大兴安岭南段小孤山锡锌矿床锡石U-Pb年龄、流体包裹体和H-O-S-Pb同位素特征  

Cassiterite U-Pb age,fluid inclusion and H-O-S-Pb isotope geochemistry of the Xiaogushan Sn-Zn deposit in the southern Great Xing an Range,NE China

作　　者：武广[1] 杨飞 李睿华[1,2] 陈公正 张彤[4] 师江朋 李士辉 WU Guang;YANG Fei;LI RuiHua;CHEN GongZheng;ZHANG Tong;SHI JiangPeng;LI ShiHui(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China;College of Earth Sciences,Hebei GEO University,Shijiazhuang 050031,China;Inner Mongolia Institute of Geological Survey,Hohhot 010020,China)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]北京大学地球与空间科学学院,北京100871 [3]河北地质大学地球科学学院,石家庄050031 [4]内蒙古自治区地质调查院,呼和浩特010020

出　　处：《岩石学报》2023年第6期1579-1599,共21页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2017YFC0601303);内蒙古玉龙矿业股份有限公司科研项目(2020110033002072);内蒙古自治区地质勘查基金项目(2015-01-YS01)联合资助。

摘　　要：毛登-小孤山地区是大兴安岭南段锡多金属成矿带代表性矿区,由小孤山锡锌矿床和毛登锡钼铋多金属矿床组成。小孤山矿床锡石U-Pb Tera-Wasserburg谐和年龄为134.8±1.9Ma,表明其形成于早白垩世。该矿床成矿过程可划分为4个阶段:锡石-黄铁矿-石英-电气石阶段(Ⅰ阶段)、锡石-黄铜矿-闪锌矿-石英-萤石阶段(Ⅱ阶段)、闪锌矿-方铅矿-石英-萤石阶段(Ⅲ阶段)、黄铁矿-石英-方解石阶段(Ⅳ阶段)。小孤山矿床主要发育富液两相包裹体(WL型)、富气两相包裹体(WG型)及含子矿物包裹体(S型)。Ⅰ、Ⅱ和Ⅲ阶段均发育WL、WG和S型包裹体,Ⅳ阶段仅出现WL型包裹体。从Ⅰ至Ⅳ阶段流体包裹体均一温度/盐度分别为420-443℃/8.3%-52.0%NaCleqv、286-379℃/4.0%-40.2%NaCleqv、214-299℃/3.8%-36.1%NaCleqv、178-195℃/2.1%-3.3%NaCleqv,表明从早阶段到晚阶段成矿流体由高温高盐度向低温低盐度转化,且前三个阶段流体盐度波动大,暗示成矿流体发生了多次沸腾。矿床的δ18O水介于-2.6‰-11.0‰,δD介于-107‰--91‰,Ⅰ和Ⅱ阶段的成矿流体以岩浆水为主,Ⅲ阶段开始有大气降水的加入。硫化物的δ34SCDT值介于-3.3‰--0.6‰,206Pb/204Pb介于17.772-18.427,207Pb/204Pb介于15.482-15.679,208Pb/204Pb介于37.668-38.622,表明成矿物质来源于早白垩世花岗质岩浆。流体沸腾和降温是矿质沉淀的两种主要机制。The Maodeng-Xiaogushan metallogenic area comprises the Maodeng Sn-Mo-Bi-polymetallic and Xiaogushan Sn-Zn deposits.Cassiterite U-Pb dating of the Xiaogushan deposit yielded an age of 134.8±1.9Ma,indicating that the deposit was formed in the Early Cretaceous.The mineralization process of the Xiaogushan deposit can be divided into four stages:the cassiterite-pyrite-quartz-tourmaline stage(stageⅠ),the cassiterite-chalcopyrite-sphalerite-quartz-fluorite stage(stageⅡ),the sphalerite-galena-quartz-fluorite stage(stageⅢ)and the pyrite-quartz-calcite stage(stageⅣ).Three types of fluid inclusions(FIs),including liquid-rich two-phase(WL-type),gas-rich two-phase(WG-type)and daughter mineral-bearing(S-type)FIs,have been distinguished in the deposit.The WL-,WG-and S-type inclusions developed in the stagesⅠ,ⅡandⅢ,while only WL-type inclusions appeared in the stageⅣ.The homogenization temperatures/salinities of the FIs from the stage I to stageⅣare in the ranges of 420~443℃/8.3%~52.0%NaCleqv,286~379℃/4.0%~40.2%NaCleqv,214~299℃/3.8%~36.1% NaCleqv and 178~195℃/2.1%~3.3%NaCleqv,respectively,indicating the ore-forming fluid successively evolved from high temperature and salinity to low temperature and salinity.The co-existing of WL-,WG-,and S-type FIs,as well as the fluctuating salinity in all of the former three metallogenic stages,suggests that multi-stage fluid boiling occurred as the ore-forming fluid evolution.Theδ18 O H 2O andδD values of ore-forming fluid range from-2.6‰to 11.0‰ and-107‰ to-91‰,respectively,indicating that it was dominantly derived from magmatic fluid,then mixed with meteoric water in the stageⅢ.Theδ34 S CDT values of sulfide samples range from-3.3‰to-0.6‰.The ratios of 206 Pb/204 Pb,207 Pb/204 Pb and 208 Pb/204 Pb of sulfides are in the ranges of 17.772~18.427,15.482~15.679,and 37.668~38.622,respectively.The S and Pb isotopes imply that the ore-forming material mainly came from the Early Cretaceous granitic magma.Fluid boiling and cooling were the two main mechani

关 键 词：锡石U-Pb年龄 流体包裹体 H-O-S-Pb同位素 小孤山矿床 大兴安岭南段 

分 类 号：P618.44[天文地球—矿床学] P618.43[天文地球—地质学]