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International audience; The Bou Jaber ore deposit is one of the numerous diapir-related Pb–Zn–F–Ba deposits of the Dome Zone in Northern Tunisia. Its location is controlled by the regional NE-SW Tajerouine Fault.Ore minerals are hosted in the Late Aptian limestones (Serdj Formation) as open space filling and stratabound replacement bodies. According to Bouhlel et al. (2016), the poly-phase mineralization resulted from the successive activity of three mineral systems, a Pb–Zn, then a barite, and eventually a fluorite deposition system. The latter, from the Late Miocene, is demonstrated in the present study.The fluorite system is characterized by the involvement of oil in the hydrothermal fluids. This oil was produced in the local environment of the deposit from the thermal maturation of the Albian Fahdene black shale source-rock at temperature range of~140 °C–~100 °C. Two brines were involved in the fluorite hydrothermal system. The first one (L1) is a Ca-rich brine (≥20 wt % bulk salinity), with Na/Ca ≤ 0.18, which is thought to have long resided in the basement, before its transfer into the Jurassic reservoir (Upper Nara Formation) and its eventual mobilization at the time of ore deposition. The second brine (L2), less saline (≤14 wt % bulk salinity) is more sodic, with Na/Ca up to 0.53, and represents unmodified brine originated from the nearby Triassic salt. The L1 brine was F-bearing, whereas the L2 brine was associated with oil. Fluorite deposition occurred at the estimated shallow depth of 1.7 km from cooling of the L1 brine due to the first isobaric cooling from ~160 °C to 135 °C under sub-lithostatic conditions (36 MPa). This stage is followed by mixing with the newly incoming L2 brines (transporting oil) along a sub-isochoric decompression path (down to the hydrostatic pressure at 17 MPa) and continuously cooling from 135 °C to 125 °C. The cooling and mixing caused fluorite deposition after which a transient heat advection episode (up to 145 °C) caused late calcite deposition prior to the end of hydrothermal circulation.

International audience; The Djebel El Hamra Pb-Zn-Ba-Sr (Hg) deposits in northern Tunisia are hosted in a post-nappe anticline with a core of a Triassicevaporite diapir affected by the NE–SW-trending Ghardimaou-Cap Serrat lineament. Three stages of mineralization occurred inthe Triassic dolostone: stages I and II caused alternating deposition of sulfate (Ba, Sr) and sulfide (sphalerite, galena) minerals;stage III formed late-stage calcite-marcasite-cinnabar. Zebra textures record the syntectonic transition from compression toextension in the Late Tortonian-Messinian interval. Two fluid end-members were involved in sulfate deposition: one lowsalinity(L1, ~3 wt% eq. NaCl) fluid, probably from a meteoric origin, and a Na-Ca-Cl brine (L2, ~22 wt% eq. NaCl) solutionwhich originated from the Triassic diapiric source. A third end-member fluid (L3) with long residence time in the basement wasalso involved in the Pb-Zn deposition. The δ34S values froma cluster of sulfates around +16‰, show a Triassic evaporate source.The sulfur in sphalerite resulted from bacterial sulfate reduction (BSR); however, crystallization in a closed system resulted in arange of δ34S between +1.6 and +26.5‰. The δ34S values in galena (−28.4 to +8.2‰) are consistent with a BSR and thermochemicalsulfate reduction (TSR) origin of the sulfur. Secondary ion mass spectrometry (SIMS) lead isotope data in galena(207Pb/204Pb: 15.595 to 16.193, 206Pb/204Pb: 18.673 to 18.939, 208Pb/204Pb: 38.330 to 40.572) point to local contributions(sedimentary and Cenozoic magmatic rocks) to the main source from the Precambrian basement. Ore deposition occurred at adepth of about 2 km at temperatures between 80 and 250 °C. A shallow magmatic heat source was the cause of these thermalfluctuations.

