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The 8# coal seam in the Benxi Formation of the southeastern margin of the Ordos Basin is a deep coal seam with abundant coalbed methane resources. Calcite veins are commonly developed within the 8# coal seam, and their formation processes and mechanisms have significant implications for the enrichment of deep coalbed methane. Genesis of the calcite veins was analyzed to reveal the impact of the calcite veins formation on coalbed methane accumulation, with an integrated application of petrographic study by thin section, cathodoluminescence analysis, carbon-oxygen isotope analysis, and homogeneous temperature measurements of fluid inclusions. The research findings indicate that the calcite veins in the 8# coal seam can be classified into three stages: C1, C2, and C3. The diagenetic fluids of C1 primarily originated from contemporaneous seawater. The fluids responsible for the formation of C2 primarily consist of organic fluids enriched in biogenic gas, whereas the fluids contributing to the formation of C3 are primarily associated with liquid hydrocarbons originated form decarboxylation of organic matter. Furthermore, the development of both C2 and C3 is influenced by deep hydrothermal fluids resulting from tectonic heating events during the Early Cretaceous. By combining analysis of the hydrocarbon accumulation history and burial history in the study area, it has been established that C2 formation occurred during the Late Triassic to Early Jurassic, while C3 formation took place during the Late Jurassic to Early Cretaceous. The exploration and production practices in the study area have firmly established the crucial significance of the formation and evolution of calcite veins within the 8# coal seam for the migration and accumulation of coalbed methane. The research outcomes provide valuable insights for the exploration of deep coalbed methane enrichment areas.

Geoscience Australia’s Exploring for the Future (EFTF) program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to a low emissions economy, strong resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government. The deep stratigraphic drill hole, NDI Carrara 1 (~1751 m), was completed in December 2020 as part of the MinEx CRC National Drilling Initiative (NDI) in collaboration with Geoscience Australia and the Northern Territory Geological Survey. It is the first test of the Carrara Sub-basin, a depocentre newly discovered in the South Nicholson region based on interpretation from seismic surveys (L210 in 2017 and L212 in 2019) recently acquired as part of the Exploring for the Future program. The drill hole intersected approximately 1100 m of Proterozoic sedimentary rocks uncomformably overlain by 630 m of Cambrian Georgina Basin carbonates. This contractor report (FIT - Schlumberger) presents hydrocarbon and aqueous fluid inclusion petrology and data (micro-thermometry, salinities etc.) on four hydrocarbon-bearing calcite veins sampled from NDI Carrara 1 between 762.56-763.60 m depth, (under contract to, and fully funded by, Geoscience Australia as part of the Exploring for the Future program).

This study integrates field structural data, petrographic and geochemical (δ18O, δ13C, Δ47, 87Sr/86Sr, and elemental composition) analyses and U–Pb dating of calcite veins cutting the Bóixols-Sant Corneli anticline (Southern Pyrenees) in order to date and to investigate the spatio-temporal relationships between fluid flow and fold evolution. This E-W trending anticline grew from Late Cretaceous to Paleocene at the front of the Bóixols thrust sheet deforming pre-growth and growth sedimentary sequences. U–Pb dating reveals Late Cretaceous to late Miocene deformation ages, which agree with the age of growth strata deposition and the sequence of deformation interpreted from field and microstructural data. Dates coeval (71.2 ± 6.4 to 56.9 ± 1.4 Ma) and postdating (55.5 ± 1.2 to 27.4 ± 0.9 Ma) Upper Cretaceous to Paleocene growth strata are interpreted to record: (i) the growth of the Bóixols-Sant Corneli anticline during the Bóixols thrust emplacement, and (ii) the tightening of the anticline during the southern tectonic transport of the South-Central Pyrenean Unit. Other ages (20.8 ± 1.2 to 9.0 ± 4.6 Ma) postdate the folding event and have been associated with the collapse of the Bóixols-Sant Corneli anticline. The geochemistry of calcite veins indicates that the fluid flow behavior varied across the Bóixols-Sant Corneli anticline through its growth, showing a compartmentalized fluid system. In the hinge of the anticline and in the upper Santonian to middle Campanian syn-orogenic sequence along the footwall of the Bóixols thrust, the similar petrographic and geochemical features between all calcite cements and host rocks point towards a locally-derived or well-equilibrated fluid system. Contrarily, along large faults such as the Bóixols thrust, and in the anticline limbs, the geochemistry of vein cements indicates a different scenario. Cements in large faults yielded the lightest δ18O values, from −8 to −14 ‰VPDB, and variable enrichment in δ13C, 87Sr/86Sr, elemental composition and δ18Ofluid. This is interpreted as the migration of fluids, through fault zones, that evolved from distinct fluid origins. Cements in the fold limbs exhibit δ18O and δ13C between −8 and −6 ‰VPDB and between −10 and + 2 ‰VPDB, respectively, the lowest Sr contents and the lowest precipitation temperatures, suggesting that the anticline limbs recorded the infiltration and evolution of meteoric waters. The paleohydrological system in the Bóixols-Sant Corneli anticline was restricted to the Bóixols thrust sheet. The Upper Triassic evaporitic basal detachment likely acted as a lower fluid barrier, preventing the input of fluids from deeper parts of the Pyrenean crustal thrust system. This study provides a well-constrained absolute timing of fracturing and fluid flow during basin inversion and folding evolution and highlights the suitability of U–Pb geochronology to refine the age of fractures and veins and their sequential evolution in orogenic belts., This research was carried out within the framework of the DGICYT Spanish project PGC2018-093903- B-C22 (Ministerio de Ciencia, Innovaci´on y Universidades/Agencia Estatal de Investigación/10.13039/501100011033/Fondo Europeo de Desarrollo Regional, Uni´on Europea), the Grup Consolidat de Recerca “Geologia Sediment`aria” (2017-SGR-824) and the Grup Consolidat de Recerca “Modelitzaci´o Geodin`amica de la Litosfera” (2017SGR-847). This work was also partially funded by ALORBE project (PIE–CSIC–202030E310). The PhD research of DML is supported by the FPI2016 (BES-2016-077214) Spanish program from MINECO. DC acknowledges the Spanish Ministry of Science and Innovation for the “Juan de la Cierva Formaci´on” fellowship FJC2020-043488-I AEI/ 10.113039/501100011033. We thank Luis Fernando Martínez for helping in the fieldwork during his master’s degree at the Universitat de Barcelona. Carbon and oxygen isotopic analyses were carried out at the Centre Científics i Tecnol`ogics of the Universitat de Barcelona. Strontium analyses were performed at the CAI de Geocronología y Geoquímica Isot´opica of the Universidad Complutense de Madrid. The elemental composition was analyzed at the geochemistry facility labGEOTOP of Geosciences Barcelona (GEO3BCN–CSIC). U–Pb analyses were performed at the Frankfurt Isotope and Element Research Center (FIERCE) from the Goethe-University Frankfurt (Germany).

