柴北缘夏日哈地区二长花岗岩锆石U-Pb定年、地球化学特征及地质意义

Zircon U-Pb dating of mafic dikes and geochemical features and significance in Xiariha area on the northern rim of Qiadam Basin

在1∶50 000区域地质填图的基础上,运用岩石学、岩石地球化学及LA-MC-ICP-MS锆石U-Pb测年等方法,对柴北缘夏日哈地区二长花岗岩体进行了详细的研究。结果表明:夏日哈二长花岗岩加权平均年龄为(453.1±1.8)Ma(MSWD=0.003 9),岩石为高硅、过铝质、钙碱—高钾钙碱性系列;稀土元素总量(ΣREE)较高,轻稀土(LREE)相对富集,重稀土(HREE)相对亏损,稀土(REE)配分曲线呈轻稀土分馏相对明显、重稀土分馏相对较弱、铕弱亏损或弱富集的右倾特征,具有埃达克(adakite)质岩石的特征,是晚奥陶世时期先期消减到欧龙布鲁克陆块之下的大洋板块部分熔融作用形成的产物。

A detailed study was conducted of Xiariha monzonitic granite of North Qaidam with pe-trology,rock geochemistry and LA-MC-ICP-MS zircon U-Pb dating methods on the basis of 1∶50 000 regional geological map .The results show that the weighted average age of monzonitic granite in Xiar-iha is （453.1±1.8）Ma （MSWD=0.0039）.According to the geochemical characteristics ,it is sug-gested that Xiariha monzonitic granite belongs to high silicon , peraluminous , calcium alkali-high in potassium calc-alkaline series .The rare earth elements （ REE ） exhibit a right dip patterns with strongly enrichment of light rare earth element （ LREE ） , and the relatively depletion of heavy rare earth elements（HREE）.The distribution patterns of light rare earth were relatively significant and of heavy rare earth were relatively weak .Europium is weak loss or weak enrichment with adakite char-acteristics of rocks .It is the product of partial melting of oceanic plate which inserted into Auron Brook landmass below during Late Ordovician period .