Matrix matching is challenging because mixes are mostly organic by volume, yet variable inorganic amendments (e.g., lime, fertilisers, and sometimes perlite) can strongly influence XRF absorption/enhancement effects. Calibration performance was optimised iteratively using QC-50 as the validation sample, until relative differences were <15% for all elements. When applied to 100% peat, agreement with ICP-OES results improved substantially for some macro-elements (e.g. Mg 10%, Ca 1%, S 19%) but remained poor for most trace elements (28–96%), demonstrating limited transferability of this calibration method across different elements and matrices tested.

Overall, these results demonstrate that loose powder preparation does not provide sufficiently robust accuracy for EDXRF analysis of organic growing media even with meticulous empirical matrix-matched calibration. We are therefore developing a pressed pellet method using a low-cost wax binder to improve sample homogeneity (packing density) and calibration transferability. Twenty unknown mixes will be analysed using both loose powder and pressed-pellet calibrations, and agreement with reference data (ICP-OES) will confirm method validation, supporting the development of EDXRF as a novel approach for growing media analysis.

How to cite: De Silva, T., Tupaz, C., Croffie, M., Daly, K., Gaffney, M., Stock, M., and Corbett, E.: Developing Matrix-Matched Empirical Calibrations for EDXRF Analysis of Peat-Alternative Growth Media, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20122, https://doi.org/10.5194/egusphere-egu26-20122, 2026.

In catchment hydrology, long-term data collection often starts as part of a (doctoral) research project. In some cases, the data collection continues on a limited budget, often using the field protocol and data management plan designed for the initial short-term project. Challenges and issues with the continued data collection are likely to arise, especially when there are multiple changes in the people involved. It is especially difficult for researchers who were not directly involved in the fieldwork to understand the data and must therefore rely on field notes and archived data. They then often encounter issues related to inconsistent metadata, such as inconsistent date-time formats and inconsistent or missing units, missing calibration files, and unclear file and processing script organization.

While the specific issues may sound very case-dependent, based on our own and other’s experiences from various research projects, it appears that many issues recur more frequently than one might expect (or be willing to admit). In this presentation, we will share our experiences with bringing spatially distributed groundwater level data collected in Sweden and Switzerland from the field to ready-to-use files. Additionally, we provide recommendations for overcoming the challenges during field data collection, data organization, documentation, and data processing using scripts. These include having a clear, detailed protocol for in the fieldwork and the data processing steps, and ensuring it is followed. Although protocols are often used, they are frequently not detailed enough or are not used as designed. The protocols might also not take into account the further use of the data, such as for hydrological modelling, beyond field collection. 

How to cite: Bremer, K., Staudinger, M., Seibert, J., and van Meerveld, I.: From Field to File: challenges and recommendations for handling hydrological data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20375, https://doi.org/10.5194/egusphere-egu26-20375, 2026.

In 2014 we developed the Wageningen Lowland Runoff Simulator (WALRUS), a conceptual rainfall-runoff model for catchments with shallow groundwater. Water managers and consultants were involved in model development. In addition, they sponsored the steps necessary for application: making an R package, user manual and tutorial, publishing these on GitHub and organising user days. WALRUS is now used operationally by several Dutch water authorities and for scientific studies in the Netherlands and abroad. When developing the model, we made certain design choices. Now, after twelve years of application in water management, science and education, we re-evaluate the consequences of those choices.

The lessons can be divided into things we learned about the model’s functioning and things we learned from how people use the model. Concerning the model’s functioning, we found that keeping the model representation close to reality has advantages and disadvantages. It makes it easy to understand what happens and why, but it also causes unrealistic expectations. Certain physically based relations hampered model performance because they contained thresholds, and deriving parameter values from field observations resulted in uncertainty and discussions about spatial representativeness.

Concerning the practical use, we found that the easy-to-use, open source R package with manual was indispensable for new users. Nearly all users preferred default options over the implemented user-defined functions to allow tailor-made solutions. Parameter calibration was more difficult than expected because the feedbacks necessary to simulate the hydrological processes in lowlands increase the risk of equifinality. In addition, lack of suitable discharge data for calibration prompted the request for default parameter values. Finally, the model was subject to unintended model use, sometimes violating basic assumptions and sometimes showing unique opportunities we had not thought of ourselves.

C.C. Brauer, A.J. Teuling, P.J.J.F. Torfs, R. Uijlenhoet (2014): The Wageningen Lowland Runoff Simulator (WALRUS): a lumped rainfall-runoff model for catchments with shallow groundwater, Geosci. Model Dev., 7, 2313-2332, doi:10.5194/gmd-7-2313-2014

How to cite: Brauer, C.: Re-evaluating the WALRUS rainfall-runoff model design after twelve years of application, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21915, https://doi.org/10.5194/egusphere-egu26-21915, 2026.

The serpentinite quarry at Jordanów Śląski is known for the first documented occurrence of nephrite in Europe (Traube, 1885). The quarry operated until the early 1980s and remained inactive for almost 40 years. Small-scale serpentine extraction started again in 2022. Recently, mining activity has increased, exposing a 20-25 m wide zone of leucocratic rocks, approximately 100 m long and 20-30 m deep. This zone most likely consists of tectonically assembled fragments of serpentinite, calc-silicate rocks, and leucogranite with pegmatite veins and nests, as well as common aplites. The discovery of scattered Sc-bearing mineralization at the contacts between granitic pegmatite and serpentinite (Sc-bearing actinolite, Sc-bearing diopside, jervisite, cascandite, scandio-winchite, heflikite, dubińskite, bazzite, kristiansenite, kolbeckite) has made this quarry one of the most important occurrences of scandium minerals in the world and the only one associated with a supra-subduction zone (Pieczka et al., 2024a-c).

This mineralization is accompanied by numerous minerals from the epidote supergroup (1) scattered throughout the pegmatite itself [clinozoisite, allanite-(Ce), allanite-(Nd), allanite-(Sm), allanite-(Y), Cr-bearing allanite-(Ce)], (2) at contacts with blackwall schists [Sc-bearing clinozoisite, Sc-bearing allanite-(Ce), heflikite], (3) at contacts with diopside-bearing rocks [allanite-(Ce), allanite-(La), dissakisite-(Ce)], (4) in zoisite-bearing calc-silicate rock [Cr-bearing clinozoisite and Cr-bearing epidote], and (5) in metasomatic and hydrothermal zones in serpentinite and altered actinolite-diopside-bearing metasomatites [Cr-bearing clinozoisite]. All minerals from the epidote supergroup associated with the pegmatite, except for allanite-(Ce) and clinozoisite, occur in fine grains not exceeding 100 μm and are enriched in lanthanides. On the other hand, minerals associated with zoisite-bearing calc-silicate rock and altered actinolite-diopside-bearing metasomatites form large crystals, reaching 2-3 cm in length, as well as string-like aggregates; they are completely devoid of lanthanides, usually found with relict chromite + Cr-bearing grossular or Al-bearing uvarovite.

The chemical compositions of pegmatite epidotes were influenced by the local compositions of the hydrated pegmatite-forming melt; those enriched in Sc and Cr could crystallize under the influence of  Sc- and Cr-bearing fluids, which were released during the rodingitization processes of the Ślęża ophiolite lithologies. Their enrichment in lanthanides may be related to the interactions of these fluids with pegmatite lithologies at their marginal parts and fractures.

References:

Traube, H. (1885) Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Beilage-Band, 2, 91–94.

Pieczka, A., Stachowicz, M., Zelek-Pogudz, S., Gołębiowska, B., Sęk, M., Nejbert, K., Kotowski, J., Marciniak-Maliszewska, B., Szuszkiewicz, A., Szełęg, E., Stadnicka, K.M., and Woźniak, K. (2024a) American Mineralogist 109, 174–183.

Pieczka, A., Kristiansen, R., Stachowicz, M., Dumańska-Słowik, M., Gołębiowska, B., Sęk, M., Nejbert, K., Kotowski, J., Marciniak-Maliszewska, B., Szuszkiewicz, A., Szełęg, E., and Woźniak, K. (2024b) Mineralogical Magazine 88, 228–243.

Pieczka, A., Stachowicz, M., Zelek-Pogudz, S., Gołębiowska, B., Sęk, M., Nejbert, K., Kotowski, J., Marciniak-Maliszewska, B., Szuszkiewicz, A., Szełęg, E., Stadnicka, K.M., and Woźniak, K. (2024c) American Mineralogist 109, 940–948.

How to cite: Woszczyna, M., Włodek, A., Gołębiowska, B., and Pieczka, A.: Epidote-supergroup minerals associated with disseminated scandium mineralization at Jordanów Śląski in Lower Silesia, Poland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-334, https://doi.org/10.5194/egusphere-egu26-334, 2026.

Expansive soils with high sulfate content pose a serious challenge to the pavement infrastructure due to the rapid formation of expansive minerals like ettringite. The conventional calcium-based stabilizers, like lime and cement, often accelerate the ettringite crystal growth and result in sulfate-induced heave. Therefore, an alternative stabiliser that prevents these adverse chemical reactions is required. This study evaluates the potential use of wollastonite powder (CaSiO₃) as a sustainable stabiliser for sulfate rich soils. The research focussed on the physico-chemical and mineralogical changes of the wollastonite powder-treated soil matrix at varied curing periods and dosages. Atterberg limits were conducted to access the modification in plasticity properties of the stabilised sulfate-rich natural expansive soil. pH and EC of the treated expansive soil were measured at different time intervals to understand the balance between calcium and sulfate ions associated with wollastonite dissolution. X-Ray diffraction (XRD) analyses was performed at selected curing periods to study the minerological transitions and to detect the presence or absence of ettringite with time. These findings support the development of low-carbon sustainable binder as an alternative to the conventional stabilisers like lime in sulfate-rich environments.

How to cite: Murugan, G. and Talari, T.: Stabilisation of Sulfate-Rich Expansive Soils Using Wollastonite Powder: A Mineralogical Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1249, https://doi.org/10.5194/egusphere-egu26-1249, 2026.

How to cite: Demirçalı Özmen, H.: The Role of Natural Clays and Fining Agents in Food Processing and Health: Fruit Juice Clarification, Toxin Removal, and Safety Assessment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2103, https://doi.org/10.5194/egusphere-egu26-2103, 2026.

The Santamu area, located in the Tabei Uplift of the Tarim Basin, is characterized by multi-stratigraphic accumulation and multi-stage charging. Integrating fluid inclusion petrography and microthermometry, in-situ U-Pb dating of calcite veins, and 1D burial history modeling, this study systematically reveals the cross-stratigraphic hydrocarbon adjustment processes and differential accumulation mechanisms within the Ordovician, Carboniferous, and Triassic reservoirs. The charging histories are precisely constrained: the Ordovician experienced three oil-charging phases (Late Caledonian–Early Hercynian, Late Hercynian, and Yanshanian) and one late gas charge, with the Late Hercynian being dominant; the Carboniferous and Triassic T3 subunits received oil during the Yanshanian and Himalayan periods, followed by gas; while the Triassic T1 subunit records only a single Himalayan oil charge. Critically, the study elucidates that the hydrocarbons in the Carboniferous and Triassic strata are not directly sourced from coeval Ordovician oils, but are products of vertical transfer and mixing. Specifically, early-charged (pre-Yanshanian) Ordovician hydrocarbons migrated upward along faults during the Yanshanian and Himalayan periods, with the T1 oil specifically derived from the vertical spillage of hydrocarbons originally trapped in the T3 subunit. The multi-stage differential activity of the NEE-trending strike-slip and Santa Mu fault systems is identified as the key controlling factor, where the opening, activity, and sealing of these faults dictated the vertical migration pathways, charging timing, and final accumulation. Consequently, a composite accumulation model is established for the area, characterized by "multi-stage generation from the Cambrian Yuertusi source rocks, fault-controlled migration, and cross-stratigraphic vertical adjustment," which deepens the understanding of hydrocarbon enrichment in complex cratonic fault zones and provides critical guidance for exploration in analogous regions.

How to cite: Peng, G. and Tian, J.: Cross-stratigraphic Hydrocarbon Adjustment Controlled by Fluid Inclusions: A Case Study of the Santa Mu Area, Northern Tarim Uplift, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2534, https://doi.org/10.5194/egusphere-egu26-2534, 2026.

Arsenic is a toxic and widespread contaminant of waters and soils, originating from both natural geochemical processes and anthropogenic activities e.g. mining, metallurgy, and agriculture. Its removal remains as a global environmental challenge. Arsenic immobilization is commonly achieved through sorption, ion exchange, or precipitation, often involving iron-, aluminum-, or calcium-based phases. However, many of these methods suffer from limited capacity, sensitivity to water chemistry, or poor long-term stability.

In this study we present an approach for arsenate AsO₄^3- removal from water based on reactive sorption on granulated Pb-zeolite. Arsenate is precipitated in the form of low-solubility solid phase - mimetite (Pb₅(AsO₄)₃Cl) - by reaction with Pb²⁺ desorbed from granulated Pb-zeolite (clinoptilolite). Pb-modified granulated zeolite was prepared by (1) sorption of Pb²⁺ from solution, (2) intensive washing to remove excess Pb and (3) granulation. For granulation, suspension of zeolite in sodium alginate solution was dropwise added to calcium chloride solution, resulting in formation of beads 2 - 4 mm in size. Dried beads provide with mechanically stable, porous and easy to handle sorbent.

Arsenate removal was investigated under static and dynamic flow-through conditions. In static batch experiments using [As] = 0.1 to 5 mg/L, arsenate removal exceeded 90% within minutes and approached 99% with increasing contact time, indicating that under well-mixed conditions the process is not limited by external mass transfer.

Column experiments were performed at varying flow rates, arsenate concentrations, sorbent masses, and column diameters in order to evaluate the effect on removal efficiency. Increased flow rate resulted in decreased arsenate removal due to shortened residence time, whereas higher sorbent mass enhanced removal by increasing the reactive contact area and the effective diffusion path length. Arsenic concentrations in the effluent increase gradually with time and the breakthrough curves follow a logarithmic rather than sinusoidal trend. This indicates sustained arsenate removal over extended periods (up to 6 days of continuous operation at the conditions of the experiment).

SEM/EDS analyses of reacted granules revealed the formation of a porous crust composed of mimetite needles on the granule surface. Mimetite precipitation does not passivate the reactive interface. The reaction front was located on the surface of granules indicating that precipitation kinetics was faster than lead desorption. Also, the porous structure of the alginate granules allowed for diffusion of Pb²⁺ from the interior outward.  Comparison of arsenic removal and lead release rates indicates a gradual, approximately linear depletion of lead with time. Precipitation of Pb₅(AsO₄)₃Cl on the surface of granules created a Pb concentration gradient which was a driving force for further Pb desorption from zeolite in the interior of the granules: lead was consumed progressively from the outer regions of the granule inward. This mechanism likely governs the extended tailing observed in the breakthrough curves.

Proposed application of Pb-zeolite alginate granules enables efficient arsenate removal through induced mimetite precipitation under both static and flow-through conditions. The combination of high removal efficiency, long-term reactivity, and physical immobilization of lead highlights the potential of this approach for water treatment applications.

This research was funded by National Science Centre project No 2024/53/N/ST10/01763.

How to cite: Stępień, E., Manecki, M., and Bajda, T.: Pb-zeolite alginate granules for arsenate removal from water: static and dynamic studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4922, https://doi.org/10.5194/egusphere-egu26-4922, 2026.

Coesite was first synthesized in the early 1950s, then discovered in nature in 1960, and first applied as an index mineral for pressure-temperature (P-T) metamorphic condition and tectonic setting in 1984 with applications in the Dora Maira Massif (Italy) and the Western Gneiss Region (Norway). Until today, several experimental studies have focused on the calibration of the coesite-quartz phase boundary, mostly at high-temperature (HT) and high-pressure (HP) conditions. Among the various studies, there is a general agreement with only small differences at HT-HP conditions. For example, at 1200 °C the coesite-quartz phase boundary ranges between 31 to 33.5 kbar. However, differences in the HT are amplified in extrapolations to lower temperatures that are relevant to several recent coesite discoveries. At 550 °C the coesite-quartz phase boundary ranges between 23 to 28 kbar, providing a wide spread of P conditions.

The increasing number of coesite discoveries from different terranes in recent years highlights the importance of precisely locating the coesite-quartz phase boundary at low-temperature (LT). This study aims to validate the coesite-quartz phase boundary at LT (550-750 °C) and HP (28-30 kbar). The chosen P-T conditions are typical for coesite crystallization in subduction zone settings. The experiments were conducted in end-loaded piston-cylinder apparatuses using 12.7-mm diameter experimental assemblies composed of MgO filler pieces, graphite heater tubes, borosilicate glass insulators, and NaCl. Silver capsules, with volumes varying from 20 to 15 mm³, were filled with amorphous SiO₂ powder and deionized H₂O (≈2:1 ratio). Ten experiments were successfully performed. The experiments were conducted along the 550 °C, 650 °C and 750 °C isotherms at 28, 29, and 30 kbar for 48-72 hours. In summary, at 750 °C, 100 % coesite formed at 30 kbar, and 100% quartz was obtained at 29 kbar. At 650 °C, we synthesized 100 % coesite at 30 kbar, 100 % quartz at 28 kbar, and both large crystals of coesite (>200 μm) and small crystals of quartz (<100 μm) at 29 kbar. At 550 °C, experiments resulted in 100 % of small coesite crystals (<70 μm) at 30 kbar, 100 % quartz crystals at 28 kbar, and both coesite and quartz at 29 kbar. Moreover, a reversal experiment was conducted from quartz to coesite. Quartz was crystallized experimentally at 700 °C and 10 kbar for 24 hours. Then, it was loaded in a new experiment at 650 °C and 30 kbar, resulting in a complete recrystallization of coesite; no quartz was left at the end of the experiment.

These results suggest that the coesite-quartz phase boundary at relatively low temperature may occur at higher pressure than previously extrapolated. The ongoing reaction reversals experiments from coesite stability field to quartz will better constrain the character of coesite-quartz phase boundary at LT-HP conditions typical for subduction zone settings, where coesite likely crystallized in natural rocks. Acknowledgements: This work was funded by the National Science Centre (Poland) through the project 2021/43/D/ST10/02305 to K. Kośmińska.

How to cite: Callegari, R., Thomas, J., and Kośmińska, K.: Experimental evaluation of the Coesite-Quartz phase boundary at low-temperature & high-pressure conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6476, https://doi.org/10.5194/egusphere-egu26-6476, 2026.

Rare earth elements (REE) constitute essential critical raw materials, driven by their role in the ongoing evolution of high-technology and green energy sectors. Growing demand is driving the search for new sources and recovery technologies. A new technology for recovering REE via coprecipitation with lead apatite - pyromorphite Pb₅(PO₄)₃Cl - has recently been proposed [1]. Different sources of REE with varying chemical compositions may contain anions that compete with Cl in the pyromorphite structure [2, 3] and potentially affect REE recovery. The aim of this study was to investigate the effect of F, Br, I, and OH, compared to Cl, on the incorporation of Ce (as a proxy for other rare earth elements) into the structure of pyromorphites.

Synthesis of pyromorphite analogs consisted of slow mixing of two solutions containing cations and anions in a reaction chamber, under atmospheric pressure, ambient temperature around 21°C and at pH=3, with vigorous stirring, and leaving the obtained suspensions for 48 hours for maturing. Ce-free phases were also synthesized as controls.

The precipitate comprises primarily appropriate anionic variety of crystalline pyromorphite: fluor-, chlor-, brom-, and hydroxyl-pyromorphite. Neither in the control experiment nor in the experiment with Ce was iodine pyromorphite formed. The crystal lattice got changed to accommodate Ce in the structure. It was expressed as change in unit cell parameters – dimensions a were elongated and the c dimensions were shortened, compared to each control. The extent of Ce substitution was not very sensitive to the anion used, with content measured at 0.44 (F), 0.57 (Cl), 0.52 (Br), and 0.43 (OH) atoms per formula unit (apfu). The precipitates of pyromorphites containing Ce were accompanied by small amounts of an additional phase, Ce₂Pb₃(PO₄)₄·nH₂O [4]. 

For the first time, anionic substitution effects (F, Cl, Br, I, OH) on cerium incorporation in the pyromorphite-type lead phosphate apatite Pb₅(PO₄)₃X has been studied. These will enable future optimization of REE recovery technologies from mineral materials of varying chemical composition, both qualitatively and quantitatively. Further extensive research is necessary to fully understand the details of REE substitutions in lead-apatites.

This research was funded by Polish National Science Center research grant no. 2021/43/O/ST10/01282. 

[1] Sordyl, J., Staszel, K., Leś, M. & Manecki, M. Removal of REE and Th from solution by co-precipitation with Pb-phosphates. Applied Geochemistry 158, 105780 (2023).

[2] Pan, Y. & Fleet, M. E. Compositions of the Apatite-Group Minerals: Substitution Mechanisms and Controlling Factors. Reviews in Mineralogy and Geochemistry 48, 13–49 (2002).

[3] Hopwood, J. D. et al. The Identification and Synthesis of Lead Apatite Minerals Formed in Lead Water Pipes. Journal of Chemistry 2016, 9074062 (2016).

[4] Staszel, K. et al. New synthetic [LREE (LREE = La, Ce, Pr, Sm), Pb]-phosphate phases. Mineralogia 54, 58–68 (2023).

How to cite: Staszel, K. and Manecki, M.: Anionic substitution effects (F, Cl, Br, I, OH) on cerium incorporation within the pyromorphite-type lead phosphate apatite Pb5(PO4)3X framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7153, https://doi.org/10.5194/egusphere-egu26-7153, 2026.

Phase transitions in olivine are considered as a key mechanism for triggering faulting at depths greater than 300 km, leading to the nucleation of deep-focus earthquakes (DFEs), under conditions where ductile flow should dominate. Olivine phase transitions are characterized by three fundamental features thought to promote faulting: an exothermic reaction, a large negative volume change, and a strong mechanical contrast. However, it is unclear whether faulting at depth requires all three characteristics or can be triggered by just one.

To address this question, we conducted a series of deformation experiments using a large-volume press at the P61b beamline at DESY synchrotron (Hamburg, Germany). Experiments were performed on novaculite, while samples were transforming into coesite. This phase transition is dominated by a significant volume reduction but involves only minor latent heat release, allowing us to investigate the role of volume change. Throughout the experiments, we simultaneously collected X-ray diffraction patterns and images, together with acoustic emission (AEs) monitoring. Our results show that the growth rate of the high-pressure phase varies strongly with pressure–temperature (P-T) conditions and equilibrium overstep. All experiments were conducted under high differential stress. Thousands of AEs were collected in each experiment, whose locations were reconstructed using arrival times from six acoustic transducers placed around the sample assembly. In experiments characterized by lower transformation rates, AE locations mark fault planes that developed within initially intact sample volumes. Analysis of the AE catalogs reveals magnitude–frequency distributions spanning a wide range of b-values, which vary with P-T conditions and transformation kinetics. We observed that brittle faulting yields an expected b-value of about 1 and was related to the nucleation of coesite grains. 

These experiments represent the first example of transformational faulting in deforming, polycrystalline quartz undergoing a high-pressure phase transition under elevated differential stress. Our findings indicate that a volume-changing phase transition with minor latent heat release can promote brittle failure at high pressure, providing new constraints on the mechanisms of deep faulting and expanding the range of mineral phase transitions potentially relevant to crustal and mantle seismicity.

How to cite: Mingardi, G., Gasc, J., Farla, R., Alvaro, M., and Schubnel, A.: Transformational faulting: Is olivine special? Evidence from quartz-coesite phase transition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7996, https://doi.org/10.5194/egusphere-egu26-7996, 2026.

Kaolinite-to-illite transformation is a common clay-mineral reaction during sedimentary basin diagenesis and can be used to constrain fluid–rock interaction and the evolution of diagenetic environments. Here we integrate XRD, SEM/TEM, EDS/EPMA, numerical simulations, and physical simulation experiments to constrain the controlling factors, regional temperature thresholds, and mechanisms of kaolinite illitization. Results show that during early diagenesis under relatively open-system conditions, meteoric-water flushing and organic-acid activity enhance feldspar dissolution, providing Si and Al sources for kaolinite formation. With increasing burial depth and temperature, the diagenetic system evolves from open to semi-closed/closed conditions; restricted fluid circulation promotes the accumulation of K⁺ released by continued feldspar dissolution in pore waters, thereby providing the key prerequisite for illite nucleation and stabilization. The onset temperature of illitization differs significantly among regions. Illite precipitation is jointly controlled by temperature, K⁺ concentration, and pH, and the critical K⁺ concentration required for illitization decreases with increasing temperature and pH. Combined mineralogical and geochemical constraints indicate that kaolinite illitization proceeds predominantly via a dissolution–reprecipitation mechanism, and its extent is governed by the coupled effects of temperature thresholds, effective K⁺ supply, and the openness of the diagenetic system. These findings provide a basis for characterizing clay-mineral diagenetic behavior and reconstructing paleo-fluid conditions.

How to cite: Lin, S., Yuan, G., and Xu, F.: Mechanism of Kaolinite-to-Illite Transformation in the Central–Southern Xihu Sag, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8650, https://doi.org/10.5194/egusphere-egu26-8650, 2026.

The Wenchang A Depression in the Pearl River Mouth Basin is a confirmed area with abundant oil and gas resources. The exploration breakthroughs of some wells have revealed the exploration prospects of the deep clastic rock reservoirs in the Wenchang A Depression. Previous studies have focused more on the reservoir research results of individual blocks, but there has been a lack of comparative research among different blocks, and the differences in the dissolution effects and formation reasons of the reservoirs in each block have not been clearly identified. Through the comparative study of the Zhuhai Formation reservoirs in Zones 9 and 10 of Wenchang A Sag, this paper clarifies the differences in the dissolution effects of the reservoirs between the two blocks. Based on rock thin section identification, scanning electron microscopy, trace element analysis, and fluid inclusions homogenization temperature testing, combined with seismic data and formation water data, the study of the differences in the dissolution effects of the Zhuhai Formation reservoirs in Zones 9 and 10 was carried out. The key conclusions are as follows: (1) Feldspar grain dissolution is the dominant dissolution process in the study area. In Zone 10, intense feldspar dissolution is observed in the thick-bedded sandstones in the middle part of the braided river delta front, whereas weak dissolution effects are noted in the fan delta and braided river delta plain reservoirs within the same zone. In Zone 9, vertical variations in dissolution intensity are insignificant; however, dissolution is enhanced in the fault transition zone horizontally, accompanied by weak authigenic kaolinite precipitation. Near the No. 6 Fault Zone, the dissolution effect is attenuated, while authigenic kaolinite extensively fills intergranular pores. (2) Elements associated with feldspar, such as Al, are detected in authigenic quartz overgrowths in Zone 10. Combined with fluid inclusion thermometry of quartz overgrowths, the results demonstrate that dissolution in Zone 10 occurred relatively late, primarily driven by organic acid derived from the thermal evolution of organic matter. (3) Elements including K, Ca, Fe, and Al are identified in quartz overgrowths in Zone 9, with the Al content significantly higher than that in Zone 10. During the deposition of the Zhuhai Formation, the Zhu III South Fault and the Fault No. 6 entered their peak activity. The dextral rotation of the stress field triggered a series of strike-slip faults, transitioning the strata from a closed system to a semi-open system. Faulting, characterized by stronger intensity in the southern segment and weaker in the northern segment, facilitated the migration of deep CO₂ fluids into the reservoirs. Integrated with numerical simulation experiments, the results demonstrate that the secondary faults associated with oil-source faults connect organic acids derived from the thermal evolution of source rocks and CO₂ fluids. This combined fluid action induces extensive dissolution of feldspar grains and enables effective migration of kaolinite within the semi-open system.This study provides a critical foundation for understanding diagenetic fluid evolution and reservoir development mechanisms in the study area, with implications for future hydrocarbon exploration in similar geological settings.

How to cite: Fang, R. and Yuan, G.: Analysis of the Differences in Feldspar Dissolution in Different Zones of Sandstone Reservoirs: A Case Study from the Zhuhai Formation, Wenchang A Sag, Pearl River Mouth Basin, China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8687, https://doi.org/10.5194/egusphere-egu26-8687, 2026.

The complexity of hydrocarbon exploration in foreland thrust belts results from multiphase hydrocarbon charging, multistage thrusting, and complex pressure evolution. Based on fluid inclusion analysis, this study constrains the multiphase hydrocarbon charging history in Cretaceous strata in the Kela-2 gas field, Kuqa Depression. Paleopressure reconstruction was conducted using PVTsim modeling. By combining compositional data from fluid inclusions of varying origins and timing, the dynamic adjustment process of hydrocarbon has been systematically elucidated. Results show that both the Cretaceous Bashijiqike Formation(K₁bs) and Cretaceous Yageliemu Formation(K₁y) dry gas reservoirs in the Kela-2 gas field experienced two phases of hydrocarbon charging, consisting of blue-fluorescent oil and natural gas. The hydrocarbon accumulation process in the Kela-2 gas field can be divided into four stages. During 23 to 15 Ma, blue-fluorescent oil charged into the K₁y reservoir. The ratio of the number of quartz grains with oil inclusions therein to the total number of quartz grains exceeds 5%, indicating the presence of a paleo-oil accumulation. During 15 to 5.3 Ma, thrust faulting triggered the upward adjustment of crude oil from the K₁y to the K₁bs reservoirs. Overpressure was absent in the reservoirs at this stage. The oil inclusions from both intervals exhibit similar geochemical characteristics, with MPI derived equivalent vitrinite reflectance (Ro) values of approximately 0.8, suggesting a common-source adjustment. During 5.3 to 2.5 Ma, intensified fault activity drove the charging of high-maturity coal-derived gas. The methane δ¹³C of gas inclusions in K₁y is -29‰, lighter than that of its present-day gas reservoir (-25.7‰). Meanwhile, the current methane δ¹³C in K₁bs is -28.3‰, which is lighter than that in the current K₁y reservoir. It indicates sustained late-stage charging of high-maturity gas, with preferential migration into the K₁y reservoir. A massive gas charging and oil displacement, triggering rapid pressurization of the reservoir to a maximum pressure coefficient of 2.0. From 2.5 Ma to the present, sustained fault activity and persistent gas charging led to the formation of a dry gas reservoir (dryness coefficient >0.99) and the continued development of overpressure. Integrated fluid inclusion analysis demonstrates a distinct temporal coupling among fault reactivation, hydrocarbon charging, and overpressure evolution, which collectively governed the final accumulation and preservation of the Kela-2 gas field.

