International workshop announcement for the 40th ...€¦ · Sedimentary basins represent one of...

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International workshop announcement for the 40th anniversary of CREGU

Basins and Resources

13-15 November, 2019, Nancy, France

International workshop for the 40th anniversary of CREGU



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International workshop

for the 40th anniversary of CREGU



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Foreword Sedimentary basins represent one of the geological environments the most exploited for metals (uranium, base metals, ...) and hydrocarbons (oil and gas), but also are excellent hosts for storage (gas, wastes, ...) due to their petrophysical features. This workshop is organized for the 40th anniversary of CREGU, a research centre based in Nancy (France) and dedicated to scientific research on ore deposits and hydrocarbons at the interface with fundamental research and industrial needs. Created in 1978 at the instigation of the CNRS and CEA departments, the Centre de Recherches sur la Géologie des Matières Premières Minérales et Energétiques (CREGU) is a civil society led by CNRS researchers and professor-researchers from the University of Lorraine. CREGU's partners are Orano Mining (50.10%) and TOTAL (49.90%). CREGU is a partner of the GeoRessources laboratory (CNRS and University of Lorraine) and a member of the ICEEL institute; its function is to establish lasting relations with the industrial community through a permanent exchange between researchers and engineers of the companies, in particular through programming carried out through two scientific councils and two steering committees per year with Orano and Total. CREGU is open to work with other companies, and has already worked with ARCELORMITTAL, EXXON, PETROBRAS, PEMEX, Mawson Resources, Vale among others. The workshop provides an unique opportunity to present and compare the most advanced results about sedimentary basins, whether on their formation or their capacity as storage of mineral, energetic resources or wastes. Open to all interested parties and targeting and an international audience, 6 different sessions with 60 contributions are scheduled over two and half days. Each session is introduced by an industrial referent who will expose the current issues for the industry, followed by a keynote lecture given by a leading scientist in the field, short communications and a poster session. The meeting and related activities will provide opportunities for friendly exchanges between the scientific and industrial worlds. We wish you an excellent workshop. The Organizing Committee

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Program of the conference

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Fluid-rock interactions :

Paleofluid characterization

and dating

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Wednesday, 13th November 2019 8h30 - Welcome to the workshop - Registration

9h00 - Welcome addresses from CNRS, Université de Lorraine, TOTAL and ORANO 9h30 - Introduction to the meeting by P. Landais, Haut Commissaire (Atomic energy Commission) : Ideas and tools for the transfer of scientific results to industry Session 1 : Fluid-rock interactions : paleofluid characterization and dating Session dedicated to new and innovative results about fluid and mineral chemistry, dating and P-T-x reconstructions 10h - Keynote lecture - Girard J-P. (TOTAL) : Challenges and tools to investigate paleo-

fluids in sedimentary basins and reservoirs 10h30 - Tarantola A. : CF-IRMS analysis of hydrogen isotopes in fluid inclusion water 10h45 - Mangenot X. : Clumped isotope composition of CH4 released by crushing methods

from quartz of the external part of the Central Alps (Switzerland) 11h - Lahfid A. : The use of the RSCM geothermometry to study the thermal anomalies of ore deposit environment 11h15 - Keynote lecture - Mercadier J. (GeoRessources) : New methodological developments to solve dating problems of the world-class U deposits from the Athabasca Basin (Saskatchewan, Canada) 11h45 - Stein H.: Re-Os for Resource Geology - The Unifying Dimension of Time and the Interrogator of Internal-External Fluids in Basins 12h - Blaise T. : In situ LA-ICP-MS U-Pb dating of fluorite 12h15 Lunch offered by CREGU 13h30 - Godeau N. : U-Pb dating of diagenetic carbonates and thermal history of presalt Kwanza basin reveal a major and early pulse

13h45 - Brigaud B. : U/Pb dating and 47 temperature determination of Jurassic

carbonates : implications for early and burial diagenesis within intracratonic sedimentary basins 14h - Barbarand J. : Fluid circulation constrained by thermochronology 14h15 - Deloule E. : Effect of Radium mobility on the U-Pb systematic and age determination of U- minerals - the Kazakstan roll front deposits Posters Hannah J. : Redox sensitive metals - recorders of fluid and metal sources and transport in sedimentary basins Le V.H. : New calibration data for determination of PVX properties of CO2-CH4-N2 gas mixtures by Raman spectroscopy. Application to natural fluid inclusions

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Challenges and tools to investigate paleo-fluids in sedimentary basins and reservoirs Girard J.P. TOTAL, EXPLO/GT/ISS, CSTJF, Pau, France [email protected]

Sedimentary basins host a large part of natural resources, in particular with respect to fossil hydrocarbons (oil, gas, coal) that remain the prime source of energy for humanity today. In the past decade, petroleum exploration has been increasingly driven towards the so-called “complex reservoirs”, i.e. those reservoirs occurring in complex geological settings such as ancient fold and thrust belts or ultra-deep distal offshore areas. As a consequence, the need for increasingly detailed, accurate and dependable techniques of reservoir characterization as well as the development of pertinent and powerful geo-indicators of past conditions have become imperative. Diagenetic transformations taking place in buried reservoirs are controlled by five main parameters: temperature (T), pressure (P), water chemistry (x), effective stress (σeff) and time (t). In order to improve our understanding of diagenetic processes and be able to develop predictive models, a number of major challenges have to be addressed. They can be grouped according to two main purposes: 1) to obtain radiometric ages of diagenetic cements and processes, so as to position successive diagenetic/fluid events in an absolute time (t) frame, and 2) to develop High-Resolution in-situ micro-analytical techniques operable directly on thin sections to measure isotopes, trace elements, fluid inclusions, etc, at the petrographic microsite scale, so as to acquire robust, texturally well-constrained information on the P-T-x conditions of fluid events. Major analytical developments have been achieved in the recent years, providing new tools that are already applied for some of them or hold great promises for others. They notably include: in-situ U-Pb dating of diagenetic carbonates by LA-ICPMS, clumped isotope geothermometry on carbonates or natural gas, isotope/chemical micro-analysis of brines in fluid inclusions, micro-fracturing of quartz grains as a proxy of paleo effective stress. All of these novel techniques have limitations and associated uncertainties, but they give access to very valuable information to unravel diagenetic and fluid circulation processes in sedimentary basins, by providing quantitative constraints on P-T-x-σeff-t parameters independently of basin modeling. As such, they supply robust input parameters that are critical to calibrate basin models finely and make them more efficient at predicting fluid events in space and time.

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CF-IRMS analysis of hydrogen isotopes in fluid inclusion water Tarantola A.1*, Rigaudier T.2, Randi A.1 1Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France 2CRPG-CNRS, Université de Lorraine, France *[email protected]

The stable-isotopic signature (C, H and O) of fluid inclusions (FIs) complements VX data and constrains the origin of the main components (H2O, CO2 and CH4 essentially) and their possible exchanges or equilibration during fluid circulation. The oxygen isotopic composition of water is buffered in most oxygen-bearing host minerals (silicates, carbonates, etc.). As a consequence, the paleo-

-mineral using empirical fractionation coefficients as a function of temperature. Only the hydrogen isotopi D) trapped in FIs is a direct measurement of the past circulating water. The conventional technique of analyzing water D/H of FIs consists of (1) the extraction of the fluid contained within the inclusions by mechanical crushing (crush-leach) or thermal decrepitation, (2) the separation of the different chemical species by appropriate thermal traps, and (3) the analysis of pure gases by mass spectrometry (Dual-Inlet method; Dallai et al.,2004). This methodology becomes inappropriate, however, when several inclusion populations occur within a sample or if the amount of sample is too low. In favorable case studies, depending on fluid inclusion size and density, the amount of material should not be less than 1 gram in order to provide the minimum 10–20 μmoles required for accurate and reproducible isotopic values of hydrogen. Our approach consists in the use of CF-IRMS technique where the minerals (quartz, halite, barite and fluorite) hosting fluid inclusions are combusted at high temperature on glassy carbon (700-1450°C) leading to the decrepitation of FIs. The released water is the reduced into H2. After chromatographic separation, the recovered H2 is analyzed by IRMS (Sharp et al., 2001; Lupker et al., 2012). By coupling this technique to an evacuated

Dual-Inlet but here with a mass of samples lower than 50 mg. References Dallai, L. et al. (2004) in: Handbook of stable isotope analytical techniques 62-77 Lupker, M. et al. (2012) Geochim. Cosmochim. Ac. 84:410-432 Sharp, Z.D. et al. (2001) Chem. Geol. 178:197-210

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Clumped isotope composition of CH4 released by crushing methods from quartz of the external part of the Central Alps (Switzerland) Mangenot X.1*, Tarantola A.2, Chailan O.3, Girard J.P.3, Mullis J.4, Eiler J.M.1 1Caltech, Geological and Planetary Sciences (Pasadena, CA, USA) 2Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France 3Total (EP / R&D, Pau, France) 4Departement of Environmental Sciences, Institute of Mineralogy and Petrography (Basel, Switzerland); *[email protected].

Hydrocarbon-bearing fluids trapped as inclusions can be regarded as time capsules of geofluids and are invaluable for understanding the evolution and migration of petroleum in sedimentary basins. These fluid inclusions can be studied using microthermometric methods to approximate the minimum inclusion trapping temperature and pressure and the gross composition of included petroleum can be derived by confocal microscopy and pressure-volume-temperature (PVT) simulation. Additional crushing or thermal decrepitation methods can also be used to release the petroleum (oil or gas) in fluid inclusions and analyze its molecular and isotopic compositions (e.g. 13C, D). Here we propose a new methodology consisting in the measure of multiply substituted (“clumped”) isotope composition of the methane trapped in fluid inclusions. Indeed, recent analytical development in isotopic ratio mass spectrometry - IRMS now permits to quantify the abundance of both 13CH3D and 12CH2D2, i.e. two isotopologues of interest of methane, with sufficient precision for direct thermometry applications. In a CH4 isotopically equilibrated system, 12CH2D2 and 13CH3D values are a direct function of the methane generation temperature, and thus can be used as a new isotopic thermometer. We present here preliminary clumped isotope thermometry results (n=8) from different generations of CH4-bearing fluid-inclusions occurring in autigenic fissure quartz in the

was generated by thermogenic cracking at high maturity. The methane released by crushing in eight of these samples (to date; August 2019) display 12CH2D2 and 13CH3D clumped isotope composition both (1) in thermodynamic equilibrium between each other and (2) in very good agreement with the fluid inclusion homogenization temperatures measured independently (c.f. 230-260 °C). Such isotopic results may be explained by two possible scenarios: (1) the methane preserved its initial formation temperature and has been generated near the fluid entrapment site from organic matter-rich flysch, or (2) the CH4 has been isotopically re-equilibrated with the H2O, meaning that the clumped isotope temperature reflects an equilibrium temperature.

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The use of the RSCM geothermometry to study the thermal anomalies of ore deposit environment. Lahfid A.1*,Lacroix B.2 1BRGM, 3 Avenue Claude Guillemin, Orléans, France 2Department of Geology, Kansas State University *[email protected]

Many ore-deposits are hosted in thermally disturbed carbonaceous materia-rich metasediments. Therefore, the knowledge of the temperature conditions reached by rocks constitutes the requirement to well constrain foreward thermal modeling of geological contexts of interest. In the case of fluid related ore-mineralization, the presence of Carbonaceous Material (CM) could provide accurate information on the thermal event and subsequent maximum temperature. Many approaches based on the characterisation of the organic matter evolution; such as Rock-Eval pyrolysis and reflectance vitrinite; were developed to decipher the peak temperature of rocks. However, these approaches may fail especially for geological contexts that underwent temperatures higher than 200°C. A geothermometric approach based on the Raman Spectroscopy of Carbonaceous Materials (RSCM) has been developed by Beyssac et al. (2002) in the range of 330-650°C and by Lahfid et al. (2010) in the range of 200-330°C. Since then, RSCM geothermometer has been applied at many time and successfully estimated peaks temperatures of metamorphic rocks. The aim of this study is to demonstrate the ability of “hot” hydrothermal fluids migrating through the sedimentary sequence to locally disturb the temperature conditions. For this purpose, we have chosen the Los Burros district in the Franciscan Complex (California, USA), which includes gold-bearing quartz veins that witness a hydrothermal overprint. Using quantitative calibration of the RSCM geothermometry, the maximum temperatures obtained reveal anomalous high values in the Los Burros district. This thermal anomaly seems to be caused by a hydrothermal overprint in the Los Burros district. This work demonstrates that the RSCM geothermometry contribute to elucidate the thermal anomalies induced by a hot fluid-flow.

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New methodological developments to solve the dating problems of the world-class U deposits from the Athabasca Basin (Saskatchewan, Canada) Mercadier J.

Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France [email protected]

The unconformity-related uranium deposits from the Athabasca Basin are qualified as world-class metal deposits due to their exceptional grades, up to 20% U at Cigar Lake or McArthur River (Jefferson et al., 2007; Kyser and Cuney, 2015). Such high grades make them a first priority target for exploration of uranium worldwide. These deposits are the subject of scientific research for more than 40 years, with a significant part of this work done at the CREGU since the pioneer work of Pagel (1975). Dating is one of the most studied areas of research for unconformity-related U deposits, the understanding of the key geological periods and duration of the processes for the formation of these deposits being a key to choose areas to explore and thus to discover new mineralization. Due to the high concentrations of U and Pb in uranium oxides, their U-Pb dating has been extensively used. The dating of clays, mainly based on Ar, has also been applied due to massive clay alteration halo accompanying the U ore within the deposits. The application of these methods has not however made it possible to define a consensus for the chronological framework of the formation of these deposits and the known ages vary on more than 1.5 billion years (ca. 1600 Ma and the present time), without an overall understanding of their meaning. One of the important limitations for the applications of these methods is the easy perturbation of the isotopic systems based on Ar and on the Pb for the two used minerals (clays and uranium oxide). To circumvent these limitations and bring indisputable time constraints, the applications of new dating methods (Re-Os or Sm-Nd for example) and/or the analysis of undated minerals so far (like phosphates, arsenides) are now tested. Such minerals are considered are more robust to fluid circulation post-dating their crystallization and their isotopic dating is possible partly due to the new in-situ analytical capabilities allowing minimizing spot size (to date for example phosphates; Rabei et al. 2017). For this presentation, the results of different tests (Sm/Nd on uranium oxides, Re-Os on arsenides, U-Pb on phosphates) will be presented. One of the important results of these tests was the first Re-Os dating of arsenides from the Cigar Lake deposit. The obtained age (1239 +33/-20 Ma) indicates that the arsenide crystallization post-dated the deposition of the primary uranium oxides (1460-1341 Ma), implying that uranium oxides and arsenides, suphides and sulfarsenides were not precipitated contemporaneously during a single event and that the formation of the Mackenzie LIP at ca. 1270 Ma drove the formation of arsenides, sulfides and sulfarsenides in the Athabasca Basin Jefferson et al. (2007), Geological Survey of Canada Bulletin, 23-67 Kyser and Cuner (2015), GAC-MAC short course Series Volume 46. Pagel (1975), Comptes Rendus de l’Académie des Sciences, 280, 2301-2304 Rabei et al. (2017), Economic Geology, 112, 1483-1507

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Re-Os for Resource Geology – The Unifying Dimension of Time and the Interrogator of Internal-External Fluids in Basins Stein H.1,2*, Hannah J.1,2 1AIRIE Program, 1482 Campus Delivery, Colorado State University, Fort Collins, CO 80523-1482 USA 2Department of Geosciences, University of Oslo, PO Box 1047, 0316 Blindern, Oslo, NORWAY *[email protected]; www.airieprogram.org

Recent work using Re-Os isotope geochemistry has queried long-standing genetic models of resources associated with sedimentary basins. Simple models of sinking brine-rich basins governed by hydraulic gradients and wandering redox fronts must now confront basin-external inputs that were unthinkable, or at least unspeakable, a few years ago. The Re-Os isotopic evidence for fluid invasion derived far beneath crustal basins is indisputable from several angles. Primitive fluids long viewed as non-participatory players in an abyss beneath petroleum systems (and Mississippi Valley-type Pb-Zn deposits) offer critical components that have shaped the resource budget in sedimentary basins. The black-and-white debate of abiotic versus biotic hydrocarbon has set our thinking back, repeatedly, when in fact the question to be asked should have been: What kind of externally derived fluids might be flirting with kerogen, and kicking-off hydrocarbon maturation and migration. We need to look beyond a basin’s depositional dowry and toward rootless fault and shear zone planes with deep access; these contribute to a basin’s fluid budget from below. Especially vulnerable is the rifted margin setting. Widespread alteration of rocks hosting mineral-hydrocarbon resources call out that external actor. How can we use Re-Os isotope geochemistry to tease forth the full resource-forming history ? In this presentation, we will walk through several Re-Os anomalies that directly interrogate long-standing models for petroleum systems. Questions highlighted include : How do we successfully sample geologic time using resource media ? What are the signals for mixing lines versus real Re-Os isochrones ? Why do Re-Os analyses of crude oils sometimes provide meaningless Re-Os ages ? These are topics that the AIRIE Program has intensively investigated with long-term support from the Norwegian petroleum industry (Eni-Norge, Aker BP, Lundin, Equinor). Markey, R.J. et al. (2017) Palaeogeography, Palaeoclimatology, Palaeoecology 466: 209-220. Georgiev, S.V. et al. (2019) Chemical Geology 522: 260-282. Georgiev, S.V. et al. (2017) Earth and Planetary Science Letters 461: 151-162. Georgiev, S.V. et al. (2016) Geochimica et Cosmochimica Acta 179: 53-75. Hurtig, N.C. et al. (2019) Geochimica et Cosmochimica Acta 247: 142-161. DiMarzio, J. et al. (2018) Geochimica et Cosmochimica Acta 20: 180-200.