International audience; Unlike most Neogene basins of the Betic Cordillera where the Salinity Crisis is dated to the Messinian, a contradictory Tortonian dating was proposed for evaporites of the Lorca Basin. As a consequence, complex structural models have been proposed in the literature to explain this discrepancy in the timing of evaporites. In order to integrate the Lorca Basin into the geological context of the western Mediterranean domain during the Late Miocene, new sedimentological and stratigraphical studies coupled with new dating were performed, which allow us to propose a Messinian age for both diatomite-bearing deposits and evaporites of the Lorca Basin. These new ages challenge the idea of a Tortonian salinity crisis in the Lorca Basin. Three main events of base-level drop were evidenced during the Messinian. Each event is correlated with successive steps of basin restriction. Shallow salina evaporites were deposited after a base-level fall during the Messinian before a final base-level drop, which led to the entire exposure of the basin. This last exposure is interpreted as coeval with the deposition of first evaporites and halite in the deep Mediterranean basins. The reflooding which allowed the deposition of brackish deposits and a short-lived marine incursion occurred at the end of the Messinian. Base-level drops occurred during eustatic falls amplified by the gradual uplift of the Betic Cordillera. The exhumation of the Tercia ridge along the strike-slip Alhama de Murcia fault system during the Messinian probably favoured the gradual restriction of the basin. A discussion on correlations of main unconformities between several Neogene basins of the Betics is proposed, suggesting a similar structural evolution at the regional scale.

International audience; The presence of external fluids in metamorphic rocks has been shown to have a profound impact on rock rheology as high fluid pressure processes promote embrittlement and favor ductile deformation by recrystallization. Moreover, it has been proposed that brittle deformation guides fluid circulation and that intracrystalline deformation is responsible for fluid redistribution at the grain scale. Nevertheless, the amount of fluid present in the metamorphic ductile crust is debated and the nature of the interaction between fluids and recrystallization processes are not clearly identified. The aim of this study is to document the spatial distribution of fluid inclusions relative to microstructures in quartz grains and aggregates from veins sampled in amphibolite facies metamorphic rocks, exposed in the island of Naxos in the center of the Attic-Cycladic Metamorphic Complex in Greece. The veins, ranging from discordant structures with sharp contacts to totally transposed structures into the metamorphic foliation, display a large variety of microstructures and fluid evidences interpreted as recording exhumation processes through the ductile/brittle transition: (i) remnants of primary quartz grains contain abundant CO2-H2O fluid inclusions, decrepitated for the most part, distributed in clusters and in fluid inclusion trails, (ii) fluid inclusions with a similar composition are less abundant in recrystallized zones and in subgrains but are concentrated along grain boundaries indicating that grain boundary migration is responsible for redistribution of CO2-H2O fluids, (iii) subgrains of the last generation are almost devoid of fluid inclusions and are characterized by thick grain boundaries with abundant metamorphic fluids locally forming a continuous film. CO2-H2O fluid inclusions aligned in parallel, regularly spaced intragranular trails, locally rooted into grain boundaries, are interpreted as reflecting the spatial redistribution of these fluids in quartz slip planes owing to the increase of fluid pressure in grain boundaries. This proposition is corroborated by the parallelism between slip planes and fluid inclusion trails. Perpendicular sets of fluid inclusion trails formed at the junctions of subgrains suggest that redistribution of fluids along quartz slip planes contributes to the initiation of subgrain rotation recrystallization. Transgranular fluid inclusion planes oriented perpendicular to the regional mineral and stretching lineations of the host metamorphic rocks mark a transition from grain to rock scale brittle behavior associated with the infiltration of H2O fluid, mixing to various degrees with the initial CO2-H2O fluid already present in the metamorphic rocks. These features indicate that, in the ductile-metamorphic crust, fluid redistribution is intimately linked to recrystallization mechanisms allowing fluids circulation under lithostatic pressure.

International audience; The ductile-brittle transition zone in extensional regimes can play the role of a hydrogeological barrier. Quartz veins developed within an orthogneiss body located in the detachment footwall of a Metamorphic Core Complex (MCC) in the Nevado-Filábride units (Betics, Spain). The detachment footwall is composed mainly of gneisses, schists and metacarbonates from the Bédar-Macael sub-unit. Schist and metacarbonate bodies show evidence of ductile deformation at the time the gneiss was already undergoing brittle deformation and vein opening during exhumation. The vein system provides the opportunity to investigate the origin, composition and PVTX conditions of the fluids that circulated in the detachment footwall while the footwall units were crossing the ductile-brittle transition.The analysis of fluid inclusions reveals the presence of a single type of fluid: 30–40 mass% NaCl > KCl > CaCl2 > MgCl2 brines, with trace amounts of CO2 and N2 and tens to thousands of ppm of metals such as Fe, Sr, Li, Zn, Ba, Pb and Cu. δDfluid values between −39.8 and −16.7‰ and δ18Ofluid values between 4.4 and 11.7 ± 0.5‰ show that the brines have undergone protracted interaction with the host orthogneissic body. Coupled salinity and Cl/Br ratios (200 to 4400) indicate that the brines originate from dissolution of Triassic metaevaporites by metamorphic fluids variably enriched in Br by interaction with graphitic schists.This study highlights the absence of any record of surficial fluids within the veins, despite the brittle deformation conditions prevailing in this orthogneiss body. The fact that fluids from the detachment footwall were isolated from surficial fluid reservoirs may result from the presence of overlying schists and metacarbonates that continued to be affected by ductile deformation during vein formation in the gneiss, preventing downward circulation of surface-derived fluids.