How to cite: Li, X., Hao, F., Tian, J., and Cong, F.: Tracing hydrocarbon accumulation and adjustment in a thrust belt using fluid inclusions: A case study of the Cretaceous system in the Kela-2 Gas Field, Kuqa Depression, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8927, https://doi.org/10.5194/egusphere-egu26-8927, 2026.

Anomalous high-conductivity layers (HCL) are a defining feature of subduction zones and play a critical role in global processes as water cycling, seismicity, and arc magmatism. Hydrous minerals, especially amphiboles (general formula AB₂C₅T₈O₂₂W₂), are considered to be major contributors to these conductivity anomalies in the Earth crust, but the atomic-scale links between mineral oxidation, charge transport, and thermal stability are still not fully understood. Given their crustal abundance, the oxidation of Fe²⁺-bearing hydrous amphiboles has therefore been extensively investigated in recent years. Electrical conductivity measurements on several amphibole species have suggested the formation of polarons (conduction electrons coupled with longitudinal optical phonons) at high temperatures (HT). However, only recently direct evidence for the existence of polarons in Fe²⁺-bearing amphiboles has been provided by Raman spectroscopy [1,2,3]. In addition, reversible delocalisation of H⁺ cations has been detected [1,3,4].

Glaucophane (□Na₂(Mg₃Al₂)Si₈O₂₂(OH)₂) is a common amphibole in blueschist facies rocks; therefore, its HT behaviour should play an important role in geological processes occurring in subduction zones. The aim of our study is to elucidate the role of ^CAl in the formation of charge carriers in glaucophane at HT. We have analysed Fe²⁺-bearing glaucophane [(□_0.91Na_0.08K_0.01)(Na_0.87Fe_0.07Ca_0.06)₂(Mg_0.54Al_0.34Fe_0.12)₅(Si_0.99Al_0.01)₈O₂₂((OH)_0.98F_0.02)₂] from Pollone (Piedmont, Italy) by in situ HT Raman spectroscopy in air [5] and under vacuum. The results indicate that, similar to ^CAl-free amphiboles, glaucophane undergoes a multi-step process controlled by structural anisotropy and cation site occupancy. The first Fe²⁺ oxidation stage occurs between ~600 and 650 K. This stage is accompanied by shifts in Raman peaks linked to TO₄ ring vibrations, indicating electron delocalization and topological reorganization of the tetrahedral framework, together with changes in the anisotropic local structure. A second oxidation stage develops between ~800 and 1000 K, where Fe²⁺ oxidation is localised in M(1) polyhedra. This stage is marked by strong intensity reductions in low-frequency lattice modes and further rearrangement of the TO₄ rings. The final stage, preceding decomposition, occurs between ~950 and 1150 K and involves progressive H⁺ cations delocalization from OH groups, with incomplete recovery upon cooling, evidencing irreversible structural changes.

Under vacuum (~10^-4 bar), both the oxidation stages and H⁺ delocalization occur at temperatures approximately 100 K higher than in air, indicating that the absence of oxygen raises the temperature required for these processes to take place. Hence, octahedrally coordinated Al does not suppressed the temperature-induced electron and H⁺ delocalization in either presence or absence of external O₂.

Results from ongoing electrical-conductivity experiments combined with in situ Raman spectroscopy at different temperatures will also be discussed.

References

[1] Mihailova et al. (2021) Commun Mater 2, 57

[2] Mihailova et al. (2022) Condens Matter 7, 68

[3] Bernardini et al. (2025) Sci Rep 15, 14244

[4] Della Ventura et al. (2017) Am Min 102(1), 117-125

[5] Kei Yin Ngan (2025) Master thesis: Oxidation and thermal decomposition of Fe-containing glaucophane. University of Hamburg, Germany

How to cite: Baratelli, L., Ngan, K. Y., Schlüter, J., and Mihailova, B.: Temperature-activated charge carriers in Fe2+-bearing glaucophane revealed by Raman spectroscopy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10029, https://doi.org/10.5194/egusphere-egu26-10029, 2026.

Quartz is a ubiquitous, durable mineral abundant in most lithologies and in sedimentary systems. Its stability during weathering and diagenesis makes it a robust provenance tracer. Quartz optically stimulated luminescence (OSL) sensitivity and electron spin resonance (ESR) signals have been empirically proposed as indicators for sediment provenance based on differences in quartz sensitivity. Sensitivity is defined as luminescence produced per unit dose (Gray: Gy) per unit mass (mg). The mechanisms driving OSL sensitisation during weathering from source rocks remain an open question in the luminescence community. While it is largely believed to be acquired by earth surface processes, recent studies bring evidence that sensitisation processes depend on source geology. Moreover, most studies focus on quartz grains deposited in the sink and infer possible sources rock by clustering.

The present study investigated a diverse suite of source rocks a wide range of geological settings, including granites, sandstones, volcanic and metamorphic rocks, and, where applicable, their derived sediments, independently dated from millions (Ma) to billions (Ga) of years. To understand the mechanism of OSL sensitivity we combined thermoluminescence (TL), OSL, ESR, cathodoluminescence (CL) and Raman spectroscopy measurements, with geochemical data obtained through laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Only in those quartzes that exhibited the [TiO₄^-Li⁺]⁰ paramagnetic centre in ESR, had notably high concentration of titanium and lithium impurities and had high blue emission in SEM-CL showed sensitisation following repeated cycles of laboratory dosing and bleaching. Samples lacking these centres did not show any laboratory OSL sensitisation by dosing and bleaching. We find a strong correlation of the degree of laboratory OSL sensitisation with the [TiO₄^-Li⁺]⁰ electron centre from ESR signal, and the titanium and lithium concentrations measured by LA-ICPMS. Our data on rocks of various ages and regions reinforce the idea that the potential for OSL sensitisation originates from specific lattice defect structures acquired by quartz during crystallisation. The results also highlight the role of Li⁺-ion impurities in forming paramagnetic centres such as [AlO₄/h]⁰ and [TiO₄^-Li⁺]⁰, advancing our understanding on interaction of radiations with specific defects in quartz.

This study is funded by the European Research Council Consolidator Grant - PROGRESS, (ERC-CoG-101043356) awarded to Prof. Alida Timar-Gabor. 

How to cite: Constantin, D., Devi, M., Grecu, S.-C., Toth, Z.-R., Brezeanu, D., Barla, A., Nesterovschi, I., Cinta-Pinzaru, S., Ducea, M., Mojzsis, S., and Timar-Gabor, A.: Multi-spectroscopic characterisation of quartz from igneous, volcanic and sandstone rocks worldwide. Insights for provenance studies based on OSL sensitivity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10121, https://doi.org/10.5194/egusphere-egu26-10121, 2026.

Magnetic properties of ferrimagnetic minerals have been studied in detail over the years. By contrast, the magnetic properties of paramagnetic minerals containing rare earth elements (REE) remain largely unexplored, even though the presence of particular rare-earth ions can give rise to complex magnetic behavior due to their unpaired 4f electrons. Consequently, filling this knowledge gap is becoming increasingly important in light of the enormous interest these minerals have attracted in recent years because of their economic value. The primary goal of this study is to characterize the intrinsic magnetic behavior of selected REE minerals at the grain scale and in relation to their crystal structures.

Six REE-bearing minerals from various Swedish localities were investigated: monazite-(Ce), xenotime-(Y), ferriallanite-(Ce), bastnäsite-(Ce), cerite-(CeCa) and fluorapatite. Electron microprobe analysis and X-ray diffraction methods were used to determine mineral chemistry and confirm crystal structures. Magnetic properties were characterized via field- and temperature- dependent magnetization measurements.

Field-dependent magnetization measured at 2 K revealed the absence of a hysteresis loop in all minerals except ferriallanite-(Ce), which exhibits a small hysteresis loop. This behavior is primarily attributed to the presence of Fe²⁺ and Fe³⁺ ions in ferriallanite-(Ce). The preliminary results show that the effective magnetic moments (μ_eff) obtained from temperature-dependent measurements are in good agreement with calculated free-ion magnetic moments (μ_calc), suggesting that paramagnetic rare-earth ions represent a major contribution to the observed magnetism.

These results provide fundamental knowledge of the intrinsic magnetic properties of selected REE-bearing minerals and improve our understanding of their crystal-chemical controls on their magnetism. Moreover, these insights form a basis for further interdisciplinary studies exploring the potential of designing novel functional materials inspired by naturally occurring compositions.

How to cite: Sordyl, J., Corona, A., Almqvist, B., Holtstam, D., Sahlberg, M., Cedervall, J., Sarkar, T., Herper, H., Vishina, A., and Eriksson, O.: Crystal-chemical controls on the magnetic behavior of REE-bearing minerals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13171, https://doi.org/10.5194/egusphere-egu26-13171, 2026.

To date, processes such as volatile-element cycling and redox reactions in subduction and the mid-crust zones are still not fully understood. Particularly, a better understanding of the redox processes in rock-forming silicate minerals is essential for developing a more accurate picture of lithospheric electrical conductivity. Amphiboles (AB₂C₅T₈O₂₂W₂) are major constituents of subduction-zone lithologies and can store substantial amounts of water in the form of W-site hydroxyl groups, making them important contributors to the global water cycling. Recent Raman scattering studies have shown that Fe²⁺-bearing hydrous amphiboles can undergo reversible temperature-induced oxidation and dehydrogenation, leading to the formation of mobile charge carriers, polarons (delocalized e⁻ coupled with polar phonons) and delocalized H⁺, and hence, to polaronic conductivity and H⁺ diffusion (Della Ventura et al., 2018; Mihailova et al., 2022; Bernardini et al., 2025).

Magnesio-hornblende (nominally ^A⧠^BCa₂^C(Mg₄Al)^T(Si₇Al)O₂₂^W(OH)₂) is of special interest in this context because it represents one of the most abundant amphibole groups, the hornblendes (^TAl-containing Ca-amphiboles), but the influence of its tetrahedrally coordinated Al on the redox processes remains largely unexplored. Thus, the goal of this study is to investigate the atomistic mechanisms of charge-carrier activation and thermal stability in magnesio-ferri-hornblende by in situ high-temperature Raman spectroscopy in the range 300–1400 K. The exact chemical composition of the studied sample was determined by wavelength-dispersive electron microprobe analysis:

^A(Na_0.06K_0.01)^B(Ca_1.94Na_0.03Mn_0.03)^C(Mg_3.54Fe²⁺_0.8Fe³⁺_0.54Mn²⁺_0.11Zn_0.02Cr_0.001)^T(Si_7.42Al_0.51Fe_0.06Ti_0.01)O₂₂^W((OH)_1.92F_0.05O_0.02Cl_0.01). Experiments were conducted under both oxidizing conditions (air) and vacuum (~ 10^-4 bar) to evaluate the role of external O₂ on the activation temperatures and reversibility of these processes.

First results obtained in air reveal that magnesio-ferri-hornblende is stable up to 1400 K. The observed temperature-induced anomalies in both framework vibrations and OH-stretching indicate the onset of oxidation of Fe²⁺ to Fe³⁺ coupled with delocalization of H⁺ next to Fe²⁺Fe²⁺Mg and Fe²⁺MgMg chemical species. These processes are expressed by the disappearance of the corresponding OH-stretching Raman peaks upon heating and characteristic Fe²⁺O₆-related Raman-active modes. At temperatures above 1150 K even H⁺ cations next to MgMgMg, but the corresponding OH-stretching peaks reappear on cooling, indicating mobile H⁺ cations in a large temperature range. Furthermore, after cooling down to room temperature, a strong direction-dependent resonance Raman scattering (RRS) is observed, demonstrating strong mutual alignment of the polaron dipoles, which is a precondition of highly anisotropic polaronic conductivity. As a next step, in situ high-temperature Raman scattering experiments under an applied external electric field will be conducted, allowing for the simultaneous monitoring of temperature-induced electron–phonon coupling, H⁺ delocalization, and the evolution of electrical conductivity.

References:

• Della Ventura, G., Mihailova, B., Susha, U., Guidi, M. C., Marcelli, A., Schlüter, J., Oberti, R. (2018): Am. Mineral., 103, 1103 -1111, https://doi.org/10.2138/am-2018-6382
• Mihailova, B., Della Ventura, G., Waeselmann, N., Bernardini, S., Xu Wei, Marcelli, A. (2022): Condens. Matter, 7, 68, https://www.mdpi.com/2410- 3896/7/4/68
• Bernardini, S., Della Ventura, G., Hawthorne, F.C., Marcelli, A., Salvini, F., Mihailova, B., (2025): Sci. Rep., 15, 14244, https://doi.org/10.1038/s41598-025-98025-9

How to cite: Fleischer, K. and Mihailova, B.: Atomistic insights into redox processes and conductivity phenomena in Hornblende, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13233, https://doi.org/10.5194/egusphere-egu26-13233, 2026.

Serpentines are widely used to investigate lithospheric strength, subduction-zone processes, and the cycling of carbon and water in the Earth. In this work we have investigated the high-temperature phase transitions in natural serpentine with respect to the time of heating. The starting material was obtained by grinding natural serpentine sample and verified using powder X-ray diffraction (λ = 1.5406 Å). The powder was heated at temperatures from 300 to 1000 °C in 100 °C increments for durations ranging from 30 minutes to 24 hours, using 1–6 hour intervals. No phase changes were observed up to 400 °C. Two forsterite (Mg₂SiO₄) peaks at 35.993° and 36.857° first appeared in the XRD pattern at 500 °C after 3 hours of heating. The first appearance of enstatite (MgSiO₃), marked by peaks at 28.188⁰ and 31.289⁰ were observed in the XRD pattern at 600⁰C starting at 8 hours of heating. Our work provides a robust temperature-time (T-t) phase diagram. The systematic T-t framework shows that serpentine breakdown and forsterite/enstatite formation depend on both temperature and duration of heating, rather than temperature alone. This can have implications for subducting slabs; where mineral transformations, fluid release, and associated changes in rheology may be governed by slab thermal histories and residence times at depth. These effects can influence interpretations of slab strength, seismic structure, and volatile cycling in subduction zones.

How to cite: Divya, R. V. and Dutta, R.: High-Temperature phase transitions in serpentine, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13441, https://doi.org/10.5194/egusphere-egu26-13441, 2026.

Quantifying hydrogen incorporated via cation vacancies in nominally anhydrous minerals (NAMs) is essential for assessing its influence on mantle physical processes such as rheology. In addition, hydrogen partitioning between NAMs and hydrous melts has been proposed as a potential mechanism to explain the oxidised nature of arc magmas. Fourier-transform infrared (FTIR) spectroscopy is the most widely used technique for quantifying trace hydroxyl (OH) in NAMs due to its accessibility and cost-effectiveness. Moreover, FTIR spectroscopy can also constrain hydrogen-incorporation mechanisms and the orientation of the OH dipole within charge-balanced vacancy structures. These distinctions are critical for identifying defects that buffer or sense oxygen fugacity. However, because of the relatively low hydrogen solubility and the diversity of incorporation mechanisms, optimising analytical resolution, both in concentration and OH-dipole orientation, remains highly desirable but has traditionally been hampered in most minerals by the intrinsic anisotropy of the OH dipole. Most studies rely on unpolarised FTIR measurements of randomly oriented crystals to avoid pre-orientation biases, but this practice reduces both precision and accuracy because birefringent crystals show strong orientation-dependent absorbance. Polarised FTIR overcomes this limitation and provides access to OH speciation and bond orientation unavailable from unpolarised measurements. We present a method to recover the full crystallographic orientation of a crystal, expressed as Euler angles, from polarised FTIR spectra acquired at different angles relative to the polarisation direction by rotating the polariser. The method requires a reference standard and a single diagnostic wavelength within the silica overtone range, which allows selection of an optimal frequency for orientation recovery and makes the approach more flexible than spectrum-range methods (Asimov et al., 2006). We validate the method using numerical simulations and a comprehensive dataset of olivine crystals with known orientations based on EBSD measurements. Implemented in an open-source Python package (FTIRkit), the approach applies to any birefringent crystalline phase and can be extended to other polarised techniques, including Raman spectroscopy and optical microscopy.

References

Asimow, P.D., 2006. Quantitative polarized infrared analysis of trace OH in populations of randomly oriented mineral grains. American Mineralogist 91, 278–284. https://doi.org/10.2138/am.2006.1937

Funding: This project has been funded through the ERC project OZ (DOI: 10.3030/101088573).

How to cite: Lopez-Sanchez, M. A. and Padrón-Navarta, J. A.: A novel method for determining crystal orientation using polarised Fourier-Transform infrared spectroscopy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13627, https://doi.org/10.5194/egusphere-egu26-13627, 2026.

The kaolinitic clays of the Şile Neogene Basin (Istanbul, Türkiye), constitute an important raw material resource for the ceramic industry. In the study area, the Istanbul Formation, composed mainly of Miocene clay, sand, and coal sediments, unconformably overlies the Upper Cretaceous andesitic volcanics of the Garipçe Formation. In this study, the relative influence of the Atterberg limits (AL), mineralogical compositions, specific surface area (SSA), and grain size distributions of six clay samples taken from three vertical sections of the İstanbul Formation were investigated comparatively. X-ray diffraction analyses of the whole rock and clay fractions show that, the dominated clay mineral is kaolinite (30-70%), accompanied by variable amounts of illite (5-25%) and smectite (0-25%). The illite-mica phase is almost entirely illite. Mixed layered phases and chlorite are absent. Non-clay minerals are mainly quartz (10-55%) and trace feldspar, siderite and anatase. In the samples, SSA values range 1.24-1.76 m²/g, and the grain size distributions are; d(0.1): 1.33-2.15 µm, d(0.5): 6.186-11.051 µm and d(0.9): 26.73-97.07 µm. The total and half-material grain sizes are approximately smaller than 40 µm and 10 µm, respectively. According to grain size distributions, the clays of Şile contain very fine-grained quartz (<10 µm) and larger-than-expected (>2 µm) clay mineral particles. AL values of the Şile clay samples are; The liquid limit (LL) was found to be in the range of 38-72%, the plastic limit (PL) in the range of 19.1-31.3%, and the plasticity index (PI) was between 19.6-41.5 (results are the average of three repeated experiments for each sample). Samples containing 5-25% smectite (four samples) exhibit systematically higher LL (60%), PL (27.90%), and PI (32.10%) ratios compared to smectite-free samples, reflecting the high surface activity and water adsorption capacity of smectite. In contrast, kaolinite and illite rich samples without smectite (two samples) display moderate plasticity (LL: 47%, PL: 23.72%, and PI: 23.28%) despite comparable grain size characteristics. This result can be explained by smectite's high specific surface area and its structural ability to adsorb more water. On the other hand, it is understood that the finest-grained samples do not always exhibit the highest plasticity. The fact that some of the quartz found in the Şile clays are fine-grained, similar to the clay minerals, may also have influenced the results. High SSA values ​​in some samples appear to be related to the total clay mineral content and, more specifically, the presence of smectite. However, samples with similar smectite content and similar AL values also have different SSA values. For example, two samples with similarly high LL, PL, and PI values ​​will have significantly different SSA values. It has been observed that the AL values in Şile clay samples are partially related to grain size and SSA, but more significantly related to mineralogical composition. In addition to kaolinite, the presence and amount of smectite, and also very fine-grained quartz will affect the results in the engineering and ceramic performances.

Key words: Atterberg Limits, Clay Mineralogy, Kaolinite, Smectite, Şile Neogene Basin

How to cite: Gargacı, M., Kahveci, S. E., Ekinci Şans, B., and Şans, G.: Mineralogical Effects on Plasticity Characteristics of Ceramic Clays: Insights from the Şile Neogene Basin (Türkiye), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14581, https://doi.org/10.5194/egusphere-egu26-14581, 2026.

The development of inexpensive and efficient methods for the recovery of critical raw materials is of increasing importance within the European Union, driven by the growing demand for rare earth elements (REE) in green technologies and electronic devices, as well as the strategic need to reduce limited reliance on external suppliers and maintain competitiveness. Recently, formation of a Pb–REE phosphate phase was reported alongside pyromorphite as a product of REE beneficiation by coprecipitation with Pb-phosphates (Sordyl et al., 2023).

Building on earlier observations, this contribution presents the results of the synthesis of mixed Pb–REE phosphates: La₂Pb₃(PO₄)₄·3.5H₂O, Ce₂Pb₃(PO₄)₄·3.3H₂O, Pr₂Pb₃(PO₄)₄·3.1H₂O, and Sm₂Pb₃(PO₄)₄·3.3H₂O, following the protocol of Staszel et al. (2023). They precipitate from aqueous solutions (pH 2-3, REE:Pb molar ratio of 3:2, at ambient temperature, open to the air) as poorly crystalline granular aggregates composed of rounded nanoparticles. The combined analytical approach including chemical analysis and microanalysis, synchrotron pair distribution function (PDF) analysis, and Raman spectroscopy confirms the incorporation of La, Ce, Pr, and Sm into the Pb phosphate structure in the same way as in the phases precipitated and described by Staszel et al. (2023). The composition of the precipitated phases is in agreement with previous reports by Staszel et al. (2023). Structural constraints derived from PDF analysis indicate that precipitated Pb-REE phosphates are similar to the rhabdophane REE(PO₄)∙0.6H2O structure (space group P3₁21). This finding differs from the previously proposed orthorhombic crystal system (space group Cmmm) (Staszel et al. 2023).  Additional techniques, such as extended X-ray absorption fine structure (EXAFS) and small-angle X-ray scattering (SAXS), will be applied to further resolve the periodic structure and the local distortions.

Resolving the crystallographic framework is essential for improving our understanding of the crystal-chemical role and structural position of REE within Pb phosphate phases. A thorough characterization of these newly described phases is therefore critical for refining the coprecipitation protocol and evaluating its applicability to REE recovery from phosphate-rich mineral sources or mining wastes, such as those associated with iron oxide-apatite deposits in northern Sweden. This work will be complemented by future in situ experiments to better monitor the nucleation processes governing the competitive formation of pyromorphite versus Pb–REE phosphate phases, with the aim of optimizing the recovery pathway toward the formation of the most effective REE-bearing phase.

The project is supported by the Wallenberg Initiative Materials Science for Sustainability (WISE) and Polish National Science Centre grant no. 2021/43/O/ST10/01282.

References

Sordyl, J., Staszel, K., Leś, M., & Manecki, M. (2023). Removal of REE and Th from solution by co-precipitation with Pb-phosphates. Applied Geochemistry, 158, 105780. https://doi.org/10.1016/j.apgeochem.2023.105780

Staszel, K., Jędras, A., Skalny, M., Dziewiątka, K., Urbański, K., Sordyl, J., Rybka, K., & Manecki, M. (2023). New synthetic [LREE (LREE = La, Ce, Pr, Sm), Pb]-phosphate phases. Mineralogia, 54(1), 58–68. https://doi.org/10.2478/mipo-2023-0006

How to cite: Ariza Acero, M. M., Staszel, K., Rzepka, P., Manecki, M., Sordyl, J., and Majka, J.: Synthesis and characterization of Pb–REE phosphate (REE₂Pb₃(PO₄)₄·nH₂O) for application in novel rare-earth element beneficiation methods, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15211, https://doi.org/10.5194/egusphere-egu26-15211, 2026.

How to cite: Feng, Y.: Clay Edges Are Dynamic Proton-conducting Networks Modulated by Structure and pH , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16110, https://doi.org/10.5194/egusphere-egu26-16110, 2026.

In geological studies, the titanomagnetite series (Fe_3-xTi_xO₄) and the titanohematite series (Fe_2-yTi_yO₃) are widely used for paleomagnetic identification, as variations in Ti content significantly affect their magnetic properties, thereby controlling the preservation of paleomagnetic signals. In this study, titanomagnetite and titanohematite series with different Ti contents were synthesized via a hydrothermal method to investigate their crystal growth mechanisms under varying Ti contents. Iron hydroxide precursors formed first and, upon heating, transformed into corundum or inverse spinel structures with Ti incorporated into the lattice. XRD results indicate that the precursor is an amorphous phase, and that the synthesized titanohematite samples consist of pure-phase titanohematite. XPS analysis shows that the relative ratio of Ti and Fe in titanohematite correspond to approximately y = 0.2, which the SEM–EDS analysis confirms the incorporation of Ti into the samples. SQUID measurements further demonstrate that low-Ti-content titanohematite exhibits antiferromagnetic behavior.

In addition, density functional theory (DFT) calculations were performed to optimize the structures and to evaluate the magnetic moments and band gaps of titanomagnetite and titanohematite series with different Ti contents. For the former series at x = 1, GGA calculations reveal that the inverse spinel structure is preserved, but with antiferromagnetic ordering while noting that the band gap was underestimated. When x = 0.5, Ti atoms partially occupy tetrahedral sites, leading to pronounced effects on the structural stability and magnetic properties. For the latter series, GGA+U calculations show that no significant structural changes are observed with increasing Ti concentration. However, a net magnetic moment emerges at y = 0.5, demonstrating that Ti incorporation beyond a critical proportion alters the cation distribution, consequently affecting the total magnetic moment.

Integrating hydrothermal synthesis parameters, crystal growth mechanisms, structural characteristics, and magnetic properties of both titanomagnetite and titanohematite series, this study provides new insights into the interpretation of paleomagnetic behavior and also offers a theoretical basis for potential applications in photocatalytic materials.

How to cite: Lee, Y.-H. and Chen, Y.-H.: Crystal growth and theorical calculations of titanomagnetite and titanohematite series, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16223, https://doi.org/10.5194/egusphere-egu26-16223, 2026.

The Kahramanmaras region (Turkey) is located between the Arabian Plate and the Tauride-Anatolide tectonic belt, making it a study area where lithological units of different ages and origins are found together. The petrography and geochemistry of ophiolitic complex units (Kocali Complex) located in northern Kahramanmaras and the sedimentary units (Karadut Formation) that tectonically overlie them were examined to reveal their roles within the tectonic system. Samples taken from the working area were examined under a polarizing microscope for their mineral composition, textural properties, and alteration degrees; major element contents were determined by XRF analysis, and trace and rare earth element contents were determined by ICP-MS analysis. 
The basalts of the Kocali Complex are generally altered basalts, with some samples being almost completely carbonated. The conglomerates of the unit are predominantly composed of angular clasts, which include rock fragments of both magmatic and sedimentary origin. Petrographic examinations indicate that the serpentinites are rich in opaque minerals and locally contain ore minerals; in addition, they exhibit a pronounced sieve texture accompanied by carbonation-type alteration. The Cenozoic Karadut Formation consists of sandy and carbonate-rich limestones, marls, and mudstones. Carbonate limestones are fine to medium-grained and display a homogeneous fabric, whereas sandy limestones are distinguished by their light to dark gray coloration. These units commonly crop out as beds with variable dip angles and occur in alternation with marls. The marls are whitish to beige in color and locally characterized by manganese coatings. Microscopic observations reveal that the siltstones and mudstones of the formation contain feldspar and very fine-grained quartz, accompanied by iron oxide precipitation and opaque minerals.
Chemical analyses show that the SiO₂ contents of the Kocali Complex rocks range from 2.41 to 87.60 wt.%, Fe₂O₃ contents from 0.60 to 11.82 wt.%, and CaO contents from 0.32 to 42.92 wt.%. In contrast, the Karadut Formation rocks display SiO₂ contents between 61.31 and 95.24 wt.%, Fe₂O₃ contents of 0.42–3.02 wt.%, and CaO contents ranging from 0.33 to 16.59 wt.%. These results indicate that the units of the Kocali Complex exhibit considerable chemical heterogeneity. The SiO₂, Fe₂O₃, and MgO values are consistent with the characteristic geochemical signature of an ophiolitic mélange. In comparison, the Karadut Formation units are characterized by elevated SiO₂ and CaO contents, reflecting a carbonate-rich sandstone geochemistry. The observed chemical contrasts point to a genetic relationship between ophiolitic source rocks and sedimentary environments. In conclusion, the observed geochemical differences between the Kocali Mélange and the Karadut Formation reveal not only lithological and source-rock diversity but also provide important clues to the geodynamic evolution of the region. In this context, the study makes a significant contribution to the understanding of geodynamic processes by demonstrating the interaction between ophiolitic rocks and the sedimentary basin.

Keywords: Geochemistry; Mélange; Ophiolite; Petrography; Türkiye

How to cite: Erol, İ., Güngör, Y., Ürkkaya, C. S., Vurmuş, Z. D., Özdamar, Ş., and Sarıkaya, O.: Petrography and Geochemistry of the Kocali Ophiolitic Complex and the Karadut Formation (Kahramanmaras, SE Türkiye), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17703, https://doi.org/10.5194/egusphere-egu26-17703, 2026.

Mycotoxins produced by certain fungi contaminate food, crops, and water, posing health risks and causing economic losses. Among the most prevalent, zearalenone (ZEN) and deoxynivalenol (DON) are difficult to remove with conventional adsorbents due to their relatively non-polar nature. Both toxins are associated with serious adverse effects, including endocrine disruption, immunotoxicity, and gastrointestinal damage. This study aims to develop a targeted removal approach for ZEN and DON and to elucidate the underlying mechanisms.

Knowing their large specific surface area, low cost, and good dispersibility, clay minerals have been employed as mineral supports. From this group, we focused on kaolinite-based materials, including a kaolinite-rich sample (M), synthetic calcined kaolinite nanotubes (MNC), halloysite purchased from Sigma-Aldrich (HS), and unpurified halloysite-containing sample (HD). The mineral supports were coated with approximately 20 wt% of TiO₂, g-C₃N₄ (GCN), or a TiO₂/GCN mixture for ZEN removal, and with TiO₂, Fe₂O₃, or a TiO₂/Fe₂O₃ for DON removal. For ZEN, a photodegradation approach using UV light was employed. In contrast, DON, being a more resistant toxin, required the addition of the oxidizing agent peroxymonosulfate (PMS, 2 mM) to achieve efficient degradation.