Based on the published data of pillow lava-hosted mineralized veins, this study compares post-magmatic fracturing, fluid flow, and secondary mineralization processes in the Troodos and Izu–Bonin supra-subduction zone (SSZ) and discusses the crucial factors for the development of distinct vein types. Thin section and cathodoluminescence petrography, Raman spectroscopy, fluid inclusion microthermometry, and trace element and isotope (87Sr/86Sr, δ18O, δ13C, Δ47) geochemistry indicate that most veins consist of calcite that precipitated from pristine to slightly modified seawater at temperatures 15 Myr after subduction initiation. Therefore, high-T mineralization (calcite, quartz, analcime) up to 230 °C is restricted to the Troodos SSZ.

The high-angle, structural genetic calcite veins of the Ordovician in the Shunnan-Gucheng area in the Tarim Basin provide a convenient study of fluid properties, hydrocarbon migration, and accumulation events in the fault zone of this area. Based on detailed core investigation, studies on fluid inclusions in calcite veins and comparison of geochemical characteristics of limestone matrix and calcite veins were carried out. Multiple types of hydrocarbons inclusion (e.g., dry asphalt inclusion,three-phase hydrocarbon inclusion, oil and water inclusion,gas-rich inclusion) were found in calcite veins. Furthermore, the coexisted aqueous inclusions with the gas–liquid phase had a high homogenization temperature (130–160 °C). The distribution characteristics of 18O-depleted (δ18O: −13.1‰ to −8.7‰), 87Sr-enriched (87Sr/86Sr: 0.708 879 to 0.710 432), relatively high total Rare Earth Elements (REEs), and positive Europium Anomalies indicated that the structural origin of calcite veins was mainly derived from the dissolution of surrounding rocks and diagenetic-hydrocarbon fluids. Participation signs of meteoric water were not proved. The rich hydrocarbon inclusions in the calcite veins indicated that the north-east strike-slip fault zone in the Shunnan-Gucheng area is an essential channel for hydrocarbon migration and accumulation.

U-Pb dating and geochemical analyzes (δ18O, δ13C, Δ47, 87Sr/86Sr and elemental composition) have been applied to fracture-filling calcite veins and host carbonates from the Bóixols-Sant Corneli anticline, which developed along the front of the Bóixols thrust sheet in the Southern Pyrenees. This robust dataset is used to determine: (i) the absolute timing of fracturing and mineralization from fluid flow; (ii) the age and duration of fold evolution; and (iii) the variations and implications of fluid behavior across the anticline, as has been described in the article “Spatio-temporal variation of fluid flow behavior along a fold: The Bóixols-Sant Corneli anticline (Southern Pyrenees) from U–Pb dating and structural, petrographic, and geochemical constraints – Marine and Petroleum Geology (2022) (Muñoz-López et al., 2022). In this new contribution, we present the raw data that have been analyzed and discussed in the related research article and, also, the whole elemental and REE composition of calcite veins and host carbonates that has not been published yet. These data may be used to unravel the age and origin of veins, to understand their sequential evolution in orogenic belts and to compare our results with those obtained in similar settings worldwide., This is a contribution to the DGICYT Spanish projects PGC2018-093903-B-C22 and PID2021-122467NB-C22 (Ministerio de Ciencia, Innovación y Universidades/Agencia Estatal de Investigación /10.13039/501100011033/ Fondo Europeo de Desarrollo Regional, Unión Europea), the Grup Consolidat de Recerca “Geologia Sedimentària” (2017-SGR-824) and the Grup Consolidat de Recerca “Modelització Geodinàmica de la Litosfera” (2017SGR-847). This work was also partially funded by ALORBE project (PIE–CSIC–202030E310).

