东昆仑造山带东段大格勒花岗岩锆石U-Pb年代学、地球化学特征及其构造意义  

Zircon U-Pb Dating and Geochemical Characteristics of Dagele Granite in the Eastern Margin of East Kunlun Orogenic Belt,China and Their Tectonic Implications

作　　者：封铿 李瑞保[1,2] 裴先治[1,2] 李佐臣[1,2] 裴磊[1,2] 刘成军[1,2] 陈国超[1] 李小兵[1] 王盟[1,2] 赵少伟 陈有炘 周海[1,2] FENG Keng;LI Rui-bao;PEI Xian-zhi;LI Zuo-chen;PEI Lei;LIU Cheng-jun;CHEN Guo-chao;LI Xiao-bing;WANG Meng;ZHAO Shao-wei;CHEN You-xin;ZHOU Hai(School of Earth Science and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;Key Laboratory of Western China's Mineral Resources and Geological Engineering of Ministry of Education,Chang'an University,Xi'an 710054,Shaanxi,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《地球科学与环境学报》2020年第4期442-463,共22页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41502191,41472191,41872233);青海省国土资源厅-中国铝业公司公益性区域地质矿产调查项目(中铝基金200801);中央高校高新技术研究培育项目(300102279204);中央高校基本科研业务费专项资金项目(300102279108);陕西省自然科学基金项目(2020JM-229,2020JQ-353,2019JM-312)。

摘　　要：大格勒花岗岩是东昆仑弧岩浆岩的重要组成部分,对解译古特提斯演化具有重要意义。通过对东昆仑造山带东段大格勒地区出露的花岗岩进行详细的岩石学、锆石U-Pb年代学与岩石地球化学研究,探讨其岩石成因和构造背景。结果表明:大格勒岩体岩石类型主体为灰白色中细粒块状花岗岩,岩体内发育大量的暗色闪长质包体;LA-ICP-MS锆石U-Pb同位素定年结果显示花岗岩和暗色闪长质包体的结晶年龄分别为(261.0±2.8)Ma和(261.6±1.6)Ma;大格勒花岗岩主体呈准铝质—弱过铝质、中—高钾钙碱性系列,具有富集轻稀土元素,亏损重稀土元素,富集Rb、Th、U等大离子亲石元素,亏损Nb、Ta等高场强元素特征,含有较低的Mg#值和Nb/Ta值,为Ⅰ型花岗岩;闪长质包体为中钾钙碱性系列,富Fe、Mg、Ca、Ti等,具有较高的Mg#值。岩石成因研究表明花岗岩为大陆下地壳基性岩部分熔融的产物,闪长质包体为镁铁质岩浆注入花岗岩快速冷凝的结果。结合区域资料认为,大格勒花岗岩形成于与布青山—阿尼玛卿洋向北俯冲相关的陆缘弧构造环境,进一步表明古特提斯洋于晚二叠世已向北俯冲于东昆北地块之下。As an important part of arc magmatic rocks in East Kunlun,Dagele granites are of great significance to the interpretation of the evolution of Paleo-Tethys.In order to study its petrogenesis and tectonic setting,the petrology,zircon U-Pb geochronology and petrogeochemistry of granites exposed in Dalage area,the eastern margin of East Kunlun orogenic belt were studied in detail.The results show that Dagele plutons are composed of grey medium-to fine-grained granites,and some dark diorite enclaves;LA-ICP-MS Zircon U-Pb ages of granite and diorite enclave are(261.0±2.8)Ma and(261.6±1.6)Ma,respectively;granites are medium-high K calc-alkaline and metaluminous to weak peraluminous series,and belong to I-type granites;the characteristics of REE show that LREEs are relatively abundant,and HREEs are relatively depleted;the characteristics of trace elements show that the granites are rich in Rb,Th,U,etc.,and poor in Nb,Ta,etc.,with low Mg#and ratio of Nb/Ta;diorite enclaves are featured by medium K calc-alkaline,and rich in Fe,Mg,Ca,Ti,etc.,with high Mg#.Petrogenesis studies show that granites are the production of partial melting of amphibolite in the continental lower crust,but diorite enclave is the production of rapid condensation of mafic magma injected into granites.Combined with regional data,it is suggested that Dagele granites form in the continental arc environment related to the northward subduction of Buqingshan-Anemaqen ocean,which further indicates that Paleo-Tethys ocean has subducted northward under North East Kunlun terrane in Late Permian.

关 键 词：花岗岩 锆石U-Pb年龄 地球化学 岩石成因 晚二叠世 俯冲作用 岩浆混合 东昆仑 

分 类 号：P597[天文地球—地球化学]