The GCN and TiO₂/GCN materials were the most effective for ZEN removal, with the MNC-based samples achieving 98.8% and 97.7% degradation, respectively, after 25 min of UV exposure. The mechanisms of ZEN degradation varied with the composite, but for the majority of materials O₂^•⁻ and •OH species played a major role. Importantly, incorporating an insulating clay mineral did not reduce photocatalytic efficiency; rather, the mineral interface appeared to enhance charge separation. Analysis of ZEN photodegradation pathways showed that oxidation and reactive oxygen species led to a breakdown of the carboxyl group and removed functional groups, forming various lower- and higher-mass intermediates [1]. Further degradation cleaved the aromatic ring, producing simpler oxygen-rich chains that can be ultimately mineralized to CO₂ and H₂O.

For DON removal, the MNC-based TiO₂/Fe₂O₃ samples were the most effective, removing 98.8% of the initial concentration after 45 min, while MNC-based samples containing only TiO₂ or Fe₂O₃ achieved 66.1% and 46.0%, respectively. Mössbauer spectroscopy and SEM confirmed the presence of the maghemite phase, showing that Fe₂O₃ loaded on the MNC support is nanosized, providing a large specific surface area for redox reactions and efficient PMS activation. Simultaneous ZEN and DON removal under UV light with PMS activation demonstrated that this approach is effective also for ZEN. Under visible light, DON was also efficiently removed, dropping below the detection limit within minutes using the MNC-based TiO₂/Fe₂O₃ sample.

The results demonstrated the potential of mineral support in photocatalysis and photoinduced chemical oxidation for ZEN and DON removal. Future research will focus on expanding the study on DON, elucidating its degradation mechanisms and pathways.

Acknowledgements
This project was supported by the National Science Centre Poland, under a research project awarded by Decision No. 2021/43/B/ST10/00868.

References
[1] K. Dziewiątka, J. Matusik, M. Herber, E.H. Hill, J. Kuc, G. Cempura, A. Jędras, Enhanced photodegradation of zearalenone with kaolin group-based nanotubular materials: Unveiling reaction mechanisms and pathways, Chemical Engineering Journal 506 (2025) 160198. https://doi.org/10.1016/j.cej.2025.160198.

How to cite: Dziewiątka, K., Matusik, J., and Błachowski, A.: Clay mineral-based materials for mitigating mycotoxin contamination: Two photoinduced removal approaches for zearalenone and deoxynivalenol, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18029, https://doi.org/10.5194/egusphere-egu26-18029, 2026.

Fe-bearing carbonates are increasingly recognized as key phases for iron and carbon storage in Earth’s deep interior, yet their physical properties at high pressure remain poorly constrained, particularly for compositionally complex and structurally disordered systems. In this study, we investigate the high-pressure behavior of ordered and disordered ankerite, Ca(Mg₁₋ₓFeₓ)(CO₃)₂ (0 ≤ x ≤ 0.7), to assess the influence of cation ordering on structural evolution, elastic properties, and Fe spin behavior[1,2]. The present work investigates the high-pressure (HP) behaviour of ankerite, Ca(Mg_1-xFe_x)(CO₃)₂ (x=0.4, 0.7), crystallizing in the R-3 space group, and disordered ankerite with R-3c symmetry. Cation ordering and disordering influence on the physical properties and phase evolution of Fe-dolomite and ankerite [1,2], with important implications for their elastic behaviour, that might help in partially explaining the observed seismic anisotropic anomalies in the mantle wedge [3] as well as contributing in the carbonate’s detection in the inner Earth [4]. Particular attention is given to comparisions with the single carbonate magnesiosiderite, focusing on the Fe spin behavior at high pressure. The analysed P conditions reach 80 GPa, higher than the range typical of the Fe spin crossover in single carbonate magnesiosiderite, i.e., ~43 GPa at room temperatures [5][6]. The results obtained in this work confirm that neither ordered nor disordered ankerite undergo a high-spin to low-spin transition up to 80 GPa, independently on the Fe content.

The project was partially funded by the ‘’BMBF-Verbundprojekt 05K2019-Nanoextrem2” and “DFG core facility for high pressure research” (2018) and “SIMP Research Grant in Crystal ‐ chemistry, in memory of Prof. Fiorenzo Mazzi” (2022).

References:

[1] Zucchini A et al. (2014) Phys Chem Miner 41(10):783-793

[2] Zucchini A et al. (2017) Eur J Mineral 29:227-238

[3] Liu X and Zhao D (2017) Geophys J Int 210:1410-1431

[4] Chariton S et al (2020) Am Miner 105(3):325-332,

[5] Cerantola V et al. (2017) Nat Commun 8:15960

[6] Liu J et al. (2014) Am Mineral 99:84-93

How to cite: Pennacchioni, L., Sakrowski, R., Appel, K., Camarda, C., Mezouar, M., Sahle, C., Zucchini, A., Morgenroth, W., and Wilke, M.: ’Spin behavior of ordered/disordered ankerite at high pressures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18658, https://doi.org/10.5194/egusphere-egu26-18658, 2026.

Modern aircraft engines might experience increased degradation when operating in regions with high contents of atmospheric mineral dust. Whilst not safety critical, this accelerated degradation might result in an increased maintenance burden. There are several distinct mechanisms of degradation caused by ingested dust in different engine parts. Particular focus has been on the damage caused by deposits on high pressure turbine (HPT) blades. Here deposits melt, infiltrate and chemically interact with porous thermal barrier coatings. This study examines the sensitivity of this kind of degradation to ingested mineral dust composition, which varies according to the geographical region of operation.

On exit from the compressor, minerals ingested into the engine can follow two different air flow paths. One is with air separated from the main flow, before entry into the combustor, which is used to cool the HPT blades. Minerals within this flow may be deposited in the HPT shank cavity and experience temperatures of ~800^°C. The second pathway is with the main air flow through the combustor. Minerals following this route experience higher temperatures (>1200^°C) and may be deposited on the HPT blade surface. A comparison of shank cavity with surface deposits isolates the effect that passage through the combustor and residency on the HPT blades has on the chemistry of the deposits. Here, we make this comparison for engines that have operated in different geographical regions.

We have analysed 8 shank cavity and HPT blade surface deposits from aircraft engines using XRD and SEM-EDS to obtain mineralogical and chemical compositions. Shank cavity deposits from a further 56 engines have also been analysed to obtain a sense of compositional variability across different operational regions. The mineral phases present in the shank cavity deposits are similar across all engines analysed and include several minerals, e.g., anhydrite and melilite, that formed in the engine from breakdown reactions of ingested dust. However, the relative abundance of these minerals varies, reflecting the likely composition of atmospheric dust in the regions of operation. The blade deposits are dominated by minerals formed by reactions between ingested minerals and thermal barrier coatings on the HPT blades, including garnets, spinels, and melilite. However, the relative abundance of these minerals also varies across regions.

Our ongoing work compares the chemistry of shank cavity deposits with HPT blade deposits using the minerals and textures to help constrain the processes causing the chemical changes. Concurrently, we seek to compare the chemistry of the shank cavity deposits with ingested dust composition. We aim to establish the extent to which the composition of the HPT deposits, and hence degradation, may be predicted from what is ingested at the front of the engine. With this knowledge, degradation mitigation strategies can then be tailored to operational region.

How to cite: Ownsworth, E., Jones, M., Pawley, A., Covey-Crump, S., Clarkson, R., Hughes, L., Bojdo, N., Dowling, J., and Liu, Y.: Mineralogy and reactions of aircraft engine deposits and relationship to geographical regions of operation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18893, https://doi.org/10.5194/egusphere-egu26-18893, 2026.

The ternary Pb₅(XO₄)₃Cl system (X = P, As, V) comprises a key group of lead apatite minerals controlling the environmental behavior of toxic elements such as Pb, As, and V. Despite their closely related crystal structures, the three binary joins within this system exhibit contrasting miscibility patterns in nature, ranging from continuous solid solutions to compositionally restricted series depending on T.

Here, we investigate the thermodynamic origin of these differences by quantifying mixing behavior along the three binary joins: Pb₅(PO₄)₃Cl pyromorphite – Pb₅(AsO₄)₃Cl mimetite, pyromorphite – Pb₅(VO₄)₃Cl vanadinite, and mimetite–vanadinite. Synthetic samples spanning the full compositional range (X_x = 0–1, Δx = 0.1) were analyzed using transmission infrared spectroscopy combined with autocorrelation analysis [1]. The δΔcorr parameter [1] was calculated independently for each binary join and used as a proxy for local structural heterogeneity related to strain induced by PO₄–AsO₄–VO₄ substitution. The analysis focused on the high-frequency vibrational modes of tetrahedral groups in the ranges 600–1200 cm^-1 (pyromorphite–mimetite), 640–1220 cm^-1 (pyromorphite–vanadinite), and 500–1000 cm^-1 (mimetite–vanadinite).

For the pyromorphite–mimetite series, excess enthalpies of mixing derived from δΔcorr (scaled to ΔH_mix [2]) vary between −0.7 and +0.6 kJ/mol whereas density-functional theory (DFT) calculations using the single-defect approach [3] yield a symmetric distribution of ΔH_mix function with a maximum of 3.8 kJ/mol at intermediate compositions X_P=0.5. This discrepancy between spectroscopically and DFT-derived mixing enthalpies remains unresolved. However, the calculated vibrational entropy of mixing [4] stabilizes the solid solution, resulting in negative Gibbs free energies of mixing with a minimum of approximately -2 kJ/mol at X_P=0.5. This thermodynamic behavior explains the absence of a miscibility gap at 300 K and the continuous nature of the pyromorphite–mimetite solid solution observed in nature [5].

In contrast, the pyromorphite–vanadinite join exhibits very small excess enthalpies of mixing derived from autocorrelation analysis, ranging from −0.23 to +0.18 kJ/mol (near 0), suggesting nearly ideal mixing and random substitution of PO₄ and VO₄ tetrahedra. Contrary, the mimetite–vanadinite series shows a slightly positive and asymmetric distribution of ΔH_mix function with a maximum of ~0.9 kJ/mol at X_As≈0.35. This agrees with DFT-derived ΔH_mix = 1 kJ/mol. Like the pyromorphite–mimetite, mimetite–vanadinite series is stabilized by the negative excess vibrational entropy term. This gives a negative Gibbs free energy of mixing oscillating about -3.5 kJ/mol at 300K.

These results demonstrate that subtle differences in local structural heterogeneity and the balance between enthalpic and entropic contributions govern miscibility in Pb-apatite solid solutions. Future work will extend this approach to the full ternary Pb₅(PO₄)₃Cl–Pb₅(AsO₄)₃Cl–Pb₅(VO₄)₃Cl system to quantify mixing energetics and local structural heterogeneity arising from coupled P–As–V substitution. Financial support for BP was provided by the National Science Center, Poland [Grant No. 2025/57/B/ST10/02894].

References

[1] Salje, E. K. et al. (2000). Eur. J. Mineral., 12, 503–519. [2] Majzlan, J. et al. (2023). Eur. J. Mineral., 35, 157–169. [3] Benisek, A. & Dachs, E. (2020). Phys. Chem. Miner., 47, 15. [4] Benisek, A. & Dachs, E. (2012). J. Alloys Compd., 527, 127–131. [5] Markl, G. et al. (2014). Am. Mineral., 99, 1133–1146.

How to cite: Puzio, B. and Benisek, A.: Local structural heterogeneity and mixing energetics in the pyromorphite–mimetite–vanadinite system, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19035, https://doi.org/10.5194/egusphere-egu26-19035, 2026.

The Niemcza Shear Zone (NSZ) represents one of the key structural elements of the Sudetic segment of the Variscan Belt, yet its tectonic significance remains under discussion. Several models have interpreted the NSZ as a major crustal boundary separating peri-Gondwanan domains. Here we present new insights into the metamorphic evolution of the NSZ based on a comparative analysis of two lithologies from its central domain: the strongly deformed Strach mylonite and the weakly deformed Buk graphitic quartzite.

An integrated approach combining white-mica and garnet–biotite geothermobarometry, Zr-in-rutile thermometry, Raman spectroscopy of carbonaceous material, and major- and trace-element zoning in tourmaline was applied. Both lithologies record similar medium-pressure, high-temperature metamorphic conditions within the greenschist- to amphibolite-facies conditions. Peak metamorphism is estimated at ~6–10 kbar and 630–710 °C, corresponding to the sillimanite stability field.

Tourmaline compositional zoning reveals two stages of prograde growth under predominantly internally buffered conditions, followed by retrograde rim formation linked to deformation-enhanced fluid infiltration, particularly within the mylonitic rocks.

Our results support interpretation of the NSZ as a long-lived, lithospheric-scale shear zone that focused deformation, magmatism and metamorphic re-equilibration during terrane amalgamation.

How to cite: Wicher-Jarząb, D., Szuszkiewicz, A., Szczepański, J., Lis, G. P., Korybska-Sadło, I., and Marciniak-Maliszewska, B.: Constraining the metamorphic evolution of the Niemcza Shear Zone, NE Bohemian Massif (SW Poland) using thermobarometry, Raman spectroscopy, and tourmaline zoning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20036, https://doi.org/10.5194/egusphere-egu26-20036, 2026.

The mining industry faces increasing demand for raw materials and stringent environmental regulations imposed by the European Union. These constraints promote the development of technologies that enable the reuse of industrial waste. Such approaches are consistent with the principles of the circular economy, which emphasize recycling and material recovery. The use of industrial by-products as partial substitutes for natural raw materials is well established in the construction sector.

Carbonate-rich flotation tailings from the Zn–Pb mining industry can partially replace sand in cement mortars. This study aimed to evaluate methods for limiting Pb release during the weathering of mortars containing such material as additive. In the experiments, cement mortars were prepared with 32 wt% of quartz sand replaced by flotation tailings from a Zn–Pb ore-processing plant. Two immobilization strategies were tested:

• Addition of phosphate ions (PO₄³⁻) utilizing Phosphate-Induced Metal Stabilization (PIMS), based on in situ precipitation of the low-solubility phase pyromorphite, Pb₅(PO₄)₃
• Amendment with natural zeolite (clinoptilolite) as a sorbent with a high affinity for Pb.

Mortars were prepared in accordance with EN 196-1. Two compositions were investigated:
(i) mortar containing flotation tailings, Portland cement (CEM I 52.5 N), and water enriched in PO₄³⁻ and Cl⁻;
(ii) mortar containing flotation tailings and clinoptilolite, with 20 wt% of the cement replaced by zeolite, mixed with deionized water.

After curing for 28 days, leaching tests were performed following PN-EN 12457-2:2006.

Phosphate addition did not reduce Pb mobility. The leached Pb concentration was at the order of 0.8 mg kg⁻¹, identical to that of the reference mortar without immobilizing additives. In contrast, zeolite amendment was fully effective. Lead concentrations in the leachate were below the detection limit (~0.05 mg L⁻¹).

These results demonstrate that cement mortars incorporating Zn–Pb flotation tailings can be produced with effective immobilization of Pb by minor additions of clinoptilolite. Further studies are required to optimize zeolite content with respect to the mechanical properties of the mortar. This approach offers a promising pathway for reducing mining waste and conserving natural mineral resources.

How to cite: Manecki, M. and Wrona, P.: Immobilization of Pb in calcite–dolomite flotation tailings used as a concrete additive, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20562, https://doi.org/10.5194/egusphere-egu26-20562, 2026.

Scandio-fluoro-eckermannite (IMA 2024-002), a new Sc-dominant amphibole-supergroup mineral, has been discovered in the Bayan Obo REE-Nb-Fe polymetallic deposit, China. The new mineral was collected from banded Fe-REE ores that have formed due to the fenitization caused by carbonatite intrusion, in the Main and East open pits at Bayan Obo. Associated minerals include monazite, bastnäsite, magnetite, biotite, fluorite, bazzite, thortveitite, and magnesio-fluoro-arfvedsonite. The new mineral occurs as euhedral to subhedral crystals and aggregates, appearing both as inner zones of a crystallization sequence from scandio-fluoro-eckermannite to magnesio-fluoro-arfvedsonite as well as homogeneous fine-grained particles, reaching up to 350 μm in size and approximately 7 wt% in Sc₂O₃ contents.

Scandio-fluoro-eckermannite displays a light yellow to light blue color under plane-polarized transmitted light, with perfect cleavage on {110}, non-magnetic, and no fluorescence. The hardness is 5-6 by analogy to eckermannite and the calculated density is 3.097 g/cm³. Electron microprobe analyses obtained the main components (average value in wt. %): Sc₂O₃ 6.39, SiO₂ 54.30, MgO 13.42, Na₂O 8.38, Al₂O₃ 1.29, MnO 1.47, CaO 1.21, K₂O 0.47, FeO_calc 6.43, Fe₂O_3calc 3.80, F 3.01, H₂O⁺_calc 0.67, F≡O -1.27, total 99.74. The composition normalized on the basis of 24 anions (O, OH, F, Cl), with the assumption of (OH, F, Cl)=2 apfu, corresponds to the empirical formula ^A(Na_0.52K_0.09□_0.39)_S1.00 ^B(Na_1.81Ca_0.19)_S2.00 ^C(Mg_2.87Fe²⁺_0.77Mn³⁺_0.18Sc_0.80Fe³⁺_0.41)_S5.03 ^T(Si_7.78Al_0.22)_S8.00 O₂₂ ^W[F_1.36(OH)_0.64]_S2.00. It leads to the simplified formula (Na,□)(Na,Ca)₂[(Mg,Fe²⁺)₄(Sc,Fe³⁺,Mn³⁺)][(Si,Al)₈O₂₂)](F,OH)₂and the ideal formula NaNa₂(Mg₄Sc)Si₈O₂₂F₂. The crystal structure was refined in the monoclinic system, space group C2/m (#12). Its unit-cell parameters are: a = 9.8212(3) Å, b = 18.0866(5) Å, c = 5.3091(2) Å, β = 103.767(4)°, and Z = 2, with the a:b:c ratio of 0.543: 1: 0.294. The crystal-structure refinement indicates that the Na is the dominant cation at the A(m) and M(4) sites, Mg is the dominant cation at the M(1) and M(3) sites, Sc is the dominant trivalent cation at the M(2) site, and F is the dominant cation at the O(3) site. Therefore, this is the Sc-dominant variety of fluoro-eckermannite. The discovery of scandio-fluoro-eckermannite highlights the importance of amphibole in controlling Sc in this type of ore-forming system. Scandio-fluoro-eckermannite might also be used as a potential recorder to investigate the enrichment process of Sc in the Bayan Obo deposit.

How to cite: Liu, S., Fan, H.-R., Gu, X.-P., Butcher, A. R., Lahaye, Y., Michallik, R. M., Jolis, E. M., Lukkari, S., Li, X.-C., and Liu, X.: Scandio-fluoro-eckermannite, ideally NaNa2(Mg4Sc)(Si8O22)F2, a new Sc-dominant amphibole-supergroup mineral from the Bayan Obo deposit (China), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22633, https://doi.org/10.5194/egusphere-egu26-22633, 2026.

Understanding rare-gas release requires interdisciplinarity. Hydrous minerals degas ³⁹Ar and ⁴⁰Ar in vacuo during structural collapse due to dehydroxylation [1,2], never by Fick's Law in an inert, homogeneous matrix. Therefore monomineralic micas always give "plateaus" [3,4] despite age-zoning. Discordant age-spectra instead proceed from polymineralic, heterochemical, diachronous mixtures, unambiguously revealed by common-denominator three-isotope correlations [5,2]. The "Bruderheim staircase archetype" [6] wasn't a "lognormal distribution of monomineralic whole-rock crystals" but a more mundane polyphase maskelynite-pyroxene-anorthite assemblage [7,8]. For micas and Bruderheim, downslope extrapolations are arbitrary.

The inertness of the Itrongay sanidine crystal structure during laboratory heating was assessed by Raman microspectroscopy from 300 to 1000 °C [9]. Raman modes define robust trends at increasing temperature and over time at constant temperature, mirroring progressive excitation of phonon modes associated with structure modifications: interatomic bond stretching/deformation; Si,Al disordering; deformation/rotation of SiO₂ tetrahedra. Differential activation of phonon modes is reversible, but disordering is are irreversible. The K-feldspar structure is not inert during laboratory heating, explaining the observed break in Arrhenian slope of Ar release rate [10]. This forbids downslope extrapolation of laboratory data to geological conditions.

The in vacuo releases between 500-1460 °C of ⁴He*, ²⁰Ne_F, ³⁷Ar_Ca, ³⁸Ar_Cl, ⁸⁰Kr_Br, ¹²⁸Xe_I, ¹³¹Xe_Ba, ¹³⁴Xe_U from irradiated fluorapatite are linear, parallel Arrhenius trajectories. E=62±5 kJ/mol is independent of atomic radius, D₀ values decrease from He to Xe by ~4 orders of magnitude [11]. Differential release diagrams show bimodal degassing patterns for Ne and Ar and a single burst above 1360 °C for Kr and Xe. The crystallographic site of Ba and I had no control on Xe release. All degassing rates steepen by 500 times at 1360 °C, and merge. The extreme Arrhenian break-in-slope and the merger of trajectories widely separated below 1360 °C reflect sudden, major, energetically very costly structural reordering at 1360 °C, which was documented by Raman spectroscopy, XRD, TEM and microchemical analysis by LIBS. Complete outgassing of Ne, Ar, Kr and Xe requires complete defluorination reaction modifying the apatite structure. Discrete phase transitions at high T make downslope extrapolations to low T incorrect.

[1] Zimmermann 1970, https://doi.org/10.1016/0016-7037(70)90045-1

[2] Villa 2021, https://doi.org/10.1016/j.chemgeo.2021.1.120076

[3] Foland 1983, https://doi.org/10.1016/S0009-2541(83)80002-3

[4] Hodges &al 1994, https://doi.org/10.1130/0091-7613(1994)022<0055:AAAGIM>2.3.CO;2

[5] Villa & Hanchar 2017, https://doi.org/10.1016/0012-821X(66)90061-6

[6] Turner &al 1966, https://doi.org/10.1016/0012-821X(71)90051-3

[7] Duke &al 1961, https://doi.org/10.1029/JZ066i010p03557

[8] Baadsgaard &al 1961, https://doi.org/10.1029/JZ066i010p03574

[9] Kung & Villa 2021, https://doi.org/10.1016/j.chemgeo.2021.120382

[10] Wartho &al 1999, https://doi.org/10.1016/S0012-821X(99)00088-6

[11] Villa &al 2024, https://doi.org/10.1016/j.chemgeo.2023.121860  

How to cite: Villa, I. M.: Ar data extrapolation from the lab to rocks: systematics of noble gas release in vacuo from micas, feldspars, etc., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3984, https://doi.org/10.5194/egusphere-egu26-3984, 2026.

Large-scale strike-slip structures in the northeastern Tibetan Plateau, such as the West Qinling Fault, have accommodated the northeastward extrusion of the plateau crust, thereby recording its outward growth. However, the Cenozoic tectonic evolution of the West Qinling Fault remains incompletely understood. In this study, we integrate new and published apatite (U-Th)/He thermochronology with exiting sedimentary and geomorphological records to refine the exhumation history of the West Qinling in response to the kinematic evolution of the West Qinling Fault. The combined apatite (U-Th)/He dataset and thermal history modeling reveal two significant episodes of accelerated exhumation in the West Qining during the Eocene (~44–36 Ma) and the Miocene (~17–10 Ma). We attribute the Eocene exhumation to enhanced thrusting along the West Qinling Fault, representing a direct far-field response to the India-Asia collision. In contrast, the Miocene exhumation is linked to oblique-slip motion along the West Qinling Fault, marking a kinematic transition of the fault from thrust- to strike-slip-dominated deformation since the middle Miocene. Integration of our findings with geophysical, sedimentary, and petrological evidence suggests that this kinematic change was caused by a rheological weakening of the lower crust due to localized asthenospheric upwelling. The synchronous kinematic shift along the East Kunlun Fault, along with its similar deep lithospheric structure beneath the Hoh Xil region, implies a genetic link between the West Qinling and East Kunlun faults. We propose that localized asthenospheric upwelling thermally weakened the lower crust beneath both fault systems, thereby driving the kinematic shift during the middle Miocene. This analogy underscores the potential major role of small-scale asthenospheric upwelling-induced thermal weakening of the lower crust in affecting surface deformation during the late stage of orogenic plateau formation.

How to cite: Guo, C., Zhang, Z., Xiao, W., Malusà, M., von Hagke, C., Wu, L., Heberer, B., Friedrichs, B., Wang, N., Xiang, D., and Grasemann, B.: Eocene thrust vs. Miocene strike-slip: Kinematic transition of the West Qinling Fault driven by localized asthenospheric upwelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5908, https://doi.org/10.5194/egusphere-egu26-5908, 2026.

 Ti-bearing andradite [Ca₃Fe²⁺Ti⁴⁺Si₃O₁₂] is generally widespread, a diagnostic accessory phase of silica undersaturated alkalic plutonic and volcanic rocks but also occurs in skarn and hydrothermal alteration assemblages, which is associated with the major economic critical metals (Nb, LREE) mineral in deposits related to carbonatite and alkaline intrusions, although it never occurs in large quantities. Because of their enrichment in incompatible elements, carbonatites and alkaline rocks have also been increasingly used by isotope geochemists to study mantle evolution processes leading to continental magmatism and to track the pathways of lithospheric recycling. For both practical and academic applications, it is important to understand the timing of carbonatite and alkaline magmatism relative to such geodynamic processes as plate collisions, rifting, crustal upcoming.

Considering its potential U-Pb dating and perseverance later alteration as well LREE-enrichment, in situ laser ablation is considered as the most suitable method to measure their U-Pb and Sm-Nd isotopic compositions. Twenty-seven Ti-bearing andradite samples from thirteen typical carbonatite and/or alkaline intrusions in Prairie Lake and Ice River, Canada, Magnet Cove, USA, Alnö, Sweden, Fen, Norway, Ozernaya and Ural, Russia, Zijinshan and Fanshan, China, Tamazert, Morocco, San Ieo, Italy, Kaiserstuhl, Germany, Schaffhausen, Switzerland, were conducted for major, trace, U-Pb and Sm-Nd measurement using Electron microprobe (EPMA) and laser ablation (multicollector) inductively coupled plasma mass spectrometer (LA-(MC)-ICP-MS). Based on development of several in-house Ti-bearing andradite reference materials (PL34, IR18, MC15) demonstrates that precise and accurate U-Pb ages can be obtained after common Pb correction. Moreover, we obtained a reliable in situ Sm-Nd isotopic data because of the relatively moderate LREE content in our samples. These results will have significant implications for understanding the genesis of carbonatite or alkaline intrusion related to metallogenic geochronology and ore deposits research.

How to cite: Yang, Y.-H., Wu, F.-Y., Zhao, H., Xu, L., Huang, C., Wu, S.-T., Xie, L.-W., and Yang, J.-H.: U–Pb dating and Sm–Nd isotopic measurement of Ti–bearing andradite: Reference material development and in situ applications by LA-(MC)-ICP-MS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6557, https://doi.org/10.5194/egusphere-egu26-6557, 2026.

Zircon is a key accessory mineral because it can retain geochronological and geochemical information. In mafic and ultramafic rocks, zircon is scarce and restricted to localised microstructural domains, making its detection difficult and largely dependent on sampling strategy. We present a reproducible workflow for locating zircon directly within mafic and ultramafic rocks, designed to improve detection efficiency while preserving textural context. The approach is based on preparing multiple small rock slabs with carefully controlled polishing quality, allowing systematic inspection of large surface areas. This slab-scale screening strategy departs from conventional thin-section-based searches and is essential for accessing zircon in zircon-poor systems. Large-area elemental mapping is performed using SEM, EPMA, and micro-XRF, all of which can identify Zr-enriched domains. Comparative testing shows that micro-XRF provides the most favourable balance between acquisition time, analysed surface area and sensitivity to zirconium, making it suitable for first-pass screening of large sample sets. Across the different analytical methodologies used, the Zr signal can be affected by spectral interferences from other elements. For this reason, zircon detection in this study relies on the combined behaviour of multiple elements and on their statistical consistency across the mapped area. Zircon candidates are retained only when they meet several independent criteria, thereby reducing misidentification due to background noise or overlapping mineral phases. This approach enables the recovery of zircon grains down to ~50 µm and can be readily adapted for the in-situ detection of other scarce accessory minerals. More generally, it provides a practical framework for accessing mineral-scale records in systems where key phases are sparse, heterogeneous and difficult to locate using conventional approaches.

Work supported by the Spanish Ministerio de Ciencia e Innovación, Fondos Feder, PID2023-149105NA-I00. M.S.F. benefits from the FPI-PRE2023-002262.

How to cite: Salguero Fuentes, M., Barcos, L., Cambeses, A., Garcia Casco, A., Molina, J. F., Montero, P., Novo Fernández, I., Pujol Solà, N., Repczyńska, M. M., and Bea, F.: How to find rare zircon in mafic and ultramafic rocks: an integrated in-situ detection workflow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6729, https://doi.org/10.5194/egusphere-egu26-6729, 2026.

Thermochronology has advanced through the development of new methods and applicable mineral systems, with multi-method approaches proving essential for bridging temperature–time gaps and improving the resolution of thermal history reconstructions. Here, we apply a zircon-based multi-method approach to investigate the thermotectonic evolution of the Araçuaí Orogen, along the São Francisco Craton in Brazil. While the Mesozoic–Cenozoic evolution of the orogen is relatively well constrained, its earlier thermal history remains poorly understood. To address this gap, we expand an existing apatite fission-track (AFT) dataset of 20 samples by adding new zircon (U–Th–Sm)/He (ZHe) ages, extending thermal constraints from the apatite partial fission-track annealing zone (APAZ; ~60–120 °C) to higher-temperature conditions (~140–220 °C). In addition, four representative samples were selected along a north–south transect across the craton–orogen interaction zone for zircon Raman multi-band thermochronology and zircon U–Pb analyses. Zircon Raman multi-band thermochronology, a recently developed approach, further extends thermal constraints to mid- and high-temperature conditions (~260–370 °C).

The ZHe dataset reveals a systematic relationship between effective uranium (eU) concentration and single-grain ages. Zircons with low eU contents (<500 ppm) yield predominantly Paleozoic ZHe ages, ranging from the Cambrian to Carboniferous (ca. 500–350 Ma), whereas grains with progressively higher eU concentrations record younger ages spanning the Late Paleozoic to Early Cretaceous (ca. 350–100 Ma). This inverse age–eU relationship is consistent with radiation-damage–controlled helium diffusion in zircon, as predicted by established diffusion models.