X Congreso Geológico de España, 5-7 Julio 2021, Vitoria - Gasteiz, Calcite veins precipitated in the Estamariu thrust during two tectonic events have been investigated in order to decipher the relationships between deformation and fluid migration in Paleozoic basement rocks. Structural observations constrain the timing of vein formation and fluid migration, whilst geochemical analyses (¿13C, ¿18O, 87Sr/86Sr and elemental composition) of the related calcite cements indicate the fluid origin, pathways and extent of fluid-rock interaction. The first tectonic event, related to the Alpine reactivation of the Estamariu Variscan thrust, is characterized by the upward migration of fluids derived from the crystalline basement, giving rise to the precipitation of calcite cements Cc1 and Cc2. The second tectonic event, developed during the Neogene extension, was responsible of the reactivation of the Estamariu thrust and the development of normal faults and shear fractures in which calcite cements Cc3, Cc4 and Cc5 precipitated. Cc3 and Cc4 precipitated from meteoric fluids that interacted at depth with basement rocks before upflowing through fault zones and related structures. Cc5 precipitated from meteoric fluids percolating from the surface through small fractures., This research was funded by the Spanish Projects CGL2015-66335-C2-1-R and PGC2018-093903-B-C22, and by the Grup Consolidat de Recerca “Geologia Sedimentària” (2017-SGR- 824). The PhD research of DM-L is supported by the FPI2016 (BES-2016-077214) Spanish program from MINECO.

The distribution of oxygen isotopes between calcite and fluid inclusions has demonstrated utility for reconstructing near-surface calcite precipitation temperatures. For calcite that formed at depth, however, the resilience of this paleothermometer to diagenetic oxygen isotope alteration is poorly constrained. Clumped isotopes also document calcite precipitation temperatures and are similarly vulnerable to diagenetic alteration. Post-entrapment isotope exchange between calcite and fluid-inclusions could alter the calcite-fluid oxygen isotope distribution (αc-fi), as well as the clumped isotope composition (Δ47) of calcite, and therefore these two seemingly independent paleo-thermometers are potentially linked via the same alteration process. Using closed-system batch fractionation equations, we have modelled various scenarios of oxygen isotope exchange between water and host-rock during burial, as well as internal oxygen isotope exchange between calcite and fluid inclusions during exhumation. Assuming both paleo-thermometers record concordant temperatures at the time of vein formation, our models predict that if a fraction of calcite is available for isotopic interaction with fluid inclusions, the fluid inclusion and clumped isotope-derived paleothermometers yield discrepant temperature estimates after exhumation. We show that the fluid inclusion thermometer is more sensitive to isotopic alteration than the clumped isotope thermometer and that the mass balance of oxygen between calcite and fluid inclusions determines the sensitivity of both paleothermometers as well as the vulnerability of fluid inclusions (δ18Ofi) to diagenetic overprinting. We applied coupled clumped isotope and fluid inclusion measurements on calcite veins from the External Albanides (Albania), which were formed at depth and subsequently exhumed, in order to compare natural samples to our isotope exchange model. These veins show strongly discrepant calcite-water equilibrium temperatures and clumped isotope temperatures, suggesting the fraction of calcite available for isotope exchange with internal fluids may indeed be a key parameter of diagenetic alteration during exhumation. Even though the clumped isotope temperatures of our samples appear to be insensitive towards internal oxygen isotope exchange, our model predicts that at low burial temperatures, the carbonate clumped isotope thermometer may be susceptible to alteration by diagenetic isotope exchange with fluid inclusions under certain conditions.

International audience; Structural mapping and microstructural analyses are combined with stable, clumped, and radiogenic isotopes to unravel deformation mechanisms and syntectonic fluid flow during upward propagation along the Fuans frontal thrust of the internal part of the Jura fold-and-thrust belt. The Fuans thrust cuts through Upper Jurassic-Lower Cretaceous carbonate deposits, branches into two splays, and generates a system of fault-propagation folds. Folding was accomodated by layer-parallel shortening and layer-parallel shear, which generated flexural slip along bedding surfaces, stylolites, and foliated fabric in marly limestone interbeds. Thrusting was characterized by cycles of mutually overprinting ductile pressure-solution and brittle processes such as frictional sliding and fracturing/veining. This generated foliated tectonites in marls and limestones without significant cataclasis of the host rock. Pressure-solution and micrometer slip along slickenfibers are evidence of aseismic slip, in agreement with the ongoing aseismic anticline growth within the Jura fold-and-thrust, while crackle-like vein texture may account for episodic seismic fracturing. Geochemical data show that Fuans thrust acted as a conduit for the downward infiltration of meteoric-derived fluids, which channelized along foliated tectonites during syntectonic fluid flow. Calcite mineralizations precipitated at temperatures between 54 °C and 10 °C, showing an increased contribution of carbon derived from organic carbon respiration in soils in colder paleofluids. This indicates a progressive opening of the system, characterized by a more efficient and extensive meteoric fluids circulation. Considering the highest recorded temperature of 54 °C and assuming the modern geothermal gradient of 30 °C/km, thrusting in the exposed outcrop initiated at burial depths of at least ∼1.4 km.