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In situ LA-ICP-MS U-Pb dating of fluorite Blaise T.1*, Lenoir L.1, Haurine F.1, Brigaud B.1, Barbarand J.1, Pagel M.1 1Géosciences Paris Sud (GEOPS), Univ. Paris-Sud, CNRS, 91405 Orsay Cedex, France *[email protected]

Unconformity-related ore deposits are often resulting from multiple fluid flow events generating mineral dissolution-recrystallization, remobilization and precipitation [1,2]. Dating crystallization events in such complex systems is a challenge, especially in the absence of significant U-bearing phases. Fluorite Sm-Nd geochronology may provide robust age estimates, but errorchrones and imprecise ages may occur. The recent development of in situ U-Pb radiometric dating of common Pb-bearing minerals such as calcite and hematite using LA-ICP-MS offered the exciting possibility to precisely date multiple crystallization events in ore deposits [1]. Here, we present preliminary results on fluorite U-Pb dating from the world-class Pierre-Perthuis unconformity-related F-Ba ore deposit (southeast of the Paris Basin, France). Such research was motivated by the presence of a zonation in fluorite that cannot be individually sampled for Sm-Nd geochronology, and by the absence of calcite or other datable authigenic minerals. Fluorite crystals display a ca. 200μm-thick external growth band in which U concentration varies between 1 to 10 ppm. We have sampled and analyzed this U-bearing growth band by LA-ICP-MS (Sector Field) to evaluate the applicability of the U-Pb small scale isochron dating method [1] in fluorite [3]. Variable U/Pb ratios result in an excellent spread of data in a Tera-Wasserburg 207Pb/206Pb vs. 238U/206Pb diagram. Unanchored linear regression gives a common initial 207Pb/206Pb ratio of 0.810, MSWD of 1.3, and an age and uncertainty of 33.4 ± 1.4 Ma. Analytical precision and accuracy are limited by variable ablation rates in fluorite and by the absence of matrix-match external standards. However, this raw age appears consistent with a known fluid circulation phase during the opening of the European Cenozoic Rift System (ECRIS). We will discuss efforts to improve precision and accuracy of fluorite U-Pb dating. References: [1] Walter B. et al. (2018) GCA 240, 11-42. [2] Chi G. et al. (2018) Econ Geol 113, 1209-1217. [3] Piccione G. et al. (2015) GSA Annual meeting abstract, vol. 47, No. 7, p. 379.

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U-Pb dating of diagenetic carbonates and thermal history of presalt Kwanza basin reveal a major and early heat pulse Godeau N.1,2*, Girard J.P.2, Guihou A.1, Hamelin B.1, Chailan O.2, Deschamps P.1 1Aix Marseille Univ, CNRS, IRD, Coll France, CEREGE, Europole de l'Arbois, Aix-en-Provence, France 2Total, CSTJF, Avenue Larribau, 64000 Pau, France *[email protected]

Since the major hydrocarbon discoveries in the Brazilian margin, the west African counter-part and particularly the offshore central segment has been intensively investigated during the last decade. In this study we report the first U-Pb ages acquired on key diagenetic/hydrothermal calcite, dolomite and silica cements encountered in the pre-salt carbonate/clastic series (Chela and Cuvo formations, Aptian) of the Kwanza basin. Our results provide important constraints on the postpositional history of fluid circulations and particularly the associated thermal regimes in these formations during the opening of the South Atlantic Ocean. Consistent U-Pb ages of ~112 Ma using isotope dilution and laser ablation were obtained for fracture-fill calcite spar associated to early hydrothermalism and moderately hot fluids. The dolomite cement was dated by laser ablation at ~108 Ma, implying pervasive dolomitization of the main reservoir at relatively shallow burial during Albian time with significantly hot fluids (ca.150°C). The silica cement (vein-filling chalcedony) yielded an isotope dilution age of 92 Ma, indicating that the bulk silicification occurred during Turonian time, some ~25 my after deposition, and is therefore not related to surficial microbial processes as previously thought. Despite the fact that we observe similarities in the sedimentological and diagenetic history, U-Pb ages combined with fluid inclusion temperature data provides unique evidence for elevated thermal regimes that developed early after deposition at relatively shallow depth. Particularly this heat pulse is responsible for an early oil migration, few Ma after salt deposition. This significant heat pulse of Albo-Cenomanian age is likely associated with hot fluid circulations triggered by sub-depositional magmatic/volcanic activity, which was previously recognized in pre-salt deposits of the northern Kwanza basin. This study illustrates that coupling U-Pb ages and fluid inclusion temperatures can bring invaluable information to reconstruct a more reliable thermal history of complex reservoirs such as the synrift-sag pre-salt deposits of the South Atlantic margins.

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U/Pb dating and Δ47 temperature determination of Jurassic carbonates: implications for early and burial diagenesis within intracratonic sedimentary basins Brigaud B.1*, Bonifacie M.2, Pagel M.1, Andrieu S.3, Calmels D.1, Blaise T.1, Haurine F.1, Barbarand J.1, Landrein P.4 1GEOPS, CNRS, Université Paris-Saclay, 91405 Orsay, France 2Institut de Physique du Globe de Paris, Université de Paris, UMR 7154 CNRS, 75005 Paris, France 3BRGM, Orléans, France 4Andra, Route Départementale 960, 55290 Bure, France *[email protected]

It is difficult to determine the temperatures of short-lived paleo-circulation from conventional geothermometers in limestones or sandstones because of sample size since these events are often only recorded by microscopic cements (quartz, calcite, etc., smaller than 200 µm) that fill the intergranular space. In addition, the difficulty in dating the main minerals that cause cementation often prevents the identification of a clear chronology of events that drastically impact the reservoir qualities of rocks. This difficulty in dating cements is a barrier to many diagenetic studies, particularly burial diagenesis where very fine cements (< 200 µm) occlude spaces between sedimentary grains. The objective of this presentation is to demonstrate the potential of coupling clumped isotope thermometry (Δ47) and in situ U-Pb dating on early (isopachous or non-isopachous dogtooth cements) and blocky calcite (sparite) filling the intergranular space of Jurassic limestones of the Paris and Aquitaine basins in France. The first stage filling the inter-granular space give in situ U-Pb ages not incompatible with the age of deposition considering the uncertainties. These ages also indicate that these cements can resist, since the Middle Jurassic, to dissolution and recrystallization processes during burial. The coupling of Δ47 temperatures and U/Pb ages obtained on later blocky calcites from the Paris Basin suggests that cementation occurred during two diagenetic stages associated with major tectonic events: (1) Early Cretaceous and (2) Eocene/Oligocene. We report unexpectedly hot brines in thermal disequilibrium with the host-rock, up to 60°C, contrasting with the lower temperatures predicted by conventional thermochronometers. We suggest that the kinetics of mineralization events prevented the recording of short-lived hot fluid flows, resulting in the failure to record atypical circulation in intracratonic sedimentary basins by conventional methods. It appears that these new data allow reconsidering the hypotheses made until now concerning the history of paleo-fluid flows of these basins, and open new perspectives to understand diagenesis and past fluid flow events in many sedimentary basins.

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Fluid circulation recorded by low-temperature thermochronology Barbarand J.1*, Blaise T.1, Brigaud B.1, Boukari C.1, Delpech G.1 1GEOPS, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France *[email protected]

Temperature is a key parameter controlling the diagenetic evolution of sedimentary rocks. Several mechanisms can be at the origin of temperature increase including, (1) deposition of sediments which will be later eroded, (2) thermal flux variation and local magmatism or (3) circulation of fluids in thermal disequilibrium with the surrounding rocks. Deciphering the respective role of these mechanisms is tricky and requires the use of complementary analytical techniques. Implications of this understanding is nevertheless fundamental as it controls - among others - the duration of heat events, the geodynamics of sedimentary basins and the spatial extent of anomalous thermal areas. We test in this study the hypothesis of fluid circulation in disequilibrium with surrounding rocks, in a geological case where evidences confirm its development. Paleotemperatures will be determined using apatite fission-track (AFT) thermochronology. Expected results are an estimate of the volume of rocks which might be affected by such circulation and the requested duration which might be recorded by AFT. Several sites have been sampled in the north-east of the French Massif Central (Morvan) where F-Ba(-Pb-Zn) concentrations are developed. Minimal trapping temperatures measured by fluid inclusion microthermometry (Gigoux et al., 2016) are in the 100-120°C range which represents a perfect temperature window for the use of AFT thermochronology (total track fading for temperatures >100°C). Published data at the scale of the Morvan are grouped at ~200 Ma (Barbarand et al., 2013). Anomalously young AFT ages are recorded close to the Pierre-Perthuis and Courcelles-Fremoy deposits (~100-120 Ma) whereas older ages are recorded in Pontaubert and Antully (~140-160 Ma), not only close to the mineralization, but also at distance (up to ~50m). In the vicinity of the ores, AFT ages are in general in agreement with the regional trend. These ages evidence the total to partial reset of the AFT system and record temperatures in the ~80-110°C range. These results show that the thermal inprint of hot fluids might be recorded, but only at distances and in sites where the circulations have deeply modified these surrounding rocks. On one side, extrapolation of this thermal effect at the scale of sedimentary basins does not appear realistic and might be excluded. On the other side, characteristics of fluid circulation might be approached using AFT, including temperature, duration but also fluid origin. References Barbarand et al., (2013) Tectonophysics 608 1310 ; Gigoux M., et al. (2016) Ore Geology Reviews 72 940

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Effect of Radium mobility on the U-Pb systematic and age determination of U-minerals the Kazakstan roll front deposits Deloule E.1*, Brouand M.2 1CRPG, UMR 5873 CNRS-Université de Lorraine, BP 20, 54501 Vandœuvre les Nancy, Cedex, France 2ORANO MINES, 1 Place Jean Millier - 92400 Courbevoie, France *[email protected]

The U-Pb radio chronometer is commonly used to date the formation of uraninite, a major component of uranium deposit. Uraninite was first used in 1905, when Rutherford determines ages up to 500 Ma in using their He/U ratio, and in 1907 when Boltwood determine the first U-Pb ages (413-535 Ma). During the last decades, in situ U-Pb datation on uraninite has been developed, either in using “chemical ages” with the determination by EMP of U and Pb contents, either in using “isotopic ages” with the determination of Pb and U isotopic ratios and contents by SIMS, providing a large amount of age from Archean up to Cenozoic ages. It is noticeable that the determination of chemical age relies on the assumption that the U-Pb system stay closed over time. This assumption can be supported by many isotopic measurements providing concordant or close to concordance 238U-206Pb and 235U-207Pb ages. In the present study, focused on the 238U, 234U, 230Th and 226Ra behavior, we will see that the U-Pb system may behave as an open system due to the mobility of the uranium series short live elements rather than the U or Pb mobility. The ion probe measurements were performed in using a 5-10 nA O- primary beam, focuses on ≈20 µm diameter areas with the duoplasmatron source, and less than 10 µm areas with a RF source. The Kazakstan deposits are active role fronts. The deposits are mainly formed by uraninite and coffinite, interstitials in sandstone, some times associated with sulfides and organic matters. The data obtained on the Kazakstan role front samples display 238U-206Pb ages ranging from 60 Ka to ≈ 10 Ma. Reported in a Wetherill Concordia diagram, most data points are discordant, with meaningless upper intercept. The measured 230Th/238U are constant within errors for all the samples and similar to the equilibrium reference value, indicating that for all samples, 230Th is at equilibrium with the 238U. Inversely the measured 226Ra/238U ratios are very variable, with Ra contents ranging from 30 to 400 ppb, compared to 360 ppb at equilibrium. For all those samples, 226Ra is depleted and at disequilibrium with the 238U and the 230Th. The 230Th – 238U equilibrium indicates an age of several hundred thousand years for the minerals formation, the 226Ra – 230Th disequilibrium indicates an active selective leaching of Ra from the minerals during the last thousand years These measurements point out the mobility of the radium in hydrothermal systems such as roll front (Kazakstan) and the resulting 226Ra – 238U and 226Ra – 230Th disequilibrium. Therefore the 238U - 206Pb behaves as an open system in these environments, when the 235U - 207Pb seems to behave as a close system. The comparison of the 238U - 206Pb and 235U - 207Pb ages indicates that the Ra loss should have stay active for several hundred thousand years, and not only recently.

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Redox sensitive metals - recorders of fluid and metal sources and transport in sedimentary basins Hannah J.1,2*, Stein H.1,2 1AIRIE Program, Colorado State University, 1482 Campus Delivery, Fort Collins, CO 80525, United States 2Department of Geosciences, University of Oslo, PO Box 1047, 0316 Oslo, Norway *[email protected] ; www.airieprogram.org

Sedimentary basins reflect their protracted and constantly evolving history, including the development of accommodation space, variable depositional input from ever-changing marginal sources, structural deformation during and after sedimentation, and fluid flow through heterogeneous and laterally discontinuous media. Ultimately, the fluids control the construction of economic resources. Successful exploration relies on a firm grasp of where fluids originated, how and when fluids traversed the basin, how multiple fluids interacted, what each fluid was carrying, and how the fluids and their cargo reacted with minerals in the basin fill. That’s a tall order! Geochemical tools aid in this challenge in three ways: (1) tracing the source of the fluids, (2) chronicling the interactions of fluids and solid media, and (3) recording the time of interactions. To be useful, however, chemistry must be locked in, held in a receptacle that fixes an event in space and time. Pitfalls abound, but one principle holds true: geochemical parameters continue to change until the system closes to further chemical exchange. A few examples: Redox-sensitive metals and their isotopes offer an opportunity to track timing and pathways of chemical exchange. For example, Re, Os, Mo, and U, are soluble in oxidizing solutions, but fixed by reduction. As a result, they lock in the conditions (and time) when the system becomes and remains reduced. But with the complexities of fluid flow in a large sedimentary basin, scale becomes important. These metals may remain fixed in an organic-rich shale within the basin. Even if oxidizing fluids course through permeable units above and below, the strong reducing power of the organic matter helps preserve the reducing environment within the shale layer (except perhaps at its margins). We have successfully dated such units using the Re-Os chronometer, and constrained their paleoenvironmental setting with Mo and U concentrations and isotopes – in basins from Eocene to Archean. In contrast, dispersed organic matter, such as plant material distributed within a permeable sandstone, provides reduced microenvironments that may entrap redox-sensitive metals. Continued flow of metal-bearing oxidized fluids results in zoned crystals or irregular distribution of redox-sensitive elements in dispersed organic matter or sulfides. In fortunate cases, the result may be exotically zoned sulfides, recording track-by-track, the passage of fluids. More commonly, the result is chaotic overprints and partial resetting that obscure the basin history. Lu, X. et al. (2017) Chemical Geology 457: 75-94. Georgiev, S.V. et al. (2012) Chemical Geology 324-325: 108-121. Funded by the Norwegian Petroleum Industry (ENI-Norge, Equinor, Lundin, Aker BP).

mailto:*[email protected]

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New calibration data for determination of PVX properties of CO2-CH4-N2 gas mixtures by Raman spectroscopy. Application to natural fluid inclusions. Le V.H.1*, Caumon M.C.1, Tarantola A.1, Randi A.1, Robert P.1, Mullis J.2 1Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France 2Mineralogisch-Petrographisches Institut, Bernoullistrasse 30, CH-4056 Basel, Switzerland *[email protected]

Raman spectroscopy is widely used since the 1970s as an alternative method to microthermometry to analyze fluid inclusions (Frezzotti et al., 2012). Quantitative Raman measurements are generally based on relative Raman scattering cross-section (RRSCS) and the variation of spectral features (peak position, peak area/intensity ratio) as a function of composition and pressure (or density). However, most of the published data were established at low pressure and without evaluating the effect of composition (Burke, 2001). Using these data can lead to considerable errors, especially when applied to geological fluids containing generally several substances at elevated pressure. CO2, CH4 and N2 are among the dominant gas species within a large variety of geological fluids. The experimental data of Seitz et al. (1993, 1996) revealed the variation trends of different Raman spectral parameters of CO2 and CH4 but no calibration was given because the results themselves were quite scattered. The aims of this work are to (i) reevaluate the composition and pressure (density) dependence of the RRSCS of CO2 and CH4 (to N2) by using nowadays performance instruments and (ii) to establish new calibration data for determination of composition, pressure and density of binary and ternary gas mixtures of CO2, CH4 and N2 over a pressure range of 5 to 600 bars. Herein, binary gas mixtures of CO2 and/or CH4 and/or N2 were prepared at different proportions (from 10 to 90 mol%). A high-pressure optical cell system (HPOC) (Chou, 2012) with a transparent microcapillary (Caumon et al., 2014) containing the prepared gas mixtures placed on a heating-cooling stage (Linkam CAP500®) were used for Raman in-situ analyses at controlled PTX conditions. Thereby, the behaviors of spectra features could be investigated to figure out the most reliable quantitative parameter. Our experimental results show that RRSCS of CO2 and CH4 remain constant with varying composition and pressure. It can be used for determining the composition of gas mixtures

osition were demonstrated to be sensitive to composition and pressure (or density). New polynomial equations are derived from our experimental data for pressure and density determination. The latter results are then applied to natural fluid inclusions hosted in quartz from the Central Alps, Switzerland (Mullis et al., 1994). A comparison between PVTX properties of fluid inclusions obtained by Raman and microthermometry measurements were made for validation. References: Seitz et al. (1993) Am. J. Sci. 293, 297–321 Mullis et al. (1994) Geochim. cosmochim. Acta, 58 (10), 2239-2267. Seitz et al. (1996) Am. J. Sci. 296, 577–600

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Burke, (2001) Lithos, 55(1-4), 139-158. Frezzotti et al. (2012) Geochem. Explor. 112, 1–20 Chou et al. (2012) in EMU Notes v.12:6:227–247 Caumon et al. (2014) Chem. Geo. 378-379, 52-61

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Fluids and metal deposition: case studies

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Wednesday, 13th November 2019 Session 2 : Fluids and metal deposition: case studies

14h30 - Keynote lecture - P. Ledru (ORANO-Canada) : Are footprints critical elements for the exploration of unconformity-related U-deposits ? 15h00 - Keynote lecture - M. Hitzman : (ICRAG-Centre, Ireland) New tools provide new insights into the structural and tectono-stratigraphic controls and genesis of base metal mineralization in the Irish Lower Carboniferous 15h30 Coffee break 16h - Grosjean M. : In-situ Cu-isotope systematics of the Copperbelt (DRC, Zambia): variations at different scale 16h15 - Cathelineau M. : Brine-regolith interactions, a key for metal extraction and re-deposition near unconformities 16h 30 - Essarraj S. : Atlasic sedimentary basins as a source for brines at the origin of the Moroccan silver-base metal deposits 16h45 - Bastrakov E. : An Integrated Perspective on Sediment-hosted Base Metal Mineral Systems : From Lithospheric Architecture to Fluid Chemistry 17h00 - Grebenkin N. : Uranium metallogeny of the late Precambrian framing of the southern part of the Siberian Craton Posters Bonhoure-Kafi J. : The manganese deposits of the Franceville Basin, Gabon Wafik A. : The Skouraz banded iron formation, Bou Azzer inlier, Central Anti-Atlas, Morocco : implication on fluid circulation and metal deposition Michels R. : Geochemical characteristics of kerogen in Kupferschiefer : relationship to the mineralisation process 17h30 -19h Poster session with refreshments

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Are footprints critical elements for the exploration of unconformity-related uranium deposits? Ledru P. Orano Canada, 810 45th Street, Saskatoon, S7K 3Z8, Canada [email protected]

Exploration of unconformity related uranium deposits mainly focuses on identification of lithological, geochemical and mineralogical footprints with an empirical approach that more footprints equals greater chances of finding a deposit. The information collected defines pathfinders that are a priori vectors towards mineralization. Common practise for unconformity mineralization drilling programs is to target conductive horizons near the unconformity trying to quantify alteration haloes and geochemical pathfinders. Less focus is put on physical properties and characterization of permeability of structures and lithologies at different scales. Experience from historical discoveries, exploration of fertile trends (i.e. along conductors) and recent discoveries in non-conventional targets, provides opportunities to reassess some of the pre-conceived ideas and empirical models. From an industry perspective, this re-evaluation is challenging as there are technical bottlenecks and methodological frontiers to face, plus scientific questions that may need significant R&D. On the other hand, it can provide a baseline to reassess strategies and to identify/prioritize the most appropriate technologies at different stages and scales of exploration, from the early regional assessment to resource estimates. Several critical elements in exploration for unconformity-related uranium deposits may not be directly linked to traditional “footprints”. Changes in paradigms may be necessary to include not only information collected from drill core but also the architecture of the main structures at regional scales and their ability during successive reactivations to enhance permeability of the systems through organized and focused fluid-flux. While footprints provide rather static observations that mainly illustrate the variety of ore deposit models, scientific and drilling targets should also focus on the characterization of the mineral systems, aiming to understanding the dynamics of paleo-hydrothermal systems and conditions for preservation of the deposits using modern geological analogs. In this perspective, the distribution of physical properties and characterization of the permeability of the systems are critical to constrain geophysical modeling and decrease the uncertainty of 3D geological models.

