广西苍梧社垌石英脉型钨钼多金属矿床流体演化及来源示踪  

Evolution and source tracing of the Shedong quartz vein type scheelite-molybdenite polymetallic deposit in Cangwu County

作　　者：张志强[1] 陈懋弘[1,2] 莫建明 肖柳阳 黄智忠 罗军 区朝辉 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [3]广西地球物理勘察院,柳州545005

出　　处：《岩石学报》2014年第1期281-291,共11页Acta Petrologica Sinica

基　　金："中央级公益性科研院所基本科研业务费专项资金"(K1015);"国家重点基础研究发展计划(973计划)"(2012CB416704);"中国地质调查局地质调查工作项目"(1212011120831)联合资助

摘　　要：广西苍梧社垌矿床是大瑶山隆起南侧新发现的一个大型斑岩-矽卡岩-石英脉型钨钼多金属矿床。本文重点对其中的石英脉型矿床进行了研究,依据脉体穿插关系及矿物共生组合将成矿过程划分为I石英-黄铁矿阶段、II石英-白钨矿-辉钼矿阶段、III石英-多金属硫化物阶段以及IV石英-方解石-萤石阶段,其中II和III阶段为主成矿阶段。从早到晚,均一温度逐渐下降(第一阶段550℃→370℃,第二阶段370℃→330℃,第三阶段330℃→210℃,第四阶段190℃→150℃),流体密度逐渐上升(0.61g/cm3→0.72g/cm3→0.82g/cm3→0.94g/cm3),盐度先升后降(第一阶段5.86%～8.55%NaCleqv,第二阶段4.49%～43%NaCleqv,第三阶段0.53%～46.37%NaCleqv,第四阶段0%～12.85%NaCleqv)。激光拉曼成分分析显示,社垌石英脉型矿床的成矿流体属于H2O-NaCl体系,但是该体系的流体成分在成矿前后发生了较大的变化,反映第I阶段以氧化环境为主,(II、III、)IV阶段则为还原环境。氢氧同位素研究显示成矿流体来自于岩浆水,后期大气降水的加入导致矿质发生沉淀。此外金属硫化物的δ34S组成(-3.8‰～+1.7‰)平均为-0.46‰,接近于零值,也表明为岩浆来源。引起矿质沉淀的主要原因是流体混合导致的温度下降等环境条件的改变。总体而言,社垌石英脉型钨钼多金属矿床的成矿流体主要来自岩浆热液,为中高温、中低盐度、低密度的NaCl-H2O流体体系,钨钼等多金属成矿与区内加里东期岩浆作用密切相关。Shedong large scheelite molybdenite polymetallic deposit in Cangwu County of Guangxi,located in the south of Dayaoshan uplift,is a porphyry-skarn-quartz vein type deposit related to granitoids. The mineralizing process of the quartz vein type deposit can be divided into four stages,namely I quartz-pyrite stage,II quartz-scheelite-molybdenite stage,III quartz-polymetallic sulfide stage and IV quartz-calcite-fluorite stage. The second and third stages are main metallogenic stages. The homogenization temperatures from Ⅰ to Ⅳ stage gradually decrease（ 550℃→370℃,370℃→330℃,330℃→240℃,190℃→140℃）. Instead,the density keeps increasing（ 0. 61g / cm3→0. 72g/cm3→0. 82g/cm3→0. 94g/cm3）. The salinities（ NaCl） increase from Ⅰ stage to Ⅲ, then decrease to the end（ 5. 86% ～ 8. 55% NaCleqv,4. 49% ～ 43% NaCleqv,0. 53% ～ 46. 37% NaCleqv,0% ～ 12. 85% NaCleqv）. The ore-forming fluid belongs to NaCl-H 2 O system,however,the composition changes during the metallogenic procedure, which is indicated by Laser Raman composition analysis. The ore-forming fluid evolved from magma,and mixed by the meteoric water later. This was implied by the isotopic composition of H-O isotopes from the quartz veins of all stages and S isotopes from sulfides（-3. 8‰ ～ ＋1. 7‰,-0. 46‰ for the average）. The primary reason for deposition is mixture of fluids. In a word,the ore-forming fluid of the Shedong quartz vein type deposit belongs to the NaCl-H 2 O hydrothermal system with medium-high temperature,midium-low salinity,and low density. And the metallogenesis is closely connected with Caledonian magmatism.

关 键 词：社垌石英脉型钨钼矿床 流体包裹体 H-O同位素 S同位素 流体来源 流体混合 

分 类 号：P618.65[天文地球—矿床学] P618.67[天文地球—地质学]