西昆仑柳什塔格南二长花岗岩SHRIMP定年、地球化学特征及其地质意义  

SHRIMP U-Pb Ages,Geochemical Characteristics and Geological Implications of the Monzonitic Granite at South Liushitage,West Kunlun

作　　者：冯江鹏[1] 曹福根[1] 宋倩倩[1] 

机构地区：[1]新疆地质矿产勘查开发局第一区域地质调查大队,新疆乌鲁木齐830013

出　　处：《西北地质》2014年第4期163-169,共7页Northwestern Geology

基　　金：中国地质调查局项目"新疆西昆仑1:5万J44E021018;J44E022017;J44E022018;J44E023017;J44E023018五幅区域地质调查"(1212011220634)

摘　　要：在柳什塔格南部的昆南增生楔中发育二长花岗岩体,侵入于古元古界双雁山岩群中深变质岩系中,其上被三叠纪阿他木帕下组不整合覆盖。该岩体主要为浅肉红色细粒二长花岗岩,局部地方渐变为花岗闪长岩或正长花岗岩,其内还发育少量后期的北东向辉长岩脉。对该岩体中的锆石进行了SHRIMP U-Pb测年,投点结果相对集中,位于谐和曲线附近,得到加权平均年龄为(455.9±7.4)Ma,为晚奥陶世早期,其岩石学、地球化学特征显示其为钙碱性序列,其高钾的含量和古老的锆石的存在说明该岩体的侵入背景为俯冲同碰撞构造环境,间接证明了昆南有限洋盆在晚奥陶世已经闭合。该发现为昆仑造山带构造演化提供了新的地质依据,具有较大的地质意义。The monzonite granite developed in the accretionary wedge in South Kunlun （South Liushitage） and intruded in the deep metamorphic rocks of Paleoproterozoic Shuangyanshan group, unconformably covered by the Triassic Atamupa formation. The rock is mainly light meat-red finegrained monzonitic granite, localized gradient to granodiorite or syenite granite, with also a small amount of gabbro occurred later in it. SHRIMP Zircon U-Pb dating is relatively concentrated and located near the concordia curve. With the weighted average age of 455.9±7.4 Ma, the monzonite granite should have formed in late Early Ordovician. The petrological, geochemical characteristics displayed as a sequence of calc alkaline. The high potassium content and the pres- ence of ancient zircons show that the rock is probably a result in subduction-collision tectonic en- vironment, indirectly certificating that the limited ocean basin in South Kunlun has closed at the Irate Ordovician. This finding has a great geological significance by providing new geological basis for the tectonic evolution of the Kunlun orogenic belt.

关 键 词：二长花岗岩 SHRIMP测年 晚奥陶世 柳什塔格 

分 类 号：P597[天文地球—地球化学]