International Ocean Discovery Program Expeditions 352 and 351 drilled into the Western Pacific Izu‐Bonin forearc and rear arc. The drill cores revealed that the forearc is composed of forearc basalts (FAB) and boninites and the rear arc consists of FAB‐like rocks. These rocks are pervaded by calcite veins. Blocky vein microtextures enclosing host rock fragments dominate in all locations and suggest hydrofracturing and advective fluid flow. Significant diffusion‐fed and crystallization pressure‐driven antitaxial veining is restricted to the rear arc. The lack of faults and presence of an Eocene sedimentary cover in the rear arc facilitated antitaxial veining. Rare earth element and isotopic (δ18O, δ13C, 87Sr/86Sr, and Δ47) tracers indicate varying parental fluid compositions ranging from pristine to variably modified seawater. The most pristine seawater signatures are recorded by FAB‐hosted low‐T (95% seawater and, Geochemistry, Geophysics, Geosystems, 21 (2), ISSN:1525-2027

The extensional Val Roveto Fault, which is the longest exhumed potentially-seismogenic structure of central Apennines, Italy, is examined to constrain earthquake-related fluid circulation and fluid sources within shallow carbonate-hosted faults. The study focuses on fault-related comb and slip-parallel veins that are calcite-filled and cut through the principal surface of the Val Roveto Fault. We observe multiple crack-and-seal events characterized by several veining episodes, probably related to different slip increments along the fault plane. We show that vein calcite precipitated in Late Pleistocene time below the present-day outcrop level at a maximum depth of similar to 350 m and temperatures between 32 and 64 degrees C from meteoric-derived fluids modified by reactions with crustal rocks and with a mantle contribution (up to similar to 39%). The observed warm temperatures are not compatible with a shallow (

Calcite veins are a common product of hydrothermal fluid circulation. Clumped-isotope palaeothermometry is a promising technique for fingerprinting the temperature of hydrothermal fluids, but clumped-isotope systematics can be reset at temperatures of > ca. 100 °C. To model whether the reconstructed temperatures represent calcite precipitation or closed-system resetting, the precipitation age must be known. LA-ICP-MS U–Pb dating of calcite is a recently developed approach to direct dating of calcite and can provide precipitation ages for modelling clumped-isotope systematics in calcite veins. In this study, clumped-isotope and LA-ICP-MS U–Pb calcite analyses were combined in basalt-hosted calcite veins from three settings in Scotland. Samples from all three localities yielded precipitation temperatures of ca. 75–115 °C from clumped-isotope analysis, but veins from only two of the sites were dateable, yielding precipitation ages of 224 ± 8 Ma and 291 ± 33 Ma (2σ). Modelling from the dated samples enabled confident interpretation that no closed-system resetting had occurred in these samples. However, the lack of a precipitation age from the third location meant that a range of possible thermal histories had to be modelled meaning that confidence that resetting had not occurred was lower. This highlights the importance of coupling clumped-isotope thermometry and LA-ICP-MS U–Pb calcite dating in determining the temperature of hydrothermal fluids recorded in calcite veins. This paired approach is shown to be robust in constraining the timing and precipitation temperature of calcite formation, and thus for tracking hydrothermal processes.

Calcite veins hosted in pillow lavas of the Late Cretaceous Troodos suprasubduction zone ophiolite provide insights into the timing and physicochemical environment of postmagmatic fracturing and fluid circulation through oceanic crust. This study presents rare earth element and yttrium (REE+Y) concentrations, δ13C, δ18O, 87Sr/86Sr, and clumped isotopic (Δ47) compositions of vein calcites in order to investigate their fluid sources, formation temperatures, and precipitation ages. These geochemical data are combined with microtextural analyses. Intersections of 87Sr/86Sr ratios of vein calcites with the Sr isotope seawater curve suggest two distinct calcite veining phases. Major calcite veining within an interval of ~10 Myr after crust formation is characterized by microtextures that point to extensional fracturing related to crack and sealing, host rock brecciation, and advective fluid flow. These vein calcites show REE+Y characteristics, 87Sr/86Sr ratios, and clumped isotopic compositions indicative of precipitation from seawater at, Key Points The Troodos oceanic crust experienced a 10‐Myr‐long major phase of predominantly low‐temperature blocky and syntaxial calcite veiningOscillatory growth‐zoned high‐temperature blocky vein calcites precipitated from hydrothermal fluids in a closed system out of equilibriumLow‐temperature diffusion‐fed antitaxial vein calcites precipitated after the major veining phase from seawater that interacted with umbers

The St. Lawrence Platform is located along the northern shoreline of Lake Ontario, currently in an intra-cratonic setting exposing relatively flat-lying middle Ordovician sedimentary strata. The purpose of this study is to gain insight on recent brittle deformation events that have deformed the bedrock. Based on structural field observations, broadly trending E-W extensional joints are the youngest stress recorded in the bedrock. These joints are partially filled and sealed with calcite mineralization and were strategically sampled to gain insight on the source and timing of fluid flow. Trace element geochemistry and stable isotope (δ18O and δ13C) analysis on calcite mineralization indicate that their compositions are analogous to the host rock, thus, fluids originate from connate fluids that were released from pore space during deformation. In addition, U-Pb geochronology via LA-ICP-MS methods yield a model age of 101 ± 6 Ma (MSWD: 2.3). The date of calcite crystallization is contemporaneous with the establishment of North America’s modern compressive stress field, and is linked to a Cretaceous tectonic plate reorganization event that was global in scale. This study demonstrates that calcite veins can serve as a tool to date brittle deformation in limestone, which could have direct applications in hydrocarbon exploration, paleohydrology, and the consideration for locating sites to host deep geological repositories.

