东昆仑哈拉尕吐岩浆混合花岗岩:来自锆石U-Pb年代学的证据  

Halagatu Magma Mixing Granite in the East Kunlun Mountains——Evidence from Zircon U-Pb Dating

作　　者：孙雨[1] 裴先治[1] 丁仨平 李瑞保[1] 冯建赟[1] 张亚峰[1] 李佐臣[1] 陈有炘[1] 张晓飞[1] 陈国超[1] 

机构地区：[1]西部矿产资源与地质工程教育部重点实验室,长安大学地球科学与资源学院,西安710054

出　　处：《地质学报》2009年第7期1000-1010,共11页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40572121);青海省国土资源厅-中国铝业公司公益性地质调查基金项目(编号中铝基金200801)资助的成果

摘　　要：东昆仑造山带东部哈拉尕吐花岗闪长岩体中发育了较多的暗色闪长质微粒包体。通过详细的野外地质调查和岩石学研究及LA-ICP-MS锆石U-Pb定年,得到寄主岩形成年龄为(255.3±3.6)Ma,暗色包体形成时代为(252.9±2.5)Ma,二者年龄基本一致,从而排除了暗色微粒包体为捕虏体或源区难熔残余物质的可能性,也排除了花岗质岩浆固结后基性岩浆侵入的可能性。这一结果从年代学的角度证明了哈拉尕吐花岗闪长岩体是晚二叠世岩浆混合作用的产物。寄主岩石花岗闪长岩是混合时的酸性端员,而暗色闪长质微粒包体则是岩浆混合时未混合完全的残余基性部分。晚二叠世时,阿尼玛卿洋向北俯冲,在区域挤压应力环境下发生幔源岩浆底侵作用,壳幔物质相互混合,形成岩浆混合花岗质的岩浆房并向上侵入形成哈拉尕吐岩体。Halagatu granodiorite rock, located in the eastern of the East Kunlun Mountains, hosts many mafic microgranular enclaves. The detailed field survey and petrology study and the LA-ICP-MS single-zircons U-Pb age demonstrate that the mag matic age is （255.3±3.6）Ma of the granodiorite and （252.9±2.5）Ma of the dioritic enclave. The two ages are basically the same, which rules out the possibility that the mafic microgranular enclaves are xenoliths or residually refractory material of the magma source region,and the possibility that the mafic magma intrude after the consolidation of granitic magma. The result proves from the chronological aspect that Halagatu granodiorite rock is the product of magma mixing in Late Permian. The host granodiorite rock is the acid member, while the dark dioritic microgranular enclaves are the residually basic part of magma mixing. Mantle-derived magma underplate under the regional compressive stress environment resulted by subduction of Animaqing ocean to the northward in the Late Permian, which caused transition between crust and mantle material, formed the magma chamber of magma mixing granite,and then intruded and formed the Halagatu rock mass.

关 键 词：东昆仑 岩浆混合花岗岩 暗色微粒包体 LA-ICP-MS锆石U-PB定年 

分 类 号：P597.3[天文地球—地球化学]