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New tools provide new insights into the structural and tectono-stratigraphic controls and genesis of base metal mineralization in the Irish Lower Carboniferous Hitzman M.1*, Torremans K.1, Güven J.1, Conneally J.1, Doyle R.1, Doran A.1, Hollis S.1, Walsh J.1, Kyne R.1,2, Turner O.1,3 1Irish Centre for Research in Applied Geosciences, School of Earth Sciences, University College Dublin, Dublin, Ireland. 2Teck Resources Limited, Suite 3300, Bentall 5 , 550 Burrard Street , Vancouver, B.C., Canada V6C 0B3 3Ivanhoe Mines Exploration, 1148-6 Avenue de la Libération, Lubumbashi, Democratic Republic of Congo *[email protected]

Lower Carboniferous strata in Ireland host a number of important zinc-lead deposits.

iCRAG’s mandate is to utilize research to aid industry in discovering additional deposits.

We utilise regional and deposit-scale geological, geochemical, reflection seismic, drillhole

and geophysical data to better define the structural and tectono-stratigraphic controls for

mineralisation as well as investigate mineralisation processes. Regional analysis, primarily

using reflection seismic data, indicates that extension during the Late Courceyan was

distributed across the Irish Midlands basin through an initially dense network of segmented

normal faults, which with increasing extension concentrated on fewer, but larger and faster-

growing faults during lower Visean time. These large basin-bounding faults strongly

controlled the internal architecture of sub-basins and distribution of sedimentary facies and

provided the means of tapping fluids from within the basement, as clearly demonstrated

by recent lead isotopic analyses. Quantitative analysis of high quality mine datasets,

including Lisheen, Silvermines and Navan, has elucidated the evolution of several

complexly segmented fault systems. The scale of relay ramps between fault segments had

a profound impact on structural evolution and fluid flow. Metal distribution patterns from

Lisheen and SIlvermines demonstrate that small-scale breached fault relay zones acted

as vertical conduits and feeder zones to individual orebodies with the position of such

feeders changing through time, in line with the evolving structural framework.The

fundamental process of mineralisation in the Irish Midlands involving the mixing of hot,

metal-bearing hydrothermal fluids with cooler fluids carrying biologically reduced sulfur

derived from seawater sulfate has been known for some time. Recent research is

demonstrating the complexity of the mineralizing process. Despite the wealth of new data,

fundamental problems remain. iCRAG is attempting to identify geochemical vectors toward

sites of mineralisation along different fault arrays. It is also looking at the importance that

regional heating, evidenced by Visean volcanism, may have played in the development of

this world-class mineral district.

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In-situ Cu-isotope systematics of the Copperbelt (DRC, Zambia): variations at different scales Grosjean M.1,2*, Turlin F.1,3, André-Mayer A.S.1, Eglinger A.1, Muchez P.4, Deloule E.5, Debruyne D.4,6, Voudouris P.7, Rouxel O.8 1GeoRessources, Université de Lorraine, CNRS, CREGU, France 2Now at: Department of Earth Sciences, University of Geneva, Geneva, Switzerland 3Now at: Université du Québec à Montréal, Département des Sciences de la Terre et de l'Atmosphère, Montréal, Canada 4KU Leuven, Geodynamics and Geofluids Research Group, Department of Earth and Environmental Sciences, Leuven, Belgium 5CRPG, CNRS, Université de Lorraine, France 6Now at Geological Engineering Department, Federal University of Pelotas, Rio Grande do Sul, Brazil 7National and Kapodistrian University of Athens, Faculty of Geology & Geoenvironment, Dept. of Mineralogy and Petrology, Athens, Greece 8IFREMER, Laboratoire Cycles Géochimiques et ressources, Brest, France *[email protected]

The internal zone of the Central African Copperbelt (CAC) is characterized by several mineralization stages. Cu isotope signatures from the Lumwana deposit were analyzed by secondary ion microprobe (SIMS). Chalcopyrite and bornite from the two main mineralization stages display both δ65Cu values between -1.37±0.23‰ and +2.95±0.19‰. These results do not allow to determine a specific metal source. These δ65Cu signatures are compared to Cu-Co deposits of the external zone of the CAC that are characterized by several mineralization stages. The latter stages involve remobilization of an earlier mineralization during the Pan-African orogeny. Copper-sulfides of the CAC present a wide range of more than 6‰ in δ65Cu values. Deposits from the external zone of the CAC have mostly negative δ65Cu values, whereas the internal zone shows 65Cu enrichment. The fractionation at the grain scale can reach up to 3‰. This is significant when compared to the regional scale fractionation. This in-situ method also reveals equilibrium fractionation between the different Cu-phases. Mechanisms for such fractionations remain to be constrained.

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Brine-regolith interactions, a key for metal extraction and re-deposition near unconformities Cathelineau M.*, Boiron M.C. Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France *[email protected]

Near unconformities, the presence of an eroded basement with regolith or weathered surface generally found down to a few tens of meters below the unconformity is the first key factor of the metal extraction during subsequent brine circulation. Thus, during peneplanation, most minerals are deeply altered, and subsequently release metals: Pb and Ba are issued from feldspars, F and probably Zn from biotite/ chlorite, U from uraninite and monazite, sometimes converted into REE-carbonates or Al-sulphate-phosphate. Metals are then sorbed onto clays and Fe–Ti oxides and hydroxides and ready for subsequent extraction during later on processes. In Western Europe, the main metal reservoir is thus the Hercynian terrane, weathered during emersion at the Triassic period. The latter produced a thick weathered and oxidized zone, well exposed in basement quarries showing the unconformity. This volume may be considered as the main reservoir of metals, as the latter are difficult to extract from fresh rocks. The presence of evaporites within the first tens of meters of the transgressive sedimentary sequence on the basement constitutes the second key factor for most deposits from Western Europe, and Morocco, and produce primary K–Mg (Na) rich brines by squeezing, and/ or secondary brines by leaching. Such brines are also recognized in most significant unconformity related U deposits over the world, and may originate from upper levels now eroded. Brines penetrating the weathered basement have all the features (temperature, chloride content, temperature) required for an optimal metal extraction and complexation, as shown by the increased metal concentrations in fluids at increasing chlorinity and temperature. When interacting with the basement, the Na(Mg)-dominated brine may drastically evolve towards a Ca–Mg brine. The ore deposits are then controlled by fluid mixing, such as the mixing of Ca2+ rich fluids with F rich fluids for fluorite deposit, the sulphate reduction or H2S introduction for the precipitation of Pb-Zn sulphides, redox processes for the deposit of U, the mixing between sulphate rich and Ba2+ bearing solutions for barite. The convection and the confinement of the processes could be favoured by the presence of a cap-rock such as clay-rich formations, and the presence of HHP granites within the basement for additional heat production and accumulation. The circulation of brines near the unconformity both in the weathered basement and the high permeability in conglomerates and coarse grain formations at the base of the sequence, is followed by deep penetration of brines through faults and dense networks of microfractures within the basement. As a consequence, ores occur both nearby the unconformity, with specific interactions depending on lithologies (silicification in silico-clastic reservoirs, dolomitization in carbonate reservoirs), and below the unconformity, along major faults and drainage zone, but are related to the same ore processes.


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Atlasic sedimentary basins as a source for brines at the origin of the Moroccan silver-base metals deposits Essarraj S.1*, Boiron M.C.2, Cathelineau M.2 1Laboratoire Géoressources, URAC 42, Faculté des Sciences et Techniques, Université Cadi Ayyad, BP 549, Marrakesh, Morocco 2Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France *[email protected]

Fluid circulations related to ore deposition have been investigated for several Moroccan deposits exploited for silver as major ore component. Studied deposits are the Ag-Hg Imiter and Zgounder (the Anti-Atlas Mountain) currently operated and the Roc Blanc and Koudia El Hamra Ag– base metal deposits (Jebilet Massif). Ores are present as quartz – carbonate veins crosscutting Precambrian to Paleozoic volcanosedimentary series metamorphosed and deformed during Panafrican (Anti-Atlas) to Hercynian (Jebilet) orogeneses. Two major multiphase ore stages are distinguished for all these deposits. The first stage corresponds to the deposition of Fe-As-(Co-Ni) sulfides in deformed quartz veins associated with the circulation of relatively low salinity and high temperature H2O-CO2-CH4-N2 fluids from metamorphic origin (<10 wt% NaCl eq, > 350°C). The second and economic stage corresponds to the deposition of base metals (Zn, Pb, (Cu) sulfides) followed by silver ores in quartz-carbonate veins. Silver ores consist in native Ag, Ag-Hg amalgam, Ag sulfides and sulfosalts. Silver ore stage is related to the circulation of brines (17 to 40 wt % NaCl-CaCl2 equiv., average T: 200 – 240°C) under hydrostatic conditions. LA-ICP-MS analyses showed that ore brines are Ag rich (Ag: up to 3,200 ppm, average 900 ppm for Imiter; up to 1000 ppm for Roc Blanc and up to 350 ppm for Zgounder). Halogene (Cl, Br) signatures, isotopic data (O, H) and paleogeographic/structural considerations indicated that silver ore fluids are basinal sedimentary brines. Brine circulations clearly postdate Precambrian to Paleozoic metamorphic-magmatic host series ruling out any genetic relationship with them. We proposed Triassic Atlasic basins coeval with Central Atlantic opening as a main source for brines (Essarraj et al., 1998, 2005, 2016, 2017a, 2017b, Nshimiyimana et al., 2018). References Essarraj, S. et al., 1998. Eur. J. Mineral 10, 1201 - 1214. Essarraj, S. et al., 2005. J. Afr. Earth Sci. 41, 25 - 39. Essarraj, S. et al., 2016. Econ. Geol. 111, 1753 - 1781. Essarraj, S., et al., 2017a. J. Afr. Earth Sci. 127, 175 - 193. Essarraj, S. et al., 2017b. Econ. Geol. 112, 1273 - 1277. Nshimiyimana, F. et al., 2018. . Afr. Earth Sci. 145, 1 – 17.

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An integrated perspective on sediment-hosted base metal mineral systems: from lithospheric architecture to fluid chemistry Bastrakov E.1*, Czarnota K.1, Huston D.1, Champion D.1, Hoggard M.2, Hauser J.3, Siegel C.3, Richards F.4, The M.1, Thorne J.1 1Geoscience Australia, Canberra ACT 2601, Australia 2Department of Earth and Planetary Sciences, Harvard University, Cambridge MA 02138, USA 3CSIRO Mineral Resources, Kensington WA 6151, Australia 4Imperial College London, London SW7 2AZ, UK *[email protected]

Exploring for sediment-hosted base metal deposits requires an integrated mineral systems approach. Most of these deposits formed at 1820-1540 Ma or 460-320 Ma (Huston et al., 2015, Zinc 2010 Proceedings, 3-18). This temporal distribution can be combined with the spatial association of these deposits with global- to province-scale geophysical and geochemical gradients. Czarnota et al. (2019; doi:10.31223/osf.io/2kjvc) found that globally 85% of these deposits, including all giant ones (> 10 Mt of metal), occur within 200 km of the edges of thick lithosphere, mapped using surface wave tomography. This observation is corroborated by other datasets. In the North Australian Zinc Belt and Western Cordillera (North America) the deposits are associated with a gradient in lead isotope μ values, and in the North Australian Zinc Belt the lithospheric thickness gradient is accompanied by crustal thinning across a major crustal boundary, a gradient in long wavelength gravity data and possibly a gradient in magnetotelluric data (e.g. Huston et al., 2019, SGA 2019 Proceedings). These features are consistent with lithospheric thinning that controls basin genesis and thereby the distribution of contained deposits. Global surface-wave tomography provides a framework for identifying fertile regions for targeted mineral exploration, which can be further reduced at the province-scale using lead isotope, gravity or, possibly, magnetotelluric data complemented by structural and stratigraphic studies. In the North Australian Zinc Belt published (Cooke et al., 1998, Economic Geology 93:1237-1263) and new data suggest extensive alteration of mafic volcanic rocks at the base of the mineralised superbasin. These volcanic rocks have been pervasively altered to chlorite ± K-feldspar ± hematite assemblages and have lost 50-90% of zinc. These data allow quantitative numerical modelling to reconstruct fluid events, compositions and alteration processes. The questions to answer are: (1) whether the observed geochemical changes can be attributed to a single large-scale flow of fluid of a particular composition; (2) whether the observed alteration assemblages can be attributed to particular geochemical clusters; and (3) whether (2) can be matched to (1). We have developed a numerical workflow that includes a clustering technique to identify the major alteration zones in the observed data and derivation of a misfit function between the model predictions (fluid infiltration accompanied by water-rock interaction) and the characteristics of the clusters (Bastrakov et al., 2019, Goldschmidt Abstracts, 213). We focus on a series of the strongly altered basalt units, a probable source of Zn and Cu for the deposits of the

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belt. Of all the geochemical models derived from variable fluid compositions, the best performing ones implicate potassium-rich fluids that might have resulted from either an evaporitic origin of brines or their interaction with felsic rocks prior to mobilisation of Zn and Cu from basalts.

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Uranium metallogeny of the late Precambrian framing of the southern part of the Siberian craton Grebenkin N.*, Pechenkin I. All-Russian Scientific-Research Institute of Mineral Resources. 31, Staromonetniy per., Moscow, 119017, Russia *[email protected]

The southern part of the Siberian craton is one of the most prospect in Russian of area for identifying of the unconformity-type uranium deposit. The geological settings of this area are similar to the known uranium-ore regions of the world – Alligator-River (Northern Australia) and Athabasca (Canada). Unlike the world's uranium ore regions, south part of Siberian Craton represents the boundary of its basement with the Baikal orogen. In this region known small uranium deposits tend to localize on the border of uplifts and depressions. The uplifts compose of crystalline schists, gneisses, granitoids and pegmatoid formation, geochemically specialized in uranium. The margin parts of such uplifts are covered by Riphean sediments, which form the large troughs. The Pb, Zn, Cu, Ni, Mn and Fe deposits tend to localize in the Central parts of the troughs. Tectonic-magmatic processes that repeatedly appeared here in the Riphean time were associated with the introduction of numerous basic intrusions. According to the results of research was developed evolutionary-geological model of Rifean U, Pb, Zn, Cu, Ni, Mn and Fe deposits. Pre-ore stage (KR2) is associated with Early Proterozoic granitization processes with the granite-gneiss domes formation and orogeny. Pegmatites, quartz-feldspar-biotite, quartz-albite-microcline metasomatites with not industrial uranium-thorium-rare-metal-rare-earth mineralization were formed in the marginal parts of the uplifts at the final stage of granitization. Ore-forming stage (RF1). Ancient dissected terrain with mountain elevations and troughs contributed to the erosive-denudation processes development. At the turn of the early middle Riphean was marked by the manifestation of basic magmatism and hydrothermal waters. Uranium was extracted from specialized rocks (pegmatites, quartz-feldspar-biotite metasomatites) and transferred to the upper parts of the section, where it was deposited within the carboniferous strata. At the same time, simultaneously with the processes of basalt magmatism in the depression iron and manganese deposits were formed. In some cases, tectonic processes have contributed to a multi-amplitude block shifts and dome structures uplifting. As a result, Lower Riphean deposition and uranium deposits were subjected to erosion and denudation. This material accumulated in depression. The next Late Riphean tectono-magmatic activization (RF3) was marked by the intrusion of the dikes, sills, and large amounts of dolerites. Apparently at that time uranium concentrations were redistributed within the Early Riphean objects, and additional metals were supplied from a geochemically specialized basement. These processes contributed to the formation of a rich uranium mineralization. The Pb, Zn, Cu, Ni, Mn and Fe deposits were formed in depressive structures. In subsequent years, the study area has experienced repeated tectonic activity. This caused the mountain region rising, and

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intensified erosion and denudation processes resulting led to the denudation of the Riphean formations, and in some places of the basement rocks. This is evidenced by rarely encountered rich ore debris. References: Grebenkin N.A. et al. (2018) Prospect and protection of mineral resources (2018) 7: 22–30 Mashkovtsev G.A. et al. (2015) Prospect and protection of mineral resources (2015) 4: 3–16

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The manganese deposits of the Franceville Basin, Gabon Bonhoure J. 1*, Pourret O.1, Corbineau L.1, Feneyrol J.2, Bosc R.2 1UniLaSalle, 19 rue Pierre Waguet - BP 30313 - F-60026 Beauvais Cedex, France 2Arethuse Geology, 1060 Rue René Descartes, 13290 Aix en Provence, France *[email protected]

