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赵海,苏文超,沈能平,谢鹏,蔡佳丽,甘文志. 2018. 广西大厂矿田高峰锡多金属矿床流体包裹体研究. 岩石学报, 34(12): 3553-3566
广西大厂矿田高峰锡多金属矿床流体包裹体研究
作者单位E-mail
赵海 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081
中国科学院大学, 北京 100049
铜仁学院, 铜仁 554300 
 
苏文超 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081 suwenchao@vip.gyig.ac.cn 
沈能平 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081  
谢鹏 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081
中国科学院大学, 北京 100049 
 
蔡佳丽 中国科学院地球化学研究所, 矿床地球化学国家重点实验室, 贵阳 550081
中国科学院大学, 北京 100049 
 
甘文志 广西高峰矿业有限责任公司, 南丹 547200  
基金项目:本文受国家自然科学基金项目(41672080、41272113)、中国科学院地球化学研究所杰出人才基金和中国科学院国家外国专家局创新团队国际合作伙伴计划(KZZD-EW-TZ-20)联合资助.
摘要:
      广西大厂锡多金属矿田是世界著名的锡矿产地之一。矿田内绝大部分锡锌资源量分布在西成矿带的高峰和长坡-铜坑两个矿床之中,其中赋存在中泥盆统生物礁灰岩中的高峰100号体以其品位高(Sn 1.79%、Zn 10.1%、Pb 5.21%、Sb 4.8%、Ag 235g/t)、规模大(矿石量超过1300万吨)而在整个大厂矿田中占据非常重要的地位。本文在扫描电镜-阴极发光(SEM-CL)图像分析的基础上,对高峰锡多金属矿床成矿早期锡石-毒砂-磁黄铁矿阶段和成矿晚期硫化物-硫盐-碳酸盐阶段的流体包裹体岩相学、显微测温学及其气相成分的激光Raman光谱进行了系统研究。结果表明,成矿早期锡石-毒砂-磁黄铁矿阶段石英和锡石中主要发育富含CO2和CH4气相流体包裹体,其均一温度和盐度分别为360~410℃和3%~6% NaCleqv;成矿晚期硫化物-硫盐-碳酸盐阶段石英中则仅发育气-液两相盐水流体包裹体,具有相对低的均一温度(270~310℃)和盐度(3%~6% NaCleqv)。石英和锡石的H-O同位素组成指示成矿流体主要来源于岩浆热液。对比矿田内其他矿床,进一步发现高峰矿床富CO2气相流体的盐度(3%~6% NaCleqv)与拉么矽卡岩型Zn-Cu矿床富CO2气相流体的盐度(7%~9% NaCleqv)相近,认为高峰矿床与拉么矿床可能具有相同的成矿流体来源,两者均来源于深部岩浆房中分异出的超临界流体。高峰矿床成矿流体可能主要来源于深部矽卡岩阶段富CO2气相流体的压缩和冷却(vapor contraction and cooling)。流体冷却过程可能是锡石-硫化物成矿的主要控制因素。高峰矿床-200m中段以上矿体,锡石和石英中的流体包裹体以富CO2和CH4气相流体包裹体为主,而缺失多子晶流体包裹体组合,推测高峰矿床-200m中段以下可能存在富含成矿金属的高密度卤水,从而形成高品位的锡多金属脉状矿体或矽卡岩型Zn-Cu矿体。
英文摘要:
      The Dachang tin-polymetallic district, Guangxi, China, is one of the largest tin ore district in the world and contains the Lamo Zn-Cu proximal skarn deposit, the Tongkeng-Changpo and Gaofeng tin-base metal deposits, and the Huile and Dafulou black shale-hosted cassiterite-sulfide deposits. They are hosted by Devonian carbonate-rich sediments near the underlying Cretaceous (91~96Ma) Longxianggai granite. The Gaofeng deposit in the district occurs in the Middle Devonian reef limestone with higher grade ore and giant resource of Sn. The mineralization includes the early ore stage of cassiterite-arsenopyrite-pyrrhotite and the late ore stage of carbonate-sulfide-sulfosalt. Petrography, microthermometry, and Laser Raman spectroscopy, combined with scanning electron microscope-cathodoluminescence (SEM-CL) analyses of fluid inclusions are used to characterize the chemical evolution of ore fluids at the Gaofeng deposit. Two types of fluid inclusions are recognized in quartz and cassiterite:CO2-CH4 vapor-rich fluid inclusions are mainly observed in quartz and cassiterite associated with cassiterite-arsenopyrite-pyrrhotite stage and have high homogenization temperatures of 360~410℃ and salinities of 3%~6% NaCleqv, whereas two-phase, liquid-rich aqueous fluid inclusions only occur in quartz related to sulfide-sulfosalt-carbonate stage and have relatively low homogenization temperatures ranging from 270 to 310℃ and salinities of 3%~6% NaCleqv. The range of salinity for all fluid inclusions is similar to those of CO2 vapor-rich fluid inclusions (7%~9% NaCleqv) in diopside and garnet in the Lamo skarn Zn-Cu deposit nearby the Gaofeng deposit. Oxygen and hydrogen isotopes of ore fluids from quartz and cassiterite indicate magmatic water in origin. Base on the physical and chemical evolution of ore fluids, it is concluded that the mineralizing fluids for the Gaofeng deposit were probably derived from intermediate density, supercritical single-phase fluid that exsolved from the deep crystallizing granite. This magmatic fluid reacted with carbonate-rich host rocks in the depth that led to phase segregation to form brine and vapor-like fluid. Vapor contraction and cooling of vapor-like fluids may deposit cassiterite and arsenopyrite, and followed by sulfides and sulfosalts at the Gaofeng deposit.
关键词:成矿流体  流体包裹体  高峰锡多金属矿床  广西大厂矿田
投稿时间:2017-11-30  修订日期:2018-07-13
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主办单位:中国矿物岩石地球化学学会
印刷版(Print): ISSN 1000-0569 网络版(Online): ISSN 2095-8927
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