南祁连地区花岗闪长岩体锆石U-Pb测年及其形成构造环境探讨  

Zircon U-Pb dating and tectonic setting of granodiorite in southern Qilian area

作　　者：张百超[1] 吕洋[1] 李建华 陈旭[1] 程双[1] 刘大业[1] ZHANG Baichao;Lü Yang;LI Jianhua;CHEN Xu;CHENG Shuang;LIU Daye(Regional Geological and Mineral Resources Survey of Jilin Province,Changchun 130021,Jilin,China)

机构地区：[1]吉林省区域地质矿产调查所,吉林长春130021

出　　处：《吉林地质》2021年第3期8-14,共7页Jilin Geology

基　　金：青海省地质勘查基金项目(青国土资矿[2011]332号)资助。

摘　　要：对南祁连地区日托卡一带花岗闪长岩进行锆石U-Pb定年及全岩分析以确定其形成时代及构造环境。定年结果表明,花岗闪长岩形成于(458±1)Ma,为晚奥陶世。全岩分析,岩石具有偏铝(w(Al_(2)O_(3))为13.14%~13.79%)和中碱(w(K_(2)O+Na_(2)O)为6.84%~6.93%)特征,属偏铝质钙碱性系列;稀土总量为(397.29~479.89)×10^(-6),为富集型,L/H值为10.87~12.66,轻稀土富集,重稀土亏损;微量元素Rb、Nb、Sr亏损,Th、Ce富集,表明该岩体的岩浆经历了较强的分异演化。综合花岗闪长岩地质及主微量元素特征,认为花岗闪长岩形成构造环境为由挤压向拉伸转换阶段,属同造山花岗岩。Zircon U-Pb dating and whole-rock analysis of the granodiorites in Rituoka area,Southern Qilian area are carried out to determine the age and tectonic setting of the granodiorites.Dating results show that the granodiorite was formed in(458±1)Ma and is late Ordovician.Whole-rock analysis shows that the rocks are characterized by aluminium-biased(w(Al_(2)O_(3))13.14%~13.79%)and moderate alkali(w(K_(2)O+Na_(2)O)6.84%~6.93%),belonging to aluminium-biased calc-alkaline series.The total amount of rare earth is(397.29~479.89)×10^(-6),which is enriched,L/H value is 10.87~12.66,light rare earth enrichment,heavy rare earth deficit;Trace elements such as Rb,Nb and Sr are depleted,while Th and Ce are enriched,indicating that the magma of the pluton has undergone strong differentiation evolution.Based on the geological and major and trace element characteristics of granodiorite,it is considered that the tectonic environment of granodiorite is a stage of compression to tension transformation,belonging to synorogenic granite.

关 键 词：南祁连 花岗闪长岩 地质特征 构造环境 

分 类 号：P588.12[天文地球—岩石学]