四川天宝山铅锌矿成矿物质来源与成矿机制:来自流体包裹体及同位素地球化学制约  

Sources of metallogenic materials and metallogenic mechanism of Tianbaoshan Pb-Zn deposit in Sichuan Province:Constraints from fluid inclusions and isotopic evidences

作　　者：王海 祝新友[2] 王京彬[2] 贾德龙[3] 石煜[1] 陈磊 许正繁 WANG Hai;ZHU XinYou;WANG JingBin;JIA DeLong;SHI Yu;CHEN Lei;XU ZhengFan(East China University of Technology,State Key Laboratory of Nuclear Resources and EnvironmentNanchang 330013,China;Beijing Institute of Geology for Mineral Resources,Beijing 100012,China;Development Research Center of China Geological Survey,Beijing 100037,China;Guangdong Provincial Key Laboratory of Radioactive and Rare Resource Utilization,Guangzhou 512026,China)

机构地区：[1]东华理工大学,核资源与环境国家重点实验室,南昌330013 [2]北京矿产地质研究院,北京100012 [3]中国地质调查局发展研究中心,北京100037 [4]广东省放射性与三稀资源利用重点实验室,广州512026

出　　处：《岩石学报》2021年第6期1830-1846,共17页Acta Petrologica Sinica

基　　金：中国地质调查局项目(DD20190159);核资源与环境国家重点实验室自主基金项目(2020Z16);广东省放射性与三稀资源利用重点实验室开放基金(2018B030322009)联合资助。

摘　　要：天宝山铅锌矿床位于扬子地台西缘,为川滇黔铅锌矿集区具有代表性大型铅锌矿床,其金属储量(Pb+Zn)可达2.6Mt,铅锌品位10%~15%。本文在系统的分析流体包裹体和C、H、O、S、Pb、Sr同位素研究的基础上,确定其成矿物质来源、成矿流体性质及来源,并探讨其成矿机制。H-O同位素及流体包裹体研究表明,成矿流体具有中低温(均一温度峰值为140~200℃)及中低盐度(盐度峰值为6%~12%NaCleqv)的特征。灯影组白云岩与海相沉积碳酸盐岩的C、O同位素组成较为相似,热液方解石与含矿白云岩O同位素组成均稍低于灯影组白云岩,表明成矿流体中的CO_(2)可能来源于海相碳酸盐岩的溶解。矿区硫化物δ^(34)S值介于1.1‰~7.5‰之间,表明S主要来源于灯影组中硫酸盐热化学还原作用和岩浆硫的混合。矿石硫化物的Pb同位素比值在Pb演化图解上主要落入上地壳与造山带之间,表明Pb具有壳源特征,成矿物质来源主要来自于盖层沉积岩和基底地层。闪锌矿的^(87)Sr/^(86)Sr值(0.71099~0.71856)及热液方解石^(87)Sr/^(86)Sr值(0.71014~0.71169)均高于灯影组白云岩^(87)Sr/^(86)Sr值(0.70773~0.71026),表明成矿流体流经了具有高^(87)Sr/^(86)Sr值的基底地层,并与其发生水岩反应及同位素交换。As one of the famous high-grade Pb-Zn ore fields in the Sichuan-Yunnan-Guizhou ore concentration area,the Tianbaoshan Pb-Zn deposit which is located on the southwestern margin of Yangtze Craton,has a total Pb+Zn reserve of 2.6 Mt with grades of 10%~15%.Geochemistry of C-H-O-S-Pb-Sr isotopes and fluid inclusions are discussed in this paper to understand the sources of the ore metals and ore-fluids.The H-O isotopes and fluid inclusions show that the ore-forming fluid of the deposit is characterized by medium-low temperature(140~200℃)and medium-low salinity(6%~12%NaCleqv).Theδ^(13)CV-PDB andδ18OSMOWvalues of the Dengying Formation dolostones are similar to that of the coeval marine carbonate,suggesting that the dolostones belong to marine carbonate.Theδ^(13)CV-PDB andδ18O OSMOW values of hydrothermal calcites and ore-bearing dolomites are lower than that of the Dengying Formation dolostone,indicating that the CO_(2)in the ore-forming fluid was derived from dissolution of the Dengying Formation dolostone.Theδ^(34)S values of ore minerals range from 1.1‰to 7.5‰,indicating the sulfurs were derived from a mixed source of Dengying Formation marine sulfate modified by thermochemical sulfate reduction and magmatic sulfate.The 207 Pb/204 Pb versus206 Pb/204 Pb discrimination diagrams show a crustal Pb origin,indicating that the ore-forming metals were derived from a mixed source of sedimentary rocks and basement rocks.The^(87)Sr/^(86)Sr values of sphalerites(0.71099~0.71856)and hydrothermal calcites(0.71014~0.71169)are higher than that of the Dengying Formation dolostones(0.70773~0.71026),suggesting that the ore-forming fluid must flow through a high^(87)Sr/^(86)Sr basement stratum which results in a water-rock reaction and isotope exchange of its ore-forming mineral sources.

关 键 词：天宝山铅锌矿 同位素地球化学 流体包裹体 成矿机制 

分 类 号：P597.2[天文地球—地球化学] P618.42[天文地球—地质学]