Solid Earth最新文献

{"title":"Anatomy of a fumarole field: drone remote-sensing and petrological approaches reveal the degassing and alteration structure at La Fossa cone, Vulcano, Italy","authors":"Daniel Müller, Thomas R. Walter, Valentin R. Troll, Jessica Stammeier, Andreas Karlsson, Erica de Paolo, Antonino Fabio Pisciotta, Martin Zimmer, Benjamin De Jarnatt","doi":"10.5194/se-15-1155-2024","DOIUrl":"https://doi.org/10.5194/se-15-1155-2024","url":null,"abstract":"Abstract. Hydrothermal alteration and mineralization processes can affect the physical and chemical properties of volcanic rocks. Aggressive acidic degassing and fluid flow often also lead to changes in the appearance of a rock, such as changes in surface coloration or intense bleaching. Although hydrothermal alteration can have far-reaching consequences for rock stability and permeability, limited knowledge exists on the detailed structures, extent, and dynamic changes that take place near the surface of hydrothermal venting systems. By integrating drone-based photogrammetry with mineralogical and chemical analyses of rock samples and surface gas flux, we investigate the structure of the evolving volcanic degassing and alteration system at the La Fossa cone on the island of Vulcano, Italy. Our image analysis combines principal component analysis (PCA) with image classification and thermal analysis through which we identify an area of approximately 70 000 m2 that outlines the maximum extent of hydrothermal alteration effects at the surface, represented by a shift in rock color from reddish to gray. Within this area, we identify distinct gradients of surface coloration and temperature that indicate a local variability in the degassing and alteration intensity and define several structural units within the fumarole field. At least seven such larger units of increased activity could be constrained. Through mineralogical and geochemical analysis of samples from the different alteration units, we define a relationship between surface appearance in drone imagery and the mineralogical and chemical composition. Gradients in surface color from reddish to gray correlate with a reduction in Fe2O3 from up to 3.2 % in the unaltered regime to 0.3 % in the altered regime, and the latter coincides with the area of increased diffuse acid gas flux. As the pixel brightness increases towards higher alteration gradients, we note a loss of the initial (igneous) mineral fraction and a change in the bulk chemical composition with a concomitant increase in sulfur content from close to 0 % in the unaltered samples to up to 60 % in samples from the altered domains. Using this approach of combined remote-sensing and in situ analyses, we define and spatially constrain several alteration units and compare them to the present-day thermally active surface and degassing pattern over the main crater area. The combined results permit us to present a detailed anatomy of the La Fossa fumarole field, including high-temperature fumaroles and seven larger units of increased alteration intensity, surface temperature, and variably intense surface degassing. Importantly, we also identify apparently sealed surface domains that prevent degassing, likely as a consequence of mineral precipitation from degassing and alteration processes. By assessing the thermal energy release of the identified spatial units quantitatively, we show that thermal radiation of high-temperature fumaroles accounts ","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lithologically constrained velocity–density relationships and vertical stress gradients in the North Alpine Foreland Basin, SE Germany","authors":"Peter Obermeier, Florian Duschl, Michael C. Drews","doi":"10.5194/egusphere-2024-2692","DOIUrl":"https://doi.org/10.5194/egusphere-2024-2692","url":null,"abstract":"<strong>Abstract.</strong> We systematically analysed density and velocity data from 41 boreholes to establish velocity-density relationships for the main lithological units in the North Alpine Foreland Basin in SE Germany. We applied these relationships to velocity data and spliced the resulting density values with actual density data and a shallow density model to retrieve complete density profiles along 55 deep wellbores, which at least penetrated the Cenozoic section in the study area. We integrated density profiles to vertical stress to investigate the spatial distribution of vertical stress gradients. Thereby, we observed an eastward decrease of vertical stress gradients, which correlates well with the geological configuration of the North Alpine Foreland Basin in SE Germany. Thereby, vertical stress gradient profiles can be reasonably estimated as a function of true vertical depth below ground level TVD in the western, central, and eastern parts of the study area using a power law relationship: West: 21 MPa/km + (TVD/325)^1/1.80, R² = 0.98 Central: 21 MPa/km + (TVD/410)^1/1.93, R² = 0.99 East: 21 MPa/km + (TVD/531)^1/1.95, R² = 1.00 In addition, we also investigated the distribution of vertical stress gradients at the top of Upper Jurassic carbonates, an important aquifer for deep geothermal energy production. Our study, therefore, provides a valuable resource for future geophysical, geomechanical, and geological studies in the North Alpine Foreland Basin, both in a fundamental and applied research context.