西藏冈底斯罗布真铅锌矿床成矿流体特征  

Characteristics of Metallogenic Fluid in the Luobuzhen Pb- Zn Deposit of the Gangdese Belt,Southern Tibet

作　　者：欧阳海涛[1] 孙祥[1] 郑有业[1,2] 吴松[1] 游智敏[1] 耿瑞瑞 王烜 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,地球科学与资源学院,北京100083 [2]中国地质大学地质过程与矿产资源国家重点实验室,资源学院,湖北武汉430074 [3]核工业北京地质研究院,北京100029 [4]辽宁省地质勘查院,辽宁大连116100

出　　处：《地质与勘探》2015年第5期816-827,共12页Geology and Exploration

基　　金：国家自然科学基金(41302063);中国地质调查局工作项目(1212011220927);教育部长江学者与创新团队发展计划(IRT14R56);教育部博士点基金项目;北京高等学校青年英才计划;中央高校基本科研业务费联合资助

摘　　要：西藏罗布真铅锌矿床位于冈底斯西缘,其矿体主要产于古新世林子宗群英安岩及斑状二长花岗岩中,并受断裂控制。成矿过程可分为石英-黄铁矿阶段(Ⅰ)和石英-多金属硫化物阶段(Ⅱ)。Ⅰ阶段石英中分布三种类型的包裹体,即:纯气相包裹体(成分为CO2或CH4)、水溶液包裹体(液相组分主要为H2O,含微量CO2,气相组分主要为H2O和CO2)和含子矿物多相包裹体。Ⅱ阶段石英中的包裹体类型及对应的成分与Ⅰ阶段石英大体相似,但部分水溶液包裹体气液相成分均为H2O;Ⅱ阶段闪锌矿中分布水溶液包裹体和含子矿物多相包裹体,二者液相组分和气相组分主要为H2O,子矿物为方解石。Ⅰ阶段包裹体均一温度集中在200~320℃,盐度集中在8%~16%Na Cleqv,Ⅱ阶段包裹体均一温度集中在180~240℃和280~320℃两个区间,盐度集中在6%~12%Na Cleqv。成矿流体为中温、中低盐度的H2O-Na Cl±CO2体系。成矿流体的δDH2O值为-91‰^-125‰,δ18OH2O值为3.9‰~6.6‰,表明其来源主要为岩浆水。以气液相分离为标志的流体不混溶是矿区硫化物沉淀的重要机制。The Luobuzhen Pb- Zn deposit in western Gangdese is hosted in the dacite of Linzizong Group and porphyritic monzogranite and controlled by faults. Its ore- forming processes can be divided into early quartz- pyrite stage（ Stage I） and late quartz- polymetallic sulfide stage（ Stage II）.Three major types of fluid inclusions are identified in quartz of Stage I,i. e. pure gaseous inclusions（ components are CO2 or CH4）,aqueous inclusions（ liquid components are mainly composed of H2 O with minor amount of CO2,and vapor components are mainly composed of H2 O and CO2） and daughter mineral- bearing inclusions. Types and the corresponding components of fluid inclusions in quartz of Stage II are similar to those in quartz of Stage I.However,both liquid and gas components of some of the aqueous inclusions in stage II quartz are H2 O. Two types of fluid inclusions are recognized in sphalerite of Stage II,i. e. aqueous inclusions and daughter mineral- bearing inclusions. Their liquid and gas components are dominated by H2 O and the daughter mineral is calcite. The inclusions of Stage I are homogenized at temperatures concentrating at 200 - 320℃ with salinities concentrating at 8 to 16% Na Cleqv. Inclusions of Stage II are homogenized at temperatures concentrating at 180 - 240℃ and 280 - 320℃,with salinities concentrating at 6 to 12% Na Cleqv. The metallogenic fluid is characterized by a H2O- Na Cl ± CO2 system with medium temperature and medium to low salinity. The δDH2Ovalues of metallogenic fluid vary from- 91‰ to- 125‰,while the δ18OH2Ovalues are between 3. 9‰ and 6. 6‰. These features suggest that the metallogenic fluid was mainly originated from magmatic water. Immiscibility is the major mechanism for deposition of sulfides.

关 键 词：冈底斯 罗布真铅锌矿床 流体包裹体 氢氧同位素 不混溶 

分 类 号：P618.42[天文地球—矿床学] P618.43[天文地球—地质学]