Fluid inclusions trapped in quartz veins hosted by a leucogneiss from the southern part of the Naxos Metamorphic Core Complex (Attic-Cycladic-Massif, Greece) were studied to determine the evolution of the fluid record of metamorphic rocks during their exhumation across the ductile/brittle transition. Three sets of quartz veins (V-M2, V-BD & V-B) are distinguished. The V-M2 and V-BD are totally or, respectively, partially transposed into the foliation of the leucogneiss. They formed by hydrofracturing alternating with ductile deformation accommodated by crystal-plastic deformation. The V-B is discordant to the foliation and formed by fracturing during exhumation without subsequent ductile transposition. Fluids trapped during crystalplastic deformation comprise two very distinct fluid types, namely a CO2-rich fluid and a high-salinity brine, that are interpreted to represent immiscible fluids generated from metamorphic reactions and the crystallization of magmas respectively. They were initially trapped at approximate to 625 degrees C and 400MPa and then remobilized during subsequent ductile deformation resulting in various degrees of mixing of the two end-members with later trapping conditions of approximate to 350 degrees C and 140MPa. In contrast, brittle microcracks contain aqueous fluids trapped at 250 degrees C and 80MPa. All veins display a similar 13C pointing to carbon that was trapped at depth and then preserved in the fluid inclusions throughout the exhumation history. In contrast, the D signature is marked by a drastic difference between (i) V-M2 and V-BD veins that are dominated by carbonic, aqueous-carbonic and high-salinity fluids of metamorphic and magmatic origin characterized by D between 56 parts per thousand and 66 parts per thousand, and (ii) V-B veins that are dominated by aqueous fluids of meteoric origin characterized by D between 40 parts per thousand and 46 parts per thousand. The retrograde PT pathway implies that the brittle/ductile transition separates two structurally, chemically and thermally distinct fluid reservoirs, namely (i) the ductile crust into which fluids originating from crystallizing magmas and fluids in equilibrium with metamorphic rocks circulate through a geothermal gradient of 30 degrees C km1 at lithostatic pressure, and (ii) the brittle upper crust through which meteoric fluids percolate through a high geothermal gradient of 55 degrees C km1 at hydrostatic pressure.