The Franceville Basin is composed of unmetamorphosed Paleoproterozoic sedimentary series unconformably deposited on an Archaean crystalline basement [1]. The carbonate series intercalated with black shales are enriched in manganese [2], and constitute the protore at the origin of secondary manganese concentrations now exploited. The manganese (Mn) deposits of Biniomi and Moanda (Gabon) are located 75 km apart from one another within lateritic plateaus. Even if the Moanda site has been well studied, Biniomi site is still poorly understood. These enrichments are induced by the manganese high redox potential, which is concentrated in sedimentary formations as early as the oxygenation of the Earth [3]. Mn, essentially precipitated into carbonates and silicates, is taken up by the supergene alteration to form oxides and oxyhydroxides of Mn (III/IV) [4] [5]. Their study showed in particular the presence of pyrolusite (MnO2), lithiophorite [LiAl2Mn3O6(OH)6], nsutite [Mn4+0.85O1.7Mn2+0.15(OH)0.3], manganite (MnOOH), associated with iron and aluminum oxides and oxyhydroxides (goethite, hematite) as well as residual silicates. The elemental distribution in the Biniomi zone is characterized by different behaviors between iron and manganese along the lateritic profile: higher levels (lateritic crust, pisolith, upper laterite) are enriched in Fe and contain little Mn, while the underlying levels enriched in Mn with few Fe. Finally, REE patterns fractionation along the profile and cerium anomalies, highlight the influence of redox phenomena in Mn precipitation processes. References: [1] Thiéblemont, D. et al. (2014). Journal of African Earth Sciences 99: 215–227 [2] Weber, F. (1968). Mém. Serv. Carte Géol. Als. Lorr. 28. 328 p. [3] Sawaki, Y. et al. (2017). Geoscience Frontiers, 8(2): 397-407 [4] Johnson J.E. et al. (2016). Geochimica et Cosmochimica Acta 173: 210–231 [5] Maynard J.B. (2014). Treatise on Geochemistry, Second Edition, vol. 9: 327-349

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The Skouraz banded iron formation, Bou Azzer inlier, Central Anti-Atlas, Morocco : implication on fluid circulation and metal deposition Wafik A.1*, Chatiby R.1, Bajbouji M.1, Oumouhamed A.1, Admou H.1, Cauzid J.2, Baoutoul H.3, Bajjdi A.3, Benhammou A.3, Bousekri I.3 1DLGR Laboratory, URAC 43, Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakech, Morocco 2Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France 3Somifer Bleida Managem Group, Twin Center, Casablanca, Morocco *[email protected]

Field survey of the Skouraz volcano-sedimentary Complex presents to us clear evidence

of deformed iron deposit of Neoproterozoic age. Oxides are the dominant iron mineralogy

and it's presented by Hematite, either under the shape of coarse grains or a band-like

shape. Secondly, geochemical analyses were regarded as evidence of a BANDED IRON

FORMATION since the samples collected in iron bands exceed 15%wt established by (14)

as a lower limit for BIF. The major elements tendency is in coherence with the literature

data, especially those of the Rapitan type because a P2O5 anomaly is observed in this

type of BIF. Presence of chlorite could lead us to the pressure and temperature of

metamorphism. Since BIF are of chemical origin their Al content must be of lower rate not

exceeding 1% but the presence of chlorite could explain this high ratio. Very poor values

of trace elements and S have observed in our samples denied a volcanic source like

Algoma type and absence of oolithic texture which is typic of Lake Superior type, could

corroborate a Rapitan type to Skoura iron rich deposits, therefore, a glaciation should be

placed in the late Lower Cryogenian early Upper Cryogenian as the age attributed to

Skouraz volcano-sedimentary Complex.Thirdly, Electron microprobe analyses plotted in

the discriminate diagrams and spider diagram in are pieces of evidence of a BIF deposit

since they follow the trend observed for this type of deposits.


54

Geochemical characteristics of kerogen in kupferschiefer relationship to the mineralization process Michels R.1*, LorgeouxC.1, Privalov V.1, Morlot C.1, Kamradt A.2 1Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France 2Economic Geology and Petrology Research Unit, Institute for Geosciences and Geography, Martin-Luther-University Halle-Wittenberg, Von-Seckendorff-Platz 3, D-06120 Halle, Germany *[email protected]

The Kupferschiefer is a wellknown polymetallic resource deposited within Permian basins of central Europe. It is the largest sediment-hosted accumulation of copper ores in the world. The sedimentary deposit is composed of three major facies, from bottom to top: sandstone (Rotliegend), black shale, limestones and evaporites (Zechstein). The marine black shale is a calciferous, carbon-rich marly clay with both, finely dispersed and vein-type ore consisting partly enriched of sulfidic copper minerals, mainly chalcocite, bornite, and chalcopyrite. Additionally, this ore also contains up to 20 other metallic and metalloid elements. The black shale contains up to 20% of organic carbon, which is a significant fraction of the whole rock. Some major part of the ore within is finely distributed along bedding planes. Questions remain about the relationship of this organic matter to the ore content. While literature mainly focused on the free hydrocarbons (studied as geochemical tracers), data indicate that 99.7% of the organic matter occurs as a solid called kerogen. Yet, very few literature actually studied the relationships of the kerogen to the ore finely dispersed within the black shale. Studied samples belong to the reduced part of the ore deposit (outside the Rote Fäule, which is a secondary redox front responsible for major metal redistribution). Sampling was performed in the Sangerhausen district (Roehrig Shaft, Thomas Muentzer Mine, Germany) as well as in the Rudna and Polkowice mine in the Lubin-Sieroszowice mining district (Poland). The kerogen has been studied using molecular geochemistry (mainly pyrolysis-GC-MS). Data reveal that kerogen is of marine origin. Geochemical differences between Sangerhausen samples and samples from Rudna and Polkowice Mine are mainly linked to the burial (i.e. heating history) within the respective sedimentary basins. Yet, scattering of data within samples sets of each mine, sometimes collected within a same horizon have to be related to local interactions with the mineralizing fluids. The most important is thermochemical sulfate reduction (TSR), which induces a significant decrease of the aliphatic/aromatic ratio of kerogen. This implies that there is a genetic relationship between kerogen and the sulfides-rich ore. Detailed analysis using SEM and X-ray tomography reveal the spatial distributions of the organic matter and sulfides. As sulfide content of the shale increases, initially isolated ore phenocrysts increase in size, appear more sub-rounded and eventually become coalescent. This indicates crystal growth under compromised conditions. Indeed, growth is controlled by TSR, which occurs within the newly formed porosity of kerogen layers. Consequences of these data onto the understanding of ore deposition and control of its spatial distribution at microscopic scale will be discussed.

56

Fluid circulations and

geodynamics : the example of

the Pyrenees

57

Thursday, 14th November 2019 Session 3 : Fluid circulations and geodynamics: the example of the Pyrenees Session dedicated to results about « fluids and faults » in the context of the Pyrenees mountain range, presenting works done at CREGU and in other research centres 8h30 - Keynote lecture - Y. Lagabrielle (Geosciences Rennes) : Peridotite - crust- sediments interactions in the frame of mantle exhumation. The Pyrenees in Cretaceous times 9h - Keynote lecture - E. Gaucher (TOTAL) : Fluids and water-rock interactions: A synthesis in the W-Pyrenean Foothill basin 9h30 - Boiron M. C. : Paleo-Fluid circulation in the Pyrénées during extensional tectonics 9h45 - Boulvais P. : Stable isotope geochemistry applied to the characterization of fluid-rock interaction during mantle exhumation at rifted margins 10h - Barré G. : Unraveling fluid circulation in western Pyrenees (France) 10h15 - Bahnan A. : Fluid circulation and diagenesis of carbonate reservoirs relative to the geodynamic history of a foreland basin: Example of the Deep Lacq reservoir (Aquitaine basin, SW France) 10h30 - Coffee break Posters González Esvertit E. : The Upper Ordovician unconformity in La Molina area (Pyrenees) : Deformation study and formation conditions of the associated quartz veins Coltat R. : Carbonation of exhumed mantle rocks at rifted margins: insights from Alpine Tethyan analogues Belkacemi A. : Stratigraphic sequential analysis and oil interest of the upper Silurian - lower Devonian (F6 reservoir) of Southeastern Algerian Sahara : case of Hassi Mazoula field and its bordering regions (Illizi basin - Algeria) Yensepbayev T. : Paleotemperature and Paleopressure of the Paleozoic rocks of the eastern and southeastern parts of Precaspian basin and the Sakmara zone of Southern Urals based on the study of gas-water inclusions

58

Peridotite - crust - sediments interactions in the frame of mantle exhumation. The Pyrenees in the Cretaceous Times Lagabrielle Y.1*, Asti R.1, Fourcade S.1

1Université de Rennes, CNRS, UMR 6118 Géosciences Rennes, Campus de Beaulieu, 35000 Rennes, France *[email protected]

We propose a review of the architecture and structural/thermal evolution of the basins which opened during the mid-Cretaceous times along the Iberia-Eurasia plate boundary. These basins exhibit peculiar synclinal-shaped profiles and are devoid of prominent fault blocks. The top of the basement is characterized by gentle slopes which dip symmetrically towards the center of the basin. The architecture of these “smooth-slopes rift basins” results from the thinning of the central basin continental crust under dominating-ductile deformation in greenschist facies conditions. The pre-rift sequences of the studied basins all include a thick basal low-strength Upper Triassic evaporites and clays layer (Keuper group) which allows mechanical decoupling and gliding of the Mesozoic cover during crustal thinning. Thus, the pre-rift sequence remains in the center of the basin as the continental crust is laterally extracted. In response to hyper-thinning and horizontal extraction of the continental crust, hot mantle material approaches the detached pre-rift cover. The major consequences of this central basin thermal anomaly are twofolds: (i) ductile deformation of the thinned continental crust beneath the detached pre-rift units, and (ii) development of HT-LP metamorphic conditions in the pre-rift sediments and at the base of the syn-rift flysch levels. Continental stretching is accommodated by shearing in the bulk upper and middle crust leading to the formation of thin tectonic lenses of mylonitic crustal material remaining welded on the exhuming mantle. The mantle exhumation process (with partial exposure of serpentinized peridotites to the seafloor) drives the circulation of fluids from various origin. Metasomatic and metamorphic assemblages which testify a variety of fluid-rock interactions are briefly listed and described. Finally, we point the genetic link between the distribution of evaporite-bearing pre-rift sedimentary formations and the development of smooth-slopes rift basins.

mailto:[email protected]

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Fluids and water-rock interactions: A synthesis in the W-Pyrenean Foothill basin Gaucher E.C.1*, Barré G.1,2, Lefeuvre N.1,3, Laurent D.1,4, Bahnan A.1,4, Motte G.1,2, Quesnel B.1,4#, Tremosa J.5, Calassou S.1 1Total, CSTJF, Pau, France 2University of Pau & Pays de l’Adour, Pau, France 3University of Grenoble, France 4CREGU and University of Nancy, France 5BRGM, Orléans, France *[email protected] #present address: University of Laval, Quebec, Canada

In the West-Pyrenean Foothill basin, the sedimentary rocks have recorded a complex fluids history. In this area, we have demonstrated the presence and the action of sedimentary brines, diluted water produced by clay compaction and dehydration, Oil and thermogenic gases, H2S, CO2 from volcanic origin and organic matter degradation, deep abiotic gases, meteoric waters. This variety of fluids evolves in a structured basin. The asymmetrical architecture of the Pyrenees is determined by the plate tectonic. This asymmetry determines also an asymmetry in the thermicity and in the types of fluids observed in the two flanks of the mountain range. For example, almost no dolomitization is observed in the South basins, neither thermogenic H2S. To the North of the Pyrénées, the thermicity is not only burial dependent but shows clearly the contribution of additional calories linked to hydrothermal circulations. The thermic asymmetry of the orogeny explains also why 2.5GBoe of hydrocarbon have been found in the Aquitaine basin for only 0.1 GBoe to the South. The type of fluids and their temperature determined also the fracturing and the dolomitization of the Mesozoic formations, two processes that are essential for the development of the reservoirs properties. The presence of sulfate brines and hydrocarbons was responsible of a huge H2S production probably very early during the rifting phase. The H2S oxidation into sulfuric acid is responsible of an intense hypogenic karstification that has been identified for the first time in Aquitaine. Finally, the discrete but real presence of abiotic gases (CH4, H2) reveals a past or active serpentinization process in the deep part of the basin. References : Barré et al., (2019) WRI Conf. Tomsk, Russia. Calassou et al., (2018) RST Conf. Lille, France. Chevrot, S. et al. (2018) Scientific Reports, 8, 1. Elias Bahnan A. et al. (2020) Marine and Petroleum Geology 111, 676–694. Renard S. et al. (2019). Chemical Geology 508, 30–46

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Paleo-fluid circulation in the Pyrenees during extensional tectonics Boiron M.C.1*., Quesnel B.1, Cathelineau M.1, Truche T.2, Kouadio M.1, Gaucher E.C.3

1Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France 2Université Grenoble Alpes, CNRS, ISTerre, F-38000 Grenoble, France 3TOTAL, CSTJF, avenue Larribau F-64018 Pau, France *[email protected]

The characterization of fluids having circulated along the North Pyrenean fault zone has been investigated in order to identify the fluids reservoirs connected to this major structural discontinuity during Pyrenean history during Albo-Cenomanian period.The extended zone of investigation includes Ariège, the area of the giant Trimouns talc deposit and its surroundings, as well as other localities at regional scale, to the western part of Pyrenees. The Trimouns talc-chlorite deposit is the most prominent occurrence of Albian metasomatism in the Pyrenees, with the largest talc deposit worldwide. This deposit is located on a major fault zone in the basement and at a lithological contact between the Saint Barthelemy gneissic dome and the overthrusted cover consisting of marbles, dolomitic formations and blackschists. Fluids as fluid inclusions in dolomite, quartz and calcite are brines with 20 to 30 wt % eq. NaCl (Boiron et al., 2005, 2007, Quesnel et al., 2019). Their chemical and isotopic features (Cl/Br close to 300 to 600, 37Cl ranging from -0.6 to 0.2‰) are compatible with primary brines expelled from Triassic evaporites. Secondary brines resulting from halite leaching, probably by marine waters are also identified. The hypothetic contribution of water uptake and chlorine enrichment at the contact with mantle rocks is not excluded but difficult to prove. Homogenization temperature close to 200°C, combined with chlorite paleothermometer estimate allow to constrain pressure around 200 MPa, and temperature close to 350°C. Strong interaction with the carbonaceous units (calcite, organic matter) and basement rocks are attested by

D signatures on quartz and chlorite associated with talc and by the presence of gas (CO2, N2 and CH4) in the brines. Similar brines brines have been also recognized in the surroundings of Trimouns as evidenced by fluid inclusions in quartz-calcite veins located at southern part of the deposit (Caussou) and attests of presence of significant amount of fluid along the deformation zone south to the North Pyrenean fault. Along a profile of more than one hundred kilometers at the regional scale, to the west, brines were recognized almost in all localities where newly formed quartz could be sampled. This attests of the pervasive penetration of Triassic brines. Trias was present as the discordant formation rather thick evaporites (gypsum, halite) were covering the overall basement surface. It acted as a slipping/ shearing/ brecciating zone in relation with tectonics of the hyper-extension during the episodes of thinning of the continental crust, and exhumation of the sub-continental mantle during the Albo-Cenomanian period. References Boiron M-C, et al., (2005) Proceedings ECROFI XVIII, Siena, Italy Boiron, M-C., et al., (2007) Proceedings ECROFI-XIX University of Bern, Switzerland Quesnel et al., (2019) Geofluids, https://doi.org/10.1155/2019/721305

64

Stable isotope geochemistry applied to the characterization of fluid-rock interaction during mantle exhumation at rifted margins Boulvais P. University of Rennes 1, Géosciences Rennes – UMR 6118, 35042 RENNES, FRANCE [email protected]

Sub-continental lithospheric mantle rocks are exhumed in the distal part of magma-poor passive margins. Besides ubiquitous serpentinization, fluid circulation is recorded through the carbonation of exhumed mantle rocks (forming the so-called ophicalcites), the alteration of pre-rift and syn-rift sediments and the formation of mineral and metal deposits. In the proximal parts of rifted margins, the continental remnants also interact with the fluids involved in such tectonic setting. In the Pyrenees, the stable isotope tool has been widely used to constrain the conditions of these fluid-rock interactions during lithospheric extension and the associated mantle exhumation during the Cretaceous. Widespread ophicalcitisation has been described by Clerc et al. (2014), alteration of the Mesozoic cover by fluids evolved from serpentinization has been characterized by Corre et al. (2018), the talc-chlorite deposits have been studied by Boulvais et al. (2006), Boutin et al. (2016) and recently by Quesnel et al. (2019); the continental basement itself was overprinted by regional-scale albitisation (e.g. Boulvais et al., 2007; Poujol et al., 2010; Fallourd et al., 2014). Among the various tools used to characterize the fluid-rock interaction, the stable isotopes provide unique information, especially when applied under the control of geological geometry. In this presentation, I will give key examples of the application of the stable isotope tool to the fluid-rock interaction system within the Cretaceous Pyrenean realm. References: Boulvais P. et al. (2006) Min. Pet. 88: 499-526 Boulvais P. et al. (2007) Lithos 93: 89-106 Boutin A. et al. (2016) Int. J. Earth Sci. 105: 747-770 Clerc C. et al. (2014) Int. J. Earth Sci. 103: 141-163 Corre B. et al. (2018) Min. Pet. 112: 647-670 Fallourd S. et al. (2014) Int. J. Earth Sci. 103: 667-682 Poujol M. et al. (2010) J. Geol. Soc. 167: 751-767 Quesnel B. et al. (2019) Geofluids (in press)

66

Unraveling fluid circulations in the Western Pyrénées (France) Barré G.1,2,*, Motte G.1, Hoareau G.1, Ducoux M.1,2, Bahnan A.E.3, Gaucher E.C.2

1CNRS/TOTAL/Univ. Pau & Pays Adour/ E2S UPPA, Laboratoire des Fluides Complexes et leurs

Réservoirs‐IPRA, UMR5150, 64000, PAU, France 2TOTAL, CSTJF, F-64018 Pau Cedex, France 3Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France *[email protected]

The western Pyrénées, mainly the sedimentary basin (Aquitaine basin) and its metamorphosed exposed analog (the Chaînons Béarnais on the south), were well studied for petroleum exploration, and different models were proposed to explain these oil/gas fields occurrences (e.g., Biteau et al., 2006). Only a few recent studies were made to explain the fluid circulations in this area (Salardon et al., 2017; Corre et al., 2018; Renard et al., 2018). However, these studies only focused on at maximum a few localities which recorded specific geological history. In this study, new data from fluid inclusions (microthermometry and Raman) and stable isotopes (C, O, Sr and multiple sulfur isotopes) analysis were performed on different samples from 15 wells and 16 outcrops both from the Aquitaine basin and the Chaînons Béarnais. These results were coupled to geodynamic study to better constrain the fluid circulations at regional scale. The main results show that fluid circulations are similar and link to the same geodynamic events whatever the location. Only the timing can varied depending on a North-South position of the sampling site. Variations on the fluid compositions are only due to local influence which are linked to the structural heritance and therefore to the temperature differences. Fluid inclusions, carbon-oxygen and strontium isotopes show that during the pre-rift (extension step) only basin fluids are present, and no external fluid (meteoric or deeper fluid) react with the sedimentary pile. All these fluids are trapped below the Sainte-Suzanne marls (lower Aptian). Only the Triassic fluids react with the hydrocarbons released by some Jurassic and Barremian source-rock, allowing H2S generation by Thermochemical Sulfate Reduction process. During the inversion and the beginning of the compression, overpressure leads to hydrothermal fracking and the migration to aqueous and gaseous fluids on the upper part of the system. To conclude, fluid circulation history in the western Pyrénées is driven by specific tectonic events (extension and beginning of the compression), but remains globally similar in the entire area, implying mostly fluids in closed system.

