OIB-like, heterogeneous mantle sources of Permian basaltic magmatism in the western Tarim Basin, NW China: Implications for a possible Permian large igneous province
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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DOI：
10.1016/j.lithos.2009.06.027
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发表时间：
2009-12
期刊：
影响因子：
3.5
通讯作者：
Mei Zhou;J. Zhao;Changyi Jiang;Jian-Feng Gao;Wei Wang;Shenghong Yang
中科院分区：
文献类型：
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作者：
Mei Zhou;J. Zhao;Changyi Jiang;Jian-Feng Gao;Wei Wang;Shenghong Yang
塔里木盆地及周边地区广泛分布着二叠纪玄武岩。塔里木盆地西南部柯坪玄武岩流和巴楚志留-泥盆系镁铁质、超镁铁质岩墙为岩浆活动的代表。柯坪玄武岩的SiO2含量为44.1%-55.5%（质量分数）和总碱（Na 2 O + K 2 O =3.20-7.79 wt.%）与巴楚基性岩脉相似，但TiO_2含量高得多（3.53- 4.33wt.%）。超镁铁岩墙具有相对低的SiO2（44.6-43.2重量%）和高MgO（19.0- 20.2wt%），反映了堆积橄榄石的丰度。所有的岩石，包括熔岩和岩墙，具有平行的，地幔标准化的微量元素模式，富集Rb，Ba，Th，Nb，Ta，Zr，Hf和轻稀土元素（LREE）。玄武岩的初始87 Sr/86 Sr比值（0.7064 ~ 0.7080）和εNd（t）值（−2.66 ~ −9.27）均高于岩墙（初始87 Sr/86 Sr比值为0.7048 ~ 0.7052，εNd（t）值为+1.64 ~+5.16）。玄武岩和岩墙的~（206）Pb/~（204）Pb（17.87-18.77）、~（207）Pb/~（204）Pb（15.52-15.58）和~（208）Pb/~（204）Pb（38.38-39.04）比值范围较窄。岩墙没有显示出显着的地壳污染，并来自OIB一样，软流圈地幔源。与此相反，玄武岩流显示不同程度（高达10%）的地壳污染，并来自OIB样，但同位素更丰富，软流圈地幔源。超镁铁质岩墙中的橄榄石Fo值高达85，对应于1300 °C的熔体温度和63的熔体Mg#。塔里木盆地岩浆活动反映了与地幔柱有关的不均匀地幔源区的部分熔融。在时间和空间上共生的镁铁质-超镁铁质和正长质侵入体及火山岩形成了275 Ma的塔里木大火成岩省。
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 initial87Sr/86Sr ratios (0.7064 to 0.7080) and lower εNd(t) values (−2.66 to −9.27) than the dykes (initial87Sr/86Sr ratios range from 0.7048 to 0.7052 and εNd(t) values from +1.64 to +5.16). Both the basalts and dykes show a narrow range of206Pb/204Pb (17.87–18.77),207Pb/204Pb (15.52–15.58) and208Pb/204Pb (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.