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首页> 外文期刊>Contributions to Mineralogy and Petrology >Metasomatism and melting history of a Variscan lithospheric mantle domain: evidence from the Puy Beaunit xenoliths (French Massif Central)
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Metasomatism and melting history of a Variscan lithospheric mantle domain: evidence from the Puy Beaunit xenoliths (French Massif Central)

机译:瓦里斯坎岩石圈地幔区域的交代作用和融化历史:来自Puy Beaunit异岩的证据(法国地块中部)

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摘要

Mantle xenoliths from Puy Beaunit (French Massif Central) are compositionally varied, ranging from relatively fertile spinel lherzolites to refractory spinel dunites. Fertile peridotites have registered a modal (amphibole-bearing lherzolites) and cryptic metasomatic event that took place before the last Permian (257 Ma) melting episode. Depletion processes have been constrained by chemical modelling: the depletion is related to different degrees of partial melting, but two major melt extraction episodes are needed to explain the range of major element composition. The second event was responsible for the local large-scale dunitification of former residues. The first melting event (F≈25%) and metasomatic enrichment are attributed to an ancient fluid and/or liquid infiltration that could be related to a pre-Variscan regional subduction (located to the north of the Beaunit area). Texture acquisition and major deformation of the mantle xenoliths were sub-contemporaneous of the subduction and would result from lithospheric delamination. The second melting event (F≈17%) produced high-Mg basalts with calc-alkaline trace element signature that gave rise to the Permian underplating episode recognised in western Europe.
机译:Puy Beaunit(法国地块中部)的地幔异岩成分从相对肥沃的尖晶石锂铁矿到难熔的尖晶石杜氏岩,成分各异。肥沃的橄榄岩已经记录了一个模态(含闪石的蛇纹石)和隐性交代事件,该事件发生在最后的二叠纪(257 Ma)熔化事件之前。消耗过程已受到化学建模的约束:消耗与部分熔融程度不同有关,但需要两个主要的熔体萃取过程来解释主要元素组成的范围。第二次事件是造成先前残留物大规模局部灭绝的原因。第一次融化事件(F≈25%)和交代富集是由于古老的流体和/或液体渗透,这可能与瓦里斯卡纳之前的区域俯冲(位于博尼特地区北部)有关。地幔异岩的质地获取和主要变形在俯冲作用的同时发生,并可能是岩石圈分层所致。第二次熔化事件(F≈17%)产生了具有钙碱性微量元素特征的高镁玄武岩,从而引起了西欧公认的二叠纪地下活动。

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  • 来源
    《Contributions to Mineralogy and Petrology》 |2004年第1期|13-28|共16页
  • 作者单位

    Laboratoire de Géochimie Isotopique et Géodynamique Chimique DSTE Université Libre de Bruxelles (CP 160/02)Centre Littoral De Géophysique EA 2612 Université de La Rochelle;

    Unité de Minéralogie et Géochimie Musée Royal de l’Afrique CentraleCentre Littoral De Géophysique EA 2612 Université de La Rochelle;

    Laboratoire de Géochimie Isotopique et Géodynamique Chimique DSTE Université Libre de Bruxelles (CP 160/02);

    Centre Littoral De Géophysique EA 2612 Université de La Rochelle;

    Laboratoire de Géochimie Isotopique et Géodynamique Chimique DSTE Université Libre de Bruxelles (CP 160/02);

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