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Early Paleozoic marine volcanic rocks were well developed in the North Qilian Mountains. The paper focuses on discussing the formation process and origin of Na element for Ordovician marine volcanic rocks during the process of spilite-keratophyre alteration. There is more Na2O in spilite-keratophyre than normal volcanic rock, because of the basaltic magma react with seawater. Therefore, the discrimination diagram involved with Na element cannot be used as the discrimination criteria for distinguishing the original magma series of keratophyre and related geotectonic setting, but the immobile elements can be used as distinguishing basis. Meanwhile, the Na2O-SiO2 diagram is proposed for reflecting the degree of spilite-keratophyre alteration. In this graphic, the boundary line for the percentage of Na element between spilite-keratophyre and normal volcanic rock is a slightly up-convex, which is stand for the content of Na element ranging from 3.5% to 4%. For the marine volcanic rocks in Dacha-Daban area, most of them fall into the distribution region of spilite-keratophyre, suggesting that the convection of seafloor hot brine was very strong at Ordovician back-arc and island-arc spreading ridge during intervolcanic eruption stage, and this area provides very favorable conditions for mineralization. Source

Dong L.-H.,Xinjiang Bureau of Geology and Mineral Exploration and Development | Wang K.-Z.,Xinjiang Geological Survey Academy | Zhu Z.-X.,Xinjiang Geological Survey Academy | Zhao T.-Y.,Xinjiang Geological Survey Academy | And 2 more authors.
Geology in China

Located in the convergence zone of India plate, TarimSino-Korean paleoplate and Siberia ancient plate, Xinjiang has complicated geological structure. With an analysis of the characteristics of large deformation as a starting point, this paper comprehensively summed up such characteristics of the large -scale deformation structure as its type, size, pattern, material composition, structural order and deformation stage, discussed the control role of the large -scale deformation structure over stratigraphic framework, magmatic activities, metamorphism and deformation, regional tectonic evolution and metallogenesis, and divided the tectonics into 34 large deformation structures. The relationship between the evolution of large-scale deformation structure and the mineralization was tentatively investigated. Source

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