硫化物矿床中闪锌矿Rb-Sr等时线定年方法研究——以湘西新晃打狗洞铅锌矿床为例

Application of Rb-Sr Isochron Dating Method in sphalerite of Sulphide Deposit——A Case Study from Dagoudong Pb-Zn Deposit in Xinhuang,Western Hunan Province

本文对用研磨法和分步溶解技术提取流体相和硫化物相的实验条件进行了系统的研究,在此基础上建立和完善了闪锌矿分相Rb-Sr等时线定年的方法流程。通过对湘西打狗洞铅锌矿床Rb-Sr定年的示范研究,进一步验证了方法的有效性和应用前景,获得闪锌矿矿物Rb-Sr等时线年龄(473±76 Ma),采用研磨法和分步溶解技术获得更精确的闪锌矿流体相+硫化物相年龄(489.6±5.9 Ma)和全矿物+矿物相(流体相+硫化物相)的年龄(490±6.5 Ma),表明湘西打狗洞铅锌矿床的成矿作用发生在早奥陶世,其成矿作用的发生可能与晚期成岩或区域构造热事件有关。

This paper takes a systematic study on the experimental conditions using the grinding method and stepping dissolution technique to extract the fluid phase and sulfide phase from sphalerite for Rb-Sr isochrone dating,and the entire analysis process was established and improved.Through the demonstration of Rb-Sr dating method used in Dagoudong Pb-Zn deposits,western Hunan,the validity of the method was further verified and showed a good application prospects.Three isochron ages are obtained：473±76 Ma for sphalerite mineral-phase,489.6±5.9 Ma for fluid phase ＋sulfide phase of sphalerite by grinding method and stepping dissolution technique,490±6.5 Ma for mineral-phase and fluid phase ＋sulfide phase of sphalerite.The isochron ages indicated that Dagoudong deposit was formed in Early Ordovician,and maybe related to later diagenesis or regional tectono-thermal events.