The Regional Institute of Shaanxi Bureau of Geological Exploration

Xianyang, China

The Regional Institute of Shaanxi Bureau of Geological Exploration

Xianyang, China
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Huang G.,The Regional Institute of Shaanxi Bureau of Geological Exploration | Niu G.,The Regional Institute of Shaanxi Bureau of Geological Exploration | Zhao P.,The Regional Institute of Shaanxi Bureau of Geological Exploration | Wang X.,The Regional Institute of Shaanxi Bureau of Geological Exploration | And 2 more authors.
Scientia Geologica Sinica | Year: 2017

The Early Devonian volcanic rocks in the Kalamaili area, East Junggar, mainly consist of basalt and basaltic andesite. This paper presents a set of new LA-ICP-MS zircon geochronology, major and trace element geochemistry for several representative basalt and basaltic andesite in Kalamaili area. By dating of the LA-ICP-MS U-Pb zircons from an andesitic sample yield 404± 1.9 Ma, suggesting that it was formed in Early Devonian. Geochemical analyses suggest that the Early Devonian volcanic rocks have high Mg#(41.25~55.32)and low Nb(1.11×10-6~2.42× 10-6), Zr(73.9×10-6~95×10-6)and ΣREE(81.50×10-6~121.80×10-6)contents, belonging to the tholeiite series. The samples have characteristics of enrichment of LILE(K, Rb, Ba)and LREE, depletion of HFSE(Nb, Ta, Ti)and slightly negative Eu anomalies. These geochemical features indicate they are typical arc volcanic rocks in supper-subduction zone. The primitive magma of the rocks was possibly generated by partial melting of a metasomatic mantle source modified by the subducted slab-derived fluid. Combining with the regional geological background we propose that the Early Devonian volcanic rocks formed in an intra-oceanic arc environment, which was the magmatic arc formed by the northward subduction of the Kalamaili oceanic basin in the Early Devonian. Meanwhile the intra-oceanic arc volcanic rocks reported in the Kalamaili area, which have important significance for Paleozoic oceanic basin evolution and regional tectonic framework in East Junggar. © 2017, Science Press. All right reserved.

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