东天山黄山西角闪辉长岩成因及其地质意义:来自锆石U-Pb年代学及地球化学的证据  

The Petrogenesis and Geological Significance of the Hornblende Gabbro in Western Huangshan of East Tianshan:Evidence from Zircon U-Pb Chronology and Geochemistry

作　　者：张海迪[1] 陈博[1] 吕鹏瑞[1] 罗彦军[1] 郭伟立[1] 康磊[1] 刘生荣[1] 任广利[1] ZHANG Haidi;CHEN Bo;L Pengrui;LUO Yanjun;GUO Weili;KANG Lei;LIU Shengrong;REN Guangli(Xi an Center of Geological Survey,China Geological Survey,Research Center for Orogenic Geology,Xi an 710054,Shaanxi,China)

机构地区：[1]中国地质调查局西安地质调查中心,中国地质调查局造山带地质研究中心,陕西西安710054

出　　处：《西北地质》2021年第3期51-65,共15页Northwestern Geology

基　　金：中国地质调查局区域地质调查项目“东天山喀拉塔格雅满苏一带戈壁荒漠浅覆盖区地质填图”(DD20179607),国家重点研发计划“深地资源勘查开采”重点专项“天山阿尔泰增生造山带大宗矿产资源基地深部探测技术示范”(2018YFC0604000)共同资助。

摘　　要：东天山觉罗塔格构造带广泛分布石炭纪—二叠纪岩浆岩,前人对其形成构造背景进行了大量研究,但仍存在较大争议。笔者对1∶5万区域地质调查新圈定的角闪辉长岩体开展了岩石学、地球化学及锆石U-Pb年代学研究。岩石地球化学分析结果显示,角闪辉长岩SiO_(2)含量为48.72%~53.09%,Al_(2)O_(3)含量为16.75%~19.48%,MgO含量为5.67%~7.87%,Mg^(#)值介于53.83~66.85,里特曼指数σ为2.37~2.95,属于钙碱性岩石系列特征。稀土元素配分呈比较平坦的右倾型,LREE/HREE=4.78~5.69,δEu介于0.95~0.98,(La/Yb)_(N)=4.66~5.80。Rb、Ba、Th、U、K、Sr等大离子亲石元素(LILE)明显富集,高场强元素Ta、Nb亏损。根据上述特征,认为角闪辉长岩岩浆源区受俯冲带流体交代作用影响。对比区域石炭纪—二叠纪岩浆作用,本次获得角闪辉长岩的锆石年龄(319.8±2.6)Ma与区域上晚石炭世早期的岩浆活动相对应,形成于北天山洋闭合后的板内伸展构造环境。The Carboniferous-Permian magmatic rocks are widely distributed in the Jueluotage tectonic belt in East Tianshan.Previous researchers have made researches into its tectonic background but there is still considerable controversy.This paper carried out studies on the hornblende gabbro,which were newly delineated in the 1∶50,000 regional geological survey,in such aspects as petrology,geochemistry,and zircon U-Pb chronology.The rock geochemical analysis shows that the SiO_(2) content of hornblende gabbro is 48.72%~53.09%,the Al_(2)O_(3) content is 16.75%~19.48%,the MgO content is 5.67%~7.87%,and the Mg# value is 53.83~66.85.The Ritman indexσis 2.37~2.95,belonging to the calc-alkaline rock series.The distribution of rare earth elements is a right-leaning pattern,LREE/HREE=4.78~5.69,andδEu is 0.95~0.98,(La/Yb)N=4.66~5.80.Rb,Ba,Th,U,K,Sr and other large ion lithophile elements(LILE)are obviously enriched,and Nb,Ta are depleted.Based on the above characteristics,it is held that the magma source of the hornblende gabbro is affected by fluid metasomatism in the subduction zone.The zircon age(319.8±2.6)Ma of the hornblende gabbro obtained corresponds to the magmatic activity of the early Late Carboniferous in the region,which formed in an extension setting after the closure of the north Tianshan Ocean.

关 键 词：觉罗塔格构造带 角闪辉长岩 年代学 地球化学 岩石成因 

分 类 号：P597[天文地球—地球化学]