西南印度洋中脊热液硫化物成矿物质来源探讨:同位素证据  

Discussion on Sources of Metallogenic Materials of Hydrothermal Sulfide from Southwest Indian Ridge:Isotope Evidences

作　　者：李小虎[1,2] 初凤友[1,2] 雷吉江[1,2] 赵宏樵[1,2] 余星[1,2] 

机构地区：[1]国家海洋局海底科学重点实验室,浙江杭州310012 [2]国家海洋局第二海洋研究所,浙江杭州310012

出　　处：《地球科学与环境学报》2014年第1期193-200,共8页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(40906036;41276055);国家海洋局海洋公益性行业科研专项项目(201005003);中国大洋矿产资源研究开发协会"十二五"专项项目(DY125-12-R-02;DY125-12-R-04;DY125-12-R-06;DY125-11-R-06)

摘　　要：报道了西南印度洋中脊47°E^55°E洋脊段热液区硫化物中He、Pb和Cu同位素特征,探讨了热液硫化物成矿物质来源特征。结果表明:硫化物N(3 He)/N(4 He)值变化范围较大(R/Ra=0.85~7.02),显示洋中脊玄武岩和海水对He来源具有不同贡献,硫化物中He主要来源于洋中脊玄武岩,也有部分放射性成因He的混入;热液硫化物Pb同位素比值变化范围很小(N(206 Pb)/N(204Pb)=18.196~18.239,N(207 Pb)/N(204 Pb)=15.479~15.490和N(208 Pb)/N(204 Pb)=37.951~38.023),与西南印度洋中脊玄武岩Pb同位素比值较大的变化范围相比,热液流体循环过程中Pb同位素发生了明显均一化;硫化物单矿物Cu同位素组成均为正值(δ(64 Cu)=(0.02~0.52)×10-3),显示西南印度洋中脊热液硫化物呈现略微富集Cu重同位素特征;西南印度洋中脊热液硫化物中He、Pb和Cu同位素记录了热液喷口流体和金属源区特征,热液硫化物成矿物质主要来源于洋中脊玄武岩和海水,但明显经历了热液流体再循环和后期改造过程。The source of hydrothermal fluid and metals of deposit is very important to understand mineralization of hydrothermal sulfide on the mid-ocean ridge. He, Pb and Cu isotopic characteristics of hydrothermal sulfide from the section of ocean ridge （47°E-55°E）of Southwest Indian Ridge were analyzed,and the characteristics of mineralization sources of hydrothermal sulfide deposit were discussed.The results show that the range of N（^3 He）/N（^4 He）of sulfide is wide with the R/R a of 0.85-7.02,so that the contributions of mid-ocean ridge basalt （MORB） and seawater to the sources of He are different,and the main source of He of sulfide is MORB with radiogenic He mixing partially;the ranges of Pb isotopic ratios of sulfide are limited with N（^206 Pb）/N（^204 Pb）of 18.196-18.239,N （^207 Pb）/N （^204 Pb）of 15.479-15.490 and N （^208 Pb）/N（^204 Pb）of 37.951-38.023,so that compared with the wide ranges of Pb isotopic ratios of basalt from Southwest Indian Ridge,the Pb isotopes during the cycle processes of hydrothermal fluid＆amp;nbsp;trend to homogeneous;the monomineral Cu isotopic compositions of sulfide are positive with the range of （0.02-0.52）×10^-3 ,so that the characteristics of hydrothermal sulfide from Southwest Indian Ridge are heavy Cu-rich appreciably;He,Pb and Cu isotope of hydrothermal sulfide from Southwest Indian Ridge record the characteristics of hydrothermal vent fluid and source of metal, and mineralization sources of Hydrothermal Sulfide are MORB and seawater with significant recycling and late reformation of hydrothermal fluid.

关 键 词：地球化学 热液硫化物 同位素 源区 成矿作用 西南印度洋中脊 

分 类 号：P597[天文地球—地球化学]