References: Biteau, J.-J. (2006) Pet. Geosci. 12(3) 247-273 Corre, B. (2018) Mineral. Petrol. 112, 1-24 Renard, S. (2018) Chem. Geol. 508, 30-46

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Fluid circulation and diagenesis of carbonate reservoirs relative to the geodynamic history of a foreland basin: Example of the Deep Lacq reservoir (Aquitaine basin, SW France) Bahnan A.E.1,2*, Carpentier C.1, Pironon J.1, Ford M.3, Barré G.2,4, Gaucher E.C.2 1Université de Lorraine, CNRS, CREGU, GeoRessources, F-54500 Vandœuvre-lès-Nancy, France 2TOTAL, CSTJF, F-64018 Pau Cedex, France 3CRPG, 15 Rue Notre Dame des Pauvres, 54501 Vandœuvre-lès-Nancy, France 4Université de Pau et des Pays de l'Adour (E2S UPPA), CNRS, TOTAL, Laboratoire des Fluides

Complexes et leurs Réservoirs‐IPRA, 64000 Pau, France *[email protected]

The geodynamics of basins can control the types, sources and timings of diagenetic fluids circulations. This applies to the Kimmeridgian-Barremian reservoir of Deep Lacq in the Aquitaine Basin located in southwestern France. The southern part of the basin is located north of the Pyrenean Mountains and evolved as a foreland during the early Cenozoic. From drill core samples, petrographic observations, coupled with isotopic and rare earth element geochemistry were used to determine the types, sources, chemistries and redox conditions of the fluids involved in diagenesis. Modeling the subsidence of the reservoir allowed the P-T conditions of the fluids to be constrained in terms of age. Our results indicate that during the Kimmeridigian to Neocomian, early diagenesis involved bacterial activity represented by micrite rims and framboidal pyrites. Reflux dolomitization in the marine phreatic zone precipitated an early phase of planar dolomites. During the gradual burial towards the mixing zone, fluctuations in redox conditions were recorded by the precipitation of a zoned ‘dog-tooth’ calcite cement. Mesogenesis started since the Aptian hyperextension rifting and involved extensional fractures that connected the Deep Lacq reservoirs with a pool of saline Mg-rich fluids, possibly Triassic in origin, that allowed the precipitation of saddle dolomite. During the Upper Cretaceous N-S convergence between the European and Iberian plates, new fluids circulated and a new phase of calcite precipitated. Another fracturing episode was associated with the circulation of large volumes of sulphate rich fluids and the precipitation of massive anhydrites immediately under the Aptian marls. These anhydrites were cross-cut by tectonic stylolites related to the Eocene Pyrenean compression. The main gas charging in Deep Lacq occurred after cementation and is suggested to be post-orogenic. Therefore, using several petrographic, geochemical and modeling proxies, it is demonstrated how the geodynamic evolution of the foreland basin controlled the salinities, chemistries and P-T conditions of the diagenetic fluids that circulated in Deep Lacq.

70

The Upper Ordovician unconformity in La Molina area (Pyrenees): Deformation study and formation conditions of the associated quartz veins González Esvertit E.1*, Casas T.1, Josep M.1, Canals A.1

1Facultat de Ciències de la Terra. Universitat de Barcelona. C/ Martí Franquès s/n, 08028 Barcelona, Spain *[email protected]

The study at different scales of infra and overlying series to the Upper Ordovician unconformity and the quartz veins present in the vicinity of La Molina (Canigó Massif, Eastern Pyrenees) has provided new data on the pre-Variscan deformation. The structural characterisation was based on detailed geological mapping, cross-section elaboration and structural analysis. Both material series and the quartz veins were petrographically characterised, and microprobe analysis of phyllosilicates (muscovites and chlorites) and fluid inclusions microthermometry on quartz from veins were carried out. Three deformation phases were established: D1, linked to the Sardic Phase (Middle Ordovician) and interpreted as a process of emersion and erosion that leads to the unconformity and the normal faults and joints; D2, related to the Variscan cycle and D3, associated to the Alpine orogeny. According their spatial distribution, orientation and deformation structures, two quartz veins generations were recognized. A first generation would be synchronic to the normal faulting episode, while for the second a post-D2 age is proposed. The combination of fluid inclusions data and the chlorite thermometry point to a T-P conditions for the second quartz veins generation of: 325-375 ºC and 2.5-3.5 Kb. Keywords: Sardic Phase; Quartz veins; Chlorite thermometry; Fluid inclusions; NW Gondwana.

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Carbonation of exhumed mantle rocks at rifted margins: insights from Alpine Tethyan analogues Coltat R.1*, Boulvais P.1, Branquet Y.1,2, Gautier P.1, Poujol M.1, Manatschal G.3 1Univ Rennes, CNRS, Géosciences Rennes - UMR 6118, F-35000 Rennes, France 2Institut des Sciences de la Terre d’Orléans, UMR 7327, Université Orléans, 45234 Orléans, France 3Institut de Physique du Globe de Strasbourg, EOST-CNRS UMR 7516, Université de Strasbourg, 67084 Strasbourg, France *[email protected]

Ocean-Continent Transitions are well-known to produce and host hydrocarbons. Rifted margins have thus been studied for decades through geophysical (Sutra et al., 2013), numerical modelling (Lavier and Manatschal, 2006) and studies on fossil analogues preserved on-land (Lagabrielle et al., 2010). An important finding was the discovery of exhumed mantle rocks in the most distal part of margins (i.e. hyper-extended margins, Boillot et al., 1987). These structures resemble those imaged at (ultra)slow-spreading oceanic ridges (Lagabrielle and Cannat, 1990) and channelize seawater-derived fluids leading to the carbonation of serpentinised mantle rocks (i.e. ophicalcites). This process is of particular interest for the understanding of volatiles (CO2, H2, CH4) budgets. A promising target to decipher this process is the Pyrenees where ophicalcites linked to Cretaceous mantle exhumation have been studied recently (Clerc et al., 2014). Liguro-Piemonte units (Platta, Totalp, Tasna nappes) belong to the same Alpine Tethys realm, except that they formed during the Jurassic. There, ophicalcites occur at the summit of the exhumed mantle rocks suggesting that the same processes may have occurred. Here we present a combined structural, petrographic and isotopic study led from the Platta and Tasna nappes. Main results are that carbonation occurred i) as a consequence of sudden fluid infiltration at the basalt-serpentinite interface (Coltat et al., 2019) ii) under extensional tectonic during the reactivation of this interface and iii) at a larger scale both at the tectonic Moho which acted as a detachment plane (Tasna nappe) and after mantle exhumation at the exhumed detachment surface (Platta nappe). This suggests that carbonation at rifted margins is a long-lived phenomenon which starts at the beginning of mantle exhumation and lasts after the exposure of mantle rocks at the seafloor during the reactivation of the exhumed surface. Boillot, G. et al. (1987) Tectonophysics (1987), 132, 335:342 Clerc, C. et al. (2014) Int. Jour. Earth Sci. (2014), 103, 141:163 Coltat, R. et al. (2019) Geology (2019), 47, 183:186 Lagabrielle, Y. and Cannat, M. (1990) Geology (1990), 18, 319:322 Lagabrielle, Y et al. (2010) Tectonics (2010), 29, 26p Lavier, L. and Manatschal, G. (2006) Nature (2006), 440, 324:328 Sutra, E. et al. (2013) Geoch. Geoph. Geosystems (2013), 14, 2575:2597

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Stratigraphic sequential analysis and oil interest of the upper Silurian - lower Devonian (F6 reservoir) of Southeastern Algerian Sahara: case of Hassi Mazoula field and its bordering regions (Illizi basin- Algeria). Belkacemi A.1*, Asses A.2, Hamdidouche R.3 1, 2Department of Gisement, Laboratory of Mineral Resources and Energy. M'Hamed Bougara 3Laboratory of Geodynamic (G.B.S.O), USTHB, University of Earth Sciences Houari Boumediene. Algeria. *[email protected] or [email protected]

The Illizi Basin is the most studied part of the algerian Sahara. All of them are

associated to important structural elements. However, the peripheral areas are less studied; quite other’s, well defined, could have great interest for up-coming explorations. The fields already discovered and drilled by some wells, need particular attention to be more prospected: their structures are unclear, sandstone bodies wrong defined and size of some ones may highly exceed their traps as is the case of Hassi Mazoula fields. Its additional exploration will undoubtedly increase reserves.

Thereby, this research aims to characterize the F6 reservoir of that field in order to draw a good sandstone bodies limits and realize a future development plan.

The sedimentological log and petrographic analyzes have defined in the upper Silurian-lower Devonian (F6) range of the Hassi Mazoula field five genetic deposit sequences corresponding respectively to: Sequence 1 (Lower Ludlow age):It consists of three sedimentary tracts: a TST (summit part only), an early HST and a late HST, deposited globally in an offshore environment evolving towards the shoreface. Sequence 2: Ludlow age, Pridoli-based. It results from the stacking of three sedimentary tracts; an LST, a TST, and an HST, broadly reflecting a fluvial environment, moving vertically to a shallow marine environment, with a return to estuarine environments towards the end of the sequence. Sequence 3: (Pridoli). It results from the stacking of three sedimentary tracts; an LST, a TST, and an HST formed by fluvial channel deposits, surmounted by fluvial bar facies and floodplain. Sequence 4: It is azoic in its lower part; its age is Praguian towards the top. It results from the stacking of two sedimentary tracts; an LST and a TST. The corresponding depositional environment evolves vertically from fluvial to braid towards the coastal plain. Sequence 5: probably of Praguian age and truncated under the frasnian unconformity. It shows a single sedimentary tract (LST), typical of meandering-like fluvial environments at the top and weakly sinuous at the base of the sequence.

The upper Silurian sequences are all aquifers in the Hassi Mazoula field. Conversely in the bordering regions, they may be oil producing. The LST of the last sequence and the height part of TST of the fourth sequence are producing oil at the Hassi Mazoula scale. Keywords: Illizi basin; Hassi Mazoula; upper Silurian-lower Devonian; F6 reservoir; sequential analysis; system tract.

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Paleotemperature and Paleopressure of the Paleozoic rocks of the eastern and southeastern parts of Precaspian basin and the Sakmara zone of Southern Urals based on the study of gas-water inclusions Yensepbayev T.1*, Yeskozha B.2, Aimagambetov M.2, Amanzhol K.1, Bazarkhan K.1,3, Ten V. 1,3 1Kazakh national research technical university, 22 Satbayev str. Almaty 050013, Kazakhstan, 2LLP « Firm Almex Plus », 15v Satbayev str. Atyrau 060011, Kazakhstan 3Université de Lorraine, cours Léopold 54052 Nancy, France (master student) *[email protected]

The fluid inclusions in calcite and quartz of Silurian, Devonian, Carboniferous and Permian series of East and South-East parts of Precaspian basin and Sakmara zone of Southern Urals were studied. Melting and homogenization temperatures of fluids in crystals, were determined. The biphasic aqueous inclusions (Lw) were sporadically observed in Viseen samples and systematically in the Devonian and Silurain. The salinities range from 2-15% NaCl equivalent weight, and a great variability of Th. Among the samples of the East part of Precaspian basin one group of biphasic fluid inclusions has very low homogenization temperatures (about 65°C). The second group of fluid inclusions has the average homogenization temperatures of 115°C. In the southeastern part (new discovered oil field Ansagan) of Precaspian basin, two groups of inclusions in Devonian samples are noted with slightly higher temperatures grouping around 109°C and 140°C. The samples of the Chanchar and Sakmara suites, the salinity of 3-6% of weight equivalents of NaCl is most typical. The homogenization temperatures have four maxima around temperatures of 100°C, 130°C, 175°C and 285°C. The interpretation of results of measurements of the samples of Precaspian basin has allowed defining most typical values of pressure and temperature equal, accordingly, 300-500 atm and 80°-130°С with geothermal gradient about 24°С/km. Analogous P/T pairs are determined by homogenization temperatures around 110-140°C of the samples of Ansagan field and the Sakmara zone. However, for the homogenization temperatures of 280-290°С, the reconstruction of the P/T pair in this zone shows an increase in the paleotemperature values to 340-430°С and paleopressure to 650-700 atm or more, which corresponds to a geothermal gradient exceeding 40°С/km. Conclusion Within the considered territory of the Precaspian basin, an increase of the temperatures of

homogenization in the southeastern direction is noted. The increase of the temperature

towards younger suites from the Silurian deposits (samples of the Sakmara suite of the

Llandoveri-Ludlowian age) - + 60 / + 225°C toward the samples of the Chanchar suite of

Prague-Em age - +110 / +290°C agrees with the geological evolution of the region. The

time of subduction processes of the Ural paleoocean along the Eastern European plate

and, accordingly, the increase of the temperature regimes occur in the Devonian period.

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Roll-front U deposits and In-situ recovery

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Thursday, 14th November 2019 Roll-front U deposits and In-situ recovery Session 4 : Roll-front U deposits and In-situ recovery Session dedicated to ISR of metals (U, Cu, Zn,…) and to research concerning by-product valorisation. 11h - Keynote lecture - A. Le Beux (ORANO) : Scientific and technical advances in the field

of In situ recovery 11h30 - Rallakis D : The uranium biochemical trap of Zoovch Ovoo: The importance of organic matter 11h45 - Pechenkin I. : Resources of uranium-bearing basins framing the Northern Pamir 12h - Jin R. : Sandstone-type uranium mineralization controlled by the vertical tectonic movements of the Mesozoic and Cenozoic basins in Northern China 12h15 lunch offered by CREGU 13h30 - Keynote lecture - V. Lagneau (School of Mines, Paris) : Modeling of Uranium recovery and reactive mass transfer in ISR 14h - Laurent G. : Laboratory and Numerical Investigations of In-Situ Bio-Leaching from Kupferschiefer Copper Ore

14h15 - Noskov M. : Groundwater contamination and self-purification at uranium production by the in situ leaching process Posters Eid A. : Clays in sandstones from roll-front deposits exploited by ISR : progresses towards their quantitative distribution using portable tools Yin C. : Sandstone-type Uranium mineralization in North China with its relationship with tectonics and oil/gas reservoir

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Optimization of low-grade uranium in-situ leaching - case study in a roll front system, Kazakhstan and opportunities Le Beux A.1*, Joubert G.1, Regnault O.2 1Orano, Paris La Défense, France 2Katco, Nursultan, Kazakhstan *[email protected]

ABSTRACT Orano Mining, through its joint-venture Katco operates mine in Kazakhstan, using the in situ recovery (ISR) method. It extracts low-grade uranium from a sandy confined reservoir, located 300 to 500-meter-deep, hosting a roll-front type mineralization. Leaching solution (dilute sulfuric acid in this case) is injected into the deposit through injector wells. Pregnant solution is then pumped out and sent through a pipeline network to the processing plant where uranium is extracted for the targeted ammonium diuranate production. The wellfield is organized in technological blocks constituted by 10 to 15 hexagonal cells (injector wells at the vertex and production well at the center). The uranium concentration curve for each technological block is a bell-shaped function with a concentration peak generally exceeding the 100 mg/L after 2 to 6 months of production and an operation time span of 3 to 5 years. The overall production is obtained through the sequencing of the operation of technological blocks over the entire deposit. After about 15 years of production, engineers from Katco and Orano have developed a strong expertise to predict chemical reaction between leached solution and host rock and to assess dissolved elements transport in the reservoir. A 3D geological model of the deposit, including mineralization, reservoir lithological facies and penalizing components, allowed for a better position of injector and production well screens. Fast processing hydrodynamic streamline simulator, using the FrontSim code, was applied to optimize acid invasion in the reservoir and acid-ore contact. Reservoir characterization and metallogenic studies provided a better understanding of uranium release mechanism in the aqueous phase and specific reactive transport models were developed using the HYTEC code (MINES ParisTech). This knowledge was then applied at operational level to highlight drivers levers for uranium recovery optimization, reduction in acid consumption, flow rate enhancement (wells cleaning technics), and enhanced reliability of long term planning sequences. This paper outlines the successful mine operation of the deposit, while providing the main operating parameters and the resulting recovery performance. Going in further into ISR mining, it will present developments to come, in order to apply this technic into non-standard reservoir and alternative metals. Keywords: Uranium in situ Recovery, Reservoir Modeling, Recovery Optimization

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The uranium biochemical trap of Zoovch Ovoo (Mongolia): The importance of organic matter Rallakis D.1*, Michels R.1, Brouand M.2, Parize O.2, Cathelineau M.1 1Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France 2ORANO Mining, Tour AREVA, place Jean Millier 1, 92084 Courbevoie, France;

*[email protected] The Cretaceous sandstone reservoir of the uranium deposit of Zoovch Ovoo is particularly enriched in detrital organic matter. Macroscopic examinations as well as organic petrography and geochemistry analyses point out that the organic matter is exclusively land-plant derived (kerogen type III) and occurs as detrital particles concentrated into clay layers, clay intraclasts or sandy laminae. The biological features of the particles are more or less preserved, depending on their transportation (proximal or distal source), while the overall thermal maturity is low (%Rr ≈ 0.3). Organic particles are very often associated to high levels of uranium, which concentration fluctuates from few percent up to 78 wt%. These high levels have never been reported for other roll-front U deposits of the large uranium province of Central Asia. The distribution of UO2 in the organic particles seems to be linked to the porosity/permeability of the organic structure, which may be a control of fluid accessibility to the macerals. Organic matter particles can be fully replaced by UO2, with partial preservation of organic structure (suggesting an epigenesis). Certain macerals show high concentrations (up to 20 wt%) of uranium which is not expressed as oxide under SEM. It is therefore suggested that U(VI) is adsorbed on carbon by forming uranyl–carboxyl groups. The organic matter particles have therefore captured U from circulating fluids at a low temperature (T<40°C). The trapping possibly occurred during sedimentation (pre-concentration stage) and continued during the roll-front events. As burial diagenesis is too early to consider reduction of U(VI) by carbonaceous moieties, it is suggested that microorganisms are mainly responsible for the reduction of U(VI), either directly through their physiological activity or by providing reduced sulfur (i.e. sulfides are replaced by uraninite). From this study it may therefore be concluded that at least two controls of different scales can be considered for the Zoovch Ovoo uranium deposit. First at the scale of the sedimentary particles, organic matter plays a capital role in uranium deposition, acting as U-trap through complexation and sustaining the U(VI) reduction mechanism into UO2 through biological activity. Secondly, at the scale of the sedimentary deposit, organic matter distribution as well as the permeability network that allows the circulation of uranium-bearing fluids are controlled by the sedimentary architecture.

