Zircon LA-ICP-MS U-Pb dating and Sr-Nd isotope study of the Guposhan granite complex, Guangxi, China  

作　　者：GU Shengyan HUA Renmin QI Huawen 

机构地区：[1]State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China [2]Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China

出　　处：《Chinese Journal Of Geochemistry》2007年第3期290-300,共11页中国地球化学学报

基　　金：Granted jointly by the State Key Fundamental Research Project （Grant No. 1999CB403209） ;the National Natural Science Foundation of China （Grant No. 40132010）.

摘　　要：Zircon U-Pb dating by the LA-ICP-MS method was applied to determining the ages of different units of the Guposhan granite complex, among which the East Guposhan unit is 160.8±1.6 Ma, the West Guposhan unit is 165.0±1.9 Ma, and the Lisong unit is 163.0±1.3 Ma in age. Much similarity in ages of the three units has thus proved that the whole Guposhan granite complex was formed in the same period of time. They were the products of large-scale granitic magmatism through crust-remelting in the first stage of the Middle Yanshanian in South China. However, the three units have differences both in petrology and in geochemistry. Besides the differences in major, trace and rare-earth elements, they are distinct in their Rb-Sr and Sm-Nd isotopic compositions. The East Guposhan unit and Lisong unit and its enclaves have a similar (87Sr/86Sr)i value of 0.7064 with an average of εNd(t)=-3.03, indicating that more mantle material was evolved in the magma derivation; whereas the West Guposhan unit has a higher (87Sr/86Sr)i value of 0.7173 but a lower εNd(t) value of -5.00, and is characterized by strong negative Eu anomalies and higher Rb/Sr ratios, suggesting that its source materials were composed of relatively old crust components and new mantle-derived components. In addition, an inherited zircon grain in the East Guposhan unit (GP-1) yielded a 206Pb/238U age of 806.4 Ma, which is similar to the ages of the Jiulin cordierite granite in northern Jiangxi and of the Yinqiao migmatic granite in Guangxi in the HZH granite zone. All this may provide new evidence for Late Proterozoic magmatism in the HZH granite zone.Zircon U-Pb dating by the LA-ICP-MS method was applied to determining the ages of different units of the Guposhan granite complex, among which the East Guposhan unit is 160.8±1.6 Ma, the West Guposhan unit is 165.0±1.9 Ma, and the Lisong unit is 163.0±1.3 Ma in age. Much similarity in ages of the three units has thus proved that the whole Guposhan granite complex was formed in the same period of time. They were the products of large-scale granitic magrnatism through crust-remelting in the first stage of the Middle Yanshanian in South China. However, the three units have differences both in petrology and in geochemistry. Besides the differences in major, trace and rare-earth elements, they are distinct in their Rb-Sr and Srn-Nd isotopic compositions. The East Guposhan unit and Lisong unit and its enclaves have a similar （875r/86Sr）i value of 0.7064 with an average of eNd（t）=-3.03, indicating that more mantle material was evolved in the magma derivation; whereas the West Guposhan unit has a higher （875r/86Sr）i value of 0.7173 but a lower eNd（t） value of -5.00, and is characterized by strong negative Eu anomalies and higher Rb/Sr ratios, suggesting that its source materials were composed of relatively old crust components and new mantle-derived components. In addition, an inherited zircon grain in the East Guposhan unit （GP-1） yielded a 206pb/238U age of 806.4 Ma, which is similar to the ages of the Jiulin cordierite granite in northern Jiangxi and of the Yinqiao migmatic granite in Guangxi in the HZH granite zone. All this may provide new evidence for Late Proterozoic magmatism in the HZH granite zone.

关 键 词：锆石 地质年代学 同位素地质学 测量方法 

分 类 号：P597[天文地球—地球化学]