Esta es una versión PREPRINT. El artículo final está publicado por GEOFLUIDS y se encuentra disponible en: http://onlinelibrary.wiley.com/doi/10.1111/gfl.12139/abstract, This is a PREPRINT version (pre-refereeing) of the paper: Dyja, V., Hibsch, C., Tarantola, A., Cathelineau M., Boiron M.C., Marignac C, Bartier, D., Carrillo-Rosúa, J., Morales-Ruano, S., Boulvais, P. (2015). From deep to shallow fluid reservoirs: evolution of fluid sources during exhumation of the Sierra Almagrera, Betics, Spain. Geofluids, doi: 10.1111/gfl.12139., Palaeo-fluids trapped in quartz and siderite-barite veins hosted by graphitic schists recorded the fluid and metal transfers during the Neogene exhumation of the Sierra Almagrera Metamorphic Core Complex. First quartz veins registered the ductile then brittle-ductile extensional shearing. The reservoir at that time was wetted by high-salinity fluids with a low density volatile phase resulting from the dissolved Triassic evaporites. Low salinity fluids occurred during the exhumation within the brittle domain as revealed by transgranular fluid inclusion planes affecting previous veins. This suggests an opening of the system and the penetration of surficial fluids from uplifted ranges during Serravalian to early Tortonian times. Transcurrent tectonics generated marine basins since late Tortonian. At depth quartz veins discordant to the foliation were associated to hematite indicating oxydizing conditions. A stop of the low-saline record is revealed by high-salinity Fe-rich fluids issued from the underlying metamorphic reservoir. The Messinian ongoing activity of the sinistral Trans-Alboran tectono-volcanic trend led to the formation of ore deposits. Reducing conditions and Fe-rich fluid led to the formation of siderite and pyrite. The subsequent formation of galena and barite under oxydizing conditions has been related to a probable increase of temperature. A higher salinity and the Cl/Br ratio indicate another source of secondary brine issued from dissolved Messinian evaporites as confirmed by δ34S signature of barite. Transcurrent tectonics clearly modified the hydrogeology of the upper reservoir. The faulting connected the deeper and upper reservoir generally separated by the brittle/ductile transition rheological and hydrogeological barrier under extensional tectonic regimes as confirmed by the stage of low-saline fluids., Université de Lorraine, GeoRessources, CNRS, CREGU, Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Universidad de Granada. Departamento de Didáctica de las Ciencias Experimentales, Universidad de Granada. Departamento de Mineralogía y Petrología, Université de Rennes 1, Géosciences Rennes - UMR CNRS, This work was supported by the Ministry of Higher Education and Research (MESR, France) and the CNRS ST-INSU-CT5 programme.

Deformations observed within Quaternary alluvium in the Champagne region (Paris Basin) comprise faults, folds and soft-sediment deformation structures. Their occurrence is linked to the subjacent weathered chalk. Previously interpreted as neotectonic features, the deformations are reinterpreted as karst subsidence features or/and soil displacements due to periglacial processes. Dissolution of chalk has produced superficial subsidence, explaining the geometry of some faults and their large offsets within surface deposits. The freezing-thawing cycles in the porous superficial layers have also favoured gravity instability and deformations, and this can explain local small-scale deformations but also mass movement (sliding). The seismotectonic hypothesis is rejected, because of the absence of regional faults able to generate such large co-seismic offsets. The fault directions and the apparent vertical offsets are not homogeneous at regional scale and they are often inconsistent with the Quaternary stress field. Moreover, the rooting of faults into the basement is not documented and therefore, the neotectonic origin is very doubtful.