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Resources of uranium-bearing basins framing the Northern Pamir Pechenkin I.*, Grebenkin N. All-Russian Scientific-Research Institute of Mineral Resources. 31, Staromonetny per., Moscow 119017, *Russia [email protected]

The epigenetic stage of development of the sedimentary basins rocks unites three ore forming systems: catagenetic, exfiltrational and infiltrational ones. Each system generates its own set of useful minerals. The infiltrational system of ore-forming systems predominates when forming polymineral uranium ores of the sandstone type. The study of tectonic problems of the mobile belts and their boundaries from the plate tectonics point of view, and hot spots allows planning new method of approach to metallogenic analysis. The research is based on two postulates: 1) the large uranium deposits of the sandstone type are located in sedimentary basins of different types, the number of which is limited, 2) each sedimentary basins passes consecutively several stages of development that correspond ore-forming systems. The sedimentary basin is considered to be an independent geological structure, but in its development it is connected with the tectonic evolution of the continental block that a joining it. The carried out analysis revealed the exceptional role of ore-concentrated process, stipulated by the effect of oxygenated uranium-bearing, underground waters in the artesian basins. The Neogene–Quaternary collision of the African, Arabian and Indian Plates with the Eurasian Plate from the south led to the formation of large Tethys orogenic belt. The most productive uranium region in the extended Tethys belt is the Indian segment. As regards intensity of orogenesis, the Indian segment has surpassed all else. The collision of the Indian Plate subducted over 1500 km below the Eurasian Plate and differentiated the orogenic area with vertical uplifts of up to more than 9000 m and subsiding basins down to below 5000 m. It is divided into the Pamir and the Himalayan sectors. They differ in structural peculiarities and the scale of their ore content. Three types of metallogenic zone controlling the roll-front type uranium deposits in the Pamir sector. Each zone has unique characteristics, but they have in common the evidence for the largest and unique deposits, which are located in the suborogen area and also in areas remote from orogeny. Installed tight spatial and paragenetic connection of the inflow of uranium waters, forming extensive roll-front type uranium deposits with the most actively advanced site located on the north part of Indian Plate – the Pamir ‘wedge’. The most productive metallogenic zones with giants roll type deposits originate at supposed sites of mantle uranium accumulation. The Pamirs ‘wedge’ shows the result of the prolonged collision of the Indian plate treading on the Eurasian one. It predetermined the unique ore concentration of the area. As a rule, large deposits of the roll type are situated on the acute point within the most distant from orogen suborogenic (activated) part of the adjoining the Turan platform and its southwestern margin, the edge of the Kazakh shield. The Himalayan sector is characterized by a more complicated geological structure in comparison with Pamir. One of the unsolved problems of the Himalayan sector is the reason for such a minor uranium content, compared with the Pamir sector. Intensive

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movement to the northeast of the orogenic area border during the Neogene–Quaternary period explains the absence of large deposits of uranium within the limits of the Himalayan sector. This impacted frequent recharge area fluctuations, active migration of hydrocarbons and an absence of regional stable centers of unloading and hampered the broad development of ore forming interlayer oxidation zones. References: Grushevoy, G. et al. (2003) Regional geology and metallogeny. 18: 63–73 Pechenkin, I. (2017). Prospect and protection of mineral resources. 12: 3–11

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Sandstone-type uranium mineralization controlled by the vertical tectonic movements of the Mesozoic and Cenozoic basins in Northern China Jin R. 1,2,*, Chen Y.1,2, Zhao F.1,2, Li X.1,2

1 Tianjin Center, China Geological Survey, Tianjin 300170, China 2 Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China [email protected]

A large number of sandstone-type uranium deposits in the Mesozoic and Cenozoic

basins in northern China Voluminous studies have focused on the geology, geochemistry,

sedimentary characteristics, uranium occurrence, redox conditions, and especially, the

metallogenesis of these uranium deposits. Previous scholars reach a consensus on the

metallogenic model which has been defined as “Interlayer Oxidation Zone Type”. In this

model, these interlayer sands are horizontally divided into primary oxidation (brownish

red/yellow and shallow grayish green), oxidation-reduction transitional (shallow grayish

green to dark grayish green) and reduction (gray) zones. These uranium ore bodies are

considered to occur as roll-type and/or tabular shape in the transitional zone.

A database was established by using data of rock colors from exploring drill holes of

several ten thousands of coal and oil fields within the basins in northern China. Based on

the data extracted from the database, three-dimensional well-tie sections are established.

Their correlation and analysis reveal vertical zoning in the color of the Jurassic–Cretaceous

sedimentary sequences, regardless of the scale of the ore clusters or the entire basin.

These features suggest that rock color zoning of the basins in northern China is a result of

the change in primary sedimentary environments.

At the early stage of Mesozoic sedimentation, the basin received a large amount of

reductive materials, such as humus, accompanied by uranium-bearing items.

Subsequently, the basin received voluminous oxidizing feldspar-quartz substances. In the

late stage, due to tectonic inversion, slop belts were formed, which could provide favorable

structural spaces for the formation of sandstone-type uranium deposits. In a word, the

sedimentation and evolution of the strata within the basins in northern China was caused

by the ups and downs tectonic movements within the basins in northern China .During

Mesozoic and Cenozoic, the basin was entirely in a sedimentary environment that varied

alternately from reduction to oxidation and from moisture to drought to moisture. At the end

of Mesozoic and the beginning of Cenozoic, the variation of water levels caused by

fluctuating tectonic movements and by wet and dry seasons led to formation of these

uranium deposits.

During the water transgression, hexavalent uranium in the oxidized sedimentary units

was dissolved and transported into the reduced sandstone that bounded by mud-sand-

mud structure by means of syphoning. In the new circumstance, the hexavalent uranium

mailto:[email protected]

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was reduced to tetravalent uranium and precipitated or still existed as hexavalent state

that absorbed in other host carriers. Multiple water transgression and water regression

processes constituted the super enrichment of the uranium which called pulsatile

circulatory mineralization. To sum up, Control of mineralization of sandstone uranium

deposits by the ups and downs of the Mesozoic and Cenozoic basins in northern China.

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Modeling of Uranium recovery and reactive mass transfer in ISR Lagneau V.1*, Regnault O.2, Le Beux A.2 1MINES ParisTech, PSL Research University, Centre de Géosciences, 7730 Fontainebleau,France 2ORANO, 92084 Paris La Défense France *[email protected]

In situ recovery is a well-established technique for uranium exploitation, representing over 50% of worldwide production, with some key advantages: low production costs and reduced environmental footprint. The economic potential and technical challenges to predict and optimize production have led to intensive research. The presentation focuses on the use of reactive transport modeling to improve the understanding of processes and their coupling: this offers in itself some opportunities to guide optimizations, improve production forecasting, and more generally help in planning. A geochemical model is built, based on ore characterization and extensive thermodynamic and kinetic databases. The model is further constrained by the geometry of the system: distribution of hydraulic properties and mineral content using geostatistical realizations of the block-model. Finally, exploitation conditions are simulated: geometry of the well field, injection fluid composition and flow-rates in injection and production wells. Most parameters of the model are constrained by field data or operational choices, with minimal adjustment, which increases the robustness of the approach. After calibration, some applications of the model are presented: optimization, estimation of production for short-term or long-term planning. Acknowledgements: this work is supported by the industrial chair ISR-U, funded by ANR and Orano. The authors also wish to acknowledge Katco for fruitful discussions and access to production data. References: Lagneau, V. et al. (2019) RiMG 85: 499

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Laboratory and Numerical Investigations of In-Situ Bio-Leaching from Kupferschiefer Copper Ore Laurent G.1,2*, Izart C.1, Lechenard B.1, Golfier F.1, Marion P.1, Collon P.1, Truche L.1, Royer J.J.1, Filippov L.1 1Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France 2Univ. Orléans, CNRS, BRGM, ISTO, UMR 7327, F–45071, Orléans, France *[email protected]

This study investigates indirect in-situ bioleaching as an alternative mining technology for minimizing waste production, environmental impact, and chemical consumption. The process consists in injecting a leaching solution into a targeted ore body for dissolving base metal bearing minerals, while iron-oxidizing microorganisms regenerate the solution. In this contribution, we present laboratory column experiments that investigate the impact of grain size on the action of an acidic oxidizing solution in contact with ore samples crushed at different grain sizes. These results are used for developing a one-dimensional reactive transport model based on PhreeqC software. In this model, porous and fractured media are approached by a dual porosity reactive transport model, where dissolution reactions are described by kinetics. Column experiments are used as a reference for calibrating the key parameters of the numerical models, which include the relative volume of mobile and immobile zones within the dual porosity medium and the exchange rate between these two volumes. This model is then adapted to in-situ conditions by considering the preferential flow of fluids through natural or artificial fractures of enhanced hydraulic conductivity.

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Groundwater contamination and self-purification at uranium production by the in-situ leaching process Noskov M.1*, Solodov I.2, Kesler A.1, Terovskaya T.1

1Seversk Technological Institute of National Research Nuclear University (MEPhI), Communistic av. 65, c.Seversk, Tomsk reg., 636036 Russian Federation 2JSC Atomredmetzoloto, 22, B. Drovyanoi Lane, Moscow, 109004, Russian Federation *[email protected]

Тhe in situ leaching (ISL) method of uranium mining has less impact on the environment than traditional underground and open pit mining methods. The uranium extraction is carried out by the engineered well system that accesses a productive horizon containing the orebody. Injection wells are supplied with leaching solutions capable of selectively dissolving uraniferous minerals. The sulphuric acid ISL method is the most widespread in the world. The pregnant solution is returned to the surface by pumping wells and is discharged into the processing complex for uranium sorption extraction. Thus, mining is carried out without lifting ore to the surface through selective dissolution of uranium minerals directly within the mineralized host strata. At the same time, deposit development is not accompanied by the formation of overburden and tailings dumps, drainage of underground aquifers, formation of wastewaters from hydrometallurgical plants, etc. However, during field development of the ISL method there is some contamination of underground waters with petrogenic and technogenic substances due to the leach solution injection and its interaction with the host rock. To monitor the productive horizon state and assess the geo-ecological effects of ISL, it is wise to use mathematical modelling methods. This is due to the process complexity occurring during ISL and the lack of information on the productive horizon state and the high cost of observation well construction. The report presents a mathematical model of uranium sulphuric acid leaching and software for forecasting the groundwater state during deposit development by the ISL method. The results of the epigenetic and predictive modelling of the change in the productive horizon state during the development of the Khokhlovsk uranium deposit by the ISL method are presented. The simulation results show that, in the case of uranium ISL, the region of groundwater

contamination is local and situated mainly within the boundaries of the operational units.

The main indicator of pollution is the sulphate ion because its content in processing

solutions with sulphuric acid ISL greatly exceeds the concentrations of other components

and it also has a high migration capability. Using its distribution in the underground waters,

it is possible to evaluate the area of productive horizon pollution. Having completed

uranium mining, there is self-cleaning of the productive horizon over a period of several

decades. The reduction in pollutant concentration occurs as the result of the interaction of

residual lixiviant solutions with rock forming minerals, formation of new minerals and

dilution with groundwaters. The self-cleaning process speed depends on the mineralogical

composition of the ore-bearing rocks in the productive horizon and the intensity of water

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exchange. In the case of low groundwater movement speed, the self-cleaning process

takes place within a region extending a little beyond the boundaries of the well units.

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Clays in sandstones from roll-front deposits exploited by ISR: Progresses towards their quantitative distribution using portable tools Eid A.R.1*, Cauzid J.1, Fabre C.1, Cardon S.2 1Laboratoire GeoRessources, Université de Lorraine-CREGU, Boulevard des Aiguillettes, BP239, F-54506 Vandœuvre-lès-Nancy, France 2ORANO Mining, R&D Dpt, 92084 Paris La Défense cedex, France *[email protected]

Abstract Clays may clog wells and consume acids required to leach Uranium resources from roll-front ores. Hence, it is necessary to characterize clays from cores before starting the in-situ recovery of U. Laboratory techniques can provide accurate results but suffer from long delays and they are expensive. The use of new portable spectroscopic tools can reduce both issues, providing quick results at cheaper costs. However, those techniques may suffer from lower analytical capabilities, common lack of expertise from the operator but they require low sample preparation. Amongst those tools, VNIR-SWIR spectrometers can be used to get the nature of the mineral phases but their precision on absolute amounts something remains not sufficient to obtain reliable results. To overcome this limitation, the combined use of VNIR-SWIR tool with a more quantitative technique is required. Amongst portable tools, X-ray fluorescence (XRF) is one of the most widespread and provides quantitative results on elemental compositions, and will be used as complementary tool for clays characterizations and quantification. This study aims to evaluate the precision and accuracy of portable X-ray fluorescence (pXRF) in acquiring bulk-rock elemental chemistry. The device is a NitonXl3t Goldd+ pXRF. It was tested on sandstones from roll-front containing various amounts of clays from Muyunkum deposits, Kazakhstan. Capsules with polypropylene films were used to enhance detection of light elements. Particle size effect was excluded by crushing and pulverizing using the same protocol for all the samples. In this study, 27 core samples were analyzed by pXRF, three times for 180 seconds, covering three different analytical conditions, each dedicated to increase detection of a set of elements. In addition, portable Raman spectroscopy (Bruker©) was also tested to quantify carbonates content. The compositions of the different major oxides obtained using pXRF are compared with

those obtained from bulk analysis (inductively coupled plasma mass spectrometry and

optical emission spectrometry). The correlation between the two tools are quite

acceptable, nevertheless MgO is under-estimated using pXRF and SiO2 presents a low

coefficient of correlation of 0.78. Errors bars for pXRF analysis were calculated with 95%

of confidence for major oxides. The average error bars estimated for major oxides are

SiO2= ±4.8%, Al2O3 = ±5.1%, Fe2O3 = ±0.1%, = MgO = ±0.8%, CaO= ±0.1%, K2O=

±0.2%.

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Sandstone-type Uranium mineralization in North China with its relationship with tectonics and oil/gas reservoir Yin C.1,2*, Peisen M.1,2, Jianguo L.1,2, Ruoshi J.1,2, Hualei Z.1,2

1Tianjin Center, China Geological Survey, Tianjin, China 300170, China; 2Laboratory of Non-fossil Energy Minerals, Tianjin Center of China Geological Survey，Tianjin, China

300170 *[email protected]

In continental basins of the north China, serial of energy resources commonly coexist in

the same basin. In Songliao basin, Ordos basin, Junggar basin, Qaidam basin and Tarim

basin, oil/gas and uranium can exist in the same tectonic unit. These tectonic elements

could be the slope in the margin of basin, or transfer zone of uplift, all of which are

companied with the development of deep fault zone. This tectonic style is beneficial to

build a cycle system of uranium mineralization fluid. In Songliao basin, the uranium bodies

are mainly located in the plunging crown of the Baixingtu uplift, and the east of Xilamulun

fault zone. In Ordos basin, the Daying-Dongsheng uranium deposits develop in one limp

of Yimeng uplift. The mineralization fluid would migrate along the Boerjianghaizi fault, and

uranium would concentrate in the Jurassic Zhiluo formation. In the Ningdong area, series

of thrust developed with the drag structures which are the benefit rooms for oil/gas and

uranium. In Jingchuan area, the uranium mineralization mainly developed in the

Cretaceous Luohe formation with the characteristics of blown sand. The uranium prospect

area is located at the side of the Changqing oil/gas area. In the western margin of Junggar

basin, uranium and oil/gas are in the same layers or in the upper or lower layers. As a

result, the sandstone-type uranium mineralization of the north China is controlled by the

basin tectonics and has a great relationship with the oil/gas reservoirs. The deep

Hydrocarbon fluid migrates upwards along the faults, combines with the oxygen-uranium

fluid at the end of faults or the beneficial oil/gas reservoirs to concentrate to be the uranium

bodies.

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Advances in modelling and subsurface flow simulations

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Thursday, 14th November 2019

Session 5 : Advances in modelling and subsurface flow simulations session dedicated to upscaling, implicit modelling of faulted reservoir, THMC modelling, 14h45 - Keynote lecture - C. Gout (TOTAL) : Multiscale, multiprocess modeling for sedimentary basin analysis 15h15 Caumon G. : Reproducibility and uncertainty in chronostratigraphic interpretation of subsurface data: why should we care ? 15h30 - Biteau J.J. : Pressures and Petroleum Geology 15h45 - Berthelon J. : Characterizing the Neuquén basin natural fracturing history using basin modeling coupled with 3D geomechanics 16h - Michels R. : Advances in hydrocarbon cracking reactions mechanisms : implication on the modelling of the thermal stability of petroleum in geological reservoirs 16h15 Coffee break 16h30 - Keynote lecture - Donzé F.V. : Hydro-mechanical modelling of fault reactivation in low permeability media 17h - Mindel J. and Driesner : Hydrologic mechanisms for interaction of multiple brines from different sources at fractured basement-basin interfaces

17h15 - Weiss P. : Numerical Modeling Constraints on the Formation of Shale-hosted Massive Sulphide (SHMS) Deposits in the Selwyn Basin, Canada 17h 30 - Tiné A-J. : Application of Digital Rock Physics to low-permeability media: issues and challenges ? 19h30 - Cocktail to celebrate 40th CREGU anniversary Ferme du Charmois – Vandoeuvre les Nancy

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Multiscale, multiprocess modeling for sedimentary basin analysis Gout C. TOTAL, Avenue Larribau, 64000 Pau, France *[email protected]

Sedimentary basins exploited for metals, hydrocarbons, for thermal energy, but also for storage are complex systems with a long history. Physical (or pseudo-physical) formulation of geological processes such as fluid flow, thermal flow, mechanical and tectonic strain, chemical and reactive transport are improving. At the same time, numerical schemes are optimized on incredibly increasing computation power. With both of these evolutions, basin models, initially designed to simulate thermal evolution of source rocks and migration of the expulsed HC, are now capable to embedding more and more coupled processes allowing to simulate the dynamic of the basins. For example, tectonic and geomechanical simulation coupled to Basin Model simulation allows to better predict natural fracture, pressure distribution or fluid flow evolution. A major hurdle for an accurate reproduction of the basin dynamic history is the boundary conditions setup. A way to face this is to run nested models at different scale and with different strategies. Simulation of kinematically constrained thermomechanical lithospheric models provide more physically realistic evolution of basin basal heat flow, subsidence or magmatic activity periods, key parameters of THMC basin models. On the other side, a more accurate description of the basin fluids dynamic should allow constraining simulation of deep fluid driven sediments generation and rocks physical transformation. For example the location of carbonate reservoirs could be defined via a forward stratigraphic simulation of continental carbonates, coupled to the history of CO2 generation and migration across the basin, computed by a basin model simulation. The major challenges we will be facing with these more and more “complex” nested and coupled multi-scale, multi-physics models are the increasing amount of parameters to master and the lack of tools to analyze and capture relevant knowledge and accurate quantities from the 4D models.