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Passive seismic imaging of ore deposits using coda wave interferometry: a case study of Akanvaara V-Cr-PGE deposit in Northern Finland","authors":"Nikita Afonin, Elena Kozlovskaya, Kari Moisio, Shenghong Yang, Jouni Sarala","doi":"10.5194/egusphere-2024-2637","DOIUrl":"https://doi.org/10.5194/egusphere-2024-2637","url":null,"abstract":"<strong>Abstract.</strong> In this study, we present an innovative method to image the inner structure of orthomagmatic ore deposits using P-wave coda of regional seismic events. We combine data processing and interpretation schemes from conventional passive seismic interferometry and teleseismic receiver function (RF) method. We hypothesize that correlation of P-wave coda recorded by three-component sensors can be used to evaluate body wave part of empirical Green's tensor, from which arrivals of reflected and converted waves could be extracted. To test our hypothesis, we installed a high-resolution seismic array (profile) with 606 seismic instruments on the Akanvaara V-Cr-PGE deposit in Northern Finland above the inclined zones of V-Cr mineralization, placed inside ultramafic intrusion. From the regional seismic catalogue, provided by the Institute of Seismology, University of Helsinki, we selected the P-wave coda of 363 regional seismic events to evaluate body wave part of empirical Green's tensor by passive seismic interferometry. Further interpretation of the tensor allowed us to identify arrivals of PS and SP waves, converted at Cr and V mineralization zones. We conducted numerical simulation of plane wave interaction with the synthetic Akanvaara deposit model compiled from geological and drilling data and found that Green's tensors evaluated from synthetic seismograms and from seismic data contain similar converted PS and SP arrivals. To calculate depths to the conversion boundaries, we obtained S-wave velocity model using MASW method. According to calculated depths and geological model compiled from drilling data we suggest that the converted arrivals correspond to continuation of the Cr and V mineralized zones. Therefore, using the empirical Green's tensor, evaluated from P-wave coda of regional seismic events can be an effective tool for orthomagmatic ore deposits exploration in both greenfield and brownfield cases. In this paper we are describing details of the passive seismic experiment, numerical simulation, data processing and interpretation.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Driven magmatism and crustal thinning of coastal southern China in response to subduction","authors":"Jinbao Su, Wenbin Zhu, Guangwei Li","doi":"10.5194/se-15-1133-2024","DOIUrl":"https://doi.org/10.5194/se-15-1133-2024","url":null,"abstract":"Abstract. The late Mesozoic igneous rocks along the coastal South China Block (SCB) exhibit complex parental sources involving a depleted mantle, subducted sediment-derived melt, and melted crust. This period aligns with the magmatic flare-up and lull in the SCB, debating with the compression or extension in coastal region. Our study employs numerical models to investigate the dynamics of the ascent of underplating magma along the Changle–Nan'ao Belt (CNB), simulating its intrusion and cooling processes while disregarding the formational background. The rheological structure of the lithospheric mantle significantly influences magma pathways, dictating the distribution of magmatism. This work reveals that the ascent of magma in the presence of faults is considerably faster than in the absence of faults, and contemporaneous magmatic melts could produce different cooling and diagenetic processes. Additionally, the influence of pre-existing magma accelerated the emplacement of underplating magma. The magma beneath the fault ascended rapidly, reaching the lower crust within 20 million years, with a cooling rate of approximately ∼ 35 °C Myr−1. Conversely, the thickened magma took 40–50 