Linking the architecture of structural conduits with the hydrothermal fluids migrating from the reservoir up to the surface is a key-factor in geothermal research. A contribution to this achievement derives from the study of spring-related travertine deposits, but although travertine depositional systems occur widely, their feeding conduits are only rarely exposed. The integrated study carried out in the geothermal Gölemezli area, nearby the well-known Pamukkale area (Denizli Basin, western Anatolia, Turkey), focused on onyx-like calcite veins (banded travertine) and bedded travertine well exposed in a natural cross-section allowing the reconstruction of the shallower part of a geothermal system. The onyx-like veins represent the thickest vein network (> 150 m) so far known. New field mapping and structural/kinematic analyses allowed to document a partially dismantled travertine complex (bedded travertine) formed by proximal fissure ridges and distal terraced/pools depositional systems. The banded calcite veins, WNW-trending and up to 12 m thick, developed within a > 200 m thick damaged rock volume produced by parallel fault zones. Th/U dating indicates a long lasting (middle-late Pleistocene) fluids circulation in a palaeo-geothermal system that, due to its location and chemical characteristics, can be considered the analogue of the nearby, still active, Pamukkale system. The isotopic characteristics of the calcite veins together with data from fluid inclusions analyses, allow the reconstruction of some properties (i.e. temperature, salinity and isotopic composition) and processes (i.e. temperature variation and intensity of degassing) that characterized the parent fluids and the relation between degassing intensity and specific microfabric of calcite crystals (elongated/microsparite-micrite bands), controlled by changes/fluctuations of the physico-chemical fluid characteristics. © 2017 Elsevier B.V.

Billi et al. (2017) proposed a new interpretation for the origin and internal structure of thermogene travertine deposits. On the basis of evidence from two quarries located in southern Tuscany (Italy), they interpreted some travertine beds as calcite veins and argued that undulating travertine beds formed by syn-diagenetic (i.e. non-tectonic) folding that was caused by laterally-confined volume expansion caused by incremental veining. They assumed that such a process causes changes to the rock properties, including porosity reduction, rock strengthening, and age rejuvenation. The interpretations by Billi et al. (2017) challenge and question the current understanding and interpretation of thermogene travertine deposits. This understanding, based on numerous studies since the 1980s, is that these deposits form from thermal water flowing downslope, and precipitating calcium carbonate. Here, we explain how the comparison with active depositional systems is essential for the understanding the origin of structures in older, inactive travertine deposits, such as those studied by Billi et al. (2017). We further argue that the three-dimensional setting of travertine deposits should be taken into account in order to discuss the possible development of secondary structures. Indeed travertine deposition on slopes typically leads to the formation of terraced morphologies with pools bordered by rounded rims and separated from each other by steep walls. The resulting three-dimensional structures can be misinterpreted as asymmetric folds in two-dimensional views (i.e., in saw-cut walls of quarry). In this paper we debate the interpretations offered by Billi et al. (2017) and their criteria to recognise syn-diagenetic, non-tectonic folds in travertine deposits, and explain why many of their ideas are questionable.

