硫化物Rb-Sr同位素定年研究进展

针对金属矿床成矿年代确定混乱的问题,国内外许多矿床学家和同位素地球化学家对金属矿物常规同位素定年方法进行了有益的探索研究,尤其是对于矿石矿物以闪锌矿、方铅矿和黄铁矿为主的铅锌矿床,硫化物矿物Rb-Sr同位素定年方法显示出了其独特的优势。结合近几年开展的工作,总结国内外硫化物Rb-Sr同位素定年研究取得的成果、闪锌矿中Rb、Sr的赋存状态与定年机理以及定年适应性问题。采用闪锌矿Rb-Sr同位素组成数据拟合成等时线源自热液流体与闪锌矿之间Rb和Sr的不同分异作用,但并不是所有的闪锌矿均适合该定年技术。要成功获得年龄,需结合野外地质特征采集代表性的矿石样品,并在镜下鉴定基础上挑选合适的单矿物;在分析测试过程中,需尽可能去除次生包裹体和粘土矿物。

Progress in Rb-Sr Isotopic Dating of Sulfide

In view of the confusion in dating the metallic ore deposit,many mineralogists and isotopic geochemists have carried through much useful research in the conventional isotopic dating of metal mineral,and sulfide Rb-Sr isotopic dating method displays unique predominance,especially to the Pb-Zn ore deposit whose ore minerals mainly comprise sphalerite,galena and pyrite.Combining with the dating technique research made in our laboratory in recent years,the authors have sums up the achievements of sulfide Rb-Sr isotopic dating,Rb and Sr residence sites in sphalerite,dating mechanism,and its adaptability.The sphalerite Rb-Sr isochron arrays derive from differential partitioning of Rb and Sr between hydrothermal fluid and sphalerite,but not all sphalerites adapt to this dating technique.To succeed in obtaining ore-forming age,it is necessary to sample the representative ores combining with the geological characteristics,and to pick out the appropriate minerals based on the thorough study of the petrography and paragenesis of samples.Furthermore,the secondary fluid inclusions and clay minerals should be wiped off during the sample analysis.