Raman ages derived from multiple zircon bands (ν1, ν2, ν3, and external bands) indicate distinct thermal responses across the transect. Two samples record Raman ages overlapping with or being older than the Araçuaí orogeny, suggesting preservation of pre- to syn-orogenic thermal signatures. In contrast, Raman ages from the other two samples correspond to the late stages of the orogeny or post-date it.

Comparison of Raman-derived ages with ZHe and AFT data provides constraints on cooling rates through successive temperature windows. Samples showing convergence of Raman, ZHe, and AFT ages indicate relatively rapid cooling through mid- and low-temperature regimes, whereas increasing separation between these chronometric results reflects more prolonged cooling histories. Variations in the thermal sensitivity of individual Raman bands, reflected in their accumulated radiation damage, constrain the rate of cooling across mid-temperature ranges: synchronous band resetting indicates faster cooling whereas differential band behavior suggest slower, stepwise cooling.

These results reinforce evidence that the craton–orogen interaction zone of the São Francisco Craton experienced significant thermal overprinting associated with the development of the Araçuaí orogenic front (ca. 500 Ma), even though the underlying crust is of Rhyacian (~2.1 Ga) and Archean (~3.2 Ga), as indicated by zircon U–Pb data. Thermal history modelling indicates that following orogenesis, the region underwent substantial cooling, allowing samples to pass through progressively lower-temperatures and reach shallow crustal levels by the end of the Paleozoic. Subsequent opening of the South Atlantic Ocean preferentially affected structurally weakened domains, particularly areas associated with deep-seated faults and shear zones.

How to cite: Fonseca, A., De Grave, J., Novo, T., J. Sieber, M., Wilke, M., Hartel, B., van Schijndel, V., Stammeier, J., Wapenhans, I., van der Beek, P., and Sobel, E.: Zircon triple dating (U–Pb, Raman, and U–Th–Sm/He) constraints on the thermotectonic evolution of the Araçuaí Orogen at the craton–orogen interface (Brazil), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7226, https://doi.org/10.5194/egusphere-egu26-7226, 2026.

Molybdenite is the principal host mineral for rare metals such as molybdenum and rhenium and is widely distributed in various hydrothermal deposits. Owing to its high rhenium content and negligible common osmium, molybdenite is an ideal target for Re–Os isotopic dating. Re–Os ages of molybdenite can directly constrain the timing of metal sulfide mineralization.

In recent years, the development of inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) has provided a new analytical approach for in situ β-decay isotopic dating, including Rb–Sr, Lu–Hf, K–Ca, and Re–Os. In this study, an i CAP ICP-MS/MS coupled with a 193 nm G2 laser and N₂O as the reaction gas was employed (Fig. 1). Based on systematic characterization of the reaction products between N₂O and Re and Os, the reaction gas flow rates were optimized, and in situ Re–Os dating of molybdenite was established.

This present protocol was applied to Re–Os age determinations of various molybdenite with ages ranging from 2.7 Ga to 0.15 Ga. The obtained results are consistent with those from ID-NTIMS or ID-ICP-MS. The study demonstrates that reliable in situ Re–Os ages can be achieved when the Re content of molybdenite more than 5 ppm. When combined with trace-element geochemical characteristics, in situ Re–Os dating of molybdenite provides important constraints on the timing of mineralization and genetic processes, offering valuable insights into the detailed geological evolution of metal sulfide deposits.

Figure 1. Schematic illustration of the basic principles of plasma tandem mass spectrometry. In the Re–Os system, reactions between rhenium (Re) and osmium (Os) with nitrous oxide (N₂O) produce oxide species exhibiting a mass shift of 64 amu. However, a small proportion of Re also reacts with N₂O to form ¹⁸⁷ReO₄, which interferes with the target ion ¹⁸⁷OsO₄, requiring appropriate interference correction.

How to cite: Wang, Y., Yang, Y., Wu, S., Chu, Z., Xie, L., and Xu, J.: In situ Re-Os dating of molybdenite by LA-ICP-MS/MS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7759, https://doi.org/10.5194/egusphere-egu26-7759, 2026.

Molybdenite is an ideal mineral for Re-Os isotopic dating, and its Re-Os isotopic systematics are widely employed to constrain the timing of hydrothermal metal mineralization. However, high-precision Re-Os isotopic dating (precision <1‰) remains a global challenge, as most published molybdenite Re-Os isotopic ages exhibit dating precisions far above 3‰, with only scarce data falling between 1‰ and 3‰, and very few cases achieving <1‰, which severely hinders the understanding of metallogenic regularity and the optimization of mineral exploration targets. In this study, the chemical separation and instrumental analysis methods for molybdenite Re-Os isotopic dating have been optimized. Using this improved isotopic dilution method, we analyzed the Huanglongpu molybdenite (a widely utilized molybdenite reference material) and molybdenite samples from four representative metal deposits. Each individual analysis achieved a dating precision of <1‰, with the best dating precision reaching 0.13‰. In addition, the weighted mean age precision of molybdenite from the Baishiding polymetallic deposit also reached 1‰. This study reveals that the molybdenite Re-Os isotopic dating can indeed serve as another reliable high-precision dating tool, complementing the well-established U-Pb dating method for deciphering Earth's geological timescale.

How to cite: Fan, X., Xu, J., Li, J., Wang, G., and Zeng, Y.: High precision Re-Os isotopic dating of molybdenites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7785, https://doi.org/10.5194/egusphere-egu26-7785, 2026.

The Cenozoic India-Eurasia collision drove widespread intracontinental deformation across Central Asia, culminating in northward indentation of the Pamir and its eventual contact with the South Tianshan. However, the timing and kinematic development of the Pamir-Tianshan convergence, as well as its influence on shaping regional topography and climate, remain debated. Here we report more than 200 new apatite (U-Th-Sm)/He (AHe), apatite fission-track (AFT), and zircon (U-Th-Sm)/He (ZHe) dates from 49 samples collected from the North Pamir-South Tianshan convergence zone in the westernmost Tarim Basin, NW China. These data, integrated with inverse thermal history modeling and probabilistic estimates of cooling onset, reveal a protracted, stepwise convergence history since the late Eocene. Initial convergence occurred from the late Eocene to the middle Miocene (~35-15 Ma), marking the onset of cooling and deformation in the hinterlands. During the middle Miocene (~15-10 Ma), deformation propagated basinward into the foreland, accompanied by the activation of frontal thrust systems in both orogens. Continued convergence during the late Miocene (~10-5 Ma) led to initial interaction between the North Pamir and South Tianshan thrust systems, followed by propagation of deformation along frontal thrusts during the Pliocene to Quaternary (~5-0 Ma), producing the present-day superimposed and imbricated thrust architecture in the convergence zone. This progressive convergence and surface uplift gradually narrowed and closed topographic corridors between the Pamir and Tianshan, restricting westerly moisture transport into the Tarim Basin and promoting the development of the Taklimakan Desert. Together with existing paleoclimate records, our results demonstrate that regional tectonic processes, acting in concert with global climatic forcing, played a dominant role in the long-term aridification of Central Asia.

How to cite: Wang, F., R. Sobel, E., van der Beek, P., L. Colleps, C., Stammeier, J., Glodny, J., and Zhu, W.: Late Cenozoic Pamir-Tianshan convergence and its tectonic-climatic implications revealed by low-temperature thermochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8250, https://doi.org/10.5194/egusphere-egu26-8250, 2026.

The Ag-Au (Cu,Pb,Zn) San Pedro epithermal system at Andacollo, Argentina, has been dated using ³⁹Ar-⁴⁰Ar together with Sr and Pb stepwise leaching. A precondition for multi-isotope analysis was a very detailed petrographic study of 12 hydrothermal pulses. Element maps were obtained by SEM-EDS on three thin sections from two drillcores, DHA-30 and -35. Twelve samples for isotope analyses, weighing ca. 2-10 mg, were cut with a steel blade from the analyzed thin sections, intentionally collecting "fresh" paragenetic adularia mantled by secondary alteration products to different degrees, in order to constrain the alteration trends in the Ar, Sr and Pb isotopic systems. Nine were analyzed by ³⁹Ar-⁴⁰Ar step-heating and three were step-leached [1] measuring both Sr and Pb isotopic compositions.

The Ar results demonstrate a plurality of alteration phases. A broad correlation trend between Cl/K (which should be zero in fresh feldspars) and step ages confirms the variable mass balance between primary adularia and secondary sericite, smectite, chlorite, kaolinite, and apatite. The end-members of the alteration trends observed in the scattered Ca/K-age correlation are different from those of the Cl/K-age correlation, requiring ≥ 4 compositionally different alteration phases. A regression to zero Cl/K in the three DHA-30 aliquots indicates that the primary adularia is 77±6 Ma old (2 sigma), consistent with cutting relations with dacitic dykes. The saline fluid inclusions, observed in different thick sections of the same cores, were decrepitated at low furnace temperature giving a very high ³⁸Ar/³⁹Ar ratio and an ⁴⁰Ar*/Cl ratio of 7.7×10^-5, the same order of magnitude as the ⁴⁰Ar*/Cl ratio measured by Turner in fluid inclusions from Cornwall [2], whereby primary and secondary fluid inclusion in Andacollo have different ⁴⁰Ar*/Cl ratios.

The six DHA-35 aliquots also show a broad Cl/K-age correlation; Cl/K ratios are higher, indicating a higher overall contamination. The extrapolated adularia age, 85±13 Ma, is statistically indistinguishabe from DHA-30.

The three Sr-Pb leach fractions gave alteration signatures very distinct from the adularia proper, both in Sr and Pb. The signature of the DHA-30 alteration is different from DHA-35. The Sr, and especially Pb, signature of both alteration fluids is very radiogenic, i.e. compatible with circulation through old country rocks. The host rocks are Carboniferous; however, significant inherited and detrital zircon contributions of Eo- to Mesoproterozoic age have been reported in both volcaniclastic and sedimentary rocks respectively [3,4]. This suggests the reworking of a Proterozoic basement, and hence a contribution to the isotopic signature of the analysed hydrothermal minerals.

The compositional and isotopic differences between the two drillcores are compatible with, but not proof of, a long-lasting alteration history as documented in other large ore deposits [5,6].

[1] Villa & Hanchar (2013) Geochim. Cosmochim. Acta 101, 24-33

[2] Turner (1988) Geochim. Cosmochim. Acta 52, 1443-1448

[3] Dicaro et al (2024) J. South American Earth Sci 148, 105158

[4] Pons et al, in preparation

[5] Kang et al (2020) Ore Geol. Rev. 122, 103527, 1-23

[6] Virmond et al (2024) Contrib. Min. Petrol. 179, 88

How to cite: Dicaro, S., Villa, I. M., and Pons, M. J.: Multi-isotopic chronology of the polygenetic San Pedro epithermal vein system, Andacollo Mining District, Argentina, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8286, https://doi.org/10.5194/egusphere-egu26-8286, 2026.

Low-temperature geochronology using multiple isotopic systems is a powerful approach for reconstructing the tectono-thermal evolution of sedimentary basins. As individual dating techniques have distinct strengths and limitations, integrating complementary geochronological methods provides a more robust framework for constraining shallow-crustal thermal events. In this study, we examine the thermal and tectonic evolution of east-central Australia, from the eastern coast to the continental interior, through isotopic dating of authigenic illitic clay minerals. We integrate new and published Rb–Sr, K–Ar, and ⁴⁰Ar/³⁹Ar illite geochronology and critically assess the applicability of these methods when applied to low-temperature mineral systems.

Our results identify multiple episodes of thermal and fluid-flow activity during the Early Jurassic (~200–190 Ma), Middle Jurassic (~165 Ma), Early Cretaceous (~120–115 Ma), and Late Cretaceous (~100–95 Ma, ~85–80 Ma, and ~70 Ma). These events broadly coincide with periods of subduction-related orogenesis and rifting along eastern Australia. Jurassic illite ages from the Permo-Carboniferous Galilee Basin are nearly synchronous with the development of the Eromanga, Surat, and Clarence–Moreton basins, and reflect contemporaneous intraplate tectonism linked to subduction processes.Early Cretaceous ages correspond with magmatic activity in eastern Queensland, including the Whitsunday Volcanic Province, and associated arc- or rift-related tectonism. Late Cretaceous ages are consistent with apatite fission-track (AFT) data and indicate a regional extensional regime that culminated in sea-floor spreading east of the Australian continent.

Although these thermal events occurred far from the active Mesozoic plate margin, they are best explained by the dynamic effects of shallow subduction and/or the transmission of far-field stresses into a mechanically and thermally weakened continental interior, resulting in widespread subsidence, extension, and enhanced heat and fluid flow. These findings have important implications for energy and resource exploration, as Cretaceous tectonic reactivation defines fault zones that currently facilitate geothermal fluid upwelling in east-central Australia. Interaction of these fluids with Precambrian granitic basement rocks enriched in incompatible and radioactive elements highlights the potential of low-temperature geochronology to constrain the timing of fluid–rock interaction and to inform exploration strategies for critical metals and carbon-free gas resources in sedimentary basins.

How to cite: Uysal, I. T., Babaahmadi, A., Zhao, J., Aykut, T., and Todd, A.:  Tectono–thermal evolution of the east-central Australian intraplate: Rb–Sr, K–Ar and 40Ar/39Ar geochronology of authigenic illite., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8468, https://doi.org/10.5194/egusphere-egu26-8468, 2026.

LA-ICP-MS/MS single-spot Rb–Sr analysis has become a powerful tool for in situ dating of ultra-radiogenic minerals such as muscovite. However, this technique relies critically on matrix-matched, highly radiogenic reference materials (RMs) for external calibration. Accurate characterization of such RMs, in turn, requires high-precision isotope dilution mass spectrometry (ID-MS).

Nevertheless, ID-MS analysis of highly radiogenic materials remains technically challenging. First, extremely high Rb/Sr ratios hinder complete separation of Sr from Rb, resulting in potential ⁸⁷Rb interference on ⁸⁷Sr during TIMS Sr isotope measurements. Second, very high ⁸⁷Sr/⁸⁶Sr ratios combined with low absolute ⁸⁶Sr abundances render analyses highly sensitive to Sr procedural blanks. Consequently, robust data quality control for ID-MS itself is essential, necessitating the availability of highly radiogenic RMs suitable for ID-MS validation. At present, however, such reference materials remain scarce.

In this study, we developed an improved Sr-specific resin separation protocol aimed at maximizing Sr recovery during ID-MS Rb–Sr analysis of highly radiogenic samples. The key modification involves dissolving HF-digested sample residues in a mixed acid of 7.5 M HNO₃ and 2.5 M HCl, rather than the conventionally used 3 M or 7 M HNO₃ alone, prior to loading onto the Sr-specific resin column. The mixed HCl–HNO₃ acid significantly enhances dissolution of fluoride-bearing residues following HF digestion. In contrast, when pure HNO₃ is used, more than 95% of Sr is coprecipitated with fluorides for muscovite samples, leading to substantial Sr loss. The improved protocol results in markedly increased Sr recovery and more reliable ID-MS measurements.

Using this optimized separation procedure, we conducted comprehensive ID-MS Rb–Sr analyses of two candidate reference materials: the pegmatite RM OU-9 (IAGeo Limited) and the muscovite Ar–Ar age RM ZMT04. OU-9 yields Rb and Sr mass fractions of 1227 ± 17 μg g⁻¹ and 13.07 ± 0.18 μg g⁻¹, respectively, with ⁸⁷Rb/⁸⁶Sr = 843.1 ± 3.8 and ⁸⁷Sr/⁸⁶Sr = 22.217 ± 0.089, corresponding to an Rb–Sr age of ~2650 Ma with an initial ⁸⁷Sr/⁸⁶Sr of ~1.2. ZMT04 contains 2494 ± 22 μg g⁻¹ Rb and 36.05 ± 0.25 μg g⁻¹ Sr, with ⁸⁷Rb/⁸⁶Sr = 832.4 ± 5.2 and ⁸⁷Sr/⁸⁶Sr = 32.60 ± 0.19, corresponding to an Rb–Sr age of ~1800 Ma with an initial ⁸⁷Sr/⁸⁶Sr of ~0.705. These results demonstrate that both materials have strong potential as highly radiogenic reference materials for ID-MS Rb–Sr geochronology.

How to cite: Chu, Z., Cui, T., Shi, W., Zhang, W., Li, Y., Yang, Y., Xu, L., and Peng, P.: Improved Sr-Specific Resin Separation Protocol and Development of High-Radiogenic Reference Materials for ID-MS Rb–Sr Geochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8484, https://doi.org/10.5194/egusphere-egu26-8484, 2026.

The West Kunlun (WKL) orogen, a pivotal boundary on the western Tibetan Plateau, records the dynamic interplay between northward underthrusting Indian lithosphere and the Tarim craton. Despite its significance, the exhumation history and mechanisms of plateau growth in this region remain contentious. Here, apatite fission-track (AFT) and (U-Th)/He (AHe) thermochronology data from three bedrock elevation transects across the WKL were used to refine the Miocene exhumation processes in the region. Our results reveal a regionally consistent two-phase acceleration in late Miocene exhumation at ca. 11–10 and ca. 7–6 Ma. Integration with regional thermochronologic, magmatic, and seismic data shows a systematic younging of cooling ages and (ultra)potassic magmatism toward the WKL, alongside increasing exhumation rates. These trends reflect outward plateau expansion driven by progressive indentation of the Indian plate into Asia. This culminated at ca. 11–10 Ma, when the cratonic Indian slab directly impinged the Tarim craton, as evidenced by rapid surface uplift and the formation of ca. 10 Ma and younger (ultra)potassic magmas in the WKL orogen. Our findings highlight the coupling between deep lithospheric processes and surface deformation, providing critical constraints on the timing of the India-Tarim collision and the mechanisms driving plateau growth along the northwestern margin of the Tibetan Plateau.

How to cite: Xiang, D.: Late Miocene rapid exhumation in the West Kunlun range: Insights into Tibetan Plateau growth and India-Asia lithosphericcollision, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9727, https://doi.org/10.5194/egusphere-egu26-9727, 2026.

Monazite U–Th–Pb ages are commonly coupled with Y and heavy rare earth element (HREE) contents to link reactions, particularly those involving the formation and breakdown of garnet, with pressure–temperature (P–T) paths to constrain and uncover orogenic processes. This link assumes that changes in garnet modal abundances reflect changes in P–T and no other processes. Here we show that protracted and cryptic fluid-driven dissolution-reprecipitation of garnet and monazite disturbed the P–T–time(t) relationship between these two minerals.

We collected samples of metapelitic schists from the Yardoi gneiss dome, southern Tibet. The central portion of the Yardoi dome comprises orthogneiss and metapelites intruded by Eocene (43–35 Ma) to Miocene (17 Ma) granitoids, providing a critical window investigate fluid–rock interaction in mid-crustal metamorphic rocks. Our data constrain prograde to peak metamorphism from 5.7 kbar and 550°C to 7.5–8.5 kbar and 650–750 °C, followed by retrograde metamorphism at 5.5–6.5 kbar and 650–700°C. Low Y+HREE monazite domains dated to 41–46 Ma indicate peak metamorphism in the presence of garnet at this time, whereas high Y+HREE contents between 23 and 15 Ma indicate the timing of garnet breakdown during isothermal decompression. These data indicate 20–30 Myr at 650–700°C, consistent with near complete resetting of garnet major element zoning in most samples.

One sample near the core of the dome displays atoll garnets along with biotite, muscovite, plagioclase, quartz, and rutile. Annuli of plagioclase, quartz, and biotite grains separate the garnet core from the rim. Monazite from this sample show a quasi-continuous age spread from 50 Ma to 19 Ma, with an increase in Y + HREE between 45 and 38 Ma, followed by a decrease after ~38 Ma. These data suggest a period of garnet breakdown followed by (re-)growth between 45 and 20 Ma. Phase diagram models show very limited variation in garnet modal abundance at >7 kbar and 600–700 °C, indicating that changes in P–T are unlikely to influence garnet modes. Additionally, there are no other phases like staurolite, which may have reacted with garnet.

We propose instead cryptic dissolution-reprecipitation of garnet. Maps of grossular content (X_Grs) shows a pebbly texture with interconnected moats of low X_Grs garnet surrounding islands of high X_Grs garnet, whereas other endmember fractions show flat garnet cores and mantles with slight increases in spessartine at the rim. We suggest that garnet recrystallization was driven by the release of magmatic-hydrothermal fluids from nearby 43–35 Ma granite intrusions. We suggest that fluid-assisted recrystallization can generate age-composition trends that mimic monazite zoning patterns of P–T path controlled garnet breakdown or growth. Misinterpretations of such data would propagating significant errors into tectono-metamorphic reconstructions, emphasizing the necessity of microstructurally constrained petrochronology when interpreting monazite U–Th–Pb ages.

How to cite: Wang, D., Walters, J., Ding, H., and Kohn, M.: Decoupling of monazite petrochronology from P–T evolution during garnet hydrothermal dissolution–reprecipitation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9890, https://doi.org/10.5194/egusphere-egu26-9890, 2026.

Establishing the age of mineral deposits and their host rock sequences is fundamental to mineral exploration, as it constrains the temporal evolution of prospective geological environments and the geodynamic processes responsible for ore formation. This is particularly critical for syn-genetic stratiform systems such as volcanogenic massive sulfide (VMS) deposits, which are typically localized along favorable stratigraphic horizons within volcanic belts and linked to episodes of regional extension and magmatism. In Archean cratons, however, VMS deposits commonly experience multiple post-ore deformation, metamorphic, and hydrothermal events that may obscure primary isotopic signatures and result in metal remobilization, complicating efforts to constrain the timing of syn-genetic mineralization.

In this study, we apply an integrated geochronological approach including U–Pb zircon and titanite, Lu–Hf garnet, Re–Os sulfide and molybdenite, and Pb–Pb galena dating to constrain the age of syn-genetic mineralization in an Archean VMS deposit metamorphosed to amphibolite facies. Our results demonstrate that the Re–Os isotopic system in syn-genetic pyrite can be preserved through high-grade metamorphism and yields ages consistent with U–Pb zircon ages of the felsic host rocks, providing a robust means to directly date VMS mineralization in highly metamorphosed Archean terranes. In contrast, Re–Os ages obtained from pyrrhotite record prograde metamorphism and align with Lu–Hf garnet ages, indicating their utility for constraining metamorphic overprinting and metal remobilization events.

We further show that Re–Os dating of bulk massive sulfide ore dominated by both pyrite and pyrrhotite produces mixed, geologically meaningless ages, rendering this approach unreliable where extensive pyrrhotite formation has occurred via pyrite desulfidation. Although molybdenite within the footwall stratigraphy yields robust Re–Os ages despite amphibolite-facies metamorphism, these ages reflect late granitoid emplacement and regional metamorphism rather than syn-genetic VMS mineralization. Collectively, our findings provide new constraints on the timing of metamorphosed VMS deposits and have significant implications for regional exploration strategies, particularly within the Yilgarn Craton.

How to cite: Dana, C., Hollis, S., Tavazzani, L., Chelle-Michou, C., Glorie, S., Kuwahara, Y., Mimura, K., Yano, M., Ohta, J., Selby, D., Kato, Y., Pashley, V., James, M., and Podmore, D.: What do Re-Os ages of sulfide minerals at amphibolite facies mean: resolving syngenetic vs metamorphic ages in an Archean VMS deposit, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9932, https://doi.org/10.5194/egusphere-egu26-9932, 2026.

In situ garnet U-Pb geochronology by laser ablation-inductively coupled mass spectrometry (LA-ICPMS) is a powerful tool for rapid and high-spatial resolution dating of metamorphic pressure-temperature–time histories. Yet, the substitution of U and Pb  into the structure of common pyralspite garnet and its influence on diffusion and potential age-resetting is poorly constrained. Studies by Mezger et al. (1989), Burton et al. (1995), and Dahl (1997) estimate U-Pb system closure temperatures in garnet of >800 °C. Similarly, Shu et al. (2024) proposed a closure temperature of  >1100 °C but suggested that recrystallization may have reset some garnet U-Pb ages. However, there is little information on how dynamic processes, such as recrystallization, may impact the closure of the U-Pb system in garnet. 

Here we examine the impacts of garnet recrystallization on U-Pb ages by examining ultrahigh-temperature (UHT) crustal xenoliths from the southwestern USA and northern Mexico. These metapelitic granulites experienced isobaric heating at >900 °C between 36 and 30 Ma and UHT conditions were maintained until eruption at <1 Ma (Droubi et al., 2024; Cipar et al., 2020; 2024). Garnet trace element zoning shows diffusively reset growth zoning overprinted by island-moat structures, which formed via melt-driven loss of REE and HFSE along now-healed fractures (Droubi et al., 2024). Zircon HREE depletions and ages suggest garnet initially formed at ca. 30 Ma, whereas diffusion modeling indicates that garnet island-moat structures formed rapidly <1 Myr before eruption (Droubi et al., 2024; Cipar et al., 2020; 2024). Our in situ U-Pb garnet ages, as measured by split-stream LA-MC-ICPMS, range from 4.6 ± 2.3 Ma (2s) to 1.77 ± 0.32 Ma (2s).  The corresponding trace element data show decreasing U contents with decreasing LREE and HFSE, consistent with significant (but partial) resetting of U contents during the formation of the island-moat structures. In contrast, Pb contents show no trends with REE and HFSE. These data, combined with the overlap of our U-Pb ages with the eruption age of the magmas that entrained the xenoliths, are consistent with complete resetting of Pb contents during melt-garnet interaction. Overall, we demonstrate that garnet ages are susceptible to (near-)complete resetting via dynamic open-system processes.

Burton et al. (1995). Earth Plan. Sci. Lett. 133, 199–211.

Cipar et al. (2020). Nat. Geosci. 13(11), 758–763.

Cipar et al. (2024). Geochem. Geophys. Geosys. 25(7), e2023GC011177.

Dahl (1997). Earth Plan. Sci. Lett. 150, 277–290.

Droubi et al. (2024). JGR Solid Earth 129, e2024JB029138.

Mezger et al. (1989). Contrib. Min. Pet. 101, 136–248.

Shu et al. (2024). Contrib. Min. Pet. 179 (49).

How to cite: Walters, J. B., Millonig, L. J., Beranoaguirre, A., Smye, A. J., Garber, J. M., Gerdes, A., and Marschall, H. R.: Garnet U-Pb ages reset during ultrahigh temperature melt-rock interaction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10272, https://doi.org/10.5194/egusphere-egu26-10272, 2026.

Carbonite forms in a wide variety of geological environments as both a primary and secondary mineral phase and may contain sufficient U for U-Pb geochronology. The limited availability of well-characterized calcite reference materials, however, has impeded its broader application in microanalysis, in particular for the low-U (<0.1 mg g^-1) calcite and dolomite. In this study, four potential carbonite reference materials (JCL03, THMT, TL-2, TL10-7) were primary characterized for in situ U-Pb geochronology. JCL03 and THMT are low-Mg calcite with Mg concentrations of ~0.35 wt.%, ~0.39 wt.%, respectively. TL-2, TL10-7 are the dolomite with Mg concentrations of ~21.5 wt.%, ~17.4 wt.%, respectively. JCL03 and THMT were characterized as low-U calcite with U concentrations of ~0.036 mg·g^-1, ~0.021 mg·g^-1, respectively. TL-2 and TL10-7 have U concentrations of ~2.3 mg·g^-1, ~1.5 mg·g^-1, respectively. JCL03 and THMT have homogeneity ages, while TL-2 and TL10-7 shows multiple dolomitization process. Multiple LA-ICP-MS analytical sessions yielded ages of 428.7 ± 5.2 Ma, 286.3 ± 7.1 Ma, 233.8 ± 4.4 Ma and 180.0 ± 6.3 Ma for JCL03, THMT, TL-2 and TL10-7, respectively. These four carbonaite are the useful additions to the widely distributed WC-1 reference material for LA-ICP-MS U-Pb geochronology.

How to cite: Xiao, F., Li, T., Wu, S., and Yang, Y.: Four potential carbonite reference materials for in situ U-Pb geochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10876, https://doi.org/10.5194/egusphere-egu26-10876, 2026.

Highly fractionated granites are important hosts for rare metals (Li, Be, Nb, Ta, Rb, Cs, Zr, Hf, etc.). Dating the mica minerals abundant within them can more accurately constrain the timing of rare metal mineralization. To investigate the episodes and chronology of rare metal mineralization in the Koktokay region, we conducted precise Rb-Sr dating by Isotope Dilution Mass Spectrometry (ID-MS) on muscovite separates, along with apatite and whole-rock powder, from six samples collected from this highly fractionated granite. The obtained age for this highly fractionated granite is 200.86 ± 0.29 Ma(2σ, n = 21), with an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.805598 ± 0.000069. This age is younger than the main Triassic magmatic phase (ca. 210 Ma) but falls within the mineralization window of the No. 3 pegmatite vein (220-175 Ma). Meanwhile, the initial Sr ratio is significantly higher than that of typical crust-derived granites (~0.720), indicating derivation from a highly evolved source.

In recent years, laser ablation (multi-collector) inductively coupled plasma tandem mass spectrometry (LA-(MC)-ICP-MS/MS) techniques for in-situ Rb-Sr analysis have developed rapidly and become indispensable tools in geological research. However, the accuracy of LA-ICP-MS/MS Rb-Sr dating relies on matrix-matched reference materials to correct for instrumental drift (e.g., sensitivity changes) and elemental fractionation effects during analysis. For high Rb/Sr systems, there is still a lack of reference materials with high ⁸⁷Rb/⁸⁶Sr and high ⁸⁷Sr/⁸⁶Sr ratios.

The six muscovite samples analyzed in this study exhibit exceptionally high ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr ratios. Electron Probe Microanalysis (EPMA) shows that these micas have high and stable Al and K contents of 10.755 ± 0.0373% and 33.39 ± 0.16%, respectively. Backscattered Electron (BSE) imaging confirms their homogeneous major element composition, devoid of impurities.

