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6 results on '"Olivier Blein"'

1. Depositional Setting of Archean BIFs from Congo: New Insight into Under-Investigated Occurrences

Author

Blandine Gourcerol, Olivier Blein, Matthieu Chevillard, Yannick Callec, Florent Boudzoumou, and Louis-Marie Joachim Djama

Subjects
BIF, Republic of the Congo, hydrothermal fluids, seawater, depositional settings, Chaillu, Mineralogy, QE351-399.2
Abstract

Archean banded iron formations (BIF) represent a major contributor to better constraining and assessing the paleogeography and evolution of Archean cratons. In this context, we conducted an exhaustive sampling and analysis campaign of BIF units in the Congo Craton, covering several greenstone belts within the Ivindo, Kelle-Mbomo, and Chaillu blocks. The REE + Y patterns suggest: (1) Interaction of seawater with Fe-oxyhydroxides, as illustrated by strong REE enrichment coupled with La and Y enrichment; (2) contributions from high-temperature (>250 °C) hydrothermal fluids, illustrated by positive Eu anomalies; and (3) detrital input as suggested by relatively consistent REE concentrations and a chondritic Y/Ho ratio. These observations suggest a typical environment of Algoma-type BIF deposition. Moreover, assessment of the Ce anomalies in a combination of HREE enrichment indicates that some basins in the Chaillu and Ivindo blocks may have known potential oxygen-rich episodes in the early Archean during the deposition of these BIFs.

Published
2022
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3. Tourmalinisation in peraluminous granitic context : from experiment to thermodynamic modelling

Author

Olivier Blein, Michel Pichavant, Julien Fort, Arnault Lassin, Stanislas Sizaret, Johann Tuduri, Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Métallogénie - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), and Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)

Subjects
13. Climate action, [SDU]Sciences of the Universe [physics], Earth science, Context (language use), Geology, ComputingMilieux_MISCELLANEOUS
Abstract

Tourmaline records the physico chemical conditions during its cristallisation, as its primary chemical zonations are generally unbalanced, its occurrence as alteration product could be used to decipher the physicochemical properties of mineralizing fluids. However, the role of the tourmalinisation in hydrothermal processes remains little studied, if not poorly understood. The complexity of its thermodynamic properties is related to the presence of four cationic sites allowing the accommodation of a wide variety of elements (Henry and Dutrow, 2018). Moreover the phenomena of deprotonation, Si-IVB and valence state, make the approach of solid solution properties complex (Hughes et al., 2001; Henry et al., 2011; Bačík, 2015; Morgan, 2016). Thus, thermodynamic properties are most often estimated (Garofalo et al., 2000; Hinsberg and Schumacher, 2007) and only a few measurements could be carried out on a reduced number of near-endmembers crystals (Kuyunko et al., 1984; Ogorodova et al., 2012).This study aims to investigate experimentally the stability field of schorl (Na-Fe) – dravite (Na-Mg) solid solution at 2 kbar total pressure between 400° and 600°C as a function of the boron content of the fluid and fO2 condition, using an internally heated gas apparatus. Those metasomatic experiments have been conducted on a mixture of naturals crystals of cordierite + albite, representing a peraluminous granite composition in a Na-Mg-Fe-Al-Si-B-O-H system, characterized by a high-Mg, low-Fe content. These experiments were performed in order to simulate a classic aluminous host of these tourmaline alterations in granitic context. The results will be studied, in terms of stability of the tourmaline species, chemistry variation and texture. They will be compared with thermodynamic models build using data from the literature (Korges et al., 2018; Pan et al., 2019 among others) . Ultimately, the objective is to characterize in a P, T, W/R space, the chemical evolution of fluids, the alteration sequence of rocks and the variations in volumes related to the successive reactions.

Published
2021

6. Structural, metamorphic and geochronological insights on the Variscan evolution of the Alpine basement in the Belledonne Massif (France)

Author

Marc Poujol, Olivier Bruguier, Kévin Fréville, Olivier Blein, Wei Lin, Jérémie Melleton, Xian-Hua Li, Pierre Trap, Michel Faure, Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Métallogénie - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Laboratoire Chrono-environnement (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), State Key Laboratory of Lithospheric Evolution (SKL), Institute of Geology and Geophysics [Beijing] (IGG), Chinese Academy of Sciences [Beijing] (CAS)-Chinese Academy of Sciences [Beijing] (CAS), Chinese Academy of Inspection And Quarantine (CAIQ), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Terre, Temps, Traçage, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), ISTO, BRGMBRGM, Laboratoire Chrono-Environnement, Observatoire des Sciences de l'Univers en Région Centre, Institut des Sciences de la Terre d'Orléans - UMR7327 ( ISTO ), Bureau de Recherches Géologiques et Minières (BRGM) ( BRGM ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Bureau de Recherches Géologiques et Minières (BRGM) ( BRGM ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ) -Bureau de Recherches Géologiques et Minières (BRGM) ( BRGM ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Chrono-environnement ( LCE ), Université Bourgogne Franche-Comté ( UBFC ) -Université de Franche-Comté ( UFC ) -Centre National de la Recherche Scientifique ( CNRS ), Bureau de Recherches Géologiques et Minières (BRGM) ( BRGM ), State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Chinese Academy of Inspection And Quarantine ( CAIQ ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Université de Montpellier ( UM ) -Université des Antilles ( UA ) -Centre National de la Recherche Scientifique ( CNRS ), Géosciences Rennes ( GR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire des Sciences de l'Univers de Rennes ( OSUR ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire des Sciences de l'Univers de Rennes ( OSUR ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Geochemistry, Metamorphism, Thermobarometry, 010502 geochemistry & geophysics, 01 natural sciences, Nappe, Alpine External Crystalline Massifs, Lineation, SIMS and LA-ICP-MS dating, Metamorphic facies, 0105 earth and related environmental sciences, Earth-Surface Processes, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Schist, Orogeny, [ SDU.STU.TE ] Sciences of the Universe [physics]/Earth Sciences/Tectonics, Massif, Variscan Belt, Geophysics, Zircon and monazite dating, Geology, Zircon, Belledonne Massif
Abstract

International audience; A structural and petrochronological study was carried out in the southern part of the Belledonne crystalline massif. A first tectonometamorphic event, Dx, corresponds to the eastward thrusting of the Chamrousse ophiolitic complex characterized by a low-temperature–moderate-pressure metamorphism reaching 0.535 ± 0.045 GPa and 427.5 ± 17.5 °C. A subsequent D1 deformation is defined by a penetrative S1 foliation that mostly dips toward the west and displays an E–W- to NE–SW-trending mineral and stretching lineation L1. D1 is associated with a top-to-the east shearing and is responsible for the crustal thickening accommodated by the eastward nappe stacking and the emplacement of the Chamrousse ophiolitic complex upon the Rioupéroux-Livet unit. This event is characterized by an amphibolite facies metamorphism (0.58 GPa ± 0.06; 608 ± 14 °C) that attains partial melting at the base of the nappe pile (0.78 ± 0.07 GPa; 680.5 ± 11.5 °C). LA-ICP-MS U-Pb dating of monazite grains from the mica schists of the Rioupéroux-Livet unit constrain the age of D1 to 337 ± 7 Ma. The D2 tectono-metamorphic event is characterized by NE–SW trending, upright to NE-verging synfolial folding. Folding associated with D2 is pervasively developed in all lithotectonic units with the development of a steeply-dipping S2 foliation. In particular, D2 involves the uppermost weakly metamorphosed Taillefer unit. LA-ICP-MS U-Pb dating performed on detrital zircon grains shows that the Taillefer conglomerates was deposited during the Visean. A zircon SIMS U-Pb age of 352 ± 1 Ma from a plagioglase-rich leucocratic sill of the Rioupéroux-Livet unit is interpreted as the age of magmatic emplacement. Our results suggest that the D2 event took place between 330 Ma and 310 Ma. We propose a new interpretation of the tectonometamorphic evolution of the southern part of the Belledonne massif, focusing on the Middle Carboniferous stages of the Variscan orogeny.

Published
2018

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