摘要
道伦达坝矿床位于大兴安岭南段,是一个中型的铜钨锡银矿床。矿体主要产于二叠系砂板岩中的断裂破碎带中,华力西期黑云母花岗岩中的断裂破碎带中亦赋存有矿体。该矿床的成矿过程可划分为4个阶段:石英-萤石-白云母-电气石-锡石-黑钨矿阶段(Ⅰ阶段)、石英-萤石-黑钨矿-黄铜矿-毒砂-磁黄铁矿阶段(Ⅱ阶段)、石英-萤石-黄铜矿-黄铁矿-磁黄铁矿-银矿物阶段(Ⅲ阶段)和方解石-萤石-黄铁矿阶段(Ⅳ阶段)。道伦达坝矿床主要发育富液两相包裹体(WL型)、富气两相包裹体(WG型)和含子矿物多相包裹体(S型)。Ⅰ和Ⅱ阶段均发育WL型、WG型和S型包裹体,两阶段的均一温度和盐度分别介于309~389℃和242~339℃、6.2%~46.3%NaCl_(eqv.)和5.3%~41.4%NaCl_(eqv.);Ⅲ阶段主要发育WL型和S型包裹体,均一温度介于153~268℃,盐度介于3.5%~35.4%NaCl_(eqv.);Ⅳ阶段仅发育WL型包裹体,均一温度介于114~188℃,盐度介于2.1%~7.6%NaCl_(eqv.)。前两个阶段为中高温、高盐度流体,Ⅲ阶段流体具中低温、高盐度特征,而Ⅳ阶段为低温、低盐度流体。矿床的δ^(18)O_(H_2O)值介于-10.0‰~7.2‰,δD值介于-127‰^-81‰,由Ⅰ阶段到Ⅳ阶段,成矿流体由以岩浆流体为主逐渐演化到以大气降水为主,表明道伦达坝矿床初始流体为岩浆热液,后期有大气降水的加入。硫同位素组成(-7.4‰^-1.2‰)表明成矿物质主要来自深源岩浆;铅同位素组成(μ值介于9.3~9.7)暗示成矿物质主要来自造山带物质部分熔融形成的岩浆。流体的多次沸腾和混合是矿质沉淀的主要机制。
The Daolundaba deposit in the southern Great Xing＇an Range,Inner Mongolia is a medium-sized copper-wolfram-tin-silver deposit.Ore bodies are hosted in faulted and shattered zones and host rocks are mainly the Permian sandstone and slate with minor amounts of Variscan biotite granite.The mineralization process can be divided into four stages：quartz-fluorite-muscovite-tourmaline-cassiterite-wolframite（stageⅠ）,quartz-fluorite-wolframite-chalcopyrite-arsenopyrite-pyrrhotite（stage Ⅱ）,quartz-fluorite-chalcopyrite-pyritepyrrhotite-silver-bearing mineral（stageⅢ）,and calcite-fluorite-pyrite（stageⅣ）stages.In this study,three types of fluid inclusions（FIs）have been distinguished in quartz,fluorite,and calcite veins including liquid-rich（WL type）,gas-rich（WG type）,and daughter mineral-bearing（S type）inclusions.The FIs in both stagesⅠandⅡ were of WL-,WG-,and S-types,with homogenization temperatures and salinities varying from 309 to389 ℃ and from 6.2 to 46.3 wt.% NaCleqv.in stageⅠ,respectively,and from 242 to 339℃ and from 5.3 to 41.4 wt.% NaCleqv.in stage Ⅱ,respectively.The FIs in stage Ⅲ contained mainly WL-and S-types,with homogenization temperatures and salinities ranging from 153 to 268 ℃ and from 3.5 to 35.4 wt.% NaCleqv.,respectively.Only WL-type FIs occurred in stageⅣ,and the homogenization temperatures and salinities varied from 114 to 188 ℃ and from 2.1 to 7.6 wt.% NaCleqv.,respectively.In general,the ore-forming fluids of stages Ⅰ/Ⅱ, Ⅲ and Ⅳ were characterized by moderate-high temperature/high salinity, moderate-low temperature/high salinity and low temperature/low salinity fluids,respectively.Theδ18 OH_2O and δD values of the ore-forming fluids were between-10.0‰ and 7.2‰,-127‰ and-81‰,respectively,demonstrating that,from the early to late stages,the ore-forming fluids of the Daolundaba deposit gradually evolved from magmatic fluids to mixtures of meteoric and magmatic waters.Theδ34 S values ranged from-7.4‰to-1.2‰,indicating S came primarily from deep magma.The Pb isotopic composition（μvalues 9.3-9.7）also indicated that Pb was mainly derived from the magma formed by partial melting of orogenic material.Thus,both S and Pb isotopic data suggest that the ore-forming materials originated mainly from magma.Overall,our study shows that the multi-stage boiling and mixing of the ore-forming magmatic fluids with meteoric water were the dominant mechanism for ore deposition.
作者
陈公正
武广
武文恒
张彤
李铁刚
刘瑞麟
武利文
章培春
江彪
王志利
CHEN Gongzheng;WU Guang;WU Wenheng;ZHANG Tong;LI Tiegang;LIU Ruilin;WU Liwen;ZHANG Peichun;JIANG Biao;WANG Zhili(School of Earth Sciences and Resources,China University of Geosciences（Beijing）,Beijing 100083,China;MRL Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chines Academy of Geological Sciences Beijing 100037,China;Faculty of Science,University of Melbourne,Melbourne 3010,Victoria,Australia;Inner Mongolia Institute of Geological Survey,Hohhot 010020,China;MOE Key Laboratory of Orogenic Belts and Crustal Evolution,Peking University,Beijing 100871,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2018年第5期202-221,共20页
Earth Science Frontiers
基金
国家自然科学基金项目(41772086)
内蒙古自治区地质勘查基金项目(2015-01-YS01)
国家重点研发计划项目(2017YFC0601303)
