滇东南嘎机多金属成矿区变质岩锆石U-Pb年代学、Hf同位素特征及其地质意义  

Zircon U-Pb geochronology and Hf isotopic characteristics of metamorphic rocks in the Gaji polymetallic metallogenic area in the southeastern Yunnan and their geological implications

作　　者：马跃华 王加昇[1] 于文修[1] 杨昌毕 郑晓军 韩欢欢 何昊 MA Yue-hua;WANG Jia-sheng;YU Wen-xiu;YANG Chang-bi;ZHENG Xiao-jun;HAN Huan-huan;HE Hao(Southwest Institute of Geological Survey,Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming 650093,China;The Second Geological Brigade,Bureau of Geology and Mineral Resources Exploration and Development of Yunnan Province,Wenshan 663000,China;Yunnan Nonferrous Geology Bureau,Kunming 650051,China)

机构地区：[1]昆明理工大学国土资源工程学院西南地质调查所,云南昆明650093 [2]云南省地质矿产勘查开发局第二地质大队,云南文山663000 [3]云南省有色地质局,云南昆明650051

出　　处：《矿物学报》2022年第2期129-140,共12页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目(编号:41772070)。

摘　　要：嘎机Pb-Zn-Cu多金属成矿区位于老君山穹窿状变形-变质岩系和花岗岩体的北部接触带上,属于滇东南W-Sn-Pb-Zn-Cu多金属矿集区的重要组成部分,是近年来新发现的、规模达到中型的多金属矿床。笔者在钻探工程基础上对矿区内隐伏的花岗片麻岩和石英片岩开展了LA-ICP-MS锆石U-Pb定年和原位Hf同位素研究。结果表明,花岗片麻岩锆石^(206)Pb/^(238)U加权平均年龄为(419.9±6.3)Ma,石英片岩锆石^(206)Pb/^(238)U加权平均年龄为(411.0±11.0)Ma,指示其原岩形成于晚志留世—早泥盆世,具有同源岩浆演化特征,为区域加里东期岩浆活动的产物,后期均发生了变质作用。花岗片麻岩锆石^(176)Hf/^(177)Hf值在0.28243~0.28252之间,ε_(Hf)(t)=-3.4~0.3,石英片岩锆石^(176)Hf/^(177)Hf值为0.28237~0.28253,ε_(Hf)(t)=-5.7~-0.2。综合分析认为,嘎机多金属成矿区花岗片麻岩和石英片岩均起源于古老地壳物质的部分熔融。该变质岩系与嘎机多金属矿床存在密切的空间关系和成因关系,暗示滇东南地区可能存在被低估的加里东期多金属成矿事件。The Gaji Pb-Zn-Cu polymetallic metallogenic area is located in the north contact between the Laojunshan dome-shaped deformed-metamorphic rock series and the Laojunshan granite.It is an important part of the Southeastern Yunnan W-Sn-Pb-Zn-Cu polymetallic ore concentration area.The Gaji deposit is a newly discovered medium-sized polymetallic deposit in recent years.The LA-ICP-MS zircon U-Pb dating and in-situ Hf isotopic studies of zircons from the hidden granitic gneiss and quartz schist in the Gaji polymetallic metallogenic area have been carried out in this paper on the basis of sample collection from drill cores.The results show that the weighted average ^(206)Pb/^(238)U age of zircons of the granite gneiss is 419.9±6.3 Ma,and that of the quartz schist is 411.0±11.0 Ma,indicating that the original rocks of granite gneiss and quartz schist,which were formed in the Late Silurian to Early Devonian,had homologous magmatic evolution characteristics are products of regional Caledonian magmatic activity,and had undergone metamorphism in the later period.^(176)Hf/^(177)Hf and ε_(Hf)(t)values of zircons from the granite gneiss range from 0.28243 to 0.28252,and from-3.4 to 0.3,respectively.Those values of zircons from the quartz schist range from 0.28237 to 0.28253,and from-5.7 to-0.2,respectively.Based on the comprehensive analysis,it is believed that the granite gneiss and quartz schist in the Gaji polymetallic metallogenic area were both originated from the partial melting of ancient crustal materials.The metamorphic rock series has close spatial and genetic relationships with the Gaji polymetallic deposit,indicating that there could be an underestimated Caledonian polymetallic metallogenic event in the southeastern Yunnan.

关 键 词：滇东南嘎机 变质岩 LA-ICP-MS锆石U-PB定年 原位Hf同位素 加里东期 

分 类 号：P597[天文地球—地球化学]