francaisLocalisees exclusivement dans l'Oxfordien calcaire moyen a superieur, des fractures verticales NNE-SSW de 10-20 m de haut, a remplissage microgranulaire, apportent des elements nouveaux sur l'histoire tectonique mesozoique de l'Est du bassin de Paris. Ces fractures affectent principalement des grainstones a entroques ou oolithiques. Leur remplissage, compose de micrite, microsparite et lithoclastes, peut correspondre a une ancienne boue calcaire issue de niveaux superieurs non encore lithifies ou a un sediment marin en cours de depot. Ces remplissages de fente peuvent donc etre qualifies de filons sedimentaires. Les figures de tri granulometrique traduisent un depot par ecoulement turbulent. Des fluages hydroplastiques per descensum et des brechifications intraformationnelles indiquent une deformation post-induration. On note la predominance des filons dans les grainstones, precocement lithifies et par consequent sujets a une fracturation, et leur rarete dans les mudstones reputes plus plastiques. Ces derniers apparaissent comme la source possible d'alimentation en boue carbonatee des filons. La geometrie des epontes et l'histoire diagenetique des remplissages permet de distinguer deux types de filons sedimentaires : le premier presente une fracturation qui dessine des epontes irregulieres contournant les elements constitutifs de l'encaissant (entroques ou ooides) voire meme leur ciment syntaxique, alors que le second recoupe nettement les elements de la roche encaissante et presente sur les epontes une frange de sparite ante-remplissage sedimentaire. Pour la premiere famille de filons, l'enchainement des evenements diagenetiques est : i) mise en place de premiers ciments syntaxiques ou intergranulaire ; ii) fracturation sous faible contrainte de confinement avec ruptures suivant les contours des grains ; iii) remplissage sedimentaire et infiltration dans la porosite. En revanche, le second type de filons est forme sous plus fort recouvrement comme l'atteste la preexistence de stylolites stratiformes et une cristallisation de sparite sur les epontes precedant le remplissage sedimentaire. La relative precocite de cette fracturation et la disponibilite d'un materiel de remplissage sedimentaire non lithifie suggerent un âge oxfordien a kimmeridgien pour l'ouverture des filons sedimentaires. L'orientation submeridienne de ces filons sedimentaires indique un regime extensif Est-Ouest qui semble se prolonger vers la fin du Jurassique par des jeux en failles normales affectees par les regimes decrochants cretaces a tertiaires. Les signatures isotopiques en [sigma]18OSMOW des microsparites et sparites de remplissage des filons sedimentaires temoignent d'une participation d'eau meteorique, soit precocement lors de leur mise en place, ou alors plus tardivement lors d'episodes de recristallisation dont les âges sont incertains. Ces filons sedimentaires sont une expression nouvelle de l'extension E-W d'âge oxfordien-kimmeridgien, mise en evidence dans la plate-forme ouest-europeenne. Elle est d'autant plus interessante que cette direction a ete le plus souvent attribuee au rifting oligocene. EnglishVertical fractures in Oxfordian limestones of the eastern part of the Paris Basin are interpreted as resulting from synsedimentary extensional deformations which occurred during the Mesozoic. These NNE-SSW striking fractures are 10 to 20 meters in height, and filled with microgranular material. The fractures mainly affect crinoidal and oolitic grainstones. Their micritic to microsparitic, lithoclast-bearing infills may have resulted from the solidification of an ancient mud injected from non-lithified, overlying layers of marine sediments. They should therefore be referred to as sedimentary dykes. Graded layering suggests deposition under turbulent flow conditions, whereas later plastic deformation and breccia formation indicate a syndiagenetic reworking. Such observations are consistent with a predominance of the sedimentary dykes in grainstones, which are more rapidly lithified and therefore subject to early fracturing. On the contrary, these dykes are rare in mudstones which may constitute the source of the material for the infills in the grainstones. Both the analysis of the wall geometry and the reconstruction of the diagenetic history of the infills make possible to distinguish two types of sedimentary dykes. The first type corresponds to a fracturation characterized by irregular walls around the rock-constituting grains (i.e. crinoidal debris or ooids), whereas the walls in the second type are cross-cutting the grains and present a fringe of sparite predating the microsparite infill. The following scenario is proposed for the first type of sedimentary dykes: i) syntaxial cementation of crinoidal debris and early cementation of ooids; ii) fracturing along grain boundaries under low burial strain; iii) filling of fractures and open porosity by the mud. The second type of sedimentary dykes was formed under deeper burial conditions, which is indicated by both pre-existing bedding-parallel stylolites and the precipitation of sparite on the walls before the sedimentary infill. This early fracturation and the availability of a sedimentary filling, non-lithified material point to a late Jurassic age for these sedimentary dykes. The [sigma]18OSMOW isotopic signatures measured for the infilling sparite and microsparite materials indicate that these were precipitated from meteoric waters, either early during the formation of the sedimentary dykes or during a later recrystallization event. The sedimentary dykes have recorded an E-W extension during the Oxfordian-Kimmeridgian period, which is in good agreement with the late Jurassic tectonic history of the western European platform. This early Oxfordian-Kimmeridgian fracturing and its associated fluid paleocirculations is of major interest in the context of the tectonic history of the Paris Basin, since most of these N-S to NNE-SSW tension gashes have been previously attributed to the Eocene Pyrenean shortening and Oligocene rifting stages.

