吉林中部江密峰花岗闪长岩锆石U-Pb年代学和岩石地球化学特征  

Zircon U-Pb chronology and petrogeochemistry of Jiangmifeng granodiorite in central Jilin Province

作　　者：孙永刚[1,2] 李碧乐[1] 王聚胜[2] 王永胜[2] 张旭[2] 詹天宇[2] SUN Yong-gang;LI Bi-le;WANG Ju-sheng;WANG Yong-sheng;ZHANG Xu;ZHAN Tian-yu(College of Earth Sciences,Jilin University,Changchun 130061,China;Geological Survey Institute of Jilin Province,Changchun 130102,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]吉林省地质调查院,长春130102

出　　处：《世界地质》2019年第4期931-943,共13页World Geology

基　　金：中国地质调查局项目(DD20160049)

摘　　要：为研究吉林中部地区早燕山期岩浆作用,并限制古太平洋板块向欧亚板块俯冲的起始时间,笔者对吉林中部江密峰花岗闪长岩进行了LA-ICP-MS锆石U-Pb年龄和岩石地球化学研究。花岗闪长岩锆石U-Pb测年结果为(179±1)Ma,为早侏罗世岩浆作用的产物。地球化学研究表明,岩石富SiO2、Na2O、K2O、Al2O3和TFe2O3,低MgO和CaO,为准铝质-高钾钙碱性,高分异I型花岗岩。岩石富集LREEs、LILEs(Rb、K)和HFSEs(Th),亏损HREEs、LILEs(Ba、Sr)和HFSEs(Nb、Ta、Ti、Zr),具有Eu负异常。岩石的形成经历了壳幔物质在源区混合形成原始岩浆,随后这一壳幔混源岩浆又经历高程度分异演化的二阶段成岩过程。结合相邻地区同时代火成岩的岩石组合特征与空间分布,笔者认为岩石形成于古太平洋板块向欧亚板块下俯冲引起的弧后伸展环境。In order to study the Early Yanshanian magmatism in central Jilin Province,and delineate the starting time of the subduction of Palaeo-Pacific Plate beneath the Eurasian continent,the authors undertook LA-ICP-MS zircon U-Pb dating and geochemical analysis of Jiangmifeng granodiorite.It shows that the zircon U-Pb age of the granodiorite is 179±1 Ma,which is the product of magmatism in Early Jurassic.The geochemical analysis results indicate that the Jiangmifeng granodiorite has high content of Si O2,Na2O,K2O,Al2O3and TFe2O3,but low content of MgO and CaO,belonging to quasi-aluminous,high-potassium calc-alkaline,highly fractionated I-type granite.The granodiorite is enriched in LREEs,LILEs(Rb,K)and HFSEs(Th),depleted in HREEs,LILEs(Ba,Sr)and HFSEs(Nb,Ta,Ti,Zr),with negative Eu anomalies.The formation of the rocks experienced the mixing of crustal and mantle materials in the source area to form primary magma and subsequently the mixed magma underwent a two-stage diagenetic process of extensive magmatic differentiation and evolution.According to the rock assemblage and spatial distribution of the contemporaneous igneous rocks in adjacent areas,the authors suggest that these rocks formed in the back-arc extensional setting which could be related to the subduction of Paleo-Pacific Plate beneath the Eurasian continent.

关 键 词：吉林中部 锆石U-PB年代学 岩石地球化学 江密峰 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]