This thesis focusses on the sealing of fractures in exhumed limestone reservoir outcrop analogues in the Oman Mountains. The work is largely based on observations at micro-scale of veins and cemented faults, which are well constrained to a regional model of successive brittle fracturing and faulting events - termed tectonic phases. Although our observations of (exhumed) deformation structures are static, we have made attempts to identify processes that create and destruct fracture permeability in limestones at burial depth. We aim to better understand the microstructural evolution of several successive fault and vein generations, hosted in limestones that were deeply buried beneath major thrust sheets in the Oman Mountains. The reconstruction of origin and pathways of vein forming fluids is a key to understand a complex, back-coupled natural system involving mechanic (fracturing), hydraulic (fluid flow and pressures) and chemical (solution, precipitation) processes under changing temperature and stress conditions.In the first chapter we present a detailed study on a complex crack-seal calcite vein mesh (network) developed in the topmost layers of the Natih A member. Stable isotope compositions of calcite veins and a calcite cemented normal fault are systematically put into context of microstructural position of analysed calcite samples and the temporal relationship of two successive stages of veining. During Stage 1 a complex mesh of crack-seal calcite veins developed. The mesh is confined to a stack of three limestone layers (VHB) - sandwiched by sedimentary rocks that are lacking any vein development. Thus, the flow-regime of vein forming fluids was layer parallel and fracture controlled during Stage 1. The oxygen isotope composition of Stage 1 veins is largely in equilibrium with the VHB host rocks. A negative excursion of δ13C values is interpreted being caused by mixing of vein forming fluids with low δ13C-CO2 originated from organic matter. Organic matter is found locally enriched at bedding parallel stylolites that predate Stage 1 veining. The Stage 2 fault crosscuts any Stage 1 vein and is filled by calcite. Stage 2 calcite carbon isotope compositions are in equilibrium with VHB host rocks, while δ18O values indicate ingress of external fluids. Oxygen compositions indicate that the fluids have equilibrated with limestones that are at least 2.5‰ 18O enriched relative to the VHB host rocks at top of Natih A. Limestone rocks with corresponding isotopic compositions are found some 40 meters below top of Natih A. Vertical variations of limestone isotopic compositions showed a continuous trend of 18O diminished values towards the top of the Natih A member. The trend is correlated with the Wasia-Aruma break - a regionally developed discordance caused by emergence of the carbonate platform that preceded nappe emplacement.In chapter 2 we define eight tectonic phases of faulting and veining in the Oman Mountains and systematically characterize their microstructure. The sealed faults and fractures are hosted in exhumed, sub-nappe limestones encompassing Cretaceous stratigraphy with a total thickness of approximately one kilometre. We used transmitted light microscopy, cathodoluminescence and scanning electron microscopy to characterize mineralogy, microfabric and crosscutting relationships of veins in more than 70 thin sections from more than 50 samples. We define six main microstructural domains and present two peculiar microstructural domains, which have not been mentioned and/or described in detail yet. The evolution of vein growth textures is discussed with emphasis on the texture of the initial sealing. We describe a model that explains the simultaneous development of crack-seal microstructures at the vein tip and growth into open space at the vein center. It is discussed how host rock inclusions can be overgrown by epitaxial growth as well as the complexity of composite vein growth kinematics in blocky veins. We suggest that the columnar texture indicates early fracture sealing at shallow burial depth. The exhumation of the studied limestones is tied to tectonic Phase V, since vein calcites of Phases 5 - 7 lack mechanical twins.The blocky-neighbor texture is described and analysed in chapter 3. The texture presents a challenge to interpret the lack of growth competition as suggested by long-established models for sealing of fractures by precipitation of one mineral phase that is chemically compatible with the host rock material (e.g., calcite veins in limestone). The fabric is generally observed in microveins that are hosted in fine-grained, micritic limestones. Epitaxial growth is observed where veins intersect larger carbonate grains (i.e. echinoderm fossil fragments) and where veins intersect each other. Scanning electron microscopy observations on broken samples shows that vein filling crystals are epitaxial overgrowth of small micrite grains. We analysed fracture surface morphologies and fracture paths of artificially broken samples. While some samples were broken at room temperature, others have been heated to 200°C. Transgranular fractures are only observed at large carbonate particles in hot samples, while in cold samples also micrite grains are transgranularly fractured. The overall microstructure in both samples is dominated by intergranular fracture trajectories. Fracture surface morphologies of transgranularly fractured grains range from planar, smooth, cleavage controlled morphologies to complex, conchoidal morphologies. We interpret that epitaxial growth in microveins at burial conditions is restricted to transgranularly fractured grains. This effect leads to a limited number of growing calcite grains that eventually seal the entire microfracture. Diameters of vein filling crystals can exceed the average host rock crystal size by several orders of magnitudes even if the vein formed by a single crack-seal event.The thesis represents the first systematic and comprehensive microstructural characterization of sealed fault and fracture systems in exhumed limestones of the Oman Mountains. The studied rocks are outcrop analogues of oil and gas reservoirs in the foreland basin of Oman. We showed in detail how changes in stress and fluid pressure conditions can lead to changes in fluid flow regimes. Those changes can be tracked by analysing the stable isotope composition of fracture cements and adjacent limestone host rocks. Some microstructures can be used to make robust inferences about timing (tectonic phases) and burial depth during fracture sealing (columnar calcite and lack of mechanical twins). The faults and associated veins analysed in this thesis have similar orientations, kinematics and geometries as those in the foreland basin. The gained knowledge on the microstructure of sealed faults should be used with care to make inferences on the present day sealing capacity and hydraulic properties of faults in the foreland. We furthermore discovered the effect of fracture mechanisms on the sealing geometry in microveins. As this geometry differs clearly from those suggested by the literature it should be considered to incorporate our model into the world of vein growth.