million years to ascend to the lower crust, cooling at a rate of ∼ 10 °C Myr−1. In contrast, magma without thickening and fault would take a considerably longer time to reach the lower crust. The ascent of magma formed a mush-like head, contributing to magmatic circulation beneath the crust and decreasing crustal thickness. Multiphase magmatism increases the geothermal gradient, reducing lithospheric viscosity and promoting underplating magma ascent, leading to magmatic flare-ups and lulls. Our findings suggest that the Cretaceous magmatism at different times in the coastal SCB may be associated with the effects of lithospheric faults under similar subduction conditions. Boundary compression forces delay magma ascent, while rising magma induces a significant circulation, decreasing the crustal thickness of the coastal SCB. This study provides new insights into the complex interplay of magmatic processes during subduction, emphasizing the role of lithospheric structure in shaping the temporal and spatial evolution of coastal magmatism.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnesium isotope fractionation processes during seafloor serpentinization and implications for serpentinite subduction","authors":"Sune G. Nielsen, Frieder Klein, Horst R. Marschall, Philip A. E. Pogge von Strandmann, Maureen Auro","doi":"10.5194/se-15-1143-2024","DOIUrl":"https://doi.org/10.5194/se-15-1143-2024","url":null,"abstract":"Abstract. Studies of magnesium (Mg) isotope ratios in subduction zone lavas have revealed small but significant offsets from the mantle value with enrichments in the heavy isotopes. However, the very high concentration of Mg in the mantle contrasts with much lower concentrations in the subducted igneous crust and oceanic sediments, making these subduction components unlikely vehicles of the Mg isotope anomalies in arc lavas. Only serpentinites, which in various proportions form part of oceanic plates, have high Mg contents comparable to fresh mantle rocks, and they have thus been regarded as a potential source of exotic Mg in the source of arc magmas. In this study we analyzed serpentinite samples from different oceanic settings for their Mg isotopic compositions. The majority of samples are indistinguishable from the depleted mantle (δ26Mg=-0.24 ‰ ± 0.04 ‰) irrespective of their origin. Only a small number of seafloor-weathered serpentinites are slightly enriched in the heavy isotopes (up to δ26Mg=-0.14 ‰ ± 0.03 ‰), implying that bulk serpentinites are unlikely sources of isotopically anomalous Mg in subduction zones. We also developed a partial dissolution method in which 5 % acetic acid for 180 min was shown to fully dissolve the minerals brucite and iowaite while leaving the serpentine mineral chrysotile essentially undissolved. Partial dissolution of 11 bulk serpentinite samples revealed Mg isotopic composition of brucite (± iowaite) that is systematically ∼0.25 ‰ heavier than that of coexisting serpentine. Thus, preferential breakdown of brucite and/or iowaite in a subducted slab prior to serpentine could preferentially release isotopically heavy Mg, which could subsequently be transported into the source region of arc magmas. Such a scenario would require brucite/iowaite breakdown to occur at pressures in excess of 3 GPa and produce fluids with very high concentrations of Mg that could be transported to arc magma source regions. Whether these conditions are met in nature has yet to be experimentally investigated.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How a volcanic arc influences back-arc extension: insight from 2D numerical models","authors":"Duo Zhang, J. Huw Davies","doi":"10.5194/se-15-1113-2024","DOIUrl":"https://doi.org/10.5194/se-15-1113-2024","url":null,"abstract":"Abstract. Investigating plate tectonics through the lens of back-arc extension in subduction systems, this study introduces a “hot region” onto an overriding plate (OP) in 2D thermo-mechanical models, simulating the role of an arc. The models identified two extension locations on the OP: Extension in the Hot region (mode EH) and Extension at a Far-field location (mode EF), which is about 750 km from the trench. The study also found that extension can occur at the same far-field location without a hot region when the OP is young and thin or when the subducting plate (SP) is old with a high sinking velocity. Our models suggest that the EH mode is common, occurring in many cases like the Mariana Trough and Lau Basin, while the EF mode is rare, potentially occurring in locations like the Japan Sea. The primary driving mechanism in our models is poloidal flow beneath the OP, and the extension process involves competition between basal drag, which thins the OP, and thermal healing, which thickens it, as well as competition between thermal weakening in the hot region and that at the far-field location. Increased trench retreat rates, facilitated by increased hot-region temperature and width, have encouraged this flow and have consequently promoted back-arc extension.