Given their exceptionally high ⁸⁷Rb/⁸⁶Sr ratios, we further analyzed these six muscovite samples using LA-ICP-MS/MS. The measured ages range from 190 Ma to 200 Ma. Rb concentrations vary from 2300 to 3700 µg/g, while Sr concentrations are low, at 2.5 and 3.5 µg g⁻¹. Among these samples, four exhibit extremely high ⁸⁷Rb/⁸⁶Sr ratios (28000-35000) and ⁸⁷Sr/⁸⁶Sr values (80-100). In contrast, the remaining two samples show moderately high ⁸⁷Rb/⁸⁶Sr ratios (11000-12000) and ⁸⁷Sr/⁸⁶Sr values (30-35). Based on the ID–MS isochron results and detailed LA-ICP-MS/MS data, all six muscovite samples show potential as candidate reference materials for LA-ICP-MS/MS Rb-Sr dating. Further detailed and systematic work is required to rigorously evaluate and validate their suitability.

How to cite: Cui, T., Chu, Z., Shen, P., Feng, H., Zhang, M., and Yang, Y.: High Rb/Sr Muscovite from the Koktokay Highly Fractionated Granites: Implications for Rb–Sr Chronology and LA-ICP-MS/MS In Situ Reference Material Development, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11115, https://doi.org/10.5194/egusphere-egu26-11115, 2026.

The PRIN 2020 CASTLES Project focuses on studying mediaeval castles in Italy, particularly their chronology and dating through archaeometric analysis of castles walls mortars. The project is based on a multidisciplinary approach and aims at establishing a new chronology for the construction sites of incastellamento (11th-12th centuries).

A multidisciplinary team integrated their expertise into exploring the subject from multiple perspectives. The team consists of archaeologists and historians (respectively the Universities of Siena and Turin), geologists and conservation scientists (University of Florence), and physicists and archaeologists (University of Campania "Luigi Vanvitelli"). The group selected several sites across three regions of Italy (Piedmont, Liguria and Tuscany). The criteria for selecting the castles were: chronology, state of conservation, historical context, available historical and archaeological data, significant historical relevance. Before starting the sampling of the walls structures mortars, and proceeding to the characterization and dating, it was of fundamental importance to geolocate the castles. This is basilar to understand the geology of the areas where the castles were located and be able to identify the supply sources of the raw materials used by workers to build them. The study was carried out by researching geological maps, aerial photographs, drone images, and scientific publications concerning each castle’s area of ​​the Piedmont, Liguria, and Tuscany regions, as well as sampling rocks of outcropping and constituting the walls. Minero-petrographic and chemical characterization of rock and mortar samples were performed, using X-Ray Diffraction Powder (XRPD), Polarized Light Microscopy (PLM) and Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS). The mineralogical and petrographical analyses of the rocks from each castle area were then compared with the components constituting the mortars (aggregate and binder) from the same castles, to identify correlations. It is essential to establish whether the materials used by the workers were sourced locally or from elsewhere. The results of this first step of the research showed that the raw material used in the realization of Ligurian and Tuscany castles was local. The origin of the rocks used to produce lime in Piedmont's castles is uncertain. In fact, limestone outcrops are very rare in the north of the region. Beyond dating, the analysis of raw materials provides important insights into medieval building organization, showing that most of studied castles relied on local geological resources, while changes in supply areas may reflect settlement expansion and/or a different and more complete organization of the sites of incastellamento.

How to cite: Intrieri, E., Pecchioni, E., Calandra, S., Garzonio, C. A., Salvatici, T., Lubritto, C., Mantile, N., Giacometti, V., di Cicco, M. R., Bellato, G., Provero, L., Fiore, A., Arrighetti, A., Buonincontri, M. P., Bardi, A., and Bianchi, G.: The Times of Castles Project: A Combined Study of Rocks and Mortars for Geological Provenance, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12199, https://doi.org/10.5194/egusphere-egu26-12199, 2026.

The transformation of medieval castles in Italy, especially between the 11th and 12th centuries during the process of incastellamento, represents a crucial yet complex phase in European history. The transition from early wooden fortifications to durable stone structures is often poorly documented and broadly dated. PRIN 2020 CASTLES Project integrates archaeology, history, geology, conservation science, and physics in a multidisciplinary framework aimed at building a new and more precise chronology of medieval castle construction in northern and central Italy. The project focuses on 25 castles in Piedmont, Liguria, and Tuscany, combining historical and archaeological evidence with archaeometric analysis of masonry to refine the dating of construction phases and improve understanding of building practices. For this purpose, radiocarbon dating (¹⁴C) is used as an absolute dating technique. In this study, the ¹⁴C method was applied for dating ancient mortars of masonry castles, targeting both inorganic material (binder and lump calcite) and organic inclusions (charcoal). However, selection of the inorganic datable fraction and elimination of potential contamination proves to be a challenge for the international radiocarbon community. To select the most suitable mortar binder for ¹⁴C dating, a key step in the research is mortar sampling and the characterisation of the raw materials used in mortars. To minimise mortar contamination, samples were carefully taken with consideration for the archaeological structure and the preservation of the masonry. Once the mortar samples were selected, penetrometric and carbonation tests were carried out on site. Subsequently, mineralogical, petrographic, and chemical analyses were performed using XRPD, OM, SEM–EDS, OM-CL, and ATR-FTIR. These analyses enabled the identification of binder types, aggregate composition, and hydraulic properties. Air-hardening lime mortars proved to be the most reliable, whereas natural hydraulic and magnesium-rich limes often introduced complications. Further analyses were performed on powders of binder-rich portions or lumps, using non-destructive techniques, such as XRPD, OM-CL, ATR-FTIR [1]. More than 120 mortar samples were analysed, from which 63 powder samples were selected and prepared for ¹⁴C dating. Mortar radiocarbon results were cross-checked with charcoal dating and archaeological data, confirming the reliability of the methodological procedure. Several case studies from Tuscan castles demonstrate strong coherence between mortar characterization and radiocarbon ages, validating the approach. On a larger scale, the project is defining chronological trends that reflect different phases of castle development, from early fortifications to fully developed lordly residences and village centers. Overall, the project offers a reproducible and multidisciplinary framework that significantly improves the chronological reconstruction of medieval castles in Italy and provides a model applicable to similar contexts elsewhere.

[1] Calandra S., et al. 2024, A new multi-analytical procedure for radiocarbon dating of historical mortars, Sci Rep, 14(1), 19979.

How to cite: Calandra, S., Pecchioni, E., Garzonio, C. A., Salvatici, T., Intrieri, E., Lubritto, C., Mantile, N., Giacometti, V., Di Cicco, M. R., Bellato, G., Provero, L., Fiore, A., Arrighetti, A., Buonincontri, M. P., Bardi, A., and Bianchi, G.: The Time of Castles Project: Characterization of Mortar Raw Materials for ¹⁴C Dating in Medieval Castles of Northern and Central Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12387, https://doi.org/10.5194/egusphere-egu26-12387, 2026.

Low-temperature thermochronology has traditionally relied on apatite and zircon minerals that are commonly absent from carbonate platforms, leaving large regions effectively blind to shallow crustal thermal reconstructions. Recent methodological advances now permit the application of (U-Th)/He dating to iron oxides, but so far this approach has only been tested in crystallization contexts and has rarely been used to quantify burial-exhumation trajectories.

Here we explore karst-hosted bauxite deposits as a new natural laboratory for oxide thermochronology. These lateritic bodies, developed on the Durancian structural high in southeastern France, contain abundant hematite and goethite that formed during intense Lower Cretaceous weathering and were subsequently buried beneath Upper Cretaceous to Cenozoic sedimentary sequences. Such conditions provide the requirement for oxide thermochronology: iron oxides that experienced post-crystallization heating.

We report a large dataset of (U-Th)/He ages obtained from more than one hundred individual hematite and goethite grains sampled across south of France. All ages postdate bauxite formation and independent depositional constraints, demonstrating that these minerals systematically record post-depositional thermal overprints.

Coexisting hematite and goethite systematically yield distinct age populations, with goethite consistently recording younger apparent ages. This reproducible offset demonstrates that these two iron oxides behave as independent low-temperature chronometers.

Because diffusion parameters for goethite remain poorly constrained, thermal history modelling was performed using hematite only. Thermal inversion modelling, is supported by regional stratigraphic and tectonic frameworks. It identifies two successive heating phases linked to Pyrenean compression and to Oligocene–Miocene rifting. Reheating during this latter event temporally correspond to goethite ages. This age comparisons between both phases provide empirical constraints on reset temperatures of goethite about 60-40°C.

Our results demonstrate that karst-hosted bauxites constitute a robust archive for oxide-based thermochronology, and provide the first natural framework for empirically constraining reset temperature in goethite. This approach opens new perspectives for reconstructing shallow thermal histories in carbonate-dominated regions where conventional chronometers are absent.

How to cite: Boschetti, L., Schwartz, S., Gautheron, C., Rolland, Y., Mouthereau, F., Balvay, M., Cogné, N., and Campillo, S.: Karst-hosted bauxites as a new archive for oxi-hydroxide (U-Th)/He thermochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12699, https://doi.org/10.5194/egusphere-egu26-12699, 2026.

This project set out to temporally constrain Carboniferous (ca. 359-299 Ma) volcanic, magmatic, and interbedded sedimentary basins which host the important Midland Valley coal seams. We are interrogating rates of eruption and temporal variations in the magma source geochemistry to link these to palaeoclimate variability as recorded by these classic sedimentary successions.

Rifting of the Midland Valley, Scotland and synchronous short-lived volcanism (ca. 30 Myr) [7] is associated with the eruption of mildly alkaline olivine basalts and associated intrusive rocks (e.g. micro-gabbro, phonolite). Remnants of this volcanism are exposed across the Midland Valley, including the world-famous geological site, Arthur’s Seat, Edinburgh. Arthur’s Seat is a classic example of a volcanic cross section with approximately nineteen lava layers and numerous vents exposed and characterised [1, 6]. Previous mapping efforts established a stratigraphy for this Site of Special Scientific Interest (SSSI) landmark, constrained by interbedded palynological zones. This has since been succeeded by direct radio-isotopic dating including K-Ar and ⁴⁰Ar/³⁹Ar geochronological techniques [2, 3, 4]. The most recent published ages constrained the eruption and emplacement of the Arthur’s Seat volcano with a precision ranging between 0.18-1.40% [5, 6].

New high precision (<0.1%) ⁴⁰Ar/³⁹Ar geochronology on lavas and CA-ID-TIMS U-Pb zircon geochronology on intrusive rocks and explosive eruptions, has been completed in addition to a suite of geochemical and isotopic data (e.g. Nd, Sr and Pb isotopes; major and trace elements). New developments in sample preparation, mass spectrometry, standard mineral characterisation, and data reduction software have enabled significant refinement of the ⁴⁰Ar/³⁹Ar technique. For example, our re-examination of the Arthur’s Seat Volcanic Formation has obtained an improved precision, achieving eruption and emplacement ages ranging 0.018-0.052%.  

Our integrated geochronologic, geochemical and isotopic data underpin a robust temporal framework that tracks the evolution of the magmatic system, places the volcano-sedimentary sequences within the global Geologic Time Scale, and constrains the ages of key fossil-bearing horizons. By directly linking the magmatism to sedimentary basin development through dating of intercalated tephras, we aim to deliver a high precision chronology for Carboniferous climate change and the evolution of flora and fauna within the Midland Valley. Our preliminary results represent an order of magnitude improvement in precision and, in some cases, are sufficient to allow Carboniferous climate variability to be examined at orbital timescales (<100 kyr).

References

[1] Clarkson, E. and Upton, B. (2007) Geological Magazine, 144(3), pp. 603–603.

[2] De Souza, H.A,. (1979) Geochronology of Scottish Carboniferous volcanism. Ph.D. University of Edinburgh.

[3] De Souza, H.A,. (1982) ‘Age data from Scotland and the Carboniferous Time Scale’.

[4] Fitch et al, (1970) Isotopic ages of British Carboniferous rock. Sheffield, 1967, (2), pp. 771–790.

[5] Monaghan, A.A. and Browne, M.A.E. (2010) British Geological Survey, pp. 41.

[6] Monaghan, A.A., Browne, M.A.E. and Barfod, D.N. (2014) Scottish Journal of Geology, 50(2), pp. 165–172.

[7] Upton et al, (2020) Scottish Journal of Geology, 56(1), pp. 63–79.

How to cite: Pegge, E., Mark, D., and Barfod, D.: Geochronology and geochemical evolution of Carboniferous volcanism in Scotland’s Midland Valley: Insights from Arthur’s Seat, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13082, https://doi.org/10.5194/egusphere-egu26-13082, 2026.

Understanding the emplacement timescales of the Cornubian Batholith is important due to the association of widespread mineralisation that is spatially and temporally linked to the magmatism. Historically, dating has been focussed on xenotime and monazite which established the magmatism to have occurred from ~295-275 Ma (Chen et al., 1993, Chesley et al., 1993). However, these minerals are less precise for dating due to issues with low U/Pb ratios and inability to perform chemical abrasion. Our project aims to build a temporal framework for the formation of nested plutons by utilising high precision zircon U-Pb dating on the Variscan S-type Cornubian Batholith of southwest England.   

To minimise issues of inheritance, cathodoluminescence scanning electron microscope imaging (CL-SEM) was used to identify inherited cores and fractures/inclusions within zircon. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was then completed on cores and rims of zircon, with the aim of selecting the best zircon crystals for further chemical-abrasion isotope-dilution thermal-ionisation mass spectrometry (CA-ID-TIMS) analysis. The LA-ICP-MS data confirmed the complicated geochronological history, with issues of inheritance and Pb-loss ubiquitous across all sampled plutons. Whilst an accurate and precise emplacement age could not be identified based on the spread of data, most sampled plutons did show promising trends that could be related to peaks in magmatism within the currently established period of activity.  Zircon rims were isolated in preparation for CA-ID-TIMS to minimise issues with inheritance.  

Applying CA-ID-TIMS, ²⁰⁴Pb and ²³⁰Th corrections, and Bayesian modelling will improve precision with the aim of filtering out complicating effects to produce reliable emplacement ages for the main phases of Cornubian magmatism. Achieving accurate zircon U-Pb ages from S-type granites is both challenging and significant as it would open avenues for reinterpreting ages from difficult-to-date plutonic bodies, a potential milestone for U-Pb geochronology.  

Bibliography
 
Chen, Y., Clark, A.H., Farrar, E., Wasteneys, H.A.H.P., Hodgson, M.J., Bromley, A.V., 1993. Diachronous and independent histories of plutonism and mineralization in the Cornubian Batholith, southwest England, Journal of the Geological Society. 

Chesley, I., J.T., Halliday, A.N., Snee, L.W., Mezger, K., Shepherd, T.J., Scrivener, R.C., 1993. Thermochronoloy of the Cornubian batholith in southwest England: Implications for pluton emplacement and protracted hydrothermal mineralization, Geochimica et Cosmochimica Acta. 

How to cite: Day, L., Mark, D., and Barfod, D.: Redefining the emplacement age of the Cornubian Batholith: applying Bayesian statistics to zircon U-Pb LA-ICP-MS data , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13084, https://doi.org/10.5194/egusphere-egu26-13084, 2026.

Constraining the depths, temperatures and rates of Archean metamorphism may provide a window into possible tectonic styles at this time. However, several Archean metamorphic terranes record polymetamorphism, and unravelling the pressure-temperature-time (P-T-t) histories of such terranes has proven difficult, with complexity inherent in both chronologic and petrologic data.

Here we synthesize results of a multi-analytical study in which (Sm-Nd) garnet and (U-Pb) monazite petrochronology, thermodynamic, diffusion, and thermal modeling were applied to Archean granulites from the Beartooth Mountains in the northern Wyoming Province. The data reveal two phases of garnet growth and high-temperature metamorphism likely driven by magmatic heat advection. Garnet cores grew coeval with emplacement of a granitoid batholith at ~2.78-2.76 Ga. This was followed by a distinct, second phase of peritectic garnet rim growth at ~2.71 Ga, during biotite breakdown melting at peak temperatures of ~750˚C. Diffusion modeling of chemical zoning in garnet rims shows that this second event was brief: near-peak temperatures were maintained for < 1 Myrs. In contrast, core and rim dates of garnet from a meta-granitoid from the same outcrop record only the initial phase of growth, most likely because a lack of grain boundary fluids inhibited further crystallization in these rocks. Evidence for this second event is cryptic in other granitoid samples, such that this period of heating to at least 750˚C, ~50-100 Myrs after initial batholith emplacement, is poorly recorded in the broader rock record of the Beartooths.

We propose that emplacement of the Stillwater Complex was responsible for high-grade metamorphism at ~2.71 Ga. 1-D thermal models suggest that the P-T-t path determined from our pelitic samples can be reproduced by emplacement of a large mafic sheet with the geometry of the Stillwater ~10 km above the current exposure of the Beartooth mountains. Our work serves as a case study in which: 1) field and petrologic evidence for polymetamorphism is cryptic, but can be revealed through detailed petrochronology, and 2) rapid granulite-facies metamorphism of mid-crustal rocks was coeval with, and likely driven by, high magmatic flux during upper crustal emplacement of a potential large igneous province. Lastly, we highlight the potential challenges associated with the dating of high metamorphic grade, Archean lithologies, which include the effects of deleterious mineral inclusions, polymetamorphism and multi-stage melting episodes.

How to cite: Dragovic, B., Guevara, V., Caddick, M., Inglis, J., Kylander-Clark, A., and Raimondo, T.: Neoarchean polymetamorphism and crustal melting due to magmatic heat advection in the northern Wyoming Province, U.S.A: insights from petrochronology and thermal modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13988, https://doi.org/10.5194/egusphere-egu26-13988, 2026.

Thermochronology provides powerful tools for reconstructing Earth’s thermal and tectonic history. Among low-temperature thermochronometers, zircon (U–Th)/He (ZHe) dating has gained particular importance due to its sensitivity to deep-time thermal events, enabling tight temperature constraints even for thermal histories that span billions of years.

Helium diffusivity in zircon is strongly controlled by radiation-damage accumulation. This causes complex diffusion behaviour and a wide range of effective closure temperatures especially in (meta-)sedimentary rocks, where detrital zircons share their post-depositional thermal history but differ in provenance age and uranium content, leading to variable radiation-damage and annealing histories.

The widely used zircon radiation damage accumulation and annealing model (ZRDAAM; Guenthner et al., 2013) predicts complete resetting of ZHe ages for samples heated above ~200 °C during burial. Consequently, highly dispersed ZHe datasets in sedimentary rocks are commonly interpreted as reflecting mixed detrital populations and limited heating below this threshold. However, this interpretation remains largely untested against natural field laboratories.

In this study, ZHe closure and annealing is re-investigated based on two field areas with independently constrained thermal histories: (1) the Austroalpine Drau Range and adjacent Southalpine units and (2) the Helvetic Glarus Alps. Peak temperatures in these regions are well defined by vitrinite reflectance, Raman spectroscopy of carbonaceous material, Kübler-Index and fluid inclusion data as well as by metamorphic assemblages. In both areas, ZHe data systematically conflict with model predictions. The Austroalpine and Southalpine (meta-)sedimentary units targeted within this study experienced upper-diagenetic to low-grade metamorphic conditions (T>200 °C), but ZHe ages are largely not reset and show strong dispersion, contrary to ZRDAAM expectations. Combined ZHe–U–Pb double dating confirms substantial differences in pre-depositional provenance ages, but this age variation cannot explain the obvious difference to modelled age predictions.

A similar pattern is observed in the Glarus Alps, where peak metamorphic temperatures range from diagenesis to greenschist facies. ZHe ages show a systematic younging trend but retain large single-grain age dispersion and partially inherited ages even under very low-grade metamorphic conditions.

Results demonstrate significant helium retention in zircons at temperatures above 200 °C and reveal limitations of our understanding of the ZHe system. Interpreting dispersed ZHe datasets solely in terms of detrital inheritance fails to explain field constraints. Ongoing work combining U-Pb-He double dating with cathodoluminescence imaging, Raman spectroscopy, and spatially resolved U-Pb and isotopic mapping aims to identify the mechanisms responsible for this behavior and to improve the interpretation of ZHe data in sedimentary and remain-grade metamorphic rocks.

Reference:

Guenthner, W. R., Reiners, P. W., Ketcham, R. A., Nasdala, L., & Giester, G. (2013). Helium diffusion in natural zircon: radiation damage, anisotropy, and the interpretation of zircon  (U-Th)/He thermochronology. American Journal of Science, 313(3), 145-198. ://WOS:000319306100001

How to cite: Heberer, B., Rahn, M., Dunkl, I., Lünsdorf, K., Neubauer, F., and Rantitsch, G.: Field constraints on zircon (U-Th)/He closure from the European Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14110, https://doi.org/10.5194/egusphere-egu26-14110, 2026.

The accumulation of alpha radiation damage and its annealing in apatite are critical to thermochronological studies but remain difficult to characterize. We conducted annealing experiments on four slices from a single Durango apatite crystal and used high-resolution Raman spectroscopy mapping to analyse peak positions and full width at half maximum (FWHM) of the ν₁(PO₄) and ν₃(PO₄) bands. Track densities were measured in different regions of the crystal, and a normalized track-density reduction model was applied to estimate the original alpha radiation damage. In addition, heavy-ion irradiation was used to simulate the fission process and enhance the visibility of confined tracks.

Our results show that the FWHM of the ν₁(PO₄) band is a robust indicator of alpha radiation damage accumulation in apatite and does not correlate with fission-track damage in Durango apatite. The spatial zoning pattern of FWHM closely matches that of effective uranium (eU), and among samples with similar eU contents, those subjected to higher annealing temperatures exhibit lower FWHM values. Furthermore, alpha radiation damage does not significantly influence the annealing behaviour of fission tracks in Durango apatite. Although the behaviour of Raman peak positions remains enigmatic, our results suggest that it is influenced by both apatite chemical composition and radiation damage accumulation. This study demonstrates that high-resolution Raman spectroscopy provides a novel and quantitative approach to directly link radiation damage with thermal history in apatite. This methodology could potentially improve thermochronological apatite models and interpretation enabling detailed, spatially resolved insights into damage accumulation and annealing processes in geological studies.

How to cite: Pastore, G., Zeng, X., Shen, C., Resentini, A., Fu, H., Yang, C., Vermeesch, P., Fox, M., Buret, Y., and Malusà, M. G.: Raman mapping reveals alpha radiation damage zonation and its annealing in Durango apatite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14548, https://doi.org/10.5194/egusphere-egu26-14548, 2026.

Thermochronological data can provide robust constraints on crustal exhumation, erosion, and burial, yet their interpretation often requires forward and/or inverse models to account for thermal evolution and the effects of surface processes. Here we present recent developments in T_c1D, a one-dimensional thermal and thermochronometer age prediction package designed to explore exhumation, burial, and other thermal processes and their effects on low-temperature thermochronometers.

T_c1D generates thermal histories by solving the transient one-dimensional heat transfer equation to predict apatite and zircon (U-Th)/He and fission-track ages using established thermochronological models, including RDAAM and ZRDAAM. The thermal model is controlled by user-defined thermal boundary conditions and prescribed vertical crustal dynamics, including erosion and burial. These histories can be parameterized through multiple erosion model options (e.g., stepwise or linearly varying rates) as well as simplified 1-D representations of tectonically driven vertical motions (e.g., thrust-sheet emplacement/removal and extensional/thrust faulting). This physics-based yet computationally efficient setup enables rapid exploration of how various thermal and crustal scenarios translate into predicted age patterns.

T_c1D adopts a complementary approach, compared to commonly used thermal history modeling tools such as HeFTy, QTQt, or Thermochron.jl, enabling direct connection between different vertical-motion scenarios, measured ages, and physical parameters (e.g., erosion rates or eroded thicknesses), while retaining fast execution times suitable for large sensitivity and ensemble analyses. Furthermore, by remaining one-dimensional, T_c1D avoids the computational cost of full 3D thermo-kinematic models such as PECUBE, while still capturing the first-order effects of vertical lithospheric processes. T_c1D is also fully open source and Python based, facilitating transparency, extensibility, and integration into reproducible research workflows.

Recent developments in T_c1D (from version 0.3) expand its scope beyond earlier releases, which were primarily limited to forward modeling and simple erosion scenarios. Recent versions introduce support for data-driven inverse modeling, flexible definitions of exhumation and burial histories, and the inclusion of additional thermal perturbations such as magmatic intrusions. T_c1D now supports parameter inversion using either the Neighborhood Algorithmor a Markov Chain Monte Carloapproach, enabling systematic exploration of exhumation and burial histories. These histories can be defined through an external input file, allowing complex, multi-stage scenarios combining piecewise constant, linear, or exponential phases of erosion/burial.

Ongoing developments focus on improving usability and physical realism. A new unified YAML-based input file is currently being developed to provide an alternative to command-line–driven usage, improving reproducibility while simplifying model design. This structure facilitates the definition and modification of complex model configurations, including multi-stage erosion and burial histories, thermal boundary conditions, and is designed to support future inversion of stage durations and erosion parameters. In parallel, software developments aim to incorporate more realistic representations of crustal structure and rock properties, including depth-dependent density variations based on mineral phase transitions, to better account for crustal composition, thermal properties, and their influence on thermal evolution and erodibility.

These developments are being applied to investigate the long-term thermal evolution of the crust in the Fennoscandian Shield, where low relief, limited sedimentary archives, episodic burial, and subtle post-orogenic exhumation pose major challenges for thermochronological data interpretation.

How to cite: Gérard, B., Whipp, D., Laaksonen, S., and Maier, A.-K.: Tc1D: a fast and flexible 1-D thermal and thermochronology modeling package for complex exhumation, burial, and transient thermal histories, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17436, https://doi.org/10.5194/egusphere-egu26-17436, 2026.

Cratons are ancient parts of the lithosphere, often characterised by long-term stability. Geological observations indicate that the Fennoscandian Shield in the East European craton has likely experienced some of the slowest erosion rates on Earth over the past approximately 1.5 billion years¹. However, a contrasting perspective has emerged based on apatite fission-track thermochronology, suggesting multiple episodes of kilometre-scale burial and exhumation during the past 1.1 Ga². This raises the question: How stable has the Fennoscandian Shield been since the Mesoproterozoic?

Since a Phanerozoic sedimentary record is not preserved in Finnish Fennoscandia, we investigate this question using new data from (U-Th)/He thermochronology and integrated modelling of multiple thermochronometer systems.

We have collected 20 samples from Finnish Fennoscandia, from which we obtained 64 single-grain zircon (U-Th)/He dates (1553 to 1.8 Ma) and 55 single-grain apatite (U-Th)/He dates (1178 to 99 Ma). In addition, we analysed 25 zircons from the Kola peninsula in Russia and obtained (U-Th)/He dates ranging from 1929 to 215 Ma. Samples from southern Finland and the Kola peninsula show a strong decrease in zircon (U-Th)/He dates with increasing U-Th concentrations, due to the effects of radiation damage. We leverage this date dispersion to determine plausible thermal histories using different inverse modelling software (QTQt³, Thermochron.jl⁴ and T_c1D⁵) and explore the complex (U-Th)/He date patterns through separate and joint inversion of the zircon and apatite data.

Preliminary inverse modelling results using QTQt and Thermochron.jl suggest that regions in southern Finland and the Kola peninsula may have experienced protracted residence at shallow upper crustal levels for at least 1 Ga. In contrast, areas in northern Finland, near the Caledonian front, show evidence of heating and cooling likely linked to burial and exhumation following Caledonian orogenesis.

Ongoing work focuses on refining the preliminary thermal history models by integrating published apatite fission track and ⁴⁰Ar/³⁹Ar data with our (U-Th)/He dataset to more effectively constrain the magnitude, timing and rates of burial and exhumation in Fennoscandia and its possible drivers (e.g. extreme glaciation, orogenies). This will not only provide insight into the exhumation history of Fennoscandia, but also the resolving power of low-temperature thermochronology for reconstructing thermal histories in cratonic areas where timescales are immense and the geological record is limited.

¹ Hall, A.M., Putkinen, N., Hietala, S., Lindsberg, E. and Holma, M., 2021. Ultra-slow cratonic denudation in Finland since 1.5 Ga indicated by tiered unconformities and impact structures. Precambrian Research, 352, p.106000. 

² Green, P.F., Japsen, P., Bonow, J.M., Chalmers, J.A., Duddy, I.R. and Kukkonen, I.T., 2022. The post-Caledonian thermo-tectonic evolution of Fennoscandia. Gondwana Research, 107, pp.201-234. 

³ Gallagher, K. (2012), Transdimensional inverse thermal history modeling for quantitative thermochronology, J. Geophys. Res., 117, B02408, doi:10.1029/2011JB008825.

⁴ Keller, C.B., McDannell, K.T., Guenthner, W.R., and Shuster, D.L. (2022). Thermochron.jl: Open-source time-Temperature inversion of thermochronometric data. 10.17605/osf.io/wq2U5

⁵ Whipp et al. (2025). HUGG/Tc1D: v0.3.2 (v0.3.2). Zenodo.  https://doi.org/10.5281/zenodo.17590819

How to cite: Maier, A.-K., Gérard, B., Whipp, D., Laaksonen, S., and McDannell, K.: How stable is the Fennoscandian Shield? Insights from low-temperature thermochronology and numerical models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17806, https://doi.org/10.5194/egusphere-egu26-17806, 2026.

Over the past 30 years, the number of low-temperature thermochronological data has grown, driven by advances in analytical techniques and the proliferation of studies. While generating and sharing these data with the scientific community presents the initial challenge, a second appears during their interpretation through inverse modelling. While performing joint data inversion on few samples is common, scaling this process to larger datasets (>50 samples) remains rare.

In recent years, several research teams have addressed the data sharing challenge by standardizing data-sharing formats (Flowers et al., 2023b, 2023a) and developing dedicated platforms for low-temperature thermochronological data (lithodat.com). Here, we test a "large data-set inversion" approach using a large dataset from Madagascar.

Madagascar has been the focus of over 10 studies since the 1990s, producing a dataset of ~250 samples analysed using two methods ((U-Th)/He and fission track) across various minerals, including apatite and zircon. In this study, we exploited available data (201 AFT and 87 AHe) in a large-scale inversion using a preliminary spatial clustering version of the Bayesian thermal history modelling software, QTQt. The clustering approach follows that presented in Stephenson et al. (2006) but allows for trans-dimensional thermal history models. The approach tries to determine both the number of clusters (i.e. sample groupings) and the thermal histories in each cluster that can reproduce the observed data.