27 pages; International audience; Several diagenetic models have been proposed for Middle and Upper Jurassic carbonates of the eastern Paris Basin. The paragenetic sequences are compared in both aquifers to propose a diagenetic model for the Middle and Late Jurassic deposits as a whole. Petrographic (optical and cathodoluminescence microscopy), structural (fracture orientations) and geochemical (δ18O, δ13C, REE) studies were conducted to characterize diagenetic cements, with a focus on blocky calcite cements, and their connection with fracturation events. Four generations of blocky calcite (Cal1-Cal4) are identified. Cal1 and Cal2 are widespread in the dominantly grain-supported facies of the Middle Jurassic limestones (about 90% of the cementation), whereas they are limited in the Oxfordian because grain-supported facies are restricted to certain stratigraphic levels. Cal1 and Cal2 blocky spars precipitated during burial in a reducing environment from mixed marine-meteoric waters and/or buffered meteoric waters. The meteoric waters probably entered aquifers during the Late Cimmerian (Jurassic/Cretaceous boundary) and Late Aptian (Early Cretaceous) unconformities. The amount of Cal2 cement is thought to be linked to the intensity of burial pressure dissolution, which in turn was partly controlled by the clay content of the host rocks. Cal3 and Cal4 are associated with telogenetic fracturing phases. The succession of Cal3 and Cal4 calcite relates to the transition towards oxidizing conditions during an opening of the system to meteoric waters at higher water/rock ratios. These meteoric fluids circulated along Pyrenean, Oligocene and Alpine fractures and generated both dissolution and subsequent cementation in Oxfordian vugs in mud-supported facies and in poorly stylolitized grainstones. However, these cements filled only the residual porosity in Middle Jurassic limestones. In addition to fluorine inputs, fracturation also permitted inputs of sulphur possibly due to weathering of Triassic or Purbeckian evaporites or H2S input during Paleogene times.

Microtectonic analysis in association with tectonic-sedimentological observations enables us not only to define palaeostress tensors but also to date each of them. Such a study, carried out in central and northeastern England and in southernmost Wales has permitted us to point out several tectonic stages during the Permian-Cenozoic period. (1) Inferred from syn-sedimentary faulting in the Late Permian series, the Permian/Early Triassic tectonic regime is characterised by a NNW-SSE-oriented extension. (2) During the Late Triassic to the early Late Jurassic, an E-W- to ENE-WSW-oriented extension was acting as suggested by syn-sedimentary normal faulting in Keuper, Lias and Middle Dogger sediments and post-sedimentary normal faulting in Oxfordian sediments. (3) The following tectonic event probably started during the Malm and was particularly active during the Early Cretaceous. It was characterised by a N-S- to NNE-SSW-oriented extension and was associated with an E-W- to WNW-ESE-oriented strike-slip tectonic regime (transtension). (4) A locally observed NW-SE-oriented transpressional strike-slip tectonic regime is thought to correspond to the ‘Laramide’ inversion phase of the Middle Paleocene. (5) The later tectonic event is characterised by a N-S-oriented transpressional strike-slip regime and affects a Paleocene tholeiitic dyke (‘Cleveland dyke’). It is supposed to be synchronous with the so-called Eocene ‘Pyrenean’ to the Early Miocene ‘Helvetic’ compressional stages. These paleostress tensors are compared with others defined in France, the Benelux countries and Germany and are also collated to the tectonic evolution of oil basins assessed from geophysical analyses. These comparisons raise discussions about the paleostress distribution within the geodynamic evolution of the West European shelf.

A detailed reappraisal of the sequence of tectonic stages that has affected the eastern part of the Paris Basin from the late Jurassic to the end of Cainozoic is presented in order to improve knowledge of the relationships between tectonics and fluid/mass palaeo-transfers in that basin. This goal was performed in two steps: i) establishing a relative tectonic chronology on the basis of numerous observations and detailed analysis of geometrical relationships between striated planes, vertical and bedding stylolites, and tension gashes, and ii) discussing the geochemical signatures ( δ 18 O and δ 13 C) of calcite from fracture infillings well positioned within the relative tectonic chronology. The resulting tectonic sequence agrees with the main events described by previous papers, but the present work details the Pyrenean s.l. (Eocene–Oligocene) and Alpine (Miocene–Pliocene) convergence stages and explains the mechanisms of the Oligocene–Miocene transition between the two previous events. The different tectonic stages are as follows: i) late Jurassic to early Cretaceous extension starting with a WNW–ESE direction but changing to E–W; ii) the Pyrenean convergence (Eocene), changing from NNE–SSW to NE–SW and finally ENE–WSW compression; iii) Oligocene transition from Pyrenean to Alpine convergence, marked by a drastic evolution of main stress which swaps from a horizontal position to a vertical one and radial extension marked by a strong reactivation of bedding stylolitisation; iv) the Alpine convergence (late Miocene to present-day), changing from WNW–ESE to NNW–SSE direction of shortening. δ 18 O- and δ 13 C-values of calcite from tension gashes associated to each tectonic stage spread from 18‰ to 27‰ (SMOW) and from 0.8‰ to 3‰ (PDB), respectively. According to the maximum thermal history of this part of the basin ( T MAX = 40 °C or 60 °C according to the available published estimates), the calculated δ 18 O-values of fluids (− 7‰ to − 4‰) involved in mass transfer processes are interpreted as meteoric. The lowest δ 18 O-values (18–20‰) are located around the main regional faults and associated with δ 13 C-values that are rather different from those of host rocks. In contrast, calcites from non-faulted area present a higher δ 18 O- (> 20‰) and δ 13 C-values close to those of host rocks. These data are explainable in terms of differences in the fluid/rock ratios prevailing during carbonate redistribution, the highest ratios being associated to discontinuities (faults, sometimes with hydraulic breccias) that were active during the Tertiary tectonic events. Outside the fault zones, the isotopic compositions of calcite from tension gashes are similar, at the regional scale, to those of calcite from geodes or cements analysed in previous studies on localized areas. As a result, we emphasize the fact that a significant part of the carbonate redistribution in the Middle to Upper Jurassic limestones from the eastern Paris Basin occurred during the Tertiary s.l., enlightening the influence of distant orogenic systems (extensive or compressive) in the matter redistribution within sedimentary basins, at variance of models inferring a porosity cementation predominantly during burial.

