湘东-赣西地区早古生代晚期花岗岩体的LA-ICPMS锆石U-Pb定年研究

LA-ICPMS zircon U-Pb geochronology of late Early Paleozoic granites in eastern Hunan and western Jiangxi provinces,South China

对湘东板杉铺岩体、宏夏桥岩体和赣西张佳坊岩体、丰顶山岩体以及山庄岩体共5个早古生代晚期花岗岩体的LA—ICPMS锆石U—Pb年龄测定结果表明，采自上述5个岩体的代表性样品分别给出了（418±2）Ma（板杉铺岩体）、（432±6）Ma（宏夏桥岩体）、（440±2）Ma（张佳坊岩体）、（402±2）Ma（丰顶山岩体）和（424±3）Ma（山庄岩体）的锆石u—Ph谐和年龄，代表了区内早古生代晚期花岗岩的形成时代。结合其他的年代学和地质资料，认为华南早古生代晚期花岗岩空间上呈面状展布，时代上主体集中在400～440Ma间，且区内早古生代晚期片麻状花岗岩和块状花岗岩的形成时代无明显差异，动力学上倾向于认为华南内部加里东事件很可能不是洋陆俯冲作用的结果。

The LA-ICPMS zircon U-Pb method was used to date the formational ages of five late Early Paleozoic granites, from eastern Hunan and western Jiangxi Provinces, South China Block. The dating results show that zircons were separated from the Banshanpu, Hongxiaqiao, Zhangjiafang, Fengdingshan and Shanzhuang granitic plutons yielded weighted m ean ^206pb/^238U ages of （418±2） Ma, （432±6） Ma, （440±2） Ma, （402±2） Ma and （424±3） Ma, respectively. These ages of 402 -440 Ma could be interpreted as the crystallization ages of the granitic plutons. Together with other published geochronological and geological data, it is proposed that the late Early Paleozoic granites in the hinterland of the South China Block were predominantly formed at 400-440 Ma and have a similar formation ages between the gneissic and massive granites. These granites exhibit additionally a planar-shaped distribution in space. It is also deduced that the granitic products of the late Early Paleozoic tectonothermal event might be the derivation of the intracontinental overthickening rather than the oceanic subduction and subsequent continental collision.