We present (very) preliminary results of this approach applied to the Madagascar dataset, that divide the data in 3 clusters. Although run for 6 weeks, we managed to do just a small number of iterations (<100), and the algorithm was not converged. The inferred 3 clusters are compared to Madagascar’s known tectono-morphological blocks, and the inferred time-temperature paths can then be tentatively assigned to these blocks, potentially offering new insights into the associated vertical dynamics of the island.

Flowers, R.M., Ketcham, R.A., Enkelmann, E., Gautheron, C., Reiners, P.W., Metcalf, J.R., Danišík, M., Stockli, D.F., Brown, R.W., 2023a. (U-Th)/He chronology: Part 2. Considerations for evaluating, integrating, and interpreting conventional individual aliquot data. GSA Bulletin 135, 137–161. https://doi.org/10.1130/B36268.1

Flowers, R.M., Zeitler, P.K., Danišík, M., Reiners, P.W., Gautheron, C., Ketcham, R.A., Metcalf, J.R., Stockli, D.F., Enkelmann, E., Brown, R.W., 2023b. (U-Th)/He chronology: Part 1. Data, uncertainty, and reporting. GSA Bulletin 135, 104–136. https://doi.org/10.1130/B36266.1

Stephenson, J., Gallagher, K., & Holmes, C. (2006). A Bayesian approach to calibrating apatite fission track annealing models for laboratory and geological timescales. Geochimica et Cosmochimica Acta, 70(20), 5183-5200.

How to cite: Derycke, A., Large, E., and Gallagher, K.: Towards large-scale low-temperature thermochronological data inversion: an assessment using a dataset from Madagascar , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18783, https://doi.org/10.5194/egusphere-egu26-18783, 2026.

The Orlica-Śnieżnik Dome is located in the NE part of the Bohemian Massif within the Sudetes, forming part of the European Variscan Belt. It comprises mostly orthogneisses, that host lenses of ultrahigh-pressure (UHP) eclogites and granulites. Peak-pressure metamorphic conditions recorded by these rocks have previously been estimated at 2.9–3.2 GPa and 750°C–830°C, based on thermodynamic modelling, conventional geothermobarometry, and Zr-in-rutile thermometry.

In this contribution, we present preliminary U-Pb zircon ages and trace element characteristics from two localities, Bielice and Nowa Wieś. The analysed zircons are mostly isometric or slightly elongated. Their internal structure was documented using back-scattered electron (BSE) and cathodoluminescence (CL) imaging prior to analysis. Zircons from Nowa Wieś predominantly display fir-tree and sector zoning patterns, whereas those from Bielice are mainly characterized by irregular and diffuse (aurora-light) zoning. Some grains from both localities contain possible inherited cores. Zircons from both localities show flat HREE patterns, a slight positive Ce anomaly, and no Eu anomaly. These features support the interpretation that zircon growth occurred under HP condition, contemporaneous with the eclogite-facies assemblage. Metamorphic zircon ages from Bielice cluster at 338.3 ± 3.4 Ma, whereas those from Nowa Wieś yield an age of 341.5 ± 3.4 Ma.

This project was supported by the Polish National Science Centre (UMO-2024/53/N/ST10/03586).

How to cite: Nowak, M., Szczepanski, J., and Anczkiewicz, R.: U-Pb zircon geochronology of coesite-bearing eclogites from the Orlica-Snieznik Dome (SW Poland) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19270, https://doi.org/10.5194/egusphere-egu26-19270, 2026.

Mafic and ultramafic rocks provide critical insights into ophiolite formation and obduction, orogenic suturing, and rock magnetism, yet they are difficult to date due to the absence of conventional radioisotopic chronometers. Magnetite and chromite are common primary or secondary mineral phases that often preserve growth zoning and complex overprinting, but extremely low eU concentrations and intragrain heterogeneity have limited the application of (U–Th)/He dating. Here we report recent progress at the University of Texas at Austin (UTChron) toward establishing protocols of routine laser ablation (LA) (U–Th)/He in-situ dating of magnetite and chromium spinel (chromite) with eU <10 ppb and ultra-low He concentrations. Our analytical procedures couple in-vacuo laser ablation and ultra-low-blank magnetic-sector noble gas mass spectrometry (Thermo Fisher SFT) for He with U–Th quantification by laser-ablation ICP-MS (Thermo Element2) and ablation pit volume measurements using white-light interferometry. This integrated workflow supports targeted analyses of discrete textural growth zones and complex intragrain textures at ~100 μm spatial resolution, with typical analytical precision of ~5–10%.

We present three applications for in-situ He dating of magnetite and chromite from mafic and ultramafic rocks: (1) magnetite and chromite from kimberlitic diatremes that yield LA-(U–Th)/He ages consistent with independent emplacement constraints, providing a practical alternative where conventional datable minerals are absent; (2) He ages from primary chromite from obducted orogenic ophiolitic units that record thermal resetting and subsequent cooling, offering new leverage on the tectonic histories of ultramafic sequences that are traditionally challenging to date; and (3) He dates from secondary magnetite growth in sheared serpentinites that provide direct constraints on fluid-rock interaction during deformation in ultramafic shear zones. Collectively, these results establish magnetite and chromite as viable targets for in situ (U–Th)/He thermochronometry and broaden the range of geological problems accessible to in-situ dating.

How to cite: Ehrenfels, M., Stockli, D., Prior, M., Patterson, D., Stockli, L., and Martin, C.: Extending Laser-Ablation (U-Th)/He to Ultra-Low-eU Magnetite and Chromite: A New Tool for Mafic and Ultramafic Rocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19596, https://doi.org/10.5194/egusphere-egu26-19596, 2026.

In-situ U-Pb carbonate geochronology is a well-established technique that directly constrains the timing and rates of important geological processes including fluid flow, diagenesis, and tectonic events. However, the fundamental controls on U behaviour in carbonate minerals remain unclear, limiting geological interpretations. Knowledge gaps include the controls on U incorporation, the highly heterogeneous distribution of U at a crystal scale, and the incorporation of U with respect to other (redox-sensitive) elements. The application of synchrotron X-ray microspectroscopy (µXAS) is ideal for investigating these topics, as it can map chemical changes and measure the valance state of key elements at the micron-scale.

Here we combine µXAS, in-situ laser ablation U-Pb carbonate geochronology, and EPMA analyses to temporally track U distribution, redox state, and dolomite-ankerite composition in a porphyry-epithermal system. Multiple generations of carbonate minerals record fluid conditions and processes which control the solubility and deposition of metals, including U. Results show that temporally distinct generations of carbonate record both oxidized UO₂²⁺ and reduced U⁴⁺ species within a single sample section. Mapping of individual carbonate crystals reveals that UO₂²⁺ and U⁴⁺ also occur within individual growth bands at a sub-millimetre scale, and in rare samples, may coexist. µXAS data from the sample suite demonstrate that local fluid conditions in the case-study mineralized system changed from more oxidized to more reduced over a period of ca. 16 Ma and corresponds with an increase in U levels in crystallizing carbonate.

The preservation of two U oxidation states during discrete precipitation events requires U retentivity within older domains, indicating that the U-Pb carbonate geochronometer is robust under hydrothermal conditions (e.g., ~200–350ºC) and through rapid local redox state changes. Furthermore, crystal zones with abundant fluid/vapour inclusions linked to boiling processes coincide with higher levels of U in the carbonate and favourable U/Pb. Our results suggest redox changes and boiling conditions may be critical for both the deposition of ore minerals, as well as increased U uptake in carbonate minerals. Targeting carbonate domains with these features may therefore increase success for U-Pb geochronology. U-Pb carbonate dating combined with µXAS can track the temporal evolution of processes critical for metal deposition in long-lived and multistage hydrothermal-magmatic ore deposit settings.

How to cite: Bowie, S., Mottram, C., Rasbury, E. T., Northrup, P., Tappero, R., and Kellett, D.: With or without U: uranium distribution and redox state in carbonate tracks protracted porphyry-epithermal mineralization through time, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20163, https://doi.org/10.5194/egusphere-egu26-20163, 2026.

Dating submarine volcanic rocks is essential for understanding the relationship between tectonics and volcanism, as well as for characterizing the evolution of volcanic systems, for instance. The K-Ar chronometer is generally used but dating young rocks (<50 ka) remains a significant challenge, particularly because their amount of radiogenic ⁴⁰Ar is low. Here, we present a comparison of K-Ar and the ⁴⁰Ar/³⁹Ar ages obtained from submarine samples from the Eastern Mayotte Volcanic Chain (EMVC; Comoros Archipelago). This volcanic chain consists of monogenetic pyroclastic cones, lava domes and lava flow fields with basanitic to phonolitic compositions. It includes the Fani Maoré, a new submarine volcano that formed a few years ago, and the Horseshoe, a potentially active U-shaped morphological structure, located only 10 km offshore Mayotte. A total of 19 samples were collected in the Horseshoe and Fani Maoré regions, by dredging and/or using the Victor6000 remotely operated vehicle (ROV), during 6 oceanographic campaigns. These samples were dated using both the K-Ar and the ⁴⁰Ar/³⁹Ar methods, on a carefully selected groundmass fraction obtained within a narrow density range with heavy liquids. Both methods used here allow dating of very young samples with ages as young as 3 ± 1 ka for phonolitic samples, with radiogenic content as low as 0.1%. The ⁴⁰Ar /³⁹Ar inverse isochrons confirm the atmospheric initial trapped ⁴⁰Ar/³⁶Ar component, suggesting that no argon fractionation affected the ages from either method, and flat ⁴⁰Ar/³⁹Ar age spectra indicate that the K-Ar system remained closed. In order to further check both methods with zero-age basanitic lavas, we have analysed samples from the 2018 and 2020 eruptions of the Fani Maoré volcano.  The relatively precise ages obtained by both methods confirmed that, following a carefully sample selection and preparation, both K-Ar and ⁴⁰Ar /³⁹Ar methods are well suited for dating submarine Holocene volcanics such as the phonolitic lavas and pyroclasts. Finally, the comparison between K-Ar and ⁴⁰Ar/³⁹Ar shows coherent results in most cases, enabling a precise temporal framework to be established for the Horseshoe region.

How to cite: Frey, M., Quidelleur, X., Ricci, J., Feuillet, N., Médard, É., Berthod, C., Komorowski, J.-C., Puzenat, V., Thinon, I., Rinnert, E., Cathalot, C., Jorry, S., Paquet, F., and Lebas, É.: Dating of submarine volcanism based on combined K-Ar and 40Ar/39Ar methods: example from the Eastern Mayotte Volcanic Chain (Comoros Archipelago)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20451, https://doi.org/10.5194/egusphere-egu26-20451, 2026.

Pyromorphite [Pb₅(PO₄)₃Cl] is an end-member phase of the apatite-group minerals. It commonly forms during supergene weathering of Pb-rich ore deposits. Owing to its chemical stability and low solubility under natural environmental conditions, pyromorphite preserves a record of supergene weathering events. The U concentration of pyromorphite is typically high (up to several thousand ppm) making it a potential as a (U-Th)/He and/or (U-Th)/Ne chronometer of paleoenvironmental change.  (U-Th)/He ages of nine pyromorphite specimens from around the globe are less than 5 Ma. The near complete absence of fission tracks in all samples, despite the relatively high U concentration (1-30 ppm), is consistent with the young He ages. Complete helium extraction requires considerably shorter heating at lower temperature than similar sized Durango apatite fragments implying that He closure temperature in pyromorphite is lower than apatite.

A detailed study of an inclusion-free pyromorphite crystal from Daoping mine, Guangxi (China) has been undertaken to determine its suitability as a chronometer of supergene mineralisation.  Incremental extraction of He from 250-500 mm fragments display good linearity on an Arrhenius diagram for temperature steps less than 220°C.  The kinetic parameters (E and ln(D₀/a²)) display a range of values that we use to determine a helium closure temperature in the range -30°C to -84°C for a nominal cooling rate of 10°C/Myr.  This range may reflect the presence of varying size sub-grains that are evident from EBSD.  Density functional theory modelling shows that the substitution of Ca²⁺ (0.99 Å) by Pb²⁺ (1.19 Å) expands the interstitial sites in the pyromorphite lattice compared to apatite, likely lowering the energy barrier for helium diffusion and changing the global minimum location, thus changing the diffusion pathway of He in pyromorphite. EBSD shows that lattice distortion is ubiquitous, perhaps due to the off-centre position of the electron pair of Pb²⁺ within its coordination environment or the substitution of V.  The dislocations may function as sinks for He and impede helium diffusion. This leads us to conclude that pyromorphite is unlikely to find use as He thermo/geochronometer but further study may aid understanding He diffusion in apatite group minerals.

How to cite: Stuart, F., Yan, M., Wang, Y., Pang, J., and Spruženiece, L.: Is (U-Th)/He dating of pyromorphite a new chronometer of weathering?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21743, https://doi.org/10.5194/egusphere-egu26-21743, 2026.

Thermal-kinematic modeling of thermochronometric datasets is widely used to reconstruct exhumation histories. Yet, the sensitivity of model outputs to input parameters is rarely evaluated, even within a given modeling framework. Comparative sensitivity analysis across multiple tools is even less common, even though these models differ substantially in their treatment of heat transport, inversion structure, and kinetic behavior. In this study, we apply the Taguchi method, a statistical design of experiments, to assess parameter sensitivity in four thermal-kinematic modeling packages. We systematically vary thermal, kinetic, and optimization parameters across each tool and quantify their influence on predicted exhumation rates. Our results reveal substantial model-specific differences in sensitivity patterns. Two modeling platforms that use the same formulation, namely, Gaussian linear inversion of an age-elevation relationship, are most responsive to different things, with one most sensitive to thermal field parameters such as heat production and thermal diffusivity, and the other strongly influenced by inversion settings, including time step and prior exhumation rate. In age2exhume, activation energy (E_a) dominates, underscoring the role of kinetic parameters in diffusion-based models. These findings demonstrate that parameter sensitivity is not intrinsic to the thermochronometric system but is shaped by modeling assumptions. As tool selection influences both interpretation and uncertainty, there is a risk that model structure may overwhelm geological signals if not explicitly tested. We advocate for broader model intercomparisons and increased flexibility in parameter configuration to support more robust and transparent thermochronologic analysis.

How to cite: Sparks, S. and Hodges, K.: Comparison of thermal-kinematic modeling approaches based on Taguchi method sensitivity analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22116, https://doi.org/10.5194/egusphere-egu26-22116, 2026.

One of the principles of Geochronology states that below a certain temperature (i.e. closure temperature), a system has cooled so that daughter isotopes no longer diffuse out of the mineral, and the geochronometer starts recording the time. However, there are multiple examples in the literature in which these geochronometers have been totally or partially reopened by subsequent geological events.

Accepting that transport in the host magma is too short-lived to thermally affect its xenolith cargo, in this contribution, we have studied the effect on the Lu-Hf and U-Pb systems of pre-entrainment percolation of high-temperature kimberlite melts, which is known to result in heating and precursory metasomatism of cratonic lithospheric mantle [e.g. 1]). We do so by analysing garnet from kimberlite‐borne eclogite xenoliths from the Namaqua‐Natal Fold Belt, at the southwestern Kaapvaal craton margin, which was affected by the 1.2-1.0 Ga Namaqua-Natal orogeny, whereas the kimberlites were emplaced in the Cretaceous ([2,3] and references therein). The xenoliths yielded emplacement pressures and temperatures of 1.7±0.4 GPa and 815-1000 ^oC, respectively ([2]). The analyses were done by LA-ICPMS for both Lu-Hf and U-Pb systems.

The results obtained for each of the geochronometers are different and not comparable. On the one hand, the U-Pb analyses result in a relatively precise Cretaceous age, similar in all samples within the uncertainty, consistent with a complete reset during interaction with kimberlite melts and/or the eruption. On the other hand, the Lu-Hf ages show a wide range of ages, from the Mesoproterozoic to the Cenozoic, in many cases with a large uncertainty. This I) may imply a partial reset of Hf during secular cooling and/or the heating produced by kimberlite melts, II) it may be associated with the higher closure temperature for the Lu-Hf system.

References:

[1] Fitzpayne et al. (2020) Lithos 370-371: 105595; [2] Le Roex et al. (2020) J. Petrol. 61: egaa040; [3] Aulbach S et al. (2024) J. Geophys. Res. Solid Earth 129: e2023JB027894.

How to cite: Beranoaguirre, A., Aulbach, S., Millonig, L. J., Kutzschbach, M., Le Roex, A., Tinguely, C., and Gerdes, A.: Effect of kimberlite melts on garnet U-Pb and Lu-Hf geochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22769, https://doi.org/10.5194/egusphere-egu26-22769, 2026.

Strain partitioning in quartzo-feldspathic rock is closely related to the degree of phase mixing. Both quartz and feldspar tend to form the load-bearing framework (LBF) in naturally deformed rocks, provided there are softer phases such as mica, which behaves as the interconnected weak layer (IWL). In cases where mica is absent, the scenario becomes complicated. Quartz in augen gneisses often behaves as the IWL and feldspar takes the role of the LBF. However, the relative degree of weakening in deformed quartz and feldspar depends on their respective deformation mechanisms. As the mechanisms are different, there is a possibility of dissimilar weaking, followed by a strength reversal.

We have studied a deformed quartzo-feldspathic vein from the Bundelkhand Craton in central India. Despite being Archean, this craton experienced long hiatuses between deformation events, which makes the delineation between different events simpler. The sample we collected from this craton is the result of the latest stage of deformation. A high-temperature fluid entered through fractures and softened the granitic country rock. The fluid, being syn-tectonic, allowed the granitic vein to facilitate different deformation mechanisms in quartz and feldspars.

We investigated the crystal-plastic behaviour of quartz and two feldspars in the deformed vein via electron backscatter diffraction. The quartz crystallographic preferred orientation (CPO) and misorientation index (M) is strongest when quartz grains are adjacent to each other. There is no significant difference in CPO strength in feldspars when the proportion of similar neighbouring phases changes. Additionally, a monomineralic quartz layer exhibits a class 3 buckling fold, implying a higher competency than the adjacent matrix, which contains recrystallised feldspar grains. However, the microstructural evidence suggests that the parent feldspar porphyroclasts are stronger than the recrystallised monomineralic quartz bands. From the inverse pole figure of low-angle (2–10°) misorientation axes in quartz, prism <a> activity is observed which is dominant in the temperature range of 500–650°C. Hence, we infer a deformation temperature of at most 650°C, although it can be lower depending upon the water weakening as such weakening activates prism <a> at lower temperatures. Randomised CPO in feldspar suggests strain accommodation via diffusion creep, followed by grain boundary sliding mechanism might have operated in feldspars. These processes could result in greater softening than that in quartz, which deformed by dislocation creep. Isolated quartz grains existing in the triple junctions of feldspars are not part of such pure dislocation creep; rather, it is more likely that they are byproducts of albitic transformation reactions. Hence, higher strength in quartz is limited to the monomineralic bands, which are purely affected by dislocation creep in the deformed quartzo-feldspathic vein of the Bundelkhand Craton.

How to cite: Sikdar, A., Wallis, D., and Misra, S.: Strength Reversal in Recrystallisation: an EBSD-based Study in a Naturally Deformed Granitic Vein, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1143, https://doi.org/10.5194/egusphere-egu26-1143, 2026.

Earthquake records preserved in rocks provide key insights into the processes that govern crustal deformation and seismic energy dissipation. This manuscript presents new approaches for identifying mineralogical signatures of paleoearthquakes using advanced microstructural analyses, including electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI). These techniques enable observations from the millimetre to nanometre scale of features associated with plastic deformation, including crystal reorientation and deformation twinning. Here, we investigate deformation microstructures in monazite, a key geochronometer, with the aim of assessing the impact of deformation on geochronological interpretations, as deformation-induced crystallographic defects can act as high-diffusivity pathways leading to Pb loss. Understanding the deformational behaviour of monazite is therefore critical for interpreting geochronological data. We examine monazite from an eclogite facies mylonite in the Musgrave Province (central Australia) to elucidate mechanisms of seismic deformation under dry (<0.002 wt% H₂O), lower-crustal conditions. The studied monazite grain is directly cross-cut by a pseudotachylite vein, indicating that the observed microstructures formed during the associated seismic event. EBSD and ECCI analyses reveal crystal-plastic deformation in the form of twinning with three distinct orientations: 180° <100>, 180° <001>, and 95° <201>. The latter is associated with dynamic recrystallization via subgrain boundary rotation. ECCI further reveals nanometre-scale (<15 nm) porosity within both parent grains and twins. These microstructures are consistent with those reported in monazite deformed during impact events. Recent studies of shocked monazite have shown that deformation by twinning can liberate Pb during rupture of rare-earth-element–oxygen (REE–O) bonds, enabling rapid diffusion along crystallographic defects and complete expulsion from the crystal, effectively resetting the geochronometer. The new insight provided by these microstructural focussed observations likely accounts for the disparity of electron probe microanalysis (EPMA)-based geochronology on the same monazite grain, which yielded ages of 1309 to 691 Ma. Seismicity in the Musgrave Province is primarily associated with the Petermann Orogeny (~550 Ma), suggesting that the younger EPMA ages were partially reset as a result of the twinning. Our results demonstrate the potential for monazite to record and date seismicity, opening new avenues for reconstructing paleoearthquake histories from deep crustal rocks.

How to cite: Dubosq, R., Camacho, A., and Britton, B.: Seismic twinning in monazite: Microstructural records of deep crustal earthquakes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4322, https://doi.org/10.5194/egusphere-egu26-4322, 2026.

Prograde metamorphic reactions that reduce solid volume are common in subduction zones and orogenic settings [1]. These reductions are often linked to irreversible deformation such as viscous compaction and deep mantle earthquakes [2]. Viscous compaction involves permanent closure of reaction-generated porosity and fluid release, making porosity transient property of metamorphic reactions [3]. The pore closure observation is often linked to the intuitive loss of the elastic strength of the rock leading to permanent strains [4, 5], but these assumptions are very rarely demonstrated experimentally. In most cases, the nature of field relationships and the design of experiments do not allow for such an assessment to be made. Time-resolved in situ experiments enable the observation of a sample volume undergoing metamorphic transformation to check such assumptions at every stage of the reaction (loading, heating, cooling and unloading).

In this contribution, we provide preliminary visual and quantitative strain mapping during the metamorphic reaction cycle of a rock sample at various stress states and reaction extent.

Using Mjolnir, an X-ray transparent miniature triaxial deformation rig, we performed a series of gypsum (Ca₂SO₄·2H₂O) dehydration experiments into bassanite (Ca₂SO₄·1/2H₂O) at constant confining pressure of 20 MPa, pore fluid pressure (5 MPa) and subjected to similar temperature paths (up to 125ºC).  We used a series of differential stresses (radial, hydrostatic and axial principal stresses) to explore how the rock volume responds mechanically while also displaying different reaction fabrics (see [6]). This dehydration reaction produces a solid volume reduction of ~30% [4] enabling the investigation of the evolution of elasticity by unloading fully and partially transformed samples.

Using synchrotron microtomography at the I13-2 beamline of the Diamond Light Source (MG34156), we performed high resolution imaging (1.625 microns/ voxel edge) during gradual unloading to observe and quantify the elastic behaviour both using the mechanical data from the Mjolnir rig [7], sample dimensions (using stitched images; [8]) and digital volume correlation (DVC) techniques (Avizo). 

Our results show the complexity of strain distribution and partial preservation in metamorphic rocks with:

• Significant elastic strain preservation during metamorphic reactions and its apparent minimisation during the ultimate stages of the reaction (textural “maturation” via pressure/solution).
• Complex strain distribution influenced by bassanite anisotropy, sample fabric, geometry, and stress state.

These experiments enable to visualise in 4D the grain-scale development of a complex porous network during the reaction. It opens pathways to document the emergence of poro-elasticity (initial solid has very low porosity) and then the release of the elastic strains. This dataset further demonstrates the importance and the complexity of elasticity in metamorphic systems, with complex displacement vector fields under relatively simple boundary conditions.

References:

[1] Brown & Johnson (2019). https://doi.org/ https://doi.org/10.2138/am-2019-6956

[2] van Keken & Wilson (2023). https://doi.org/10.1186/s40645-023-00573-z

[3] Putnis (2015). https://doi.org/10.2138/rmg.2015.80.01

[4] Leclère et al. (2018). https://doi.org/10.1016/j.epsl.2018.05.005

[5] Llana-Fúnez et al. (2012). https://doi.org/10.1007/s00410-012-0726-8

[6] Gilgannon et al. (2024). https://doi.org/10.1130/G51612.1

[7] Butler et al. (2020). https://doi.org/ 10.1107/S160057752001173X

[8] Turpin et al. in prep

How to cite: Freitas, D., Gilgannon, J., Duggins, D., Butler, I., Rizzo, R., Turpin, L., Chen, B., Reinhard, C., and Bourne, N.: The complex evolution of elasticity during metamorphic transformation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4517, https://doi.org/10.5194/egusphere-egu26-4517, 2026.

Deformation and metamorphism are fundamental processes that act synchronously throughout the Earth; however, their interaction remains unclear. Theoretical models predict that an applied tectonic stress has both a dramatic effect or no effect at all. While the small set of deformation experiments that document the interaction between reaction and deformation are either hard to compare or cannot provide the necessary time resolution to test the various theories. These disagreements of predictions and the gap in data invites new time-resolved experiments to be run that can probe details of model predictions and connect existing datasets from different materials deforming at a range of metamorphic conditions. To this end, we use state-of-the-art time-resolved synchrotron-based x-ray microtomography (4DSµCT) deformation experiments to map out the effect of a differential stress on the kinetics of the dehydration of polycrystalline gypsum samples. Our experiments are highly resolved in space (µm) and time (s), which allows us to track and contrast the emergence of the first small crystals (~100 µm3) and their growth through time in hydrostatic and differentially stressed conditions. We find that the kinetics of a metamorphic reaction are profoundly affected by the addition of deformational energy. Differentially stressed samples transform up to ~90% sooner than in the hydrostatic case, and reaction rates increase by a factor of ~5 with increasing differential stress. Importantly, our findings can be expanded to other published data for reactions occurring in the lower crust and the mantle to show that it is changes in the elastic strain energy that drive accelerated metamorphic kinetics. We find that, when we compare kinetic data from these different reactions and normalise the differential stress to each material’s yield strength, a trend emerges that shows stresses larger than the yield do not contribute to accelerating a reaction. Our results showcase the material-independent effect of a differential stress on metamorphic reactions and support theoretical models which place emphasis on the role of changes in stored energy. Current geodynamic models largely ignore the role of stored energy because it is assumed that it is not relevant at long time scales, our results show that its effect is important and should be accounted for when coupling deformation and metamorphism.

How to cite: Gilgannon, J., Vass Payne, E., Butler, I., Freitas, D., and Fusseis, F.: The material-independent effect of a differential stress on metamorphic kinetics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6735, https://doi.org/10.5194/egusphere-egu26-6735, 2026.

The study of the evolution of petrophysical properties and alteration of host rock in an active fault system is essential for understanding the mechanisms of deformation localization. The distribution of alterations is closely linked to fluid flow paths, while the formation of new deformation structures depends on the mechanical contrasts induced by these alterations. Our study focuses on granodiorite samples from a borehole drilled in 1996 at Hirabayashi by the Geological Survey of Japan, one year after the Nanbu-Kobe earthquake. Crossing the active Nojima fault, this borehole intersects the fault core at 625 m. The analyses include imaging of samples using neutron and X-ray microtomography (ILL – NeXT) and thin sections, as well as mineralogical quantification by X-ray diffraction (XRD). X-ray diffractograms on oriented slides and Rietveld analyses of XRD data acquired on disoriented powders reveal the presence of secondary mineral phases (e.g., montmorillonite, kaolinite, laumontite, siderite, ankerite), representative of different fluid-rock interaction conditions during the exhumation of the massif. Their proportions, which increase as they approach the fault, reach more than 30% of the volume of a sample at 625 m. Whereas X-ray µ-tomography imaging allows us to observe density contrasts within the samples (e.g., mineral phases and fracture network). On the other hand, neutron imaging allows us to observe the distribution of hydrated mineral phases due to the high neutron absorption coefficient of hydrogen (e.g. for 25 meV neutrons, hydrogen attenuation is 3.44 vs 0.17 and 0.11 for oxygen and silicon, respectively). Neutron and X-ray image registration in the same reference frame allows us to perform joint image segmentation, using gaussian-mixture-model to quantify uncertainties, based on the neutron and X-ray coefficients of absorption of the pre-identified mineral phases. The volumes segmented in this way enable us to (i) quantify in a non-destructive way the volume of secondary mineral phases present in the samples along the fault damage profile and (ii) obtain their spatial distribution and assess the anisotropies of distribution in relation to the deformation structures. This work will subsequently enable us to understand the impact of both the distribution of secondary mineral phases and the network of microfractures on the evolution of the petrophysical and mechanical properties of a seismogenic fault.

How to cite: Jamet, M., Baron, F., Beaufort, D., Dazas, B., Patrier, P., Tengattini, A., Iaquinta, R., Doan, M.-L., Pezard, P., Gibert, B., and Luquot, L.: Neutron and X-ray µ-tomography-based 3D imaging of alteration phases in faulted granodiorite at Nojima (Japan), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7324, https://doi.org/10.5194/egusphere-egu26-7324, 2026.