International audience

The main types of seismites are reviewed following the proposed classification and are illustrated by our own case studies. The large variety of seismites, depends on the sedimentologic, hydrodynamic and diagenetic characters of the deposits subject to seismic shocks. On a given site, generally different types of seismites cane be related to the same seismic event. These peculiar but widespread sedimentary structures are not always univocal and may often be related to different causes. Therefore, the structures discussed must necessarily be placed in a detailed geological context.

This paper documents normal fault sets observed in chalks exposed in widely separated localities in the UK and France. These faults are characterized by having a wide range of strikes at any one locality, are developed entirely within the chalk succession and do not seem to interconnect to deeper or shallower structures. These structures may result from two different mechanisms: (1) complex polyphase deformational histories involving contrasting stress states; or (2) a single deformational phase in which the faults develop to accommodate compactional strains. Evidence is presented from microstructural and petrographic data to support the latter interpretation. In particular, the association of calcite and marcasite mineralizations with fracture surfaces and fault zones and textural observations relating flint occurrence to early fault formation point towards fault propagation at a very early stage of burial and compaction of the chalky sediments. An analogy is drawn between these outcrop-scale structures and polygonal fault systems at a larger scale recognised from seismic observations of chalk sequences deposited at passive continental margins. The origin of these structures may be related to syneresis at an early stage of deformation followed by pressure solution phenomena that may reactivate this early-inherited polygonal fault pattern until the present day.

We studied the Holocene fluvial-lacustrine sediments of the northern Quito Basin to determine a paleoseismic history for Quito, the capital of Ecuador. Fault-controlled sedimentation and coseismic deformation demonstrate the Holocene activity of the Quito reverse fault system. In the 450 years of historical seismicity, just a few events recorded in Quito could be related to local seismic sources. Numerous liquefaction horizons are possible evidence of paleoseismic activity in Quito. Potential paleoseismic horizons have a maximum thickness of 1.5 m and were produced in a lacustrine environment. Several horizons have been successfully correlated throughout the basin thanks to the presence of six volcanic marker beds. We found no evidence of widespread liquefaction processes originating in an aerial environment at water-table depth, clearly suggesting a present-day low liquefaction potential for the city. Assuming a seismic origin for contorted bedding features, we compared thickness distributions of these horizons and intensity distributions from the historical seismicity record, and proposed a methodology for the determination of seismic paleointensities. We constructed a paleoseismic history which suggests the occurrence of 28 earthquakes of intensity > V for a roughly 1500-year time span, prior to the historical record. From these 28 earthquakes, we determined the probable occurrence of a major event of intensity X (MSK) between the 10th and the 16th centuries. The correlation between its paleoseismic horizon and buried coseismic faulting in the Quito Basin suggests the occurrence of a local earthquake. The occurrence of a MM 6.5–7.0 event due to the rupture of the entire Quito fault appears to be the most probable origin for this high seismic intensity which exceeds the maximum recorded historical intensity by almost one degree.

