黔东南新元古代花岗质岩石地球化学特征及大地构造背景研究

黔东南地区南加、刚边花岗岩体是黔桂边境摩天岭花岗岩基的北延部分,对其采样并进行常量元素及微量元素地球化学测试。花岗岩SiO2含量介于69.14%-77.14%之间,Na2O+K2O含量为6.92%-7.73%,在侵入岩TAS图解上落入花岗闪长岩及花岗岩区,为亚碱性钙碱系列岩石,轻重稀土比值(LREE/HREE)在3.22-7.41之间,轻稀土较重稀土明显富集,且显示明显的负铕异常。综合研究表明:黔东南刚边及南加花岗岩是碰撞的大地构造背景上的花岗岩,形成于主碰撞之后,即属碰撞后花岗岩;本区花岗岩形成与地幔柱活动无关,且不能作为Rodinia裂解的岩石证据。

Geochemical Characteristics and Tectonic Setting of Neoproterozoic Granitic Rocks in Southeastern Guizhou, China

By sampling and testing the major elements and the trace elements of Nanjia granite and Gangbian granite in southeast Guizhou that are the north part of Motianling granite in the frontier of Guizhou-Guangxi.The results is that the content of SiO2 is in the range of 69.14% to 77.14%,and the content of Na2O＋ K2O is in the range of 6.92% to 7.73%.They belong to granodiorite and granite according to the TAS diagram of intrusive rocks,and they belong to sub-alkaline and calc-alkaline rocks.The ratios of LREE and HREE are in the range of 3.22 to 7.41,and LREE is richer than HREE and show a obviously Eu negative anomaly.The comprehensive studies show that the Nanjia granite and Gangbian granite in southeast Guizhou are the granites which were formed after the main collision,and belong to the post-collision granite.The rocks are not connected with the mantle plume and cannot be a rock evidence of Rodinia supercontinent breakup.