滇西羊拉铜矿床稳定同位素地球化学研究

STABLE ISOTOPE GEOCHEMICAL CHARACTERISTICS OF THE YANGLA COPPER DEPOSIT IN WESTERN YUNNAN PROVINCE

滇西羊拉铜矿是近年来发现的大型铜矿床。作者系统地研究了该矿床的S、Pb、C、O、Si同位素组成，研究表明该矿床不同矿石的硫同位素组成变化范围一致，其平均值靠近零值且具有塔式分布特征，表明硫来源于上地幔或岩浆作用；该矿床矿石中方解石的C、O同位素组成与矿区大理岩的C、O同位素组成明显不同，其δ13C(PDB)为-3.27‰～-4.89‰，与上地幔射气及岩浆作用形成的CO-2的碳同位素组成一致，因此矿石中方解石中碳亦来源于上地幔射气或岩浆作用；铅同位素特征表明早期热水沉积形成的块状硫化物矿石铅主要来源于上地壳，而中晚期形成的夕卡岩型矿石及蚀变破碎带型矿石的铅具有上地幔铅的特征。

The Yangla copper deposit is a large-scale copper deposit whi ch was discovered in recent years in western Yunnan Province. The authors system atically studied the geochemical characteristics of S, C, O, Si stable isotopes and concluded: (1) Different rocks and ores have the same S isotopic composition , whose values are close to zero and exhibit a tower-shaped distribution. This shows that S may come from the upper mantle or be derived from magmatism. (2) Th e C and O isotopic compositions of calcites in ore are different from those of m arble in the ore field. The C isotopic compositions range from -3.27‰～-4.89‰, which are similar to the C isotopic compositions of the upper mantle and magmat ism. So C in ore might come from the upper mantle or magmatism. (3) Pb isotopic compositions show that the lead of massive sulfide ore, which was formed at the early period, is mainly from the upper crust; and that the lead in the skarn-ty pe and filled-replaced-type ores, which were formed in the middle and late pe riods are mainly from the upper mantle.