扬子西南缘大红山铁铜多金属矿床矿化方解石脉方解石Sm-Nd定年及意义

Sm-Nd isotopic dating of calcite in the ore-bearing calcite vein from the Dahongshan iron copper polymetallic deposit in the southwestern margin of Yangtze block and its significance

扬子西南缘是我国重要的铁铜金矿产资源产区,分布许多铁铜多金属矿床,而本次研究的大红山矿床属扬子西南缘内最大的铁铜多金属矿床之一。铁、铜矿化方解石脉中方解石测年结果表明,Sm-Nd等时线年龄为(818±3) Ma,代表方解石脉中磁铁矿、黄铜矿矿化年龄为818 Ma。结合扬子西南缘成岩成矿关系、背景研究,揭示该矿化事件与Rodinia超大陆裂解期大陆裂谷环境有关。据方解石Sm-Nd同位素体系中(143Nd/144Nd)i值0.5112649和εNd(t=818 Ma)值范围介于-6.3~-6.2之间的组成特点,指示方解石中Nd为壳幔混源,且以幔源为主。

The southwestern margin of Yangtze block,known as the Kangdian copper metallogenic belt,is an important production area of iron-copper polymetallic resources in China,as there are many small-large iron-copper polymetallic deposits.The Dahongshan deposit which is studied in this study is one of the biggest iron-copper polymetallic deposits in the southwestern Yangtze block.The dating results of calcites in Fe-Cu-mineralized calcite veins indicate that the Sm-Nd isochron age of 818±3 Ma represents the mineralization age of magnetite and chalcopyrite in calcite veins.Combined with researches on the relationship and background of diagenesis and metallogenesis of the southwestern margin of Yangtze block,it is suggested that the mineralization event could be related to continental rift environment in the breakup period of Rodinia supercontinent.Based on compositional characteristics of the Sm-Nd isotope system of calcites including the(143Nd/144Nd)i value of 0.5112649 and εNd(t=818 Ma) values ranging from-6.3 to-6.2,it is indicated that the Nd in calcite could be from a mixed source of crust and mantle,with majority of the mantle source.