西昆仑东段宿营地晚三叠世中性脉岩的锆石U-Pb定年、岩石地球化学特征及其意义  

Zircon U-Pb Dating and Geochemistry of Late Triassic Intermediate Dykes in Suyingdi,Eastern Section of West Kunlun and Their Geological Significance

作　　者：黎有为 魏启荣[1] 王程[1] 丁鹏飞[1] 刘小念[1] 张小强[1] 王敬元[1] 刘文平[1] 农明智 

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]贵州省山地资源研究所,贵州贵阳550001

出　　处：《地球科学（中国地质大学学报）》2017年第6期909-926,共18页Earth Science-Journal of China University of Geosciences

基　　金：中国地质调查局项目(No.1212011220636);贵州省工程技术研究中心项目(黔科合G字[2014]4004号);贵州省科技计划项目(黔科合SY字[2012]3031号)

摘　　要：为了研究西昆仑造山带东段古特提斯构造-岩浆演化,提升区域研究程度,对宿营地脉岩进行系统的野外地质调查、岩相学、LA-ICP-MS锆石U-Pb定年、岩石地球化学研究.脉岩呈NE向成群成带分布;岩石类型为(含石榴)闪长玢岩、角闪安山玢岩及闪斜煌斑岩;获得(含石榴)闪长玢岩LA-ICP-MS锆石U-Pb加权平均年龄(214±1)^(219±1)Ma,形成于晚三叠世,是印支晚期构造-岩浆活动产物;脉岩主要为钙碱性系列岩石,表现出中Si(SiO_2=53.92%~62.95%)、高Al(Al_2O_3=15.99%~17.69%)、富Na(Na_2O=2.63%~6.09%、Na_2O/K_2O=1.09~8.30)、低Ti(Ti_2O=0.50%~0.76%)、低P(P_2O_5=0.14%~0.23%)、Mg(Mg~#=37.73~59.32)变化大等主量元素特征,铝饱和指数(A/CNK)为0.92~1.36;脉岩富集LREE、Rb、Th、U、K,亏损HREE、Nb、Ta、P、Ti,(La/Yb)N=7.24~20.02,Ce、Eu异常不明显.结果表明,宿营地中性脉岩是西昆仑东段南缘晚三叠世古特提斯弧后拉张作用引起的壳-幔混合作用的产物.order to understand tectonic-magmatic evolution of eastern section of West Kunlun orogen,a systematic field geological surveying,microscopic petrographic examination,LA-ICP-MS U-Pb zircon dating,and geochemistry study were carried out for the Suyingdi dykes.These dykes occur in groups or belts along an NE trending.The rock types of dykes include（garnet-bearing）diorite-porphyrite,hornblende andesite-porphyrite,and proterobase spessartite.Using LA-ICP-MS method,zircons in the（garnet-bearing）diorite-porphyrite samples show a weighted average age between 214±1and 219±1Ma,indicating that they formed in Late Triassic epoch,and they are probably tectonic-magmatic products of late period of Indosinian.The rocks belong to the calc-alkaline series,showing intermediate Si（SiO2=53.92%-62.95%）,high Al（Al2O3 =15.99%-17.69%）,rich in Na（Na2O=2.63%-6.09%,Na2O/K2O=1.09-8.30）,Ti（Ti2O=0.50%-0.76%）,P（P2O5=0.14%-0.23%）.The rocks also show a large range of Mg（Mg-#=37.73-59.32）,and their A/CNK values vary from 0.92 to 1.36.They show enrichment in LREE,Rb,Th,U,K;depletion in HREE,Nb,Ta,Ti,P;（La/Yb）N=7.24-20.02 and weak Ce and Eu anomalies.Suyingdi intermediate dykes are the product of crustal-mantle magma mixing which caused by back-arc ex-tention of eastern section of West Kunlun in Late Triassic.

关 键 词：中性脉岩 锆石U-PB定年 地球化学 构造环境 西昆仑 年代学 

分 类 号：P588.1[天文地球—岩石学]