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Luminescence and a New Approach for Detecting Heat Treatment of Sapphire","authors":"Teerarat Pluthametwisute, Lutz Nasdala, Chutimun Chanmuang N., Manfred Wildner, Eugen Libowitzky, Gerald Giester, Gamini Zoysa, Chanenkant Jakkawanvibul, Waratchanok Suwanmanee, Tasnara Sripoonjan, Thanyaporn Tengchaisri, Bhuwadol Wanthanachaisaeng, Chakkaphan Sutthirat","doi":"10.5194/egusphere-2024-1529","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1529","url":null,"abstract":"<strong>Abstract.</strong> For decades, unravelling heat treatment of sapphire has been a challenging issue. The present study offers new aspects that support the detection of heat treatment of sapphire. Natural unheated sapphire is distinguishable from heated sapphire by its orange to red luminescence under long-wave ultraviolet (LWUV, 365 nm) light, whereas blue luminescence under short-wave ultraviolet (SWUV, 254 nm) light indicates their heated counterparts. UV-excited photoluminescence shows a linkage between a broad emission spectrum within the orange to red region and orange to red luminescence of natural unheated sapphire under LWUV illumination, as well as an emission spectrum around the green region and blue luminescence of heated sapphire under SWUV illumination. Furthermore, the presence of melt inclusions within dissolved silks may be used as an indicator of heat treatment of sapphire. It seems that Fourier-transform infrared (FTIR) spectroscopy alone is inadequate for distinguishing unheated and heated sapphire. The application of orange to red, and blue luminescence together with melt inclusions offer a novel and practicable procedure for more precise differentiation of unheated versus heated sapphire.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Selection and characterization of the target fault for fluid-induced activation and earthquake rupture experiments","authors":"Peter Achtziger-Zupančič, Alberto Ceccato, Alba Simona Zappone, Giacomo Pozzi, Alexis Shakas, Florian Amann, Whitney Maria Behr, Daniel Escallon Botero, Domenico Giardini, Marian Hertrich, Mohammadreza Jalali, Xiaodong Ma, Men-Andrin Meier, Julian Osten, Stefan Wiemer, Massimo Cocco","doi":"10.5194/se-15-1087-2024","DOIUrl":"https://doi.org/10.5194/se-15-1087-2024","url":null,"abstract":"Abstract. Performing stimulation experiments at approximately 1 km depth in the Bedretto Underground Laboratory for Geosciences and Geoenergies necessitates identifying and characterizing the target fault zone for on-fault monitoring of induced fault slip and seismicity, which presents a challenge when attempting to understand seismogenic processes. We discuss the multidisciplinary approach for selecting the target fault zone for experiments planned within the Fault Activation and Earthquake Ruptures (FEAR) project, for which the aim is to induce the fault slip and seismicity for an earthquake magnitude of up to 1.0 while enhancing the monitoring and control of fluid-injection experiments. Structural geological mapping, remote sensing, exploration drilling and borehole logging, ground-penetration radar, and laboratory investigations were employed to identify and characterize the target fault – a ductile–brittle shear zone several meters wide with an intensely fractured volume spanning over 100 m. Its orientation in the in situ stress field favors reactivation in normal to strike-slip regimes. Laboratory tests showed slight velocity strengthening of the fault gouge. The fault's architecture, typical for crystalline environments, poses challenges for fluid flow, necessitating detailed hydraulic and stress characterization before each of the FEAR experiments. This multidisciplinary approach was crucial for managing rock volume heterogeneity and understanding implications for the dense monitoring network. Successfully identifying the fault sets the stage for seismic activation experiments commencing in spring 2024.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleoseismological evidence of multiple, large magnitude earthquake surface ruptures on the active Mt. Morrone normal fault, central Apennines, Italy","authors":"Irene Puliti, Alberto Pizzi, Stefano Gori, Emanuela Falcucci, Fabrizio Galadini, Marco Moro, Michele Saroli","doi":"10.5194/egusphere-2024-2399","DOIUrl":"https://doi.org/10.5194/egusphere-2024-2399","url":null,"abstract":"<strong>Abstract.