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仲巴地体是雅鲁藏布江缝合带西段南北蛇绿岩带之间的重要构造单元,目前对其是否存在早古生代构造-热事件记录及构造属性判别尚不明确.通过野外观测、岩石地球化学研究和年代学分析,在仲巴地体中段的公珠错一带识别出一套侵入到黑云斜长片麻岩中的片麻状二长花岗岩,其锆石U-Pb年龄为~478Ma,表明岩石形成时代为早奥陶世;该套花岗岩具有高Si、富Al和总碱含量较高的特点,铝饱和指数A/CNK=1.13~1.20,富集大离子亲石元素Rb、K,相对亏损Ba、Sr、Nb、Ti等,属于钙碱性强过铝质花岗岩.这是首次在雅鲁藏布江缝合带西段仲巴地体内部识别出代表早奥陶世构造-热事件的地质记录,该套花岗岩形成过程与原特提斯洋向冈瓦纳大陆北缘俯冲结束后的上地壳熔融相关,证明仲巴地体在早古生代应为东冈瓦纳大陆北缘的组成部分.
The Zhongba terrane is an important tectonic unit between the North and South ophiolite belts in the western part of the Yarlung Zangbo suture zone and it is still not clear whether there is a tectonic-thermal event record and tectonic attribute discrimination of the Early Paleozoic.Through the field observation and the study of rock geochemistry And chronological analysis, a set of gneissic monzogranite intruded into the biotite plagiogneiss is identified in the Zhuangzhu fault zone in the middle part of the Zhongba terrane. The zircon U-Pb age is ~ 478Ma, indicating that The age of the rock is Early Ordovician. The granite has high content of Si, Al and total alkali. The saturation index of aluminum is A / CNK = 1.13 ~ 1.20. The enrichment of large ion lithophile elements Rb, K, Loss of Ba, Sr, Nb, Ti, etc. belongs to calc-alkaline strong peraluminous granite.This is the first time that a geological record representing the tectono-thermal events of the Early Ordovician has been identified within the mid-arboreal zone of the Brahmaputra suture The granitoids formation process is related to the melting of the upper crust after the subduction of the original Tethyan ocean to the northern margin of the Gondwanaland, indicating that the Zhongba terrane should be part of the northern margin of the East Gondwanaland during the Early Paleozoic.