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《Mineral Deposits》 2009-05
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Geochemical and Sr-Nd isotopic characteristics of Dongbei basalts in Huichang area, Jiangxi Province, and their geological implications

LI YinQi1, LI ZiLong1, MAO JianRen2, LUO XueQuan2, XU YiGan3 and WANG HuiHui1 (1 Department of Earth Sciences, Zhejiang University, Hangzhou 310027, Zhejiang, China; 2 Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, Jiangsu, China; 3 No. 912 Geological Party, Jiangxi Bureau of Geology and Mineral Resources Exploration and Development, Yingtan 335001, Jiangxi, China)  
The Late Mesozoic Dongbei basalts, located in Huichang area of Jiangxi Province, have SiO2 contents of 49.06%~50.14% and K2O 1.26%~1.63%. They are rich in large-ion lithosphile elements and poor in high field strength elements, and have ∑REE of (135.5~146.8)×10-6, (La/Yb)N of ca. 10 and LREE enrichment, with strong negative Nb and Ta anomalies and no obvious Eu anomalies in the MORB-normalized spider diagram. The Sr-Nd isotopic compositions show that Dongbei basalts have high initial 87Sr/86Sr ratios of 0.70678~0.70695 and low εNd(t) of -2.46~-2.18. These geochemical characteristics indicate that the Dongbei basalts might have been derived from the source of EMⅡ-type lithospheric mantle under the tectonic setting of an active continental margin. The low values of Nb/U (7~8) suggest that the basalts probably experienced the addition of some subduction-related materials and/or a certain degree of crust contamination. The characteristics of the Dongbei basalts are similar to those of the basalts with the tectonic settings of an active continent margin, indicating that Huichang area lays in an active epicontinental environment during the late stage of Late Cretaceous (ca. 85 Ma). The Dongbei basalts might have had an intimate contact with the paleo-Pacific plate subduction underneath the Eurasia plate in the late Yanshanian period. The basaltic underplating may have provided fluid components and heat for the metallogenic magma of Huichang area during the late Yanshanian period, which contributed to the formation of copper deposits.
【Fund】: 江西瑞金-会昌地区矿产远景地质调查(项目编号:矿调[2005]13-6);; 中国地质调查局科技外事部基础研究项目(1212010611805)的联合资助
【CateGory Index】: P588.145
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