L’evoluzione a lungo termine dei prismi di accrezione è caratterizzata da interazioni complesse tra tettonica, forze di volume gravitazionali, e processi superficiali. E' influenzata da cambiamenti delle condizioni geodinamiche a grande scala, della configurazione geometrica dei margini di placca convergenti, delle proprietà meccaniche dei materiali coinvolti nella deformazione, e delle condizioni climatiche. In questo contesto, deformazioni contrazionali ed estensionali possono coesistere in porzioni diverse di uno stesso prisma o interessare ciclicamente la stessa area. Pulsi estensionali sviluppati durante la storia orogenica contrazionale di prismi di accrezione, in particolare, sono stati documentati in numerosi contesti e previsti dai modelli geo-meccanici. Le strutture deformative associate a tali pulsi estensionali contribuiscono all’evoluzione a scala regionale degli orogeni, influenzando la circolazione dei fluidi nella crosta superiore e modificando le proprietà meccaniche dei prismi di accrezione. I pulsi estensionali sin-contrazionali hanno perciò una notevole importanza scientifica ed economica. Nell’ambito di questa Tesi di Dottorato vengono investigate strutture deformative sviluppate durante la storia orogenica contrazionale di due prismi di accrezione: le Montagne dell'Oman e l'Appennino Settentrionale. Le attività di ricerca sono caratterizzate da un approccio multidisciplinare; l'evoluzione paleoidrologica delle strutture e i loro effetti sulla circolazione dei fluidi nella crosta superiore sono investigati con particolare attenzione. Il caso di studio di Jabal Qusaybah (Oman) offre la possibilità di studiare una struttura anticlinale sviluppata a livelli strutturali superficiali, al fronte del cuneo tettonico. Nonostante la sua posizione strutturale, l'evoluzione della piega è caratterizzata da interazioni tra deformazioni contrazionali, estensionali, e trascorrenti. I casi di studio nell'Appennino Settentrionale comprendono strutture estensionali chilometriche associate all'evoluzione di interi settori del prisma. Nel caso della Val di Lima, un sistema di faglie estensionali a basso angolo è univocamente inquadrato in un contesto contrazionale, essendo coinvolto in un piegamento successivo associato a sovrascorrimenti fuori sequenza. Nel caso di studio di Tellaro, il sistema di faglie estensionali taglia l'anticlinale di Punta Bianca, essendo associato all'assottigliamento tardo-orogenico del settore interno del prisma Appenninico. Il caso di Studio della Lunigiana include entrambi gli scenari precedenti. The long term evolution of orogenic wedges is characterized by complex interactions between tectonics, gravitational body forces, and surface processes. It is influenced by changes of large-scale geodynamic conditions, geometrical configuration of plate margins, mechanical properties of the materials involved in the deformation, and climate conditions. Within this framework, contractional and extensional deformations may coexist in different sectors of a thrust wedge or cyclically affect the same area. In particular, extensional pulses developed during the contractional orogenic history of thrust wedges have been documented in various contexts and predicted by geo-mechanical models. Deformation structures associated with such extensional events contribute to the regional-scale evolution of orogens, influencing fluid circulation within the upper crust and modifying mechanical properties of thrust wedges. Therefore, sin-contractional extension have remarkable scientific and economic significance. This Ph.D. thesis investigates extensional deformation structures developed during the orogenic contractional history of two thrust wedges: the Oman Mountains and the Northern Apennines. Research is done with a multidisciplinary approach, and close attention is paid to the palaehydrological evolution of the deformation structures and their influence on fluid circulation through the upper crust. The case study of the Jabal Qusaybah (Oman) allows investigating on an anticline developed at shallow structural levels, at the front of a thrust wedge. Despite this structural position, the evolution of the fold is characterized by interactions between contractional, extensional, and left-lateral strike-slip deformations. The Northern Apennines case studies involve km-scale extensional structures associated with the evolution of entire wedge sectors. In the Val di Lima case, a low-angle extensional fault system is unequivocally framed within the contractional orogenic history, being affected by superimposed folding due to out-of-sequence thrusting. In the Tellaro case, the extensional fault system cuts through the Punta Bianca anticline, being likely associated with the late orogenic thinning of the internal sector of the Northern Apennines. The Lunigiana case includes both the previous scenarios.

International audience; During compressive events, deformation in sedimentary basins is mainly accommodated by thrust faulting and related fold growth. Thrust faults are generally rooted in the basement and may act as conduits or barriers for crustal fluid flow. Most of recent studies suggest that fluid flow through such discontinuities is not apparent and depends on the structural levels of the thrust within the fold-and-thrust belt. In order to constrain the paleofluid flow through the Jaca thrust-sheet-top basin (Paleogene southwest-Pyrenean fold-and-thrust belt) this study compares on different thrust faults located at different structural levels. The microstructures in the different fault zones studied are similar and consist of pervasive cleavage, calcite shear veins (SV1), extension veins (EV1) and late dilatation veins (EV3). In order to constrain the nature and the source of fluids involved in fluid-rock interactions within fault zones, a geochemical approach, based on oxygen and carbon stable isotope and trace element compositions of calcite from different vein generations and host rocks was adopted. The results suggest a high complexity in the paleohydrological behaviors of thrust faults providing evidence for a fluid-flow compartmentalization within the basin. Previous studies in the southern part of the Axial Zone (North of the Jaca basin) indicates a circulation of deep metamorphic water, probably derived from the Paleozoic basement, along fault zones related to the major basement Gavarnie thrust. In contrast, in northern part of the Jaca basin, the Monte Perdido thrust fault is affected by a closed hydrological fluid system involving formation water during its activity. The Jaca and Cotiella thrust faults, in turn, both located more to the south in the basin, are characterized by a composite fluid flow system. Indeed, stable isotope and trace element compositions of the first generations of calcite veins suggest a relatively closed paleohydrological system, whereas the late calcite vein generations, which are probably associated with the late tectonic activity of the basin, support a contribution of both meteoric and marine waters. Based on these results, a schematic fluid-flow model is presented. This model allows visualization of three main fluid flow compartments along a N-S transect.

International audience; In fold-and-thrust belts, shortening is mainly accommodated by thrust faults which are preferential zones for recrystallisation and mass transfer. This study focuses on a detachment fault related to the emplacement of the Monte Perdido thrust unit in the southern Pyrenees. The studied fault zone consists of a 10 m thick intensively foliated phyllonite developed within the Millaris marls, of Eocene age. The lithological homogeneity of the hanging wall and footwall allows us to compare the Millaris marls outside the fault zone with the highly deformed marls located in the fault zone and to quantify the chemical, mineralogical and volumetric changes related to deformation processes along the fault. The Millaris marls are composed of detrital quartz, illite, chlorite, minor albite and pyrite, in a micritic calcite matrix. In the fault zone, the cleavage planes are marked by clay minerals and calcite ± chlorite veins attest to fluid-mineral interactions during deformation. The mineral proportions in all samples from both the fault zone and Millaris marls have been quantified by two methods: (1) X-ray diffraction and Rietveld refinement, and (2) bulk chemical analyses as well as microprobe analyses to calculate modal composition. The excellent agreement between the results of these two methods allows us to estimate mineralogical variations using a modification of the Gresens' equation. During fault activation, up to 45 wt% of calcite was lost while the amounts of quartz and chlorite remained unchanged. Illite content remained constant to slightly enriched. The mineralogical variations were coupled with a significant volume loss (up to 45%) mostly due to the dissolution of micritic calcite grains. Deformation was accompanied by pressure solution and phyllosilicates recrystallisation. These processes accommodated slip along the fault. They required fluids as catalyst, but they did not necessitate major chemical transfers.

