阿拉善龙首山地区古元古代晚期变质‒深熔事件及其地质意义  

Late Paleoproterozoic Metamorphic-Anatexis Events and Their Tectonic Implications in Longshoushan Area,Alxa Block

作　　者：关燕鹤 曾认宇 赖健清[2] 毛先成[2] 苏惠 Guan Yanhe;Zeng Renyu;Lai Jianqing;Mao Xiancheng;Su Hui(School of Water Resources and Environment Engineering,East China University of Technology,Nanchang 330013,China;Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education,Central South University,Changsha 410083,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,China;Department of Earth Sciences,Durham University,Durham DH13LE,UK)

机构地区：[1]东华理工大学水资源与环境工程学院,江西南昌330013 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083 [3]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [4]东华理工大学地球科学学院,江西南昌330013 [5]杜伦大学地球科学学部,杜伦DH13LE

出　　处：《地球科学》2023年第11期4034-4052,共19页Earth Science

基　　金：国家自然科学基金项目(Nos.41902075,42030809,42002095,42162013);核资源与环境国家重点实验室开放基金项目(No.2020NRE13);有色金属成矿预测与地质环境监测教育部重点实验室(中南大学)开放基金资助项目(No.2022YSJS10);江西省自然科学基金资助项目(No.20232BAB213061);国家留学基金委访问学者项目(No.202008360018).

摘　　要：阿拉善地块位于华北克拉通的西南缘,其早前寒武纪地质演化及构造归属存在争议,这严重制约了华北克拉通构造格局和演化的研究.龙首山杂岩为阿拉善地块少有的早前寒武纪变质基底,记录了古元古代多期变质事件,可为解决上述争议提供依据.以龙首山地区中部金川矿区内、龙首山杂岩中的花岗伟晶岩和黝帘斜长角闪岩为研究对象,系统开展岩相学、锆石和全岩的元素地球化学,以及锆石U-Pb年代学的研究.花岗伟晶岩的SiO_(2)介于69.70%~73.08%,属于弱过铝质、钾玄岩的范畴,为混合岩化过程中地壳岩石低程度部分熔融的产物.在花岗伟晶岩中锆石核部获得了1892±7 Ma(MSWD=0.76)的上交点年龄,代表花岗伟晶岩的形成年龄.黝帘斜长角闪岩的SiO_(2)介于41.51%~48.92%,其原岩为拉斑玄武质的辉绿岩.黝帘斜长角闪岩中的锆石均为变质锆石,所获得的1830±8 Ma(MSWD=0.61)加权平均年龄代表了一期角闪岩相变质事件的时间.结合前人的研究,龙首山地区在古元古代晚期存在强烈的变质/深熔事件,可能与碰撞造山事件有关.而通过构造热事件的对比,认为阿拉善地块与华北克拉通的孔兹岩带在早前寒武纪具有亲缘关系.The Alxa block is located in the southwestern margin of the North China craton.The Early Precambrian tectonic evolution and tectonic affinity of the block remain unknown or controversial,which restricts the study of the tectonic framework and evolution of the North China craton.The Longshoushan complex is one of the few Early Precambrian metamorphic basement rocks in the Alxa block,and records multiple Paleoproterozoic metamorphic events.Hence,which makes it possible to solve the above problems.It presents petrography,whole-rock geochemistry,and mineralogy,mineral geochemistry and chronology of zircon for the granitic pegmatite and zoisite amphibolite in the Longshoushan complex from the Jinchuan mining area in the central part of the Longshoushan area.The granitic pegmatite is characterized by SiO_(2)contents of 69.70%-73.08%,belongs to weak peraluminous and shoshonite series,and formed from low degree partial melting of crustal rocks during migmatisation.The intersection ages of 1892±7 Ma(MSWD=0.76)were obtained from the core of zircon in granitic pegmatite,representing the formation age of the granitic pegmatite.The zoisite amphibolite is characterized by SiO_(2)contents of 41.51%-48.92%,and is the metamorphic product of tholeiitic diabase.Zircons in the zoisite amphibolite are amphibolite facies metamorphic zircons.The weighted average age of 1830±8 Ma(MSWD=0.61)represents an amphibolite facies metamorphic event in the Longshoushan area.Combined with previous studies,there was a strong metamorphic-anatexis event in the Late Paleoproterozoic in the Longshoushan area,which is most likely related to a collisional orogeny.Through the comparison of tectonic-thermal events,it suggests that the Alxa block and the Khondalite belt of the North China craton have affinity in the Early Precambrian.

关 键 词：华北克拉通 阿拉善地块 龙首山地区 变质/深熔事件 锆石 工程地质 

分 类 号：P591[天文地球—地球化学] P597[天文地球—地质学]