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首页> 外文期刊>Journal of Asian earth sciences >A lower crust origin of some flood basalts of the Emeishan large igneous province, SW China
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A lower crust origin of some flood basalts of the Emeishan large igneous province, SW China

机译：中国西南峨眉山大火成岩省某些洪水玄武岩的下地壳成因

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High seismic velocity layers within the lower crust (i.e. similar to 40 km) of the Yangtze Block are interpreted as mafic underplated rocks derived from the Late Permian Emeishan mantle plume. However, the region experienced a previous magmatic event during the Neoproterozoic (similar to 800 Ma) that produced the Kangdian basalts and associated mafic intrusions and therefore the lower crust seismic velocity layers may represent a mixture of two different magmatic episodes. The identification of inherited Neoproterozoic (i.e. similar to 750 to similar to 850 Ma) zircons within Emeishan magmatic rocks indicates either assimilation of older material during emplacement or that the rocks could be derived from a mafic Neoproterozoic precursor. Equilibrium partial melt modeling of Neoproterozoic Kangdian basalts can produce compositions similar to Emeishan basalt at a pressure of 1.2 GPa (i.e. approximate to 440 km depth). It is suggested that the injection of high temperature picritic magmas into the lower crust of the Yangtze Block could be sufficient to induce high degrees of melting of the lower crust and produce magmas that are similar in composition to some Emeishan mafic rocks and/or produce melts that could contaminate 'pristine' Emieshan magmas. (C) 2015 Elsevier Ltd. All rights reserved.
机译：扬子地块下地壳（即约40 km）内的高地震速层被解释为源自晚二叠世峨眉山地幔柱的镁铁质底板岩。但是，该地区在新元古代（约800 Ma）期间经历了一次岩浆事件，产生了康甸玄武岩和相关的镁铁质侵入体，因此下地壳地震速度层可能代表了两种不同岩浆事件的混合。在峨眉山岩浆岩中鉴定出继承的新元古代（即类似于750到类似于850 Ma）的锆石，表明要么就位过程中吸收了较旧的物质，要么这些岩石可能来自镁铁质新元古代的前体。新元古代康甸玄武岩的平衡局部熔融模拟可以在1.2 GPa（即约440 km的深度）压力下产生与峨眉山玄武岩相似的成分。建议向扬子地块的下地壳注入高温pic水岩浆可能足以引起下地壳的高度熔融，并产生与某些峨眉山铁镁质岩成分相似的岩浆和/或产生熔体可能会污染“原始的”艾米山岩浆。 （C）2015 Elsevier Ltd.保留所有权利。

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