大兴安岭北段卜奎沟岩体地球化学和锆石U-Pb年代学研究  

Geochemical and zircon U-Pb geochronology of Pukuigou granite,Northern Great Xing’an Rang

作　　者：洪文武 李松彬 刘钧沅 董帅 包久荣 王建青 刘高杰 徐如磊 HONG Wenwu;LI Songbin;LIU Junyuan;DONG Shuai;BAO Jiurong;WANG Jianqing;LIU Gaojie;XU Rulei(Tianjing North China Geological Exploration General Institute,Tianjing 100370,China)

机构地区：[1]天津华北地质勘查总院,天津100370

出　　处：《矿产勘查》2023年第7期1026-1033,共8页Mineral Exploration

基　　金：内蒙古自治区地勘基金项目(NMKD2014-20)资助。

摘　　要：目前对于大兴安岭地区中生代岩浆活动的构造背景存在多种不同认识,且该区中侏罗世侵入岩研究较为薄弱,岩浆岩的研究能够为该区中生代大地构造演化提供新的证据。因此,本文对大兴安岭北段卜奎沟岩体进行了岩石学、地球化学及锆石U-Pb年代学测试。岩体低硅(SiO_(2)=58.19%~61.08%)、富钾(K_(2)O=0.76%~3.20%)、富碱(Na_(2)O+K_(2)O=5.76%~9.51%)、过铝质(A/CNK=0.92~1.02)的特征,属钙碱性-高钾钙碱性系列。富集大离子亲石元素Rb、Ba、K,亏损高场强元素Nb、Ta、Ti和P,Sr/Y比值较高。轻稀土稍富集,重稀土相对亏损(LREE/HREE=4.31~13.13,(La/Yb)_(N)=4.59~16.36,具Eu负异常(δEu=0.75~0.91)。卜奎沟岩体锆石U-Pb年龄为(175±1)Ma,时代属中侏罗世。该岩体为蒙古—鄂霍茨克洋闭合后,岩石圈减薄的产物,形成于造山后拉张伸展环境下。The tectonic background of Mesozoic magmatism in the Great Xing’an Rang is still controversial.Reserch of the Pukuigou pluton can provide new evidence fore tectonic evolution of the Great Xing’an region Rang.Research on Middle Jurassic intrusive rocks in the northern section of the Great Xing’an Rang is weak.Petrological,geochemical and zircon U-Pb chronology tests were performed on the Pukuigou rock mass in this paper.The results show that the zircon U-Pb age of the Pukuigou monzonitic porphyry is(175±1)Ma,indicating that the formation age should be Middle Jurassic.They are characterized by low silicon(SiO_(2)=58.19%-61.08%),high potassium(K_(2)O=0.76%-3.20%),and alkali-rich(Na_(2)O+K_(2)O=5.76%-9.51%),with high potassium calc-alkaline series and peraluminous(A/CNK=0.92-1.02).Pukuigou rock mass are enriched in Rb、Ba、K,but depleted in Nb、Ta、Ti、P,and high Sr/Y ratio.It has light rare earth’s enrichment,heavy rare earth’s loss;LREE/HREE of 4.31-13.13,(La/Yb)_(N) of 4.59-16.36,and Eu negative anomalies(δEu=0.75-0.91).The Pukuigou rock mass is a product of lithospheric thinning after the closure of the Mongolian-Okhotsk Ocean and the extensional environment after the orogenic period.

关 键 词：锆石U-PB年龄 蒙古—鄂霍茨克 中侏罗世 大兴安岭北段 

分 类 号：P588.12[天文地球—岩石学] P597[天文地球—地质学]