| Geochronology and geochemistry of Yanchangbeishan biotite Adamellite of Lenghu area in Qinghai and their geological significanceEI北大核心CSCD |
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| 作者单位： | 1.MLR Key Laboratory of Mineralization and Prospecting in Magmatism, Xi'an Center of Geological Survey/Xi'an Institute of Geology and Mineral Resource, CGS, Xi'an, 710054, ShaanxiShaanxi;2.Qinghai Coal Geological Prospecting Institute, Xi'ning, 810000, QinghaiQinghai;3.The Eleventh Geological Brigade of Hebei Bureau of Geology and Mineral Resources, Xingtai, 054000, HebeiHebei; |
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| 摘 要： | The Yanchangbeishan biotite adamellite in the Lenghu area of Qinghai is located in the west segment of the north margin of Qaidam. The rocks have high SiO2 (73.92%-75.98%) and K2O contents (3.71%-4.78%), but low MgO and CaO contents. The alumina saturation index (A/CNK) varies from 1.03 to 1.11, indicating the biotite adamellite is peraluminous. The chondrite-normalized REE patterns of the rocks are right dipping and display weak Eu anomalies. The rock contains the Al-rich mineral like garnet and possesses normative corundum contents of 1%. It has low Th and Y contents which are negatively correlated with Rb, suggesting the source rock was sedimentary rock. Thus, the biotite adamellite belongs to S-type granite. The granite was produced by partial melting of the crust material due to the underplating of mantle-derived magma. LA-ICP-MS zircon U-Pb dating shows that the formation age of the rock is 254±4 Ma. Based on the regional geological background and the geochemical characteristics of the rocks, we consider that the formation of the Yanchangbeishan biotite adamellite was related to subduction, which is illustrated by the characteristics similar to those of the island-arc igneous rocks. Therefore, the results reveal that the north margin of Qaidam was in active continental margin tectonic environment during Late Permian epoch. ©, 2015, Science Press. All right reserved.
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