新生代贡嘎山花岗岩中的流体包裹体面测试及其应力场分析  

Fluid Inclusion Planes Measurement and Paleostress Field Analysis for Cenozoic Gonggashan Granite

作　　者：孙圣思[1] 贾东[1] 胡潜伟[1] 陈竹新[1] 贾秋鹏[1] 罗良[1] 李一泉[1] 邓飞[1] 

机构地区：[1]南京大学地球科学系南京大学成矿作用国家重点实验室,南京210093

出　　处：《高校地质学报》2007年第2期344-352,共9页Geological Journal of China Universities

基　　金：国家自然科学基金项目(编号40372091和40672132);中国石油天然气集团公司创新基金;南京大学地球科学系国家基础科学人才培养基金联合资助

摘　　要：贡嘎山花岗岩侵位年代距今12.8±1.4Ma,是平行青藏高原东缘大型活动左旋走滑断裂——鲜水河断裂展布的同构造花岗岩。沿横穿岩体的川藏公路剖面和牦牛沟—塔公草原剖面采集了10个点的定向样品。利用费氏台测试统计的流体包裹体面(FIP)产状数据显示,贡嘎岩体中的FIP主要是东西走向,倾角近于直立,推断贡嘎岩体遭受了近东西方向的水平挤压应力,这与鲜水河断裂的左行走滑相吻合。显微激光拉曼分析和冷热台测温数据表明,FIP中流体包裹体主要是NaCl-H2O包裹体,可以划分两种类型:A型冰点温度-9.0～-8.2℃(盐度11.9%～12.8%),均一温度为126.0～197.0℃;B型冰点温度为-4.7～-0.5℃(盐度0.9%～7.4%),均一温度144.0～314.6℃。贡嘎岩体中的FIP记录了两期地质流体的填充作用,两期流体都表现出由高温高盐度向低温低盐度演化的趋势。深入研究贡嘎山同构造岩浆作用及其与鲜水河断裂关系,对于认识青藏高原内部变形机制具有重要科学意义。Gonggashan granite is a syntectonic granite, emplaced at 12.8 ±1.4 Ma. It extends parallel to Xianshuihe fault, which is a major active sinistral strike-slip fault in eastern Tibet Plateau. Along Chuanzang Road cross section and Maoniugou to Tagong Grassland cross section, 10 oriented specimen were collected to conduct the fluid inclusion planes （FIP） study. The attitudes of FIP measured on Fedoroff universal stage show that the preferred orientation is EW and subvertical. The FIP results indicate that the Gonggashan granite suffered E-W horizontal compression, which is consistent with the sinistral slip of Xianshuihe fault. Laser Raman Microspectroscopy data reveal that most of fluid inclusions in FIP are of NaCl-H2O composition. Microthermometric analysis of fluid inclusions allows distingction of two general types： Type A is characterized by Tm ice in the range of - 9.0 to - 8.2℃ （salinity 11.9%-12.8%）, Th varies from 126.0 up to 197.0℃ . Type B is characterized by Tm ice in the range of -4.7 to - 0.5℃ （salinity 0.9%-7.4%） , Th varies from 144.0 up to 314.6℃. The FIP of Gonggashan granite reveals two stages of fluid percolation, and both evolved with declined temperature and salinity. Paying more attention to syntectonic Gonggashan granitic magmatism and its relationship with Xianshuihe faults is of very important scientific significance in understanding the deformation mechanism of Tibet Plateau.

关 键 词：鲜水河断裂 新生代花岗岩 流体包裹体面(FIP) 古应力场 包裹体测温 

分 类 号：P599[天文地球—地球化学]