摘要
东昆仑造山带东段发现一套早泥盆世双峰式侵入岩岩体组合。本文对该套双峰式侵入岩开展了岩石学、锆石U-Pb年代学、岩石地球化学、Sr-Nd及Hf同位素研究,结果显示:(1)该套双峰式侵入岩主要由橄榄辉长岩、辉长岩和碱长花岗岩组成,其定年结果分别为410.3±2.7Ma、409.3±2.7Ma和410.5±1.8Ma,表明其形成于早泥盆世。此外,基性岩浆在侵位过程中捕获了形成于晚奥陶世至中-晚志留世(445-428Ma)的锆石。(2)橄榄辉长岩和辉长岩位于钙碱性系列-低钾拉斑质系列区域,Mg#=82-84,相对富集Rb、U、K、Pb、Nd等,相对亏损Ba、Nb、Ta、P等;碱长花岗岩具有高Si、K,高FeOT/MgO,低Al、Mg、Ca,相对富集Rb、Th、U、K、Pb、Nd等,亏损Ba、Nb、Ta、Sr、P、Eu、Ti等,显示出A型花岗岩特征。(3)基性岩εNd(t)=-3.38--6.21,εHf(t)=-4.04-+2.83(大部分为负值),Nd和Hf模式年龄分别为tDM2(Nd)=1282-1511Ma和tDM2(Hf)=1236-1914Ma;碱长花岗岩εNd(t)=-3.33--3.65,εHf(t)=-0.03-2.45,Nd和Hf模式年龄分别为tDM2(Nd)=1277-1303Ma和tDM2(Hf)=1245-1396Ma。岩石地球化学、Sr-Nd及Hf同位素特征揭示该套双峰式侵入岩的基性端元和酸性端元来源于不同的岩浆源区,基性端元来自于EMII型富集地幔并遭受地壳混染,经历了橄榄石、辉石的分离结晶;酸性端元为低压高温条件下长英质地壳的部分熔融。结合区域构造演化认为,原特提斯洋在早泥盆世已经完成闭合,此时东昆仑地区处于后碰撞伸展环境。
The Early Devonian bimodal intrusive rocks are reported in eastern segment of the Kunlun Orogenic Belt.This paper studies the petrology,geochemistry,zircon U-Pb ages and Sr-Nd-Hf isotopes of the bimodal intrusive rocks in Wulonggou area,East Kunlun Orogen,and the results suggested that:(1)The bimodal intrusive rocks are mainly composed of olive gabbro,gabbro and alkali granite,whose LA-ICP-MS zircon U-Pb ages are 410.3±2.7Ma,409.3±2.7Ma,410.5±1.8Ma,respectively,representing their formation ages are Early Devonian.During their emplacement,the mafic magma captures the zircons with ages of Late Ordovician to Late Silurian(445-428Ma).(2)The olive gabbro and gabbro plots in the calc-alkaline series and low K(tholitic)series,with Mg#=82-84.In addition,they are enriched in Rb,U,K,Pb,Nd,etc.,and depleted in Ba,Nb,Ta,P,etc.Alkali granites are characterized by high Si,K,FeOT/MgO and low Al,Mg,Ca;enriched in Rb,Th,U,K,Pb,Nd,etc.,and depleted in the Ba,Nb,Ta,Sr,P,Eu,Ti,etc.,which is similar to A-type granite.(3)The mafic rocks have values ofεNd(t)=-3.38--6.21,εHf(t)=-4.04-+2.83(mostly negative),tDM2(Nd)=1282-1511Ma and tDM2(Hf)=1236-1914Ma.Meanwhile,the alkali granites have values ofεNd(t)=-3.33--3.65,εHf(t)=-0.03-2.45,tDM2(Nd)=1277-1303Ma and tDM2(Hf)=1245-1396Ma.The results of geochemistry and Sr-Nd-Hf isotopes reveal that the magmatic sources of the acidic rocks and the mafic rocks are different,i.e.,the mafic rocks come from EMII enrichment mantle and then contaminated by crust,while the acidic rocks derive from partial melting of the upper crust.The bimodel intrusive rocks show that the Proto-Tethys Ocean have already completely closed in Early Devonian,and the Wulonggou area in East Kunlun Orogen belongs to a post-collision extension setting during this period.
作者
张亮
李碧乐
刘磊
王盘喜
李良
ZHANG Liang;LI BiLe;LIU Lei;WANG PanXi;LI Liang(Zhengzhou Institute of Multipurpose Utilization of Mineral Resources,CAGS,Zhengzhou 450006,China;China National Engineering Research Center for Utilization of Industrial Minerals,Zhengzhou 450006,China;College of Earth Sciences,Jilin University,Changchun 130061,China;School of Earth Sciences,Yunnan University,Kunming 650500,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第7期2007-2028,共22页
Acta Petrologica Sinica
基金
中国地质调查局地质矿产调查评价项目(DD20190186)资助。
关键词
东昆仑
双峰式侵入岩
早泥盆世
后碰撞伸展
地球化学
岩石学
East KunlunOrogen
Bimodalintrusiverocks
EarlyDevonian
Post-collisionalextensionalsetting
Geochemistry
Petrology