This thesis aim at characterizing the types of fluids concerned structural levels and style of deformation. Results from Sierra Bedar point out the role played by metal-rich brines during late stages of fluid flows within the ductile crust within a domain was still isolated from surficial fluids. Brine concentration drop in the eastern Sierra Almagrera which was progressively more impacted by the major transcurrent system with volcanism and metal ore deposits. At reaching the brittle domain, quartz veins trapped surficial fluids. Soon after, quartz veins indicating the return of metamorphic fluids. Following siderite-pyrite-galena-barite veins display higher salinities and Cl/Br ratios indicate the contribution of another secondary brine coming from early Messinian evaporites. This major transcurrent tectonics clearly modified the partitioning on both sides of the brittle-ductile transition, La thèse cherche à caractériser les types de fluides à différents niveaux structuraux et types de déformation. Les résultats de la Sierra Bédar indiquent le rôle d'une saumure enrichie en métaux lors des derniers stades de circulation au sein de la croûte ductile dans un domaine encore isolé des fluides de surface. Cette saumure est plus diluée à l'est dans la Sierra Almagrera et où l'impact du système décrochant va devenir de plus en plus important avec du volcanisme et de nombreux gisements. Dans le domaine fragile, des veines de quartz enregistrent des fluides de surface. Suivent des veines de quartz indiquant la réapparition des fluides métamorphiques sous-jacent. La formation de veines de sidérite-pyrite-galène-barytine montre de plus forte salinité et des rapports Cl/Br indiquant la contribution d'une autre source de saumures secondaires issues cette fois des évaporites messiniennes. Le décrochement a modifié le compartimentage de part et d'autre de la transition fragile-ductile

Président : M. B. LATHUILIERE Professeur, U.H.P Nancy 1 Rapporteurs : M. F. GUILLOCHEAU Professeur,Université de Rennes 1 M. O. LACOMBE Professeur, Université de Paris 6 Examinateurs : M. CATHELINEAU Directeur de recherche CNRS, Nancy M. C. HIBSCH Maître de conférence, U.H.P Nancy 1 M. B. BEAUDOIN Professeur, Ecole des Mines, Paris Invités : M. S. FOURCADE Professeur, Université de Rennes M. P. ELION Ingénieur ANDRA, Paris M. A. TROUILLER Ingénieur ANDRA, Paris; The succession of different fracturing and fluid circulation events has been established for the Eastern part of the Paris Basin. Synsedimentary deformations in the Jurassic units, palaeostresses and fluid palaeocirculations are described on the basis of new field observations, drilling data and geochemical and isotopic analyses of diagenetic and tectonic materials. On the basis of the new decompaction data and the discovery of sedimentary dykes, an extension tectonic context is defined from the end of Dogger to the Malm. These early deformations fit in a general tectonic timetable, starting from the end of the Mesozoic to the present, and in which the palaeostresses relative to the Late Cretaceous to Tertiary tectonic stages have been integrated. A detailed study of bedding stylolites has confirmed their role during compaction as well as during later tectonic reactivation. Finally, analysis of the isotopic composition (δ18O and δ13C) of calcites from tension gashes and rocks provide important constraints on the origin and nature of the palaeofluids which circulated in the Paris Basin from Jurassic to Tertiary.; L'enchaînement des épisodes de fracturation et de circulation de fluides ainsi que les phases de déformations synsédimentaires a été caractérisé dans les terrains jurassiques de l'Est du Bassin de Paris. L'étude s'appuie sur une base importante d'observations nouvelles de terrain et sur des données de forages ainsi que sur la caractérisation géochimique et isotopique de différents objets diagénétiques et tectoniques. Sur la base de données de décompaction des terrains et de la découverte de filons sédimentaires, un contexte tectonique extensif est défini entre la fin du Dogger et le Malm. Ces déformations précoces s'intègrent dans un calendrier tectonique partant de la fin du Mésozoïque jusqu'à l'Actuel, dont l'enchaînement des paléocontraintes associées aux phases tardi-crétacées et tertiaires est précisé. L'étude détaillée des stylolites stratiformes a confirmé leur rôle pendant la compaction et lors de réactivations tectoniques. L'analyse des signatures isotopiques (δ18O et δ13C) des calcites de fentes de tension et des roches encaissantes a permis de proposer plusieurs origines et modes d'écoulements pour les paléocirculations depuis le Jurassique jusqu'au Tertiaire.