南秦岭勉略构造带三岔子地区田坝辉绿岩地球化学、锆石U-Pb年龄及地质意义  

Geochemical Characteristics,Zircon U-Pb Dating and Geological Significance of Tianba Diabase in Sanchazi Area,Mianlue Tectonic Belt of South Qinling

作　　者：王一烽 裴先治[1,2] 李佐臣[1,2] 李瑞保[1,2] 裴磊[1,2] 刘成军[1,2] 王盟[1,2] 赵少伟[1,2] 陈有炘 周海[1,2] WANG Yifeng;PEI Xianzhi;LI Zuochen;LI Ruibao;PEI lei;LIU Chengjun;WANG Meng;ZHAO Shaowei;CHEN Youxin;ZHOU Hai(Sechool of Earth Science and Rexources,Chang’an University,Xi'an 710054,Sihanxi,China;Key Laboratory of Western China's Mineral Resources and Gixlogical Enginering,Mimistry of Education,Xi'an 710054,Shanxi,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]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：《西北地质》2021年第2期1-18,共18页Northwestern Geology

基　　金：国家自然科学基金项目“扬子地块西北缘碧口群构造属性及与Rodinia超大陆聚合-裂解关系”(41872233);国家自然科学基金面上项目“秦岭-祁连结合部位早古生代晚期岩浆事件及其对构造演化的启示”(41872235)、“西天山温泉地区温泉岩群榴闪岩年代学、地球化学及变质作用研究”(41802234);“腾冲地块金竹寨花岗岩体成分复杂性成因机理研究”(41902046);陕西省自然科学基金面上项目“勉略宁地区中新元古代中酸性侵入岩构造属性研究”(2019JM-312);陕西省自然科学基金青年项目“西昆仑造山带西段曲什曼蛇绿混杂岩物质组成及构造属性研究”(2020JQ-353);中央高校基本科研业务费资助项目“西昆仑布伦口-麻扎地区三叠纪花岗岩类形成时代、岩石成因及其构造背景”(300102279108)

摘　　要：报道了南秦岭勉略构造带三岔子地区田坝辉绿岩的LA-ICP-MS锆石U-Pb年龄、主量元素及微量元素研究成果,并讨论了研究区勉略构造带新元古代时期的构造演化。田坝辉绿岩LA-ICP-MS锆石U-Pb测年结果为(805.9±2.6)Ma(MSWD=0.033,n=9),限定其形成时代为新元古代中期。田坝辉绿岩属钙碱性系列,稀土元素配分曲线呈右倾型,Eu负异常不明显(δEu平均为0.91),微量元素配分曲线显示富集Rb、Ba、Sr等大离子亲石元素和轻稀土元素,亏损Nb、Ta等高场强元素,相对亏损P和Ti。综合研究表明,田坝辉绿岩具有陆缘弧岩浆岩的地球化学特征,为俯冲流体交代富集的岩石圈地幔在伸展构造环境下部分熔融的产物;结合前人研究,勉略构造带及其邻区在新元古代中期(800Ma左右)由区域性的汇聚环境向后碰撞-裂解环境转变。This paper presents an analysis of LA-ICP-MS zircon U-Pb dating,major elements and trace elements of Tianba diabase in Sanchazi area of Mianlue tectonic belt,south Qinling.It discusses the tectonic evolution of the Mianlue tectonic belt in Neoproterozoic.The LA-ICP-MS zircon U-Pb dating is(805.9±2.6)Ma(MSWD=0.033,n=9),indicative of a middle Neoproterozoic formation age.The geochemical data show that the Tianba diabase belongs to the calc-alkaline series.The REE pattern shows enrichment of LREE;The REE patterns show rightward incline.Eu negative anomaly is not obvious(the averageδEu is 0.91).The trace elements pattern shows enrichment in LILEs(Rb,Ba,Sr,etc),and LREEs,and depletion of HFSEs(Nb,Ta),relatively depletion of P and Ti.Comprehensive study indicates that Tianba diabase has the geochemical characteristics of continental marginal magmatic rocks,which was formed by partial melting of the subduction fluid metasomatised enriched lithospheric mantle in an extensional setting.Mianlue tectonic zone and its adjacent areas was from regional convergent environment to postcollision-cracking environment in the middle Neoproterozoic(about 800 Ma).

关 键 词：勉略构造带 田坝辉绿岩 伸展环境 新元古代 

分 类 号：P581[天文地球—岩石学]