四川拉拉铁氧化物铜金矿床硫同位素地球化学

Sulfur Isotope Geochemistry of the Lala IOCG Deposit in Sichuan Province

硫的来源对于了解铁氧化物铜金矿床的形成过程和成因具有重要的意义。文中统计了拉拉铁氧化物铜金矿硫化物的硫同位素数据,并结合地质特征和矿相学研究,分析和讨论了硫的同位素组成特征和硫的来源。结果表明,拉拉铜金矿硫同位素组成变化较大(不考虑一个异常样品,δ34S值极差达到14.9‰),表明成矿硫来源的多样性;其中,黄铁矿δ34S值范围为-1.4‰～4.9‰(平均1.8‰),黄铜矿的δ34S值范围为-5.9‰～9‰(平均1.5‰)。结合硫化物的生成机制分析,并与其他典型矿床硫同位素数据对比,表明海水沉淀的蒸发岩是黄铁矿和黄铜矿的重要硫来源,但也不能排除岩浆硫的贡献。目前没有证据支持变质作用减少拉拉矿区硫化物的硫同位素组成差异。

The source of sulfur is vital to understand the ore-forming process and genesis of IOCG deposits. We summarize the data of sulfur isotope from the Lala deposit in Siehuan Province, and discuss sulfur isotope compositions of sulfide and their sources on the basis of geologic and ore microscopic studies. The large variability in sulfur isotope indicates that the ore-forming sