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首页> 外文期刊>Contributions to Mineralogy and Petrology >Multistage evolution of the European lithospheric mantle: new evidence from Sardinian peridotite xenoliths
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Multistage evolution of the European lithospheric mantle: new evidence from Sardinian peridotite xenoliths

机译：欧洲岩石圈地幔的多阶段演化：撒丁岛橄榄岩橄榄石异物的新证据

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摘要

Peridotite xenoliths entrained in Plio-Pleistocene alkali basalts from Sardinia represent fragments of the uppermost lithospheric mantle, and are characterised by an anhydrous four-phase mineral assemblage. They range in bulk rock composition from fertile spinellherzolites to residual spinel-harzburgites. The Sr-Nd isotope and trace element composition of clinopyroxene mineral separates varies between LREE-depleted samples with (87)~Sr/(86)~Sr as low as 0.70262 and (143)~Nd/(144)~Nd up to 0.51323 and LREE-enriched samples with (87)~Sr/(86)~Sr up to 0.70461 and down to 0.51252. The available data suggest that all the studied peridotite samples suffered variable degrees of partial melting during Pre-Mesozoic times (based on Nd model ages relative to CHUR and DMM). The overprinted enrichment is related to a subsequent metasomatism, induces by fluids rising through the lithosphere that preferentially percolated the originally most depleted domains. Despite the occurrence of orogenic volcanism in the area, preferential enrichment in elements typically associated with slab derived fluids/melts (K, Rb, Sr, Th) relative to LREE has not been detected, and metasomatism seems to be more likely related to the infiltration of highly alkaline basic melts characterised by an EM-like Sr-Nd isotopic composition. similar (87)~Sr/(86)-~Sr(143)~Nd/(144)~Nd compositions, characterised by an EM signature, are observed in anorogenic mafic lavas and peridotite xenoliths form widespread localities within the "European" plate, whereas they have not previously been recorded in peridotite xenoliths and associated alkaline mafic lavas from the stable "African" lithospheric domain.
机译：来自撒丁岛的上新世-上新世碱性玄武岩夹带的橄榄岩异岩代表最岩石圈地幔的碎片，其特征是无水的四相矿物组合。它们的块状岩石组成从肥沃的尖晶石沸石到残留的尖晶石-哈兹伯格石。斜辉石矿物分离物的Sr-Nd同位素和微量元素组成在贫稀土样品中（87）〜Sr /（86）〜Sr低至0.70262和（143）〜Nd /（144）〜Nd最高至0.51323）富集稀土元素的样品（87）〜Sr /（86）〜Sr分别为0.70461和0.51252。现有数据表明，所有研究过的橄榄岩样品在中生代时期都经历了不同程度的部分融化（基于相对于CHUR和DMM的Nd模型年龄）。叠印的富集与随后的交代作用有关，后者是通过岩石圈上升的流体引起的，这些流体优先渗透到原本最贫乏的区域。尽管该地区发生了造山活动的火山活动，但相对于LREE，尚未发现通常与板坯衍生的流体/熔体（K，Rb，Sr，Th）有关的元素优先富集，而交代作用似乎更可能与渗透有关。碱性高碱性熔体，其特征是类似EM的Sr-Nd同位素组成。在厌蚀的镁铁质熔岩中观察到了类似的（87）〜Sr /（86）-〜Sr（143）〜Nd /（144）〜Nd成分，其特征是具有EM签名，橄榄岩异岩在“欧洲”板块中形成了广泛的位置。 ，而以前从未在稳定的“非洲”岩石圈地区的橄榄岩异岩和相关的碱性镁铁质熔岩中记录到它们。

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