吉林延边闹枝金矿区粗面安山岩锆石U-Pb年代学、地球化学特征及其构造意义  

Geochronology and Geochemistry of Trachyandesite of Naozhi Gold Deposit in Yanbian Region,Southern Jinlin Province and Its Geological Significance

作　　者：刘金龙[1] 孙丰月[1] 林博磊[1] 王冠[1] 许庆林[1] 奥琮 

机构地区：[1]吉林大学地球科学学院,长春130061

出　　处：《吉林大学学报（地球科学版）》2015年第5期1394-1404,共11页Journal of Jilin University：Earth Science Edition

基　　金：中国地质调查局地质调查项目(1212011085485)

摘　　要：对延边闹枝金矿区金沟岭组粗面安山岩进行了锆石LA-ICP-MS U-Pb年代学和地球化学特征的研究,结果表明：金沟岭组粗面安山岩中的锆石自形程度较好,主要为长柱状,具有较为清晰的韵律环带结构,Th/U值为0.43～0.71（〉0.40）,表明锆石岩浆成因;锆石定年结果显示,金沟岭组粗面安山岩形成时代为早白垩世（（130±2）Ma,MSWD=1.8）;岩石属于钙碱性系列,明显富集大离子亲石元素（如K、Ba、Rb）、LREE和强不相容元素（如Th、U）,相对亏损高场强元素（如Ta、Nb、Ti、P）,高Mg#值（43～52,平均为47）,Na2O/K2O值为1.73～2.25,平均值为1.93（〉1.17）,其地球化学特征与活动大陆边缘背景下形成的火成岩相似。结合岩石Nb/Ta值（14.40～14.72）、Rb/Sr值（0.10～0.18）、Th/Nb值（0.29～1.04）、Ba/La值（17.61～23.92）等特征值,认为岩浆由壳幔混合而成。综合前人研究成果,认为金沟岭组粗面安山岩形成于古太平洋（伊泽奈崎）板块斜向俯冲亚洲大陆的活动陆缘环境。LA-ICP-MS zircon U-Pb dating and geochemical data of the trachyandesite rocks from Jingouling Group in Yanbian region are obtained to figure out their formation time and the regional tectonic background.The zircons from the trachyandesite rocks are euhedral in shape with oscillatory ring displaying in CL images with high Th/U valwes 0.43-0.71（〉0.40）.This implies their magmatic origin.The dating results indicate that these rocks formed in Early Cretaceous（130±2 Ma,MSWD=1.8）.The composition of these rocks fall into the calc-alkaline category with enrichment in LILE（suchas K,Ba,Rb）,LREE and more mobile incompatible elements,such as Th,U,relative depletion of HFSE（such as Ta,Nb,Ti,P）.Combined with their high Mg#values（43-52）and Na2O/K2O=1.73-2.25（1.17）,it shows the characteristics of the rocks from an active continental margin magma.Based on its Nb/Ta（14.40-14.72）,Rb/Sr（0.10-0.18）,Th/Nb（0.29-1.04）,and Ba/La（17.61-23.92）,we conclude that the magma was a mixture of crust and mantle material.Together with the research of regional tectonics,the corresponding geodynamic mechanisms responsible for the formation of the rocks may be closely related to the subduction of Paleo-Pacific plate and Izanagi plate towards Eurasia continent.

关 键 词：锆石U-PB年龄 地球化学 金沟岭组 粗面安山岩 活动大陆边缘 闹枝金矿 

分 类 号：P588.144[天文地球—岩石学]