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Reproducibility and uncertainty in chronostratigraphic interpretation of subsurface data: why should we care ? Caumon G.1*, Lallier F., Edwards J., Baville P., Apel M., Hoth S., Borgomano J., Fournier F., Viseur S., Wu X. 1Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France *[email protected]

Summary: Stratigraphy is an essential aspect to describe, analyze and understand the functioning of sedimentary basins. Indeed, it provides the time frame necessary to characterize basin evolution. Stratigraphic layers also control petrophysical heterogeneity, which in turn affects thermo-hydro-mechanical processes in the subsurface. However, fathoming the stratigraphic architecture from available susbsurface data is difficult, as only sparse outcrop and borehole observations are typically available. Reflection seismic data provide very useful features, but may also be sparse and only provide information down to decametric resolution at best. In this talk, I review some recent approaches to combine interpretation with borehole data to come up with reasonable stratigraphic correlations. In spite of the tremendous computational complexity of the problem, I show that workable computational methods can be designed to address the correlation problem. These approaches raise fundamental questions about what is a good stratigraphic interpretation. They can help sedimentologists make interpretive concepts more explicit and reproducible, and to test the impact of a particular type of information or of a particular interpretation concept. From an applied geology point of view, they open new perpectives to better account for stratigraphic uncertainties in resource and reserve assessment.


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Pressures and Petroleum Geology Biteau J.J.1* 1Retired from Total, former 2017-2019 EAGE President, *[email protected]

Introduction This talk aims at exploring the links between Pore pressures and Petroleum geology. Pressure, seals and traps are some of the basic components for the Petroleum System to work efficiently. The compaction of sediments is related to fluid expulsion mainly water but also hydrocarbons, i.e oil, gas, and mineral dispersed or concentrated in solutions. Method and theory Pressure is defined as the ratio between a force and an area (Newton per sq.m). Analyses of pressure through tests, whatever they are, remain fundamental for the petroleum geologists and the reservoir engineers. Pressure is considered normal when hydrostatic, in a normally drained system, and abnormal, when overpressure is developed in undrained systems. Pw is the aquifer pressure, Phc is the pressure related to the buoyancy of hydrocarbons, Pn is the normal hydrostatic pressure. OVP is the overpressure, ie.Pw-Pn. Sealing intervals for hydrocarbons are related to impermeable rocks (where flows in a Darcian sense are impossible) and ruled mainly by two physical processes: capacity and integrity. The capacity of a seal is linked to its entry pressure and wettability, the more this one, the more the hydrocarbon column. The integrity of a seal is related to its resistance to hydraulic fracturing, the closest the pressure to the minimum stress S3, the weakest is the sealing and the hydrocarbon column. There is another but marginal phenomenon that is the gas molecular diffusion but which is much more longer at geological time scale. Behaviour explanations: the two different concepts - Capacity : Hydrocarbon trapping is the result of a contrast of a reservoir having a low entry pressure and a seal having a highest entry pressure. There is no dichotomy between those rock fabrics as it was emphasized in the seventies. The reservoir has a macroporosity and the seal a microporosity. Indeed pore throat radius differs the between both types of rocks. Permeabilities are very different in reservoirs and in seals, while porosities can be in the same range. So entry pressure is a pre-requisite condition for flows to develop in the seal (leakage) according the Darcy’law i.e permeabilities, and the type of fluid water, nor oil or gas. Rock intergranular space content permeabilities then can then regulate the fluid flows pending upon the type of rock and the presence of different elements able to change the permeability such as faults (their gouge nature) or facies changes ( introducing major restrictions of permeabilities and porosities). - Integrity : If there is an important and significant excess of pore pressure in the aquifer or/and if, in addition, the HC column (due to buoyancy) is high, the pressure can be close to the hydraulic fracturation criterion which may induce relative pulses of leakages and retentions of hydrocarbons or water coming from the reservoir through the hydrofractured sealing layer.


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References Biteau J.J., Baudin F. (2017) EAGE english publication (2019) Petroleum Geology Chiarelli A. (1973) PhD thesis Grosjean Y. et al. (2009) IPTC abstract Hubbert M.K. (1940) Journal of Geology, Columbia University, 1940 Hubbert M.K. (1953) Bulletin of AAPG Vol 37, N° 8 1953 Mitchell A., Grauls D. (2000) Overpressures in Petroleum Exploration, TECHNIP, 2000 Swarbrick R.E. et al. (2002) American Association of Petroleum Geologists Memoire 76, 1-12 Yardley G., Swarbrick R.E. (2000) GeoPOP, Department of Petroleum Engineering Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK.

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Characterizing the Neuquén basin natural fracturing history using basin modeling coupled with 3D geomechanics Berthelon J.1*, Brüch A.1, Colombo D.1, Frey J.1, Cacas-Stenz M.C.1, Cornu T.2 1: IFPEN, 1-4 avenue de Bois-Préau, Rueil-Malmaison, France 2: Total Exploration Production Research and Development, Pau, France *[email protected]

Basin modeling provides the ability to reproduce the burial history of the sedimentary basins. It is a key tool for understanding the geological evolution of any reservoir and its surroundings. As such, it delivers critical information for any large-scale geological system characterization linked with oil and gas exploration or carbon-free energy industry. Current challenges notably involve to characterize together the thermal and stress state, fluid flow and chemical transfers in porous media, where in-situ measurements can only provide limited information. Basin modeling thus remains particularly pertinent, since it couples thermal and pressure evolution through time. In this work, we propose a demonstration of the integration of 3D geomechanical process in basin model to deliver a full 3D stress description and natural fracturing history in both space and time. The Neuquén basin developed along the eastern foothills of the Central Andes and experienced intraplate deformation during several shortening phases from the Cretaceous to present-day. Low permeability shale reservoirs have been found with exceptionally high overpressure despite the latest erosional history coeval with the current basin shortening. Classical basin models use 1D model to simulate compaction and associated pressure evolution. This approach is not sufficient to match the observed pore pressure in the Neuquén basin while keeping realistic permeability values, let alone to discuss the coupling between natural fracturing and the basin hydrodynamics. Here we consider a 3D geomechanical framework using an appropriate formulation of the poroplasticity to describe efficiently both compaction and rock failure through the basin history. Initial simulations using simple 3D compaction law highlight the role of tectonic compression in the Neuquén basin hydrodynamics, as they allow us to design geological models calibrated in both pressure, stress and temperature using adequate permeability values for the reservoirs. Thus, the fluid history can be properly linked to both burial and tectonic compression. Simulations using a more realistic poroplastic constitutive law address the issue of the stress field evolution during the burial and deformation, and allows us to discuss the coupling between overpressure, fracturing and fluid flow.

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Advances in hydrocarbon cracking reactions mechanisms : implication on the modelling of the thermal stability of petroleum in geological reservoirs Michels R.1*, Burklé-Vitzthum V.2, Bounaceur R.2, Lorgeoux L.1, Marquaire P.M.2, Scacchi G.2 1Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France 2LRGP CNRS- Université de Lorraine UMR 7274, Nancy, France *[email protected]

In order to assess the thermal evolution of petroleum in geological reservoirs during geological time, it is mandatory to set up robust kinetic models for the thermal reactions occurring at high pressure (10-100 MPa) and low temperature (423-493 K). However, for kinetic reasons, such reactions can only be studied in the laboratory by increasing reaction temperatures (typically to the 250°C-450°C range) as to reduce reaction time to a few hours to weeks. Such experiments may be conducted on whole oils or oil fractions, yet the deciphering of the chemical reactions involved is very limited because of the complexity of the reacting system. Consequently, it is necessary to simulate the thermal reactions at the laboratory scale by conducting pyrolysis kinetic studies on model compounds and their mixtures. Therefore, we have developed a long lasting fundamental research on the kinetic modelling of explicit reaction mechanisms applied to mixtures of hydrocarbons pyrolyzed at high pressure. An important feature of our strategy relies on the fact that hydrocarbons classes are not studied in accordance to their chemical structure, but to their kinetic effects. Indeed, in complex mixtures, hydrocarbons react as to have a kinetic influence on each other. This influence depends on their kinetic class: neutral (no kinetic effect), accelerators or inhibitors. The recognition of the kinetic effect is of foremost importance to the understanding of the cracking kinetics of complex mixtures. The thermal stability of petroleum thus relies on the nature and concentration of these kinetic compound classes. We will demonstrate this by presenting experimentation results and kinetic modelling using radical reaction networks dedicated to various hydrocarbons mixtures. Geological petroleum reservoirs are characterized by their high hydrostatic pressures (from several tens to thousands of bars). However, data on the effects of pressure on hydrocarbons cracking are scares, ill understood and usually disregarded in kinetic models. Our research allows to explain how pressure acts on the reaction mechanisms and how it influences the thermal stability of petroleum. Another important aspect in the understanding of petroleum thermal stability is the capacity to extrapolate experimental data to the geological P-T conditions. The modelling based on explicit radical reaction networks takes into account the changes in kinetics implied by the decrease of temperature from laboratory to reservoir conditions. This has profound, sometimes counter-intuitive effects on the cracking behaviour of the hydrocarbons mixtures. This aspect will be illustrated by selected examples.

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Hydro-mechanical modelling of fault reactivation in low permeability media Donzé F.V.1*, Tsopela A.1, guglielmi Y.2, Henry P.3, Gout C.4 1Université Grenoble Alpes, Université. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France. 2Lawrence Berkeley National Laboratory, Earth and Environmental Science Area, 1 Cyclotron road, M/S 74R316C, Berkeley, CA 94720. 3CEREGE, Aix-Marseille University–CNRS–IRD, Marseille, France 4Total S.A., Pau, France. *[email protected]

Fracture interaction mechanisms and reactivation of natural discontinuities under fluid pressurization conditions inside fault zone can represent critical issues in risk assessment of caprock integrity. A field injection test, carried out in a damage fault zone at the decameter scale i.e. mesoscale, has been studied using a Discrete Element Model. Considering the complex structural nature of a fault zone, the contribution of fracture sets on the bulk permeability has been investigated during a hydraulic injection. It has been shown that their orientation for a given in-situ stress field plays a major role. However, if homogeneous properties are assigned to the fracture planes in the model, the limited irreversible displacements cannot be reproduced. Despite these limited displacements (40 µm maximum), the transmissivity increased by a factor of 10-100. These results provide insights in fracture controlled permeability of fault zones depending on the geometrical properties of the fractures and their resulting hydro-mechanical behavior for a given in–situ stress field.

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Hydrologic mechanisms for interaction of multiple brines from different sources at fractured basement-basin interfaces Mindel J.1*, Driesner T.1 1Inst. of Geochemistry and Petrology, Clausiusstrasse 25, 8092 Zürich, Switzerland *[email protected]

Mixing of brines of different origin is considered a key process in the formation of basin-hosted ore deposits. However, hydrological models explaining possible mechanisms have rarely been advanced beyond qualitative conceptual ideas. We performed numerical simulations of generic geological scenarios to search for and understand the role of evaporitic brine invasion in the establishment of fluid flow patterns that may ultimately lead to ore deposit genesis. Our results show that it is reasonable to assume that evaporitic brine invasion is able to enhance the mixing of resident basin and basement brines by triggering convective plumes or promoting existing ones. Large fracture zones appear to play a favorable role in downward migration of the evaporitic brine. Pooling above low permeability layers allows focused and prolonged influx of invading heavier evaporitic brines into the basement, in turn displacing resident basement brines into overlying sedimentary layers and promoting heat mining. We also observed that upon reaching the basement-basin interface, the generated evaporitic brine fingers tend to increase flow parallel to the discontinuity, thus promoting mixing of up to three brines (evaporitic, resident basin and basement brines) where basement-fractures intersect the interface. All of these flow characteristics increase the chances of chemical reactions generating localized deposition in larger concentrations and some of the simulation results may resemble actual ore-forming hydrologic conditions.

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Numerical Modeling Constraints on the Formation of Shale-hosted Massive Sulphide (SHMS) Deposits in the Selwyn Basin, Canada Rodríguez A.1*, Weis P.1*, Magnall J.M.1, Gleeson S.A.1 1GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany *[email protected], [email protected]

Shale-hosted massive sulphide (SHMS) deposits within marine intra- or epicratonic rift sedimentary basins are major resources for Zn, Pb and Ag, but their formation by basin-scale hydrothermal mass and energy transport processes is still poorly understood (e.g. Leach et al., 2005). Using the ancient passive margin of the Selwyn Basin (Canada) as a case study (e.g. Magnall et al., 2016), we apply quantitative numerical fluid flow modeling to explore the effect of strata permeability, timing of fault opening and increased heat flow in controlling fluid migration, metal leaching and ore formation during an extensional tectonic event. The results indicate that tapping hot fluids from a confined and permeable aquifer at several km depths by means of permeable normal faults is a key factor for the formation of economic Zn-Pb deposits. The hot (282 °C) ore-forming fluids are transported to the shallow subsurface shortly after the initiation of a rifting event (within 90 kyr), before the development of extensive basin-scale convection patterns that lead to stronger cooling and a reduction in the capacity of the hydrothermal system to make an economic deposit. Such a hydrothermal event can result in metal endowments comparable to the deposits of the Selwyn Basin. References: Leach D. et al (2005) Econ. Geol., 100th anniversary volume 561-607 Magnall, J.M. et al. (2016) Geochim. et Cosmochim. Acta 193: 251-273

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Application of Digital Rock Physics to low-permeability media: issues and challenges ? Tinet A.J.1, Golfier F.1*, Dymitrowska M.2, Collon P.1, Prat M.3, Vicente J.4 1Université de Lorraine, CNRS, GeoRessources, 54000, Nancy, France 2IRSN, PRP-DGE/SRTG/LETIS, BP 17, 92260 Fontenay-aux-Roses, France 3Institut de Mécanique des Fluides de Toulouse (IMFT), Université de Toulouse, CNRS, Toulouse, France 4Université Aix Marseille, CNRS, IUSTI UMR 7343, 13013 Marseille, France. *[email protected]

Understanding of the multiphase flow inside the compacted sedimentary clay formations is of big interest in many engineering applications such as construction of deep geological radioactive waste repositories where the clay serve as a long term natural barrier effectively preventing the spreading of the radioactive substances. Developments in digital rock physics allow us to study this phenomenon numerically. However, specific attention needs to be paid for application to nano-porous materials. First, such low permeability materials may have a high overall porosity but the majority of this porosity is constituted by pores smaller than 100 nm and whose distribution is still poorly known. The connectivity and the topology of these pores influence the porous media properties, for instance in regards to gas transport. These high-resolution constraints are particularly challenging and raise concerns about the mesh accuracy and the size of the REV of interest. Second, pore scale simulations can be complicated by the very slow flow rates typical of nano-porous media resulting in very small capillary number values. These conditions may necessitate long convergence times and generate convergence issues. Serious questions arise about the legitimacy of such numerical predictions. In this talk, we address this topic and illustrate the strategy with recent results. First, we explore the possibility to reconstruct a coherent 3D configuration of the nano-porous structure from 2D SEM sections of compacted illite at the REV scale. Then, one-phase and two-phase transport properties (intrinsic permeability and Klinkenberg effect, relative permeabilities and retention curve) are numerically calculated using pore-scale simulation method based on these images. For this purpose, a Lattice Boltzmann Model (LBM), a Smooth Particle Hydrodynamics (SPH) model and a morphological model based on Pore Network Model (PNM) are applied. The results obtained by these numerical methods are compared and analyzed.

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Reservoir and

resources

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Friday, 15th November 2019 Reservoir and resources Session 6 : Reservoir and resources Session dedicated to basins as reservoir or storage for different commodities or materials : Hydrocarbon, H2, H2S, methane, unconventional gas, CO2, nuclear repository, 8h30 - Keynote lecture - Plas F. (ANDRA) : Scientific challenges in nuclear waste storage 9h Grgic D. : X-ray tomography applied to self-sealing experiments on argillites 9h15 Tremosa J. : Reconsidering the role of smectite dehydration on overpressures in sedimentary basins 9h30 - Keynote lecture - Truche L. (ISTerre) : Hydrogen (H2) migration in sedimentary basins: resource and storage 10h - Fritz B. : A hydro-geochemical modeling approach of possible abiotic hydrogen generation from the granitic basement in the Soultz-sous-Forêts EGS site (Rhine Graben, France) 10h15 Coffee break 10h30 - Sterpenich J. : Annex gases in the geological storage of CO2 : the example of the solubility of NO in aqueous solution up to 600 bar determined by Raman microspectrometry and molecular simulation 10h45 - Bruno J. : Water-rock processes in deep geological storage of wastes and energy : experimental approaches and model predictions 11h - Abuaisha M. : On the validity of the uniform thermodynamic state approach for underground caverns during fast and slow cycling 11h15- Michels R. : Dissolved hydrocarbon gases as tracers of solute transfer within a low maturity lithological column of east Paris Basin

11h30 – End of the meeting - Conclusions

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Multi-thematic and multi-scale approaches of the Paris Basin geology for the progressive development of the Cigéo project Plas F.1*, Ego F.1, Cochard J.1, Huret E.1 1Andra, 1/7 rue jean Monnet, Chatenay-Malabry 92290, France *[email protected]

The objective of long-term management for HL/ILL radioactive waste is to protect human beings and environment from the radioactivity over a time period up to 1 Myr. In this way and given the dangerousness of these radwaste, the French reference solution is the deep geological disposal to isolate them through geological media at significant depth (> 200-300 m) in order to limit any return to the biosphere. That is the objective of the Cigéo project located in the eastern part of the Paris Basin in the Meuse/Haute-Marne region, whose target host formation is the Callovian-Oxfordian argillaceous clay layer formation. The location of the Cigéo project in the Paris basin is the result of a long process taking into account the favorable characteristics of the site and the Callovo-Oxfordian formation to limit the migration of radionuclides to biosphere. The Paris basin is an intracontinental sedimentary basin whose history began some 250 Myr ago during Triasic time, following the Hercynian and Late Hercynian tectonic phases. Its current structure results from the combination of two distinct but superimposed processes: • A long-term thermal subsidence in response to Permo-Triassic rifting leading to the deposition of nearly flat-Iying thick (up to 3500 m) and continuous sedimentary series over most of the Paris Basin; • Several tectonic episodes related to distant geodynamic events (eg, tethysian and Atlantic riftings and openings, Europe-Africa collision ...) at the origin of the remobilization of the Hercynian and late-Hercynian structures. The Paris Basin is one of the tectonically most stable areas of the Western European platform if not the world, away from major influences of the Alpine collision. Indeed, it rests on a 35 km thick Hercynian crust, which behaves like a rigid block in isostatic equilibrium. The seismic activity and the deformation rate in this area are very low, and even close to zero, conferring on the region an aseismic and inactive character. The integration over time of the results of characterization campaigns by Andra, coupled with modellings and fieldworks, has made possible, thanks to the deployment of means, high techs and tools of measurements, to acquire a set of data and knowledge that is significant and sufficient to support the development of Cigéo project, in particular the feasibility principle in 2005. This allows Andra to have a solid and robust knowledge and confidence in the overall site environment characteristic (geology, sedimentology, structural…) and stability, the confinement capacity of the Callovo-Oxfordian host rock and surrounding formations and the deep groundwater flow and solute transfer, regarding to the expected safety functions. This sharp characterization from local scale (35 km²) to regional scale is transposed into a 3D geological block. Since 2005, the continuation of characterization study and engineering studies were conducted to submit a licensing application by 2020. For the future, some topics on geology, sedimentology and tectonic deserve to be studied

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in order to consolidate knowledge and evaluate/quantify the margins of safety. These topics are for example: • In the basement, its geometry and the relationship between the Sarro-lorrain Basin and the Vittel fault, as well as the nature of the basement and the occurrence of a volcanic massif ; • In the host layer and surroundings, understand the origin of the overpressure in the Callovo-Oxfordian as well as that of the anisotropic character of the in situ stress tensor, and their potential relationship with the Alpine collision; • In surface, the understanding of the formation of the karstic network and associated flows regarding to the properties of the Barrois limestones; • In far field, the response and the behavior of the Paris basin regarding to the Alpin glacial isostatic adjustment and its implication on the local state of stress and the potential triggering of earthquake along regional major faults.

