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首页> 外文期刊>Lithos: An International Journal of Mineralogy, Petrology, and Geochemistry >OIB-like, heterogeneous mantle sources of Permian basaltic magmatism in the western Tarim Basin, NW China: Implications for a possible Permian large igneous province
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OIB-like, heterogeneous mantle sources of Permian basaltic magmatism in the western Tarim Basin, NW China: Implications for a possible Permian large igneous province

机译：中国西北塔里木盆地二叠纪玄武岩浆岩的OIB样，异质地幔源：对一个可能的二叠纪大火成岩省的启示

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摘要

Permian basalts are widely distributed in the Tarim Basin and surrounding areas of NW China. The magmatism is represented by basaltic flows in Keping and mafic and ultramafic dykes in Silurian-Devonian strata in Bachu, southwestern Tarim Basin. The basalts in Keping have SiO2 (44.1%-55.5 wt%) and total alkalis (Na2O + K2O = 3.20-7.79 wt.% similar to the mafic dykes in Bachu, but with much higher TiO2 (3.53-4.33 wt%). An ultramafic dyke has relatively low SiO2 (44.6-43.2 wt.%) and high MgO (19.0-20.2 wt.%), reflecting the abundance of cumulate olivine. All the rocks, including both lavas and dykes, have parallel, mantle-normalized trace element patterns enriched in Rb, Ba, Th, Nb, Ta, Zr, Hf, and light rare earth elements (LREE). The basalts have higher initial ~(87)Sr/~(86)Sr ratios (0.7064 to 0.7080) and lower eNd(t) values (-2.66 to -9.27) than the dykes (initial ~(87)Sr/~(86)Sr ratios range from 0.7048 to 0.7052 and eNd(t) values from +1.64 to + 5.16). Both the basalts and dykes show a narrow range of ~(206)Pb/~(204)Pb (17.87-18.77), ~(207)Pb/~(204)Pb (15.52-15.58) and ~(208)Pb/~(204)Pb (38.38-39.04) ratios. The dykes do not show significant crustal contamination and were derived from an OIB-like, asthenospheric mantle source. In contrast, the basaltic flows show variable degrees (up to 10%) of crustal contamination and were derived from an OIB-like, but isotopically more enriched, asthenospheric mantle source. Olivine from the ultramafic dyke has Fo values up to 85, corresponding to a melt temperature of 1300 °C and a melt Mg# of 63. The Tarim Basin magmatism reflects partial melting of heterogeneous mantle sources related to a major mantle plume. Spatially and temporally associated mafic-ultramafic and syenitic intrusions and volcanic rocks form the ～275 Ma Tarim large igneous province.
机译：二叠纪玄武岩广泛分布在塔里木盆地和中国西北地区。岩浆作用表现为塔坪盆地西南部巴楚地区柯坪的玄武岩流和志留系-德文统地层的镁铁质岩浆和超镁铁质岩浆。柯坪的玄武岩具有SiO2（44.1％-55.5 wt％）和总碱度（Na2O + K2O = 3.20-7.79 wt。％），与巴楚的镁铁矿岩相似，但TiO2含量高得多（3.53-4.33 wt％）。超镁铁质岩浆的SiO2含量较低（44.6-43.2 wt。％），MgO含量较高（19.0-20.2 wt。％），反映出丰富的累积橄榄石，所有岩石，包括熔岩和岩浆，都具有平行的，地幔归一化的痕迹玄武岩的初始〜（87）Sr /〜（86）Sr比率较高（0.7064至0.7080），且富含Rb，Ba，Th，Nb，Ta，Zr，Hf和轻稀土元素（LREE）。 eNd（t）值比堤坝低（-2.66至-9.27）（初始〜（87）Sr /〜（86）Sr比率范围为0.7048至0.7052，eNd（t）值范围为+1.64至+5.16）。玄武岩和堤坝的〜（206）Pb /〜（204）Pb（17.87-18.77），〜（207）Pb /〜（204）Pb（15.52-15.58）和〜（208）Pb /〜范围很窄（204）Pb（38.38-39.04）的比率：堤坝没有显示出明显的地壳污染，并且源自类似OIB的软流圈地幔rce。相反，玄武质流显示出不同程度（最高10％）的地壳污染，并且来自类似OIB的同位素，但同位素更富集的软流圈地幔源。来自超镁铁岩脉的橄榄石的Fo值高达85，对应的熔融温度为1300°C，熔融Mg＃为63。塔里木盆地的岩浆作用反映了与主要地幔柱相关的非均质地幔源的部分熔融。时空相关的镁铁质-超镁铁质和年纪侵入体和火山岩形成了〜275 Ma Tarim大火成岩省。

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