</strong> The Mt. Morrone active normal Fault (MMF) and the related Sulmona intermountain basin constitute one of the most characteristic examples of the extensional tectonic landscape carving the central Apennines (Italy). Above the ⁓22 km MMF, thousands of inhabitants concentrate on a thriving reality and a historical and cultural heritage of great significance. According to the current knowledge, the last activation event of the whole MMF occurred ⁓2000 years ago and the maximum expected magnitude is M 6.6–7. Thus, the MMF today constitutes one of the most problematic structures in the central Apennines seismotectonic setting in terms of large-magnitude earthquake probability. Despite this, information on the activity of the MMF is presently relatively few, both for associated historical seismicity and paleoseismological data. To strengthen these knowledge weaknesses, we performed new extensive paleoseismological analyses (employing four trenches) in the central sector of the fault. Our goal was to supplement the limited existing dataset, constituted by a single paleoseismological study close to the northwestern tip of the fault. Additionally, we aimed to incorporate findings from a pair of studies focused on archaeoseismological and speleoseismological secondary evidence. Through these analyses, we unveiled four significant surface rupture events of the MMF, three of which occurred over the past 6000 years BP. Specifically, the youngest identified event occurred after 3.6–3.5 kyr BP, being thus chronologically consistent with the event in 2^nd century CE; a penultimate event after 4.4 kyrs BP; a previous event occurred after 5.4–5.3 kyr BP; and the oldest event took place after 9–8.9 kyr and (presumably) before 5.8–5.7 kyr BP. Considering that the cumulative minimum vertical displacement estimated encompassing the last three events is ⁓140 cm, and based on the length of the fault at the surface, we can confirm that earthquakes with M 6.6–7.0 may be expected from the activation of the MMF with an inferred average recurrence interval not longer than 1800 years over the last ⁓5.4 kyr.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of fluid redox in a fault zone of the Pic de Port Vieux thrust in the Pyrenees Axial Zone (Spain)","authors":"Delphine Charpentier, Gaétan Milesi, Pierre Labaume, Ahmed Abd Elmola, Martine Buatier, Pierre Lanari, Manuel Muñoz","doi":"10.5194/se-15-1065-2024","DOIUrl":"https://doi.org/10.5194/se-15-1065-2024","url":null,"abstract":"Abstract. In mountain ranges, crustal-scale faults localize multiple episodes of deformation. It is therefore common to observe current or past geothermal systems along these structures. Understanding the fluid circulation channelized in fault zones is essential to characterize the thermochemical evolution of associated hydrothermal systems. We present a study of a palaeo-system of the Pic de Port Vieux thrust fault. This fault is a second-order thrust associated with the Gavarnie thrust in the Axial Zone of the Pyrenees. The study focused on phyllosilicates which permit the constraint of the evolution of temperature and redox of fluids at the scale of the fault system. Combined X-ray absorption near-edge structure (XANES) spectroscopy and electron probe microanalysis (EPMA) on synkinematic chlorite, closely linked to microstructural observations, were performed in both the core and damage zones of the fault zone. Regardless of the microstructural position, chlorite from the damage zone contains iron and magnesium (Fetotal / (Fetotal + Mg) about 0.4), with Fe3+ accounting for about 30 % of the total iron. Chlorite in the core zone is enriched in total iron, but individual Fe3+/Fetotal ratios range from 15 % to 40 %, depending on the microstructural position of the grain. Homogeneous temperature conditions about 280–290 °C have been obtained by chlorite thermometry. A scenario is proposed for the evolution of fluid–rock interaction conditions at the scale of the fault zone. It involves the circulation of a single hydrothermal fluid with homogeneous temperature but several redox properties. A highly reducing fluid evolves due to redox reactions involving progressive dissolution of hematite, accompanied by crystallization of Fe2+-rich and Fe3+-rich chlorite in the core zone. This study shows the importance of determining the redox state of iron in chlorite to calculate their temperature of formations and to consider the fluid evolution at the scale of a fault.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}