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X-ray tomography applied to self-sealing experiments on argillites Grgic D. Université de Lorraine, CNRS, GeoRessources, 54000, Nancy, France [email protected]

During the excavation of underground galleries in a rock mass, reorganisation of the stress field around the site results in damage to the surrounding material. In the framework of research undertaken at the ANDRA underground laboratory in France, galleries have been excavated in a Callovo-Oxfordian argillite formation. The damage has manifest as a number of fracture systems in the adjacent rock. Observations have shown that fractures generated during excavation and storage exploitation are able to self-seal during re-saturation of the site in the post-closure stage. Although indirect evidence for argillite self-sealing has previously been reported, from experiments performed both in situ and on samples, no direct observations of self-sealing have yet been made. For the present study, we performed a range of self-sealing experiments using a newly-

developed triaxial compression cell placed within a nano-CT scanner with a 10 µm

resolution. The body of the compression cell is X-ray transparent, allowing sample healing

to be monitored directly. The samples contained an artificial fracture that had been

generated in the laboratory, into which a fluid was injected. The fractures were orientated

either perpendicular or parallel to the plane of anisotropy of the material. Our initial results

demonstrate that when fluid is injected perpendicular to the plane of anisotropy, the flow-

rate has no apparent influence on the kinetics of fracture closure. Permeability varies

significantly, from 2.10-14 to 2.10-18 m2 over 116 hours. Post-test observations of the

fracture lips show swelling that appears to be orientated perpendicular to the fracture plane

and therefore parallel to the plane of anisotropy. Initial results for an injection parallel to

the plane of anisotropy suggest that, in this case, the rate of flow affects the kinetics of

fracture closure. For a flow-rate of 0.25 ml/min, closure begins after around one minute. In

contrast, for a rate of 0.05 ml/min, it is necessary to wait several minutes before partial

sealing of the zone is observed. The reduction in permeability is again significant, from

2.10-15 to 4.10-18 m2 over 96 hours. After completion of the test, swelling was observed

in elongated zones that lie parallel to the fracture plane and therefore to the plane of

anisotropy.

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Reconsidering the role of smectite dehydration on overpressures in sedimentary basins Tremosa J.1*, Gailhanou H.1, Gaucher E.C.2 1BRGM, 3 avenue Claude Guillemin, 45060 Orléans, France 2TOTAL S.A., Avenue Larribau, 64018 Pau, France *[email protected]

Smectite dehydration is invoked as a diagenetic reaction that can contribute to the generation of overpressures in clay-rich sediments of sedimentary. However, it is a challenge to identify to contribution of smectite dehydration amongst other hydraulic, mechanical and diagenetic mechanisms in play during the burial of a sedimentary pile. Here, we present a coupled chemical and thermo-hydro-mechanical code (Tremosa et al., 2020) that calculates the overpressure generation and fluid evolution because of sediment compaction, temperature increase, water flow and smectite dehydration, handled with a solid solution thermodynamic model. The overpressure accounting for smectite dehydration during the burial of a sedimentary pile was calculated in an application case in petroleum provinces of the Niger Delta. These calculations allowed identifying a contribution of smectite dehydration that can reach 30 % of the present-day fluid overpressure. References: Tremosa et al. (2020) Marine Petrol. Geol., 111, 166-178

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Hydrogen (H2) migration in sedimentary basins: resource and storage Truche L. Université Grenoble Alpes, CNRS, ISTerre, F-38000 Grenoble, France. [email protected]

Hydrogen behavior in the lithosphere and in sedimentary basins in particular attract considerable attention both for fundamental scientific questions (e.g. prebiotic chemistry, deep microbial ecosystems) and industrial applications. From an engineering point of view, H2 behavior in the sedimentary formations is a critical issue for both the deep nuclear waste disposal safety assessment where steel canisters corrosion will produce copious amount of hydrogen, and the large-scale underground hydrogen storage as a future key component for electrical power grid management. Beyond its migration in porous media, H2 may interact at low temperature with oxidized species in solution (e.g. oxy-anions) or in the host-rock (e.g. sulfide, sulfate, carbonate and oxide), in the presence of suitable catalysts or microbial activity (Truche et al. 2013). These reactions may lead to a loss of hydrogen or compromise the integrity of the geological formation. Hydrogen may also occur naturally in sedimentary basins. Hydrogen seepages have been recently discovered in sub-circular depressions located in intra-cratonic basins (Larrin et al. 2015, Zgonnik et al., 2015) or in wells near mid-continent rift systems (Coveney et al., 1987). The nature of the source is currently highly debated. Two recent discoveries have also revealed that H2 may be trapped in deep sedimentary formations overlying intra-cratonic crystalline basements. Large accumulations of H2, stored in several stacked reservoirs covering an estimated area higher than 8 km, have recently been discovered in the Taoudeni Basin (Mali) (Prinzhofer et al., 2018), and surprisingly high H2 contents (up to 500 ppm) have been found adsorbed in the clay-rich rocks surrounding the Cigar-Lake uranium deposits (Truche et al., 2018). These discoveries raised the question of a potential new primary energy resource. Sedimentary basins may represent fertile environments for H2 exploration, and the surprising discovery of H2-bearing reservoirs in the Taoudeni basin, in Mali, could be a turning point in this nascent endeavor. Thus, it now appears necessary to study how H2 migrates and becomes trapped in the Earth’s crust in order to reasonably assess the recovery potential of this primary natural production. Many unknown H2 sources and reservoirs are awaiting explorers to reveal their potential. References : Coveney et al., AAPG Bulletin 71, 39-48. Larin et al., Nat Resour Res 24, 369-383 (2015). Prinzhofer et al., Int J Hyd Ener 43, 19315-19326 (2018). Truche et al., Chem. Geol. 351, 217-228 (2013) Truche et al., Earth Planet Sci Lett 493, 186-197 (2018) Zgonnik et al., Prog Earth Planet Sci 2, 31 (2015).

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A hydro-geochemical modeling approach of possible abiotic hydrogen generation from the granitic basement in the Soultz-sous-Forêts EGS site (Rhine Graben, France) Murray J.1,4, Fritz B.1*, Schmittbuhl J.2, Clément A.1, Bordmann V.3, Fleury J.M.3 1Université de Strasbourg/EOST,CNRS, LHYGES, 1 rue Blessig, 67084, Strasbourg, France 2Université de Strasbourg/EOST, CNRS, IPGS, 5 rue René Descartes, 67084, Strasbourg, France 3TOTAL, 2 place Jean Millier, 92078, Paris La Défense, France 4IBIGEO, Conicet – Universidad Nacional de Salta, Av. 9 de Julio 14, Rosario de Lerma, Salta, Argentina *[email protected]

In the world scenario of energetic transition the question of natural abiotic hydrogen-gas (H2) has appeared in various recent investigations of new CO2-free energy sources. In natural systems the generation of natural H2 has been studied in the context of serpentinization or ophiolites alteration. In these scenarios the source of H2 is linked to the presence of Fe(II) bearing minerals, candidates to iron oxidation with associated Hydrogen production by reduction of protons (H+). Possible abiotic processes where crustal H2 can be generated, like in thinned-crust basins, have been less explored. In this study we contribute to the study of H2 generation in this kind of less explored environments by focusing our research in the context of the Enhanced Geothermal System (EGS) of Soultz-sous-Forêts (France), Upper Rhine Graben. We applied a geochemical and reactive transport modeling to investigate the possibilities of abiotic H2 generation from a biotite rich granite in the basement of the geothermal site. In this system, with a high local thermal gradient, three wells up to 5000 m deep were drilled penetrating the granite basement below the sedimentary basin of the Rhine Graben creating a heat exchanger for electricity production. The basement is a massive granite with different petrographic types, very rich in biotite and amphibole, with different grades of fracturation and hydrothermal alteration that host a Na-Cl brine at temperatures up to 200 ˚C. Our modelling approach indicates that the generation of abiotic H2 could be possible in the granite by hydrothermal alteration of the biotite under low redox conditions at different temperatures.


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Determination of the solubility of NO in aqueous solution up to 600 bar by a coupled approach: Raman microspectrometry and molecular simulation. Sterpenich J.1*, Caumon M.C.1, Lachet L.2, Creton B.2, El Jarmouni M.1, Randi A.1, Robert P.1 1Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France 2IFP Energies nouvelles, 1 et 4 avenue de Bois-Préau, 92852 Rueil-Malmaison, France *[email protected]

Depending on hydrocarbon source and CO2 capture processes, the combustion gas from boilers may contain impurities that can be co-injected into a geological repository. These gases, such as SOx, NOx or O2, can interact with reservoir fluids, rocks and well materials and thus potentially affect storage safety. However, there is currently little data on the behavior of such gas mixtures, as well as their chemical reactivity, especially in the presence of water. One reason for this lack comes from the difficulty of handling because of the dangerousness and the high chemical reactivity of SOx, NOx and O2. The aim of this study is to combine Raman spectrometry and Monte Carlo molecular simulations to acquire new thermodynamic data for NO / water systems under deep storage conditions. An innovative experimental setup is coupled with Raman microspectrometry to identify and quantify compositions of fluid phases. Transparent micro-capillaries of silica (internal diameter of 100 μm) are loaded with NO(g) and water to visualize and measure the volume of the different phases and to analyze the chemical composition of the system by Raman spectrometry. These micro-reactors make possible to investigate temperature ranges from 83 K to 773 K and pressures up to 1.5 kbar under safe conditions (micro-volumes of dangerous gases). A quantitative method for determining the solubility of NO in water is developed using molecular simulations (Monte Carlo simulations). The thermophysical properties of the NO-H2O system are computed thanks to a precise calculation of interactions between molecules and to a sampling of all positions that these molecules can adopt. The quantification process is validated by i) determining the speciation of aqueous species, ii) validating the low pressure calibration curve by Henry's law, and iii) verifying the linearity between Raman signal and solubility predicted by molecular simulations. The precise chemical composition of the NO-H2O system is thus given for the first time under pressure and temperature of a geological storage of acid gases. This study is partly funded by the ANR SIGARRR and the Carnot Institute of Lorraine (ICEEL).

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Water-rock processes in deep geological storage of wastes and energy: experimental approaches and model predictions Bruno J.*, Grandia F., Román-Ross G., Arcos D. Amphos 21 Consulting S.L. *[email protected]

Amphos21 has been involved in the last 2 decades in the assessment of the interaction between fluids and host rocks in the geological storage of gases such as CO2 of H2, and high-level nuclear waste. In this assessment, a number of approaches have been developed, from predictive model simulations to underground laboratory experiments and injection of CO2-rich fluids at pilot plant scale. The design of lab scale experiments in underground facilities has commonly fed on preliminary model calculations in which the extent and timing of the processes involved in the experiment can be constrained. These initial simulations have been further used to calibrate the results released by the experiments itself. In this respect, Amphos21 has developed complex, multiphase reactive transport simulations in Mont Terri, Grimsel, Tono and Aspo underground laboratories, in projects such as SR-LOT (effect on water saturation and reaction with clay accessory minerals in heated bentonite rings), In a recent experiment we have been working on the impact of sulphide generation by microbial sulphate reduction in clay rocks), In Grimsel we developed and modelled the CRR experiment where colloidal transport of radionuclides was investigated in situ The outcome of all these projects has not only contributed to a better design of the experiments but has also boosted the improvement of the capabilities of the numerical tools used. A further step in which Amphos21 is developing research is the design of experiments to quantify the gas production (i.e., CO2, CH4 or H2) related to the storage of high-level radioactive waste Amphos21 has been also working on the quantification of the interaction between injected gases and the host geological media, mainly CO2 and H2, in pilot plant experiments. Among the more relevant projects, it is worth mentioning the CarbFix EC project, based on the mineralisation of CO2 through reaction with basaltic rocks in Iceland. This is a very successful approach of permanent disposal of greenhouse effect gases which are currently at the commercial stage and Amphos21 is mainly involved in the development of complex reactive transport modelling. Lessons from this project can be exported to conventional CO2 storage in the risk assessment perspective, since dissolved gas reactivity with seal, clay-rich formations is still an open issue that is currently performed at laboratory scale. Another project of interest in the field of gas storage has been the assessment of geological storage of hydrogen in sedimentary rocks; Amphos21 has actively developing multiphase model approaches in the Duero and Paris basins that can be also fostered in projects of CO2 and methane storage. In this context, we will present these relevant experiences based on all these projects that have contributed to improve our expertise in this domain providing a wide point of view valuable for designing and managing complex experiments and to develop predictive quantitative models.

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On the validity of the uniform thermodynamic state approach for underground caverns during fast and slow cycling AbuAisha M.1*, Rouabhi A.1 1MINES ParisTech, PSL Research University, Centre de Géosciences, 35 rue Saint Honoré, 77300 Fontainebleau, France *[email protected]

Gas storage in underground caverns provides a promising technique to reply efficiently to the renewable energy needs through periods of intermittency. An appropriate prediction of the cavern performance, in terms of thermal inventory and the quantity of stored or retrieved gas, depends on the gas thermodynamics and the thermo–mechanical response of the surrounding rock. The rate of injected or withdrawn mass to/from caverns controls the spatial heterogeneities of the temperature and pressure fields. It also controls the magnitude of gas velocity which represents the driving force for the convective heat transfer with the surrounding rock domain. In order to consider as many industrial concerns during cycling as possible (for instance rock creep and gas diffusion), researchers tend to simplify the cavern thermodynamic problem by neglecting the spatial variations of pressure and temperature which leads to a cavern uniform state. This reduces tremendously the simulation cost, yet it raises up a question about the validity of such assumption during fast cycling. We addressed this concern by performing simplified (uniform thermodynamic state) and complete simulations that took into account all the complexities of this computational fluid dynamics problem. We then compared both simulations for seasonal and daily cycling of underground caverns. A margin of error of up to 7% was observed in the simplified simulations in the case of fast/daily cycling. References : AbuAisha, M. and Rouabhi, A. (2019). Int. J. Heat Mass Transf. Volume 142: 118424

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Dissolved hydrocarbon gases as tracers of solute transfer within a low maturity lithological column of east Paris basin Michels M.1*, Panfilova I.2, Vinsot A.3, Wechner S.4 1Université de Lorraine, CNRS, CREGU, GeoRessources, F-54000 Nancy, France 2LEMTA, CNRS-Université de Lorraine, UMR7563, Vandoeuvre-les-Nancy, France 3Andra, Centre de Meuse/Haute-Marne, France 4Hydroisotop GmbH, Schweitenkirchen, Germany *[email protected]

In order to study the underground geology and hydrogeology of the eastern Paris basin, the 2000m deep well EST433 (Montiers sur Saulx, France) was drilled by Andra and investigated by a research laboratory consortium. Among major objectives were the reconstruction of the burial and thermal history of the Triassic to Malm sedimentary layers as well as the reconnaissance of aquifers and their dynamics. As part of the diverse research fields investigated, organic geochemistry was applied as to contribute to the thermal reconstruction. The presence of hydrocarbon gases at trace concentrations in aquifers and clay layers was also recorded. For each sample collected, the abundance and nature of dissolved hydrocarbon gases were determined as well as their isotopic compositions. The study of the nature, origin and distribution of hydrocarbons trace gas distributions was expected to shed light on solute migration possibilities in the sedimentary column. Geochemical diagrams indicate that all sampled gases have geochemical characteristics compatible with thermogenic sources. While the overall profile of the trace gas composition in the stratigraphic section seems to follow increasing dryness with depth, detailed analysis of distribution reveals a more complex pattern that needed to take into consideration the sedimentological organization of lithologies. Therefore, geochemical data were interpreted in association to their distribution within the rock facies along the depth profile. In order to better understand the dissolved methane distribution in the well, a 1D dissolved gas diffusion modelling was performed using Comsol software. Among 28 variables considered, the model is taking into account lithology, permeability, current geothermal gradient, dissolved methane effective diffusion coefficient. Calculations allow to highlight the dynamic aspects of methane migration in the geological column. Rock hydrocarbon source potential, clay lithologies and communication with aquifers are major parameters which govern gas diffusion. The overall complex pattern can be reproduced by the model and set a physical framework to combined geological and geochemical interpretation. Compared to chlorine as hydrological tracer the results are complementary yet reveal an original view of transfer regimes. This study shows that dissolved hydrocarbon gases can be useful tracers to understand fluid and solute transfer issues in geological systems even in sedimentary basins sections where thermal maturity of source rocks is not significant. The methodology employed could also be useful to establish diagnosis of the natural state of hydrogeological systems at depth.

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https://www.cregu.fr

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International workshop for the 40th anniversary of CREGU



International workshop announcement for the 40th ...€¦ · Sedimentary basins represent one of...

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