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Geochemistry of the subduction-related magmatic rocks in the Dahong Mountains, northern Hubei Province--Constraint on the existence and subduction of the eastern Mianlüe oceanic basin

查看全文 作　　者：DONG Yunpeng, ZHANG Guowei, ZHAO Xia, YAO Anping & LIU Xiaoming The Key Laboratory of Continental Dynamics, Ministry of Education, Department of Geology, Northwest University, Xi抋n 710069,China 高影响力作者 出　　处：《Science China Earth Sciences》索引2004年第47卷第4期,共12页高影响力期刊 基　　金：This work was supported by the National Natu-ral Science Foundation of China (Grant Nos. 49732080, 40003003,40234041). 摘　　要：The existence and subduction of the eastern Mianl黣 oceanic basin in the south Qinling belt are keys to understand the Qinling orogen. Based on geological mapping, several volcanic slices have been identified in Tumen, Zhoujiawan, Xiaofu and Yuantan areas, which distribute in the northern margin of the Dahong Mountains (DHM), and thrust into the Sanli-gang-Sanyang fault. These slices consist mainly of diabases, basaltic-andesitic lavas, pyroclastic rocks and a minor tuff. The geochemistry of the basalts, andesites,and diabases is characterized by depleting in Nb and Ta, enriching in Th and LILE (e.g.K, Rb, Ba), and undifferentiating in HFSE. These geochemical characteristics suggest that the original magma of these rocks was derived from a mantle wedge above a subduction zone, and formed in an island-arc setting in Carboniferous-early Triassic. Comparing with the ophiolites and island-arc volcanic rocks in Mianxian-Leyang area to the west, it is reasonable to consider that there had been an oceanic basin connecting with the Mianle ancient ocean to the westward, distributing along the south edge of the Tongbai-Dabie block. In view of the ophiolite in Huashan area and these island-arc volcanic rocks along the north of the Dahong Mountains, it is suggested that there had been a plate tectonic evolutionary history with oceanic basin rifting and subduction in this region. 关 键 词：geochemistry, subduction, Mianlue ANCIENT OCEANIC basin, Dahong Mountains, south Qinling.
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