During the International Ocean Discovery Program (IODP) Expedition 402 in the Tyrrhenian Sea, two of the six drilled sites, the U1613 and U1617, were located on the thinned continental crust of the Cornaglia and Campania terraces, where the deposition of evaporites during the Messinian Salinity Crisis (MSC) had been imaged with seismic data. Expedition 402 recovered Messinian evaporites beneath a relatively thin sedimentary cover at both drill sites. At Site U1613, the Messinian section is extremely thin (a few meters only). In contrast, at Site U1617, a complete 102 m-thick evaporitic sequence ranging from gypsum-enriched terrigenous sediments through anhydrite to halite layers was sampled. This scientific drilling site is the only one in the Mediterranean that penetrated the complete Messinian evaporitic sequence, providing a unique opportunity to study the properties of the so-called Upper, Mobile and Lower units. A series of physical property measurements was performed on these cores on board of the JOIDES Resolution drillship, including P-wave velocity, density, magnetic susceptibility, natural gamma ray and thermal conductivity. In addition, we collected representative discrete samples to measure P-wave velocity (Vp), bulk density, grain density and porosity. These data allowed us to analyze the sealing properties of the halite unit and its interaction with salt-induced tectonics. Furthermore, from Vp and density used as input to calculate reflection coefficients, we generated a 1D synthetic seismogram at Site U1617. We compared this synthetic seismogram with the multi-channel seismic data acquired across the drill site, namely the Medoc 6 line. These new data allowed us to compare the Messinian units recovered in situ with multichannel seismic data and thereby revise seismic interpretation of these units. Thanks to the unique opportunity offered by the IODP Expedition 402, we now have reliable data on the physical properties of Messinian evaporites and we are able to provide new constraints on the interpretation of Messinian facies.

How to cite: Loreto, M. F., Ligi, M., Filina, I. Y., Abe, N., Shuck, B. D., Pezard, P. A., Estes, E. R., Malinverno, A., Ranero, C. R., Yang, L., and Zitellini, N.: A new concept of Messinian Salinity Crisis based on physical properties from the IODP Exp.402 in the Tyrrhenian Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7733, https://doi.org/10.5194/egusphere-egu26-7733, 2026.

The mechanisms of intraslab earthquakes at depths of > 40 km are fundamentally different from those of shallow earthquakes because the frictional strength of silicate rocks is proportional to the confining pressure. To understand the process triggering intraslab earthquakes, many experimental studies on faulting of slab-forming rocks have been conducted at upper mantle pressures. Previous studies have revealed that shear localization induced by dehydration of hydrous minerals (e.g., Okazaki & Hirth, 2016) or adiabatic shear heating (e.g., Kelemen & Hirth, 2007) is essential for the occurrence of faulting at high pressures. Although acoustic emission (AE) monitoring technique for D-DIA apparatuses enabled us to discuss the process of microcracking at high pressures, mechanical behavior at the onset of faulting is still unclear due to low time-resolution stress/strain measurements using synchrotron X-rays. The cause of bottleneck in stress/strain measurements is a long exposure time required for the acquisition of a two-dimensional X-ray diffraction pattern of minerals. Considering that the timescale of stress drop associating faulting is on the order of 0.01 sec (e.g., Okazaki & Katayama, 2015), a significant improvement for time resolution of stress/strain measurements is required. To improve the time resolution of stress/strain measurements, we installed a series of new devices at BL15XU, SPring-8.

We conducted in situ triaxial deformation experiments on olivine aggregates at pressures of 1-3 GPa and temperatures of 700-1250 K under nominally dry conditions using a D-DIA apparatus, installed at BL15XU, SPring-8. Two-dimensional radial X-ray diffraction patterns and radiographic images were alternately acquired by adjusting sizes of the incident slit and operating a flatpanel detector and a CCD camera using a high-flux pink beam (energy 100 keV) from an undulator source (0.2 s of exposure time for both ones). Pressure and differential stress were determined from the d-spacing of olivine. Strains of deforming samples were evaluated from the distance between platinum strain markers. AEs were recorded continuously on six sensors glued on the rear side of the 2^nd-stage anvils, and three-dimensional AE source location were determined.

Stress increased with strain at the beginning of sample deformation, and it reached the yielding point at strains of ~0.1 or less. AEs from the deforming sample were detected when stress exceeded ~1 GPa and the amplitude of AE is positively correlated with the magnitude of stress. At strains higher than 0.1 (i.e., beyond the yielding point), both softening (i.e., decrease in stress and/or increase in strain rate) and a decrease in AE rate were observed prior to the occurrence of faulting. Faulting was observed at 880-1150 K. Most of unstable slips proceeded within 1 s and associated a sudden stress drop (~0.5 GPa) and temporal radiation of large AEs. In contrast, neither stress drops nor AEs were associated with a few “aseismic” unstable slips. Differential stress continuously increased when stable slip proceeded and the stable slip was terminated by the occurrence of another unstable slip. Our observations suggest that unstable slips can be divided into two types (i.e., seismic and aseismic ones) under the P-T conditions of shallow subducting slabs.

How to cite: Ohuchi, T., Higo, Y., Tsujino, N., Kakizawa, S., Ohsumi, H., and Yabashi, M.: In situ observation of faulting in olivine at high pressures and high temperatures using high-flux synchrotron X-rays, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7751, https://doi.org/10.5194/egusphere-egu26-7751, 2026.

Evidence for the nature of fault slip across the seismic cycle is hard to decipher. Fault-related deformation near the fault surface develops over the seismic cycle, characterized by rapid coseismic slip and intense deformation, followed by slower interseismic slip and stress accumulation. While considerable focus has been placed on characterizing deformation through fracturing and mesoscale structures, the analysis of grain-scale plastic processes has been largely neglected. However, transient temperature increases due to frictional heating, combined with the ability of calcite-bearing rocks to deform plastically at relatively low temperatures, suggest that microstructural damage and subsequent recovery processes could leave diagnostic evidence in carbonate fault rocks. Indeed, Pozzi et al. (2019) demonstrated that shearing gouge at seismic rates (~1 m/s) develops a crystallographic preferred orientation (CPO), accompanied by grain growth and sintering. These observations, however, were confined to nanometer-scale grains, localized at the fault surface.

Here, we present a detailed microstructural analysis of carbonate samples from the North Anatolian Fault Zone. We used Electron Backscatter Diffraction to map the calcite grains' orientations and characterize intragrain deformation and grain-boundary morphologies. We identify three distinct layers extending from the fault surface to a distance of ~4 mm. Layer I, with a thickness of tens of µm to 0.5 mm, exhibits predominantly angular grains with grain sizes ranging from unresolved (<1 µm) to tens of µm. Layer II, with a thickness of 0-200 µm, is comprised of small equant grains (1-5 µm) and some larger grains (10-30 µm), characterized by wavy grain boundaries, suggesting active grain boundary migration. No CPO was observed in layers I and II. Layer III, with a thickness of ~2-3 mm, contains large grains (hundreds of µm) that can be divided into two populations of grains. Rounded grains with wavy grain boundaries indicate the progressive consumption of smaller grains. At the core of the layer, grains contain faceted boundaries and are elongated parallel to the fault surface. This layer is the only one to exhibit a distinct CPO with the c-axis oriented normal to oblique to the slip surface. Importantly, the large grains in layer III also comprise small, isolated ‘islands’ of finer grains.

We infer that deformation mechanisms vary systematically with distance from the fault surface. Layer I records cataclastic flow at the fault surface, whereas layer II, characterized by very small grain sizes, exhibits shearing by grain boundary sliding that resulted in grains with low intragrain misorientation and the absence of CPO. The most striking microstructural record is preserved in layer III, which initially shows strong evidence for recovery processes by abnormal grain growth. We propose that this latter process occurred during or immediately after coseismic frictional heating, resulting in the consumption of previously deformed grains, which maintains the CPO record of deformation and provides a microstructural record of the seismic cycle at millimeter-scale distances from the fault surface.

Pozzi, et al., 2019. Coseismic ultramylonites: An investigation of nanoscale viscous flow and fault weakening during seismic slip. Earth and Planetary Science Letters.

How to cite: Boneh, Y., Levi, T., Nuriel, P., and weinberger, R.: Abnormal grain growth in carbonate samples from the North Anatolian Fault: Microstructural evidence of the seismic cycle, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7796, https://doi.org/10.5194/egusphere-egu26-7796, 2026.

X-ray ptychography is a lensless, coherent-diffraction imaging technique developed over the last 20 years that affords 10-nm resolution for optically thick specimens¹. It reconstructs the optical transmission function (OTF) of a sample from raster-scanned overlapping 2D transmission diffraction patterns through iterative phase retrieval algorithms^1,2. The OTF projects the refractive index of the sample along the incident beam and thus quantifies the phase shift and amplitude attenuation of the transmitted beam², which in turn relate to the projected electron density of the specimen. X-ray ptychography is therefore an ultramicroscopy technique that is very well suited to mapping nano- and micron-sized objects with significant density differences relative to the bulk such as pores and dense accessory minerals.   

In this contribution, we present a primer for the application of X-ray ptychography to nano- and micro-scale studies of rocks. First, we illustrate the underlying physical principles that guide the data processing and interpretation of ptychographs. Then, we show exemplary applications to a wide range of rock samples (e.g., seismogenic brittle fault rocks, mylonites, veins, shale, and micrite) imaged at the XFM beamline of the Australian Synchrotron³ over the last 5 years^4,5. Application examples include the measurement of sample surface roughness, imaging of cracks and pores, 3D porosity measurements, and the detection of buried accessory phases.

References

1          Pfeiffer, F. X-ray ptychography. Nature Photonics 12, 9-17, doi:10.1038/s41566-017-0072-5 (2018).

2          Wittwer, F., Hagemann, J., Brückner, D., Flenner, S. & Schroer, C. G. Phase retrieval framework for direct reconstruction of the projected refractive index applied to ptychography and holography. Optica 9, 295-302, doi:10.1364/OPTICA.447021 (2022).

3          Howard, D. L. et al. The XFM beamline at the Australian Synchrotron. Journal of Synchrotron Radiation 27, 1447-1458, doi:doi:10.1107/S1600577520010152 (2020).

4          Jones, M. W. M. et al. High-speed free-run ptychography at the Australian Synchrotron. Journal of Synchrotron Radiation 29, 480-487, doi:https://doi.org/10.1107/S1600577521012856 (2022).

5          Schrank, C. E. et al. Micro-scale dissolution seams mobilise carbon in deep-sea limestones. Communications Earth & Environment 2, 174, doi:10.1038/s43247-021-00257-w (2021).

How to cite: Schrank, C. E., Jones, M. W. M., Kewish, C. M., van Riessen, G. A., Hinsley, G., Berger, A., Herwegh, M., Schwichtenberg, B., Bishop, N. D., Howard, D., Langendam, A. D., and Paterson, D. J.: Nano- and micro-scale imaging of rocks with X-ray ptychography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8362, https://doi.org/10.5194/egusphere-egu26-8362, 2026.

Dehydration embrittlement is the dominant mechanism proposed to explain deep-focus earthquakes between 100–350 km in depth. Antigorite dehydration was extensively investigated in previous experimental studies, which demonstrated contrasting results regarding the seismic potential of antigorite dehydration. Additionally, microstructural aspects of antigorite dehydration and their implications for deep seismicity are scarce. Localized dehydration, on the other hand, might generate strain weakening, potentially leading to failure at depths relevant to deep earthquakes. Localized antigorite dehydration is demonstrated to occur in nature and the laboratory; however, it is not clear if this is a passive or dynamic process.

To better understand the micro-mechanisms of localized antigorite dehydration, we conducted high-pressure, high-temperature experiments under isostatic and non-isostatic conditions. Experiments were run at 3 GPa and temperatures within and above the antigorite stability field (530 °C–800 °C). Antigorite cores with 2 mm diameter were mounted in cubic assemblies and deformed in a 6-ram multi-anvil press at the Bayerisches Geoinstitute. Pure shear deformation was applied by inserting one pair of anvils while simultaneously removing the remaining two pairs orthogonal to it.

Results show that isostatic dehydration of antigorite at 3 GPa starts at ~530 °C and completes at ~800 °C. Localized dehydration occurs in isostatic and non-isostatic conditions within the antigorite stability field. It is enhanced during deformation experiments, resulting in the formation of nanocrystalline veins and networks containing olivine and pyroxene. These results demonstrate that localized dehydration might occur through passive and dynamic processes with the development of different microstructures.

How to cite: Silva Souza, D., Thielmann, M., Heidelbach, F., and Frost, D.: Localized dehydration of antigorite during experimental deformation at subduction zone conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9434, https://doi.org/10.5194/egusphere-egu26-9434, 2026.

U-Pb geochronology via Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is a fast and reliable method for in-situ dating of calcite that is used across disciplines in earth science. However, the heterogeneous distribution of U (and Pb) in individual calcite crystals represents a yet unmitigated challenge and identifying zones of sufficiently high U concentrations that can provide precise constraints on timing of calcite precipitation is an inefficient “hit or miss” process. Moreover, it is challenging to confirm that targeted domains of a calcite crystal retain their pristine geochemical signature, given the range of post-crystallization dissolution-reprecipitation and solid diffusion processes that can affect this mineral. There is thus an urgent need to understand the spatial and temporal mechanisms of U incorporation and mobilization in calcite to ultimately improve this key geochronological tool. To determine where specific trace elements are located within calcite crystals, investigate how they are incorporated during crystal growth and how they are affected by post-crystallization fluid-assisted deformation processes, we applied Synchrotron X-Ray Fluorescence Microscopy (XFM) with emphasis on U mapping, Electron Backscatter Diffraction (EBSD), and LA-ICP-MS to a set of calcite veins. Samples were collected from drillcores through the Middle and Upper Jurassic carbonates and marls (max. 85°C) in the Neogene Molasse Basin in central northern Switzerland. By combining high-resolution trace element maps with information on the crystal lattice structure of calcite we show two main textural types of trace element distributions within syntaxial calcite veins: 1) oscillatory crystal growth zonations that reflect preferential incorporation of trace elements into structurally different growth steps and faces of growing calcite crystals during growth and, 2) complete overprint of the initial growth zonation upon potential secondary fluid infiltration and trace element replacement. The anti-correlation between Fe, Mn and Sr, U demonstrates the role of kinetic factors during trace element partitioning between fluid and calcite, pointing to the inhibition of Fe incorporation at higher growth rates. Where the Sr uptake during calcite growth is generally enhanced with growth rate. The results of this project give valuable insights in the complexity of fluid overprint during multi-staged deformation cycles in the modification of trace elements in calcite, with clear implications for the applicability and reliability of U-Pb geochronometer in calcite.

How to cite: Akker, I. V., Schrank, C. E., Jones, M. W. M., Howard, D., Tavazzani, L., and Morales, L.: Trace element mapping in vein calcite with synchrotron XFM: implications for U-Pb geochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9614, https://doi.org/10.5194/egusphere-egu26-9614, 2026.

Salt caverns are formed in the subsurface during solution mining of salt. After the end of salt production, caverns need to be safely abandoned or may be repurposed for storage of energy carriers such as hydrogen. Salt caverns locally disturb subsurface stresses, leading to creep of the surrounding rock salt. Creep can cause cavern convergence at depth and may result in surface subsidence, with consequences for infrastructure and public safety. Accurate forecasting of cavern stability during abandonment or assessment of suitability for storage requires a deep understanding of the grain scale deformation mechanisms and processes controlling rock salt strength and creep rate. For rock salt, important deformation mechanisms are dislocation creep and pressure solution creep. Laboratory experiments have shown that dynamic recrystallization (DRX) associated with dislocation creep can be activated and contribute to mechanical weakening. However, the weakening effect of DRX is not included in engineering constitutive laws used in salt cavern numerical models. These laws are commonly based on low-strain laboratory experiments, where the influence of DRX is limited, and microstructural data are relatively rarely reported. The aim of this study is to experimentally investigate the dominant DRX process in deforming natural rock salt and its effect on the mechanical behaviour.

Lab experiments have been carried out on natural wet salt samples from the Zechstein formation. We conducted constant strain rate experiments using a triaxial compression apparatus. Experiments were performed at a confining pressure of 20 MPa and a temperature of 125 °C, using constant displacement rates corresponding to strain rates of approximately 5 × 10⁻⁵ s⁻¹ and 5 × 10⁻⁷ s⁻¹, up to 30–40% axial strain. After the experiment, all samples were studied using optical microscopy. Electron backscatter diffraction (EBSD) analysis was performed on the starting material and on two deformed samples, one from each strain-rate condition.

For all samples, we observed an initial transient creep stage followed by a quasi-steady state stage. The transition to quasi-steady occurred at a strain of about 10% for samples deformed at a strain rate of ~5 × 10^-7 s^-1. For samples deformed at the faster strain rate of ~5 × 10^-5 s^-1, continuous hardening occurred up to axial strains of 30%, with a gradually decreasing hardening rate approaching steady state. Light optical and EBSD microstructural analysis revealed grains with a dense substructure including subgrain walls, euhedral shape grains with low to no substructure, and grains with irregular shaped grain boundaries including bulges. We infer that the dominant deformation mechanism in the tested natural samples was dislocation creep, providing sufficient local differences in dislocation density to activate DRX dominated by grain boundary migration processes. DRX led to rheological weakening and quasi-steady deformation. We are working on robust understanding of the parameters controlling DRX as this is essential to evaluate the zones prone to weakening by DRX around salt caverns.

How to cite: Dialeismas, E., de Bresser, H., Hangx, S., and ter Heege, J.: An experimental investigation of dynamic recrystallisation processes and their influence on the mechanical properties of natural rock salt samples, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9678, https://doi.org/10.5194/egusphere-egu26-9678, 2026.

Bio-cementation is a new, environmentally-friendly soil-reinforcement process. It is used for civil engineering purposes, such as the fabrication of construction materials, as well as the preservation of monuments. This process uses bacterial activity, mainly that of Sporosarcina Pasteurii, that is capable of  hydrolysing the urea present in the medium, leading to the precipitation of CaCO₃ (calcite) crystals between sand grains, therefore binding them together, and reinforcing the soil. The macro and micro (contact scale) mechanical properties of bio-cememted sand have been extensively studied. However, the microstructure of the precipitated calcite crystals remains undiscovered, which induces mechanical differences under different conditions of cementation. The goal of this study is to investigate the microstructure of biogenic calcite, issued from bio-cementation of sand, and how it varies under different cementation conditions. For this, high resolution synchrotron diffraction imaging at the ESRF was performed, utilizing scanning 3DXRD (s-3DXRD) on ID11 and Dark-Field X-ray Microscopy (DFXM) on ID03. For this, the main experiment was performed on three samples that consist of 3D printed resin cells in which cementation was performed under different conditions, by varying the substrate on which the calcite was grown (between sand grains and glass beads), as well as varying the salinity of the medium. After each cementation cycle, and for each sample, layer measurements were acquired using s-3DXRD. A significant difference was observed between the sand and glass bead cases: the precipitated crystals on the glass beads were much smaller than those precipitated on the sand grains. DFXM measurements showed defects that are only present in the case of high concentration of NaCl in the medium, which could potentially alter the mechanical properties of the material. These two complementary techniques allowed for an in-depth study of the microstructure of the precipitated calcite crystals.

How to cite: Sarkis, M., Detlefs, C., La Bella, M., Naillon, A., Geindreau, C., Emeriault, F., Watier, Y., Ball, J. A. D., and Yildirim, C.: High-resolution microstructural study of calcite crystals precipitated through bio-cementation under different conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11242, https://doi.org/10.5194/egusphere-egu26-11242, 2026.

When deformed by dislocation creep the dominant slip (Burgers) vectors of olivine dislocations are parallel to [100] or [001]. Dislocations with an [010] Burgers vector component (b dislocations) have been recorded rarely. Here we show an experimentally deformed olivine sample has a substantial population (17%) of b dislocations. Electron Backscatter Diffraction maps of crystal orientations provided information on dislocations from the orientation gradients. Maps show the b dislocations form subgrain walls like those formed by other dislocation types and are interpreted to form similarly by glide and climb, so b dislocations are mobile. To confirm our approach, we used EBSD maps to select an area for Transmission Electron Microscopy imaging, down to an atomic scale image of a b dislocation. Our sample was deformed within range of subduction zone conditions; our approach can be used to investigate the scale and conditions of b slip in the mantle more widely.

How to cite: Wheeler, J., Hunt, S., Eggeman, A., Donoghue, J., Gholinia, A., Li, Y., Tillotson, E., and Haigh, S.: Olivine Deformation: to B Slip or not to B Slip, that is the Question, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11671, https://doi.org/10.5194/egusphere-egu26-11671, 2026.

The Cation Exchange Capacity (CEC) of clay minerals has been extensively studied in wide applications / purposes, using various imaging techniques to highlight changes of the clay sheet chargeability. Among the clay minerals, swelling clays such as smectite or vermiculite are particularly interesting regarding their adsorption-desorption properties strongly related to their high CEC (80-150 to 100-150 meq/100g respectively). To better monitor and predict cation exchange processes, the CEC has been investigated by different methodological approaches, including X-ray absorption spectroscopy (XAS) and geoelectrical methods. The Spectral Induced Polarization (SIP) is particularly well designed to quantify CEC because its complex conductivity measurements (in phase and quadrature) characterizes the electrical conduction of charge carriers (liquid) and the polarization phenomenon resulting from the local accumulation of electrical charge carriers in the porous medium (mineral interface).

The aim of this work is to investigate in situ how K cations are incorporated within the interlayer of a Ca-montmorillonite by coupling XAS and SIP experimental methods. This novel approach brings multi-scale information at the atomic and clay-sheet levels, providing new insights on enhancing the understanding of CEC mechanisms in terms of time and space and our ability to monitor it with SIP. The experiment was carried out on LUCIA (Soleil synchrotron), at the low energy of potassium K-edge with a microbeam size (2.5 x 2.5 µm²).

We used a 1.7 mm³ cell filled with 0.1 g of Ca-Montmorillonite isolated in a 0.8 µm sieve to avoid flushing of the clay sample during the experiment. The cell was subjected to a solution flux of a few cc per minute with 4 different KCl salinities (0.01, 0.05, 0.1, 1 M of KCl).  In situ SIP spectra are compared with XAS to conjointly monitor the CEC exchange at different scales. Preliminary results are shown to test-proof the methods as a new in situ / in operando cross-scale methods for CEC spatio-temporal characterization. Overall,this work is the first step of a technological development project, merging the approaches of geophysicists, mineralogists and physicists to monitor in real time the cation exchange processes of a Ca-montmorillonite by K in swelling clay minerals. 

How to cite: Courtin, A., Jougnot, D., Paineau, E., Roy, D., Vantelon, D., Dallaporta, A., and Léger, E.: Combining X-ray absorption and Induced Polarization Spectroscopies for in situ monitoring of Cation Exchange in clay materials, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11961, https://doi.org/10.5194/egusphere-egu26-11961, 2026.

The evolution of orogens is steered by complex deformation processes that act at several crustal levels, evolving over time from syn- to post-orogenic. Investigating how strain and deformation localize in the ductile domains of the deep crust and brittle domains of the shallow crust can improve our understanding of the processes ultimately controlling the exhumation of deeply seated rocks. Within this framework, the Sestri-Voltaggio Zone (SVZ) of the Italian Ligurian Alps provides a record of rocks and structures attesting to the complete subduction-exhumation cycle during the Europe-Adria convergence. The SVZ is a mature fault zone characterized by a polyphase tectonic evolution and a high lithological variability, which tectonically juxtaposes high-pressure (HP) metamorphic units to non-metamorphic rocks. It also represents an abrupt structural-metamorphic boundary between the Voltri Massif (an eclogitic domain defining a southern culmination of the Western Alps) to west, and the Northern Apennines units (anchi-metamorphic or non-metamorphic) to east. The exhumation processes that led to the current outcropping units of the SVZ occurred following a multi-stage progression from early ductile to later brittle conditions. However, open questions remain reflecting the generalized lack of systematic descriptions of structural fabrics formed during the exhumation-related events of the SVZ units. In this recently launched study we further explore the exhumation mechanisms of the SVZ by investigating how the pre-existing metamorphic fabrics helped localize the brittle deformation that occurred at later stages at shallow crustal levels. Preliminary field observations and structural analyses document N-S to NNE-SSW-striking brittle faults separating lenses of HP-mafic (metagabbros and metabasalts) and carbonate lithotypes from the enveloping phylladic schists and serpentinites. The enclosed lenses exhibit a pervasive internal schistosity that strikes either parallel or at high angle to the orientation of the main SVZ boundaries. By mapping the orientation of the rock fabric as a function of distance, perpendicular to the main tectonic boundaries, it is possible to identify systematic geometric trends between the metamorphic foliations and the bounding brittle faults. Within the matrix, the metamorphic schistosity wraps around the lenses, varying both in strike and dip. Brittle faults, with dominant oblique kinematics, are characterized by a double behavior: they truncate the metamorphic schistosity when approaching massive lenses; but they tend to rework the schistosity within the phylladic matrix. The overall structural record of the investigated units highlights the distribution of strain localization within the deeply exhumed units, suggesting a distinction between episodic vs. progressive transition from ductile to brittle during exhumation. In this sense, the SVG can be considered a useful example of the deformation history of the Western Alps-Northern Apennines tectonic junction, with noteworthy implications on the first-order mechanisms leading to the exhumation of deeply seated rocks.

How to cite: Generi, A., Viola, G., and Vignaroli, G.: Characterizing ductile-to-brittle exhumation of polymetamorphic units along the Sestri-Voltaggio Zone (Ligurian Alps, Italy)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13049, https://doi.org/10.5194/egusphere-egu26-13049, 2026.

Microstructural investigations of halite are essential for understanding deformation mechanisms relevant to salt tectonics and underground storage applications, including radioactive waste disposal and salt caverns. However, the identification of subgrain boundaries, dislocation structures, acting creep mechanisms and fluid-related features remains challenging due to the optical transparency and inherently low defect contrast of halite. Gamma decoration provides a powerful solution by inducing radiation-related colour centers that selectively highlight lattice defects and deformation structures.

At the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II, TUM), gamma decoration has been implemented since over a decade, recently we re-established and systematically optimized it using older spent fuel elements characterized by comparatively low dose rates. This contribution focuses on methodological developments and parametric studies that enable reliable gamma decoration under these conditions, extending the applicability of the technique beyond high-dose irradiation facilities.

We present results from controlled irradiation experiments on halite thin sections covering a wide range of total doses, irradiation times, and temperatures, combined with post-irradiation optical microscopy, spectroscopy, and digital colorimetry to quantify and optimize suitable optical contrast. Our experimental results from long-term irradiations are compared with theoretical models describing dose-rate-dependent radiation effects on defect formation in natural rock salt. This parametric approach allows identification of threshold conditions required for effective defect visualization, as well as optimization strategies to compensate for reduced dose rates, including extended irradiation times and temperature control.

These results establish gamma decoration at FRM II as a robust and versatile experimental method for salt-rock research, providing a valuable link between laboratory testing, microstructural analysis, and mechanical modelling, and ensuring continued applicability of this technique with ageing irradiation infrastructure.

How to cite: Hutanu, V., Li, X., and Schmatz, J.: Gamma decoration at FRM II: recent optimisations and parametric studies for microstructural investigations of halite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13462, https://doi.org/10.5194/egusphere-egu26-13462, 2026.

Spatial phase distributions can be grouped into random, clustered or anticorrelated/distributed based on the probability to encounter a given nearest neighbour. This property can also be probed with respect to intervals of directions, frequently revealing an anisotropy in the spatial phase distribution. In this study, several high temperature ultramylonites with variable composition from felsic to ultramafic as well as coarse grained deformed rocks (e.g. eclogite from Münchberg, Germany) were investigated. Measurements of phase distribution anisotropy frequently manifest in a pronounced direction of phase clustering and one direction of anticorrelation. Especially in the investigated ultramylonites but also in deformed eclogites and amphibolites, those two directions are found not to be orthogonal and not to coincide with finite strain axes (as far as manifested by foliation and stretching lineation). Clustering phases (e.g. qtz, plg or grt, depending on the rock type) form stacks antithetically tilted against the sense of shear. These stacks are separated by phases such as kfs, bt or cpx. Below a certain volume threshold of the stack-forming phase, stacking is not observed.

In addition to the phase distribution, truncated chemical zonations and/or indications of directed growth are frequently observed. On the other hand, there is a lack of microstructures which can reasonabley be associated with steady state dislocation creep.

It is suggested that the observed microstructures in combination indicate deformation by a mechanism best described by dissolution-precipitation accommodated granular flow (or "diffusion creep" in the broadest sense). Stack-forming phases undergo mostly rigid-body rotation and translation temporarily forming transient force chains before being disintegrated again. Since these stacks can be observed in the rock record, the residence time in the force chain position must be greater than in a randomly distributed position, compatible with jamming of particles during granular flow.

The presence of this particular type of anisotropic spatial phase distribution may not only serve as a shear sense indicator but could in general be useful for the identification of deformation mechanisms.

How to cite: Kilian, R.: Spatial phase distribution and deformation processes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13669, https://doi.org/10.5194/egusphere-egu26-13669, 2026.

Serpentinites are key components in subduction zones, acting as primary carriers of water into the deep Earth and critically influencing seismic behavior. Several studies suggest that fluid-saturated deformation in serpentinized subduction channels may control a variety of processes associated with Intermediate-depth seismicity (~50 to 300 km depth) . A key problem in their rheology is the discrepancy between experimentally deformed serpentinites, which exhibit predominantly brittle behavior, and their naturally deformed counterparts, which show ductile fabrics. While the dominant deformation mechanism in subduction settings—whether crystal plasticity, dissolution-precipitation, or a combination— also remains poorly documented. Moreover, there is a lack of constraints on how serpentinites deform during and after partial dehydration at (ultra)high-pressure conditions and transformation to olivine and pyroxene-dominated assemblages. To address these issues, we present an integrated microstructural and geochemical study of serpentinites across a hectometer-scale strain gradient within the Zermatt-Saas meta-ophiolite, documenting the evolution of deformation and major element mobility during subduction and exhumation. In low-strain samples, dehydration forms coarse-grained olivine-diopside-clinohumite-magnetite veins. Host antigorite shows weak crystallographic preferred orientations (CPOs) and twinning. With increasing strain, deformation localizes around these veins, where olivine develops a weak B-type CPO, but with grains showing no evidence of intracrystalline deformation. Progressively, antigorite develops a strong, penetrative foliation with a (001) maximum normal to foliation and grain size reduction, while olivine veins are folded and boudinaged. Low angle grain boundaries are related to fracturing of olivine. In high-strain serpentinite mylonites, transposed olivine veins form isoclinal folds, and S-C' fabrics develop. Antigorite CPO strength increases considerably, something that is not observed for olivine. Whole thin section XRF mapping reveals an increase of Ni and S in the more deformed serpentinites, where pentlandite defines the C' fabric and wraps around olivine porphyroclasts. Antigorite mm thick bands show Cr depletion accompanied by grain size reduction, while Fe-Mn occur normally associated with each other. In the transposed olivine veins there is an increase of Fe content in comparison to the original olivine vein composition.  When present, Al-rich phases such as chlorite are mostly undeformed but can breakdown locally and transform into tremolite + magnetite in late shear bands. Our data document a fluid-assisted progression from localized brittle-ductile to distributed ductile deformation. Microstructural and chemical evidence indicate that deformation was primarily controlled by dissolution-precipitation processes, with limited crystal plasticity in antigorite and predominantly brittle olivine deformation. This study provides a rare dataset on metamorphic olivine deformation in subduction zones and highlights the fundamental coupling between element mobility, metamorphic reactions, and strain localization in the subduction interface and mantle wedge.