The Denizli Basin in the West Anatolian Extensional Province in western Turkey is known for its numerous Quaternary travertine occurrences. Travertine morphology is often dependant on the relative position of the deposition with respect to basin-bounding faults. The travertine occurrences examined in this study are situated at the intersection of the locally E-W oriented Denizli Basin and the adjacent NE-SW oriented Baklan Graben in the NE. Based on an extensive field campaign, including LIDAR scanning, several high-resolution fault/fracture maps of five large quarries (>300m in length and >60m in height) are constructed in which this world-class travertine deposit is currently excavated. A structural analysis is performed in order to determine the tectonic overprinting of the travertine body and to derive the stress states of the basin after travertine deposition. The mostly open, non-stratabound joints are several tens of metres long and often bifurcate creating a dense fracture network. Minor infill of the joints resulted in the presence of a few colour-banded calcite veins. Based on the E-W, NE-SW and NW-SE orientation of three dominant joint sets it is concluded that the joint network is caused by local N-S extension, alternated by NW-SE and NE-SW extension exemplifying the presence of stress permutations in the Quaternary. High angle E-W to WNW-ESE faults cross-cut the quarries. Faults are filled with travertine debris and clastic infill of above lying sedimentary units indicative of the open nature of the faults. The specific E-W fault orientation in the locally E-W trending Denizli Basin indicates that they initiated as normal faults. A paleostress inversion analysis performed on kinematic indicators such as striations on the clayey fault infill and the sinistral displacement of paleosols shows that some of the normal faults were reactivated causing left-lateral deformation in a transient strike-slip stress field with a NE-SW oriented ?1. © 2013 Elsevier B.V.

The origin and evolution of CO2 inclusions and calcite veins in peridotite xenoliths of the Pannonian Basin, Hungary, were investigated by means of petrographic investigation and stable isotope analyses. The fluid inclusions recovered in paragenetic olivine and clinopyroxene belong to distinct populations: type A (texturally early) inclusions with regular shapes (often with negative crystal forms) forming intragranular trails, type B (texturally late) inclusions defining randomly oriented trails that reach grain boundaries Type B inclusions are often associated with silicate melt (type C) inclusions Stable carbon isotope compositions in inclusion-hosted CO2 were obtained by vacuum crushing followed by conventional dual inlet as well as continuous flow mass spectrometry in order to eliminate possible lab artifacts. Olivines, clino- and orthopyroxenes of the host peridotite have oxygen isotope compositions from 5.3 to 6.0 parts per thousand (relative to V-SMOW). without any relationship with xenolith texture. Some of the xenoliths contained calcite in various forms veins and infillings in silicate globules in veins, secondary carbonate veins filling cracks and metasomatic veins with diffuse margins The former two carbonate types have delta C-13 values around -13 parts per thousand (relative to V-PDB) and low Sr contents (

The study of c-axes distribution from sparry grains that fill microveins were used to define maximum horizontal extension directions (

The study of c-axes distribution from sparry grains that fill microveins were used to define maximum horizontal extension directions (

Compressional Pyrenean tectonic activities induced fractures in the Toarcian shales of the experimental site in the Toumemire tunnel (Aveyron, France). A combined petrological, mineralogical and geochemical study of oriented fractures, mainly filled with calcite, allowed observation and characterisation of four mineral parageneses (calcite, calcite and framboidal pyrite, calcite and cubic pyrite, and calcite and barite). Major- and trace-element contents of the vein calcite are positively correlated with those of the host rocks, especially at the shale-marl transition. These relationships are interpreted as resulting from short-distance migrations for the considered elements (Fe, Mn, Cu, Mo, ... ). The relatively constant chemical composition of the calcite implies negligible variations in the physico-chemical crystallisation conditions. Low uranium and high iron contents of the vein calcite suggest circulation of reducing fluids. The 87Srf86Sr ratios of the vein calcite range narrowly from 0.70841 to 0.70858, favouring a buffering by the surrounding shales. The two extreme 87Srf86Sr values were determined in samples located in or near the main faulted and brecciated zone, suggesting either external inputs or different water-rock ratios. With the exception of this main faulted and brecciated zone, microfissuring most probably favoured local and limited fluid migrations.

Detailed geochemical investigations of calcite veins, genetically related to intrusions and vein-hosting bedrock, have been used to indicate fluid evolution during intrusion-related hydrothermal mineralization, involving fluid mixing and water rock interaction. The area of investigation is located in the southeast of Sweden. The 1.85 Ga granitoid country rocks and the 0.9 Ga dolerite vein-related intrusions differ in chemical, geochemical, and stable isotope composition. The variation in rare earth and stable isotope composition across calcite veins and the presence of two groups of fluid inclusions suggests mixing of two types of fluids. Light rare earth enrichment and increasing 87 Sr/ 86 Sr-ratios suggest water rock interaction of one/both fluids.