湘东垄上矽卡岩型锡多金属矿床流体包裹体特征及成矿机制研究  

Characteristics of fluid inclusions and metallogenic mechanism of the Longshang skarn type tin polymetallic deposit in eastern Hunan Province,China

作　　者：王旭东 袁顺达[3] 吴胜华 徐丽燕[1] 赵盼捞[3] WANG XuDong;YUAN ShunDa;WU ShengHua;XU LiYan;ZHAO PanLao(Yuanpei College of Shaoxing University,Shaoxing 312000,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China;MNR Key Laboratory for Exploration&Technology of Critical Mineral Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]绍兴文理学院元培学院,绍兴312000 [2]自然资源部成矿作用与资源评价重点实验室,中国地质科学院矿产资源研究所,北京100037 [3]自然资源部战略性金属矿产找矿理论与技术重点实验室,中国地质大学,北京100083

出　　处：《岩石学报》2023年第6期1743-1756,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(92062218、42203042、42272092);中国博士后科学基金项目(2022M712969)联合资助。

摘　　要：矽卡岩型锡矿是全球重要的锡金属来源,但是锡石沉淀成矿机制仍存在较大的争议。垄上矽卡岩型锡矿床位于湘东锡田锡多金属矿田中部,是南岭钨锡成矿带内矽卡岩型锡矿的典型代表。本文在野外考察、矿石矿相学、流体包裹体岩相学研究的基础上,采用流体包裹体组合法对垄上矽卡岩矿床不同矿化阶段代表矿物中的流体包裹体进行了详细研究。结果显示,垄上矽卡岩型多金属矿床成矿阶段可划分为矽卡岩阶段、退化蚀变阶段、云英岩-氧化物阶段、石英硫化物阶段以及萤石碳酸盐化等5个阶段,其中,锡石主要形成于云英岩-氧化物阶段。与锡石密切共生的石英中发育流体包裹体类型主要为富液相、富气相两相水溶液包裹体,含液相CO_(2)三相水溶液包裹体和纯CO_(2)型包裹体。流体温度和盐度具有较大的变化范围(200-400℃和2%-9%NaCleqv),指示流体在降温过程中经历了显著的不混溶。与硫化物共生的石英中主要为富液相两相水溶液包裹体,温度和盐度主要集中在190-261℃和3%-7%NaCleqv,指示流体冷却过程同时经历了流体混合。本次研究提出锡田矽卡岩型矿床中流体不混溶是导致云英岩-氧化物阶段锡石沉淀成矿的主要机制,而流体冷却和混合是导致硫化物沉淀的主要原因。Global tin mineral resource is mainly derived from skarn-type Sn deposits,however,its formation mechanism remains highly debated.Longshang skarn-type Sn deposit,located in the middle part of Xitian Sn polymetallic orefield,eastern Hunan Province,is a typical skarn-type Sn deposit in the world famous Nanling W-Sn metallogenic blet.Based on geological observation,ore structure study and fluid inclusions investigation,we conduct systematic study upon fluid inclusions from different ore-forming stages of this deposit by using the method of fluid inclusion assemblage.The results show that the mineralization of Longshan skarn-type deposit can be divided into skarn,retrograde,greisen-oxide,quartz-sulfide and fluorite-carbonate stages,with the cassiterite forming mainly in the greisen-oxide stage.Fluid inclusions in quartz coexisting with cassiterite of the deposit include liquid-rich and vapor-rich two-phase fluid inclusions,liquid CO 2-bearing three-phase fluid inclusions and pure CO 2 fluid inclusions.The homogenization temperature and salinity of the fluid inclusions have a relatively large range of 200~400℃ and 2%~9% NaCleqv,indicating the ore-forming fluid experienced immiscibility.The fluid inclusions in quartz coexisting with sulfide is mainly liquid-rich ones with a temperature and salinity range of 190~261℃and 3%~7% NaCleqv,suggesting the fluid experienced cooling and immiscibility.Our studies suggest that fluid immiscibility is the major reason that leads to the formation of Sn deposit in the greisen-oxide stage,while fluid cooling and immiscibility is the major mechanism for the formation of sulfide.

关 键 词：流体包裹体 成矿阶段 矽卡岩型锡矿床 垄上 锡田 

分 类 号：P618.2[天文地球—矿床学]