How to cite: Morales, L. F. G., Muñoz-Montecinos, J., Ceccato, A., Kilian, R., and Volante, S.: Dissolution-Precipitation dominated deformation in (ultra)high-pressure serpentinites from the Zermatt-Saas Meta-Ophiolite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14234, https://doi.org/10.5194/egusphere-egu26-14234, 2026.

Olivine is a fundamental rock-forming mineral for which microstructures are closely tied to deformation conditions. However, visualization of olivine deformation has traditionally been limited to two-dimensional observations, ranging from petrographic microscopy at the millimetre– to micrometre scale to electron-based techniques probing crystallographic distortion and ordering at the micro- to nanometre scale (e.g., EBSD and TEM). Here, we introduce dark-field X-ray microscopy (DFXM) and present its first application to geological materials, conducted at beamline ID03 of the ESRF.

Using a focused line beam produced by compound refractive lenses, DFXM enables non- destructive, in-situ imaging with spatial resolution down to ~35 nm. By selectively illuminating a ~500 nm thick volume with the line beam, DFXM allows “slicing” through depth of the crystal volume. By translating the sample through the X-ray beam, the layers can be stacked and reconstructed into full 3D datasets.

In this work, we reconstruct the 3D microstructures of the mineral olivine across a range of deformation settings, spanning from hydrothermal single crystal olivine, to olivine in Åheim orogenic peridotite which experienced long-term dislocation creep, to olivine in heavily shock-metamorphosed martian basalt with relict crustal strain. We observe individual static dislocations and associated lattice strain field in the hydrothermal olivine single crystal, to arranged low-angle boundaries (LABs) formed by geometrically necessary dislocations (GNDs) in the Åheim peridotite, to chaotic dislocation networks connected by dense, short, and randomized LABs in shocked martian basalts.

By bridging conventional 2D crystallographic observations with volumetric 3D microstructural reconstructions, our work enables robust observations of microstructures developed in distinctive deformation conditions, providing a powerful and advanced 3D imaging technique for geological materials. Our study expands the application of DFXM to Earth and planetary materials and demonstrates the power of multi-scale, three-dimensional imaging for resolving complex deformation histories in geological systems.

How to cite: Li, Y., McCaulsand, P., Flemming, R., Yildirim, C., and Detlefts, C.:  Microstructure Across Deformation Regimes: 3D Imaging of Olivine by Dark-Field X-ray Microscopy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15191, https://doi.org/10.5194/egusphere-egu26-15191, 2026.

The fault damage zone of the active Milun Fault in eastern Taiwan exhibits fractured and altered fault-rock textures, including spotted schist, serpentinite, and associated gouge. In the vicinity of the upper boundary of the damage zone, the recovered drill core hosts a non-cohesive, pulverized quartz body (~20-30 cm in length) within the fault rocks. The pulverized quartz is sandwiched between fractured schist and millimetre-scale laminae subparallel to the zone boundary. Microanalytical observations show that the quartz is shattered into a fine powder without an evident shear sense or preferred fracture orientation. No shear-induced amorphous phase is detected, whereas Laue diffraction indicates pronounced lattice distortion and elevated residual stress. The pulverized quartz displays a dense tensile fracture network, a feature commonly reported for seismically pulverized rocks along seismogenic faults, suggesting a dilatational, tensile-dominated fragmentation mechanism rather than progressive shear comminution. We propose that the quartz pulverization resulted from high strain rates associated with transient tensile stresses during coseismic rupture, potentially favoured by specific lithologic conditions.

How to cite: Wu, W.-J., Lien, P., Huang, T.-H., Chiu, W., Chiang, C.-Y., and Kuo, L.-W.: Microanalytic characteristics of extremely fractured quartz in fault damage zone and implications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15835, https://doi.org/10.5194/egusphere-egu26-15835, 2026.

The interactions between fluid and solids in fault zones are governed by slip, slip rate, and constituent properties. These interactions are recorded by particle shape and size distributions, fracture patterns, and the geochemical composition of material within the deformation zone. The evolution of near-surface sediment microstructures and yielding behaviors under tectonic loading and at variable fluid saturation remains an open question. We collect undisturbed 10 x 40 mm cores from unconsolidated silt-sized sediments (fines) surrounding, and along, a fault strand that slipped while saturated, and likely experienced aseismic slip under variable saturation over the past 300 years. We use X-ray microtomography to analyze voids within the fines and found that they are ellipsoidal, have volume distributions that are best fit by a truncated power-law, orient sub-parallel to the fault strike, and sometimes merge into tabular or irregularly shaped fractures. The volume range for power-law scaling in the distributions separates a smaller population of voids with markedly different distributions in sphericity, tortuosity, aspect ratio, and minor/major axis lengths from a larger population of voids. The power-law truncation is likely due to the finite core size. We interpret the voids as initially small gas bubbles that nucleated where cavities existed within the fines and then grew via diffusion of immiscible gases when saturated, or via brittle/ductile yielding of the fines under variable saturation. Several fractures cross-cut or branch off some voids, indicating multiple deformation events and suggesting that the void boundaries are weak spots within the fines that accommodate tectonic strain. Similar growth mechanisms have been observed in magmatic systems, where ductile yielding of the melt occurs from the merging of bubbles that primarily orient at acute angles from the maximum extension direction. These findings suggest that, in addition to sands, pore structures in finer-grained sediments preserve a record of near-surface aseismic slip and may provide a relative estimate of near-surface strain. The findings further imply that a process akin to ductile yielding deformed the fines and, in turn, the pore voids. 

How to cite: Dasent, J., Chang, M., Su, K., Wright, V., and Manga, M.: Memory of brittle-ductile yielding within near surface fault zone sediments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16278, https://doi.org/10.5194/egusphere-egu26-16278, 2026.

The mineralogical-geochemical composition and texture of salt rocks plays an important role for the site selection and construction of a repository for heat-generating, highly active radioactive waste. As the bromide content in halite depends on the degree of evaporation and subsequent processes, Br is frequently analyzed to estimate the genetic history of the rocks (Braitsch 1971). Typically, geochemical analytical methods are applied on powder samples (e.g. ICP-OES, XRF), and textural analyses (e.g. using EBSD) require extensive sample preparation. In this study, first results of diapiric Upper Permian rock salt samples are presented using non-destructive µXRF on polished rock samples.

The µXRF Bruker M4 Tornado Plus (Nikonow & Rammlmair 2016) was used to map and quantify element distributions in rock salt. For calibration, in a first step, a certified reference material (CGL), consisting of mostly halite (NaCl) with minor content of anhydrite (CaSO₄), and sylvite (KCl), was pressed into pellets of 2 g and 1 cm diameter. For representativity, three spot measurements and a mapping of the center (1 cm²) were chemically quantified. The µXRF measurements correlate with the certified values yielding an R² of 0.995. In a second step, pressed pellets with a range of defined concentrations of Br in halite and Rb in sylvite were prepared to estimate the concentration ranges measurable by µXRF. For Br, the concentrations range from 1 to 0.005 wt.% Br in halite, and for Rb the concentrations range from 0.4 to 0.005 wt.% Rb in sylvite. Both data sets show a good correlation with R² of 0.99 (n=21 for Br and n=17 for Rb). Therefore, µXRF seems suitable for quantification of Rb and Br in salt rocks.

Furthermore, naturally deformed halite samples were analyzed simultaneously for their geochemically and textural properties, which were previously analyzed using “conventional” methods (ICP-OES and EBSD, respectively; Mertineit et al. 2023). The bromide content in halite is ca. 200 µg/g and thus comparable to the known values. The textural results show misorientations of few degrees within single halite grains and pronounced misorientations at halite grain boundaries, indicating bending of the crystals, but no pronounced texture of the bulk rock.

Although the results are in good agreement with published data, further test should follow, especially on the textural analyses including the misorientation angle resolution and the indexing of the halite crystal axis. However, the application of µXRF on salt rocks offers a fast, non-destructive method providing reliable combined geochemical and textural information.

References

Braitsch 1971. Springer-Verlag, https://doi.org/10.1007/978-3-642-65083-3

Mertineit et al. 2023. Tectonophysics 847, https://doi.org/10.1016/j.tecto.2023.229703

Nikonow & Rammlmair. 2016. Spectrochim Acta B 125, https://doi.org/10.1016/j.sab.2016.09.018

How to cite: Nikonow, W., Mertineit, M., and Schramm, M.: Combined geochemical and textural analyses of halite: First results of non-destructive µXRF measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17303, https://doi.org/10.5194/egusphere-egu26-17303, 2026.

Recent advances in microanalytical imaging and machine learning enable quantitative, multiscale characterization of geological materials with direct relevance for subsurface energy storage. This study presents an integrated workflow combining Broad Ion Beam (BIB) sample preparation, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and advanced machine learning to quantify pore structures, mineralogy, and their spatial relationships from the micrometre to nanometre scale (Klaver et al. 2021).

High-resolution secondary electron (SE2) and backscattered electron (BSE) imaging, complemented by low-resolution EDX data, provides multimodal datasets for automated analysis. Pore networks are segmented using a pre-trained U-Net deep learning model, enabling efficient and accurate porosity quantification. Mineralogical phases are identified and quantified through a semi-automatic, decision-tree–based segmentation approach. The alignment of SE2 and BSE datasets allows porosity to be directly correlated with specific mineral phases, establishing a robust link between microstructure, mineral composition, and petrophysical properties (Jiang et al, 2021).

The applicability of this technology-driven approach is demonstrated through two case studies. Case study 1 investigates geological hydrogen storage in underground salt caverns, focusing on the impact of biotic and abiotic reactions on anhydrite. Flow-cell experiments combined with cryogenic BIB-SEM analyses enable early detection of microstructural, mineralogical, and pore-space changes induced by hydrogen, hydrogen sulfide, and microbial sulfate reduction. Despite slow reaction kinetics, microstructural observations reveal the substantial onset of chemical alteration, biofilm formation, and evolving pore connectivity at the submicron scale, providing essential constraints for geochemical and hydraulic models (Berest et al., 2024).

Case study 2 examines fault sealing in mechanically layered limestone–marl successions. Oriented transfer samples from normal fault systems were analysed using multiscale microanalytical workflows to capture marl smearing, mechanical mixing, fracturing, and cementation processes. High-quality microstructural datasets serve as ground truth for training machine learning algorithms for efficient interpretation of 2D image data. The results show that fault cores are composed of recurrent structural building blocks whose distribution and sealing capacity are strongly controlled by the presence and properties of marly interbeds (Schmatz et al., 2022).

Overall, the integrated microscopy–machine learning framework provides a transferable, data-driven approach for quantifying coupled structural, hydraulic, and geochemical processes in complex geological systems.

References

Berest et al.,2024. Risk assessment of hydrogen storage in a conglomerate of salt caverns in the Netherlands. KEM-28 report. https://www.kemprogramma.nl/documenten/2024/04/03/kem-28-project-rapportfinal-report-kem-28-h2c3-240403_v2

Jiang et al., 2021.Workflow for high-resolution phase segmentation of cement clinker from combined BSE image and EDX spectral data. Journal of Microscopy, 1-7.

Klaver et al., 2021. Automated carbonate reservoir pore and fracture classification by multiscale imaging and deep learning. 82nd EAGE Annual Conference & Exhibition, Oct 2021, Volume 2021, p.1 – 5.

Schmatz et al., 2022. Prediction of Fault Rock Permeability With Deep Learning: Training Data from Transfer Samples of Fault Cores. 83rd EAGE Annual Conference & Exhibition, Jun 2022, Volume 2022, p.1 – 5.

How to cite: Schmatz, J., Jiang, M., and Schmitz, J.: Advanced Microscopy and Machine Learning for Multiscale Analysis of Porosity and Mineralogy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17416, https://doi.org/10.5194/egusphere-egu26-17416, 2026.

The investigation of microstructural characteristics in concrete constitutes a fundamental basis for advancing its performance in civil engineering construction. Existing expertise in digital rock physics (DRP), developed for natural rock materials, is transferred and adapted for concrete. DRP utilizes non-destructive X-ray computed tomography (XRCT) to examine the internal microstructure of concrete, allowing for the visualization of features such as phase distributions, pore space, and microcracks. In this study, high-resolution digital concrete twins are created to capture and quantify internal microstructural changes induced by external mechanical loading. To overcome limitations in phase and microstructure identification caused by the restricted resolution of XRCT, these digital investigations are complemented by detailed microstructural analyses using standard polarization microscopy and scanning electron microscopy (SEM). The results show that externally applied stresses significantly influence the microstructural response of concrete and thus affect the accuracy of physical measurements conducted under high-pressure conditions.

XRCT datasets with varying spatial resolutions were acquired under in-situ confining pressures ranging from 0.1 MPa to 46 MPa. CT images of concrete in unloaded and mechanically loaded states were subsequently analyzed and compared to identify stress-induced microstructural changes, with particular emphasis on the segmentation workflow. Here, particular focus is on large and small concrete aggregates, grain/phase boundaries within the aggregates, (micro-)porosity, and especially the interfacial transition zone (ITZ), which represents a major source of uncertainty in phase assignment during segmentation.

Image quality was first assessed by identifying artifacts and evaluating grayscale histograms. Subsequently, global thresholding was applied for phase assignment and initial segmentation, which was iteratively refined using complementary microscopic analyses of thin sections, including SEM, as reference data. The resulting segmentation of the concrete subvolume (600x600x769) distinguishes large and small aggregates (<80 % quartz, ca. 20 % phyllosilicates), pore space, phyllosilicate-composed matrix, silica-composed matrix, and inclusions (mainly rutile, zircon, apatite, iron oxides). Small changes can be seen in the distribution of the individual phases at the different pressures. With increasing pressure, the porosity decreases, and partially areas with characteristic phase arrangements arise along the large aggregates, potentially indicating the influence of the ITZ.

However, the quantitative determination of the interfacial transition zone remains challenging using XRCT data, and microcracks are likewise difficult to reliably resolve and segment. Therefore, the high-resolution microstructural investigations are also required to adequately capture these features. Overall, the study highlights the necessity of detailed microstructural characterization for the reliable interpretation of XRCT data and the assessment of stress-induced changes in concrete.

How to cite: Beiers, L. M., Balcewicz, M., Lebedev, M., and Saenger, E. H.: Digital Concrete Physics – Microstructural Characterization of Concrete under Confining Pressure: Insights from X-ray Computed Tomography and Microscopy , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17609, https://doi.org/10.5194/egusphere-egu26-17609, 2026.

Ultramafic rocks exposed adjacent to mid-ocean ridges in the footwall to large slip oceanic detachment faults provide unique insight into deformation and reaction when transforming from peridotite to serpentinite. In contrast to orogenic serpentinites, oceanic serpentinites have not subjected to superposed metamorphic and/or tectonic overprinting. A suite of samples from mostly fresh peridotites (~20% alteration), with preserved olivine and pyroxene, to completely serpentinized rocks (100% alteration), dominated by serpentine (lizardite) and magnetite, were collected from a ~1.2 km long drill core from IODP Expedition 399 at the Atlantis Massif oceanic core complex.

A combined approach of synchrotron diffraction and electron backscatter diffraction in order to analyze the crystallographic preferred orientation (CPO), and micro X-ray fluorescence mapping and optical microscopy in order to image and analyze the microstructure, is used to explore the variable microstructures.

Magnetite forms polycrystalline aggregates defining a foliation, which ranges from anastomosing to highly parallel. In partially serpentinized, mylonitic peridotites showing olivine grain size reduction and CPO development; magnetite aggregates trace the preexisting mylonitic fabric. Lizardite and magnetite both have a variable CPO strength and different CPO types, suggesting that different processes and parameters influence the formation of these microstructures. Further, late stage deformation, is evident from microfaulting, sheared serpentine veins and dissolution features. The individual contributions of deformation and serpentinization reaction to the final microstructure will be evaluated and discussed.

How to cite: Kühn, R., Schlickum, L., Kilian, R., Morales, L., Parsons, A., John, B., and Deans, J.: Deformation and reaction in the microstructural record of oceanic serpentinites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18276, https://doi.org/10.5194/egusphere-egu26-18276, 2026.

Lithium is a trace component, which is frequently observed in salt deposits and salt solutions collected in salt mines, respectively (Mertineit & Schramm 2019). So far, no naturally formed Li-bearing salt mineral is known, thus, the origin of Li in salt deposits must be related to other sources, e.g. to detrital phyllosilicates (Braitsch 1971). Detailed investigations on the Li content, the occurrence within a mine and the mineralogical composition of specific stratigraphic layers enable the reconstruction of rock-fluid interaction and fluid migration pathways. This is important for the construction, design and dimensions for a repository for radioactive waste in rock salt.

To verify which minerals are Li-hosts, diapiric Upper Permian (Zechstein) samples from the uppermost Staßfurt-Formation and the lower Leine-Formation were investigated for their mineralogical-geochemical composition. The succession contains salt clays, anhydrite and carbonate rocks as these rocks reveal the highest Li content (up to 159 µg/g bulk rock). The samples were previously investigated using ICP-OES, ICP-MS, XRD, SEM and thin section microscopy. Beside typical salt minerals in varying amounts (halite, anhydrite, magnesite, sylvite, carnallite), most samples consist of quartz, illite-muscovite, chlorite (clinochlore) and biotite, all of them with a grain size of ≤100 µm, often <20 µm. Only few samples contain traces of kaolinite, koenenite, hydrotalcite, anatase and tourmaline.

Additionally, µXRF and imaging LIBS (Laser Induced Breakdown Spectroscopy) analyses were performed at the same specimen to obtain detailed information of the element distribution including Li on thick section scale (Nikonow et al. 2019).

The clay containing rocks are intensively deformed by boudinage and subsequent brittle fracturing. The fractures are oriented in different directions and are filled with halite and/or carnallite and single grains of anhydrite and magnesite. Relics of bedding are present, but the phyllosilicates do not show a pronounced shape-preferred orientation. Shear strain is indicated by a slight rotation of single rock fragments. The spatial distribution of Li shows that Li is enriched in certain areas. Li accumulations are observed in single silicate grains, which are unequally distributed in a very fine-grained clay matrix. Furthermore, Li is enriched at the fracture rims, often associated with seams of Fe-bearing phases and probably organic matter.

Depending on the mineralogical composition of the investigated rocks, the Li content varies significantly. Li probably originates from illite-muscovite and a Li-bearing variety of a tourmaline (elbaite). Li was mobilized during brine-host rock interaction and precipitated in fracture infill, probably at reducing geochemical conditions. However, due to the limited spatial resolution of most used methods compared to the very small grain size of the rocks, a distinct relation of Li content to a specific mineral phase requires further analysis.

Braitsch 1971. Springer-Verlag, https://doi.org/10.1007/978-3-642-65083-3

Mertineit & Schramm 2019. Minerals 9, 766; doi:10.3390/min9120766.

Nikonow et al. 2019. Mineralogy & Petrology 113, https://doi.org/10.1007/s00710-019-00657-z

How to cite: Mertineit, M., Schramm, M., Nikonow, W., and Meima, J.: Lithium content and mineralogical composition of fractured salt clay (Upper Permian), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18322, https://doi.org/10.5194/egusphere-egu26-18322, 2026.

The properties of fault slip surfaces, gouge characteristics, and fluid-rock reactions are tightly coupled and control earthquake mechanics. To visualise and quantify the role of this coupling, we have developed a new operando imaging approach that allows the documentation of fast direct-shear deformation experiments in time-resolved 2- and 3-dimensional image data at low single-digit micrometer resolution. A direct-shear inset developed for the X-ray transparent Heitt Mjölnir triaxial deformation apparatus enables experiments at 20 MPa normal stress under fluid-pressurised conditions and allows real-time permeability measurements.

We apply this platform to three fault systems: 1) Slip surfaces in basaltic rocks, imaged while sliding at 1 mm.s^-1, reveal how asperities, phenocrysts, and surface roughness control stick-slip behavior and damage localization during fast slip. 2) Reactive quartz-gypsum gouges imaged during velocity stepping and healing experiments, enable the direct linking of evolving frictional properties to microphysical developments. 3) A shearing, dehydrating gypsum gouge provides insights into transient rheologies and the resulting strain distributions.

These datasets demonstrate that 4D imaging resolves coupled mechanical, chemical, and hydraulic fault evolution in real time. Our approach allows documenting microphysical processes underlying the frictional properties of faults and thereby constitutes a potent tool for studying faults in a variety of tectonic settings.

How to cite: Jayawickrama, E., Harpers, N., Schwichtenberg, B., Bell, A., Ng, A., Rizzi, R., Cordonnier, B., Herwegh, M., and Fusseis, F.: Recent Developments in 4D X-ray Tomography for Real-Time Observation of Fault Slip and Gouge Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18619, https://doi.org/10.5194/egusphere-egu26-18619, 2026.

The deformation and interaction of amphibole grains are crucial for comprehending the rheological behavior and physical properties of middle to lower crust. However, the mechanisms of strain accommodation and grain boundary processes in amphibolites are poorly studied. In this study, we analyzed a naturally deformed amphibolite from an exhumed continental strike-slip shear zone. The amphibole grains can be categorized into two distinct types: type I and type II, with the type II being embedded within type I. Type I amphibole grains exhibit typical plastic deformation behavior, distinguished by the presence of discernible dislocation arrays and formation of subgrains. In contrast, type II amphibole grains predominantly display microfractures in the middle of grains and voids occur in their elongated tails. Meanwhile, we identified three types of low-angle boundaries in amphibole grains with varying microstructural and nanoscale characteristics. Our findings indicate that low-angle boundaries in minerals are not exclusively associated with crystal-plastic deformation. Furthermore, the deformation characteristics in type II amphibole grains are related to grain boundary sliding (GBS) process. To relieve stress concentration during grain boundary sliding in type II amphibole grains, two accommodation mechanisms are proposed: (i) Grain boundary diffusion with elimination of grain boundary irregularities. (ii) Intragranular deformation of adjacent grains through either a brittle or a ductile process. Our findings hold significant implications for understanding the stress concentration and accommodation during deformation process in amphibolite

How to cite: Liu, J., Cao, S., and Cheng, X.: Development of low-angle boundaries in amphibole and their implications for accommodating grain boundary sliding in naturally deformed amphibolite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20317, https://doi.org/10.5194/egusphere-egu26-20317, 2026.

The origin of the intense damage found in active fault cores is still a matter of debate. We investigated the potential co-seismic contribution to this damage by studying the Nojima fault, which ruptured during the 1995 Kobe earthquake (Mw 6.9). Drilled just a year after the event, the Hirabayashi borehole offers a snapshot of the fault zone’s state shortly after a major rupture.

Working within the French ANR AlterAction, we analyzed drill core samples using X-ray computed tomography (CT) at a resolution of ~50 μm. Instead of relying on complex segmentation of fracture geometries, we applied a 3D fractal analysis to the spatial distribution of voids (empty space) versus the rock matrix. This method allowed us to quantify damage intensity and organization using the fractal dimension D. This metric, ranging from 2 (highly clustered voids) to 3 (homogeneous distribution), tracks the transition from localized fracture networks to diffuse pulverization and correlates well with fracture porosity.

We observed a damage zone extending roughly 70 m on either side of the fault core. While open fracture density generally spikes toward the core, it drops sharply in the immediate vicinity, likely due to rapid post-seismic healing. Our analysis shows D values near 2 in clustered zones, rising toward 3 where damage becomes volumetric. Interestingly, some samples display intense micro-fracturing but lack significant macroscopic deformation, resembling the "pulverized rock" seen at other active faults. This texture suggests high strain-rate loading occurred during the earthquake.

To test the dynamic origin of this damage, we ran Split Hopkinson Pressure Bar (SHPB) experiments on intact borehole samples to reproduce pulverization in the lab. We found a linear link between strain rate and absorbed energy. When combined with the CT data, this relationship helps distinguish two modes of propagation: diffuse pulverization (matching near-fault observations) and sparse, poorly connected networks. Crucially, the fractal dimensions of the experimental samples confirm these contrasting morphologies.

These results suggest that the intense damage in the Nojima fault core likely stems from co-seismic processes, marked by specific fractal patterns associated with high strain rates. We conclude that 3D fractal analysis of void space offers a robust tool, independent of geometry, for identifying the dynamic origins of fault zone damage.

How to cite: Iaquinta, R., Doan, M.-L., and Donze, F. V.: 3D Fractal Analysis of Co-seismic Damage in the Nojima Fault Using X-Ray Tomography and SHPB Experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21052, https://doi.org/10.5194/egusphere-egu26-21052, 2026.

Direct observations of geological processes are often limited by available observation time, the spatial resolution of imaging techniques or the accessibility of active sites. These limitations also apply to fault healing, whereby faults progressively regain strength throughout the interseismic phase of the earthquake cycle. Here, conventional approaches either capture a static snapshot of the final microstructure in exhumed natural fault rocks or focus on the bulk mechanical behaviour through slide–hold–slide or direct shear experiments. However, these approaches generally fail to resolve the dynamic evolution of the microstructural record, and the associated chemo-mechanical feedback that controls a rock’s hydraulic properties. To overcome these limitations and constrain the spatiotemporal coupling between mechanical, chemical, and hydraulic processes in healing fault gouges, we conducted a series of direct shear experiments on analogue fault gouges composed of a quartz–hemihydrate mixture. We then monitored their microstructural evolution using operando 4D synchrotron-based X-ray CT imaging.

Our experiments, performed at constant shear rates of 0.3–1 µm/s, were designed to mimic gouge-rich faults in the uppermost continental crust during the interseismic phase. In the presence of a reactive pore fluid, we simulated chemical fault healing through dissolution-reprecipitation and cementation, which are associated with the hydration reaction of CaSO₄ hemihydrate to gypsum. In our deforming samples, these time-dependent healing processes compete with mechanical weakening processes, such as frictional granular flow.

Our novel approach combines an innovative experimental setup [1, 2] with high-resolution 4D imaging and advanced image analysis techniques, including digital volume correlation (DVC). In this contribution we discuss the benefits of integrating micromechanical data with high-resolution 4D imaging by linking active deformation mechanisms to the evolving mechanical and hydraulic response of the simulated fault gouge. Further, we demonstrate a shear-rate-dependent competition between time-dependent healing processes and mechanical weakening.   

[1] Freitas, D. et al. (2024): Heitt Mjölnir: a heated miniature triaxial apparatus for 4D synchrotron microtomography. Journal of Synchrotron Radiation 31, 150-161. doi.org/10.1107/S1600577523009876 

[2] Jayawickrama, E. et al. (2026): Recent Developments in 4D X-ray Tomography for Real-Time Observation of Fault Slip and Gouge Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18619.

How to cite: Schwichtenberg, B., Fusseis, F., Jayawickrama, E., Cordonnier, B., Harpers, N., and Herwegh, M.: Probing active deformation - Fault healing through the lens of 4D operando imaging, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21418, https://doi.org/10.5194/egusphere-egu26-21418, 2026.

How to cite: yang, J. and cheng, F.: Thermally Induced Diagenesis and Pore Space Evolution of Trona-Nahcolite Aggregates in Continental Alkaline Lacustrine Shale Oil Reservoirs , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1838, https://doi.org/10.5194/egusphere-egu26-1838, 2026.

Carbonate rock formations constitute common hydrocarbon reservoirs and are often considered as candidates for geological CO₂ storage, where acid-driven carbonate dissolution may occur in the near-wellbore region. Calcite dissolution can substantially reconfigure pore networks, altering permeability and influencing storage efficiency and long-term containment integrity. While carbonate dissolution has been extensively studied experimentally and numerically, its detection and characterization using non-invasive monitoring tools remain challenging. Nuclear magnetic resonance (NMR) is a particularly promising tool as it is sensitive to pore geometry and fluid distribution. However, a quantitative framework that links regime-dependent pore-scale dissolution patterns to NMR observables remains underdeveloped. In this work, we establish such structure–signal mapping by coupling pore scale reactive transport simulations of calcite dissolution with forward modeling of low-field NMR responses, generating synthetic observables from dynamically evolving pore geometries due to calcite dissolution. By varying the relative timescales governing advection, diffusion, and surface reaction rates, we analyze the evolution of three representative dissolution patterns: uniform face dissolution, conical channeling dissolution, and wormholing dissolution. To capture the spatial heterogeneity of these features, we segment the pore geometry along the flow axis and derive an NMR T₂ relaxation time distribution for each section, constructing flow-direction T₂ profiles. In contrast, bulk T₂ distributions derived from the entire pore volume tend to average out the spatial heterogeneity of dissolution patterns. Furthermore, to capture the propagation of reaction fronts and characterize the permeability of emerging channels, we formulate specific NMR-based metrics: a pore-enlargement index E_i(t), a heterogeneity index H(t), and a connectivity index C(t). Dissolution breakthrough, defined by k/k₀ ≥ 10, occurs at PV₁₀ ≈ 314 for face dissolution, 138 for channeling, and 144 for wormholing. While H(t) consistently evolves non-monotonically, breakthrough is governed by the emergence and strengthening of an inlet-to-outlet pathway. Accordingly, C(t) closely tracks breakthrough during channeling, whereas in wormholing it indicates early connectivity without an immediate permeability increase. Our weighted pore network connectivity by cumulative enlargement yields a single metric that correlates with permeability growth across regimes. This structure–signal framework provides a workflow for using spatially distributed NMR signals to identify pathway formation and provide an early indication of permeability surges. The framework for mapping structures to signals enhances the interpretation of NMR signals in dissolution reactive settings and provides a quantitative foundation for interpreting NMR monitoring signals and informing risk assessment for geological CO₂ storage in settings where carbonate dissolution may alter flow pathways.