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<datestamp>2018-01-11</datestamp>
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<title lang=en>New occurrence of UHP eclogites in Limousin (French Massif Central): Age, tectonic setting and fluid-rock interactions</title>
<creator>Berger, Julien</creator>
<creator>Femenias, Olivier</creator>
<creator>Ohnenstetter, Daniel</creator>
<creator>Bruguier, Olivier</creator>
<creator>Plissart, Gaelle</creator>
<creator>Mercier, Jean-Claude C.</creator>
<creator>Demaiffe, Daniel</creator>
<contributor>Département d'Informatique [Bruxelles] (ULB) ; Université Libre de Bruxelles [Bruxelles] (ULB)</contributor>
<contributor>Centre de Recherches Pétrographiques et Géochimiques (CRPG) ; Université de Lorraine (UL) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>LIttoral ENvironnement et Sociétés - UMR 7266 (LIENSs) ; Université de La Rochelle (ULR) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<source>ISSN: 0024-4937</source>
<source>Lithos</source>
<publisher>Elsevier</publisher>
<identifier>hal-00512835</identifier>
<identifier>https://hal.archives-ouvertes.fr/hal-00512835</identifier>
<source>https://hal.archives-ouvertes.fr/hal-00512835</source>
<source>Lithos, Elsevier, 2010, 118 (3-4), pp.365-382. 〈10.1016/j.lithos.2010.05.013〉</source>
<identifier>DOI : 10.1016/j.lithos.2010.05.013</identifier>
<relation>info:eu-repo/semantics/altIdentifier/doi/10.1016/j.lithos.2010.05.013</relation>
<language>en</language>
<subject lang=en>UHP eclogite</subject>
<subject lang=en>Zoisite</subject>
<subject lang=en>Zircon U-Pb dating</subject>
<subject lang=en>French Massif Central</subject>
<subject lang=en>Variscan subduction</subject>
<subject lang=en>Fluid-rock interaction</subject>
<subject>[SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry</subject>
<subject>[SDE.MCG] Environmental Sciences/Global Changes</subject>
<type>info:eu-repo/semantics/article</type>
<type>Journal articles</type>
<description lang=en>Kyanite and zoisite eclogites from the Limousin area in the Variscan French Massif Central (FMC) have been formed by deep subduction to 100 km depth at peak pressure-temperature conditions around 660 degrees C and 2.9 GPa. They belong to a thin tectonic unit comprising ophiolitic bodies devoid of HP-UHP markers and forming a transported suture zone now separating the two main lithotectonic units of the FMC with contrasted tectono-metamorphic features (namely the lower and upper allochthons). Composition of kyanite-eclogites is similar to supra-subduction-zone basalts found in back-arc basins or island arcs (LREE depleted, negative Nb-Ta anomalies, epsilon Nd: +6 to + 9). Zoisite eclogites have the major-element fingerprint of ultrabasic iron-rich plagioclase cumulates common in continental intrusions or forming Fe-Ti oceanic gabbros. The distribution of immobile trace-elements is however more comparable to alkaline Si-undersaturated rocks, but the Sr-Nd isotopic composition (Sr-87/Sr-86: 0.706; epsilon Nd: -3 to -5) suggests the intervention of an old radiogenic crustal component during their petrogenesis. The chemical composition of hydrous zoisite eclogites does not correspond closely to a common magmatic precursor. It is thus suggested that, by analogy with well exposed worldwide HP-UHP terranes, at least a part of the trace-element signature and the isotopic compositions are controlled by channelled fluid-rock interaction at UHP conditions, leading to localised segregation of zoisite that hosts nearly all Sr and LREE budgets of the bulk eclogite. Sr-Nd isotopic composition of these samples is thus controlled by zoisite and probably represents the isotopic composition of the fluid phase present during UHP recrystallisation. Zircons extracted from a zoisite eclogite were dated in-situ by LA-ICP-MS. Crystallisation of the magmatic precursor is bracketed between 489 and 475 Ma and the UHP event is dated at 412 +/- 10 Ma, in agreement with published ages for the Eo-Variscan HP stage in the FMC. A late resetting of the U-Pb isotopic system at 382 +/- 7 Ma is related to an anatectic high pressure-medium pressure event, well known in the Limousin area. The oceanic eclogites dated in this study are tentatively linked to the Galicia-South Brittany Lower Paleozoic Ocean; they show evidence of the existence of an intra-oceanic subduction zone at the Lower Ordovician and of partial closure of this oceanic domain by ocean-continent subduction during Early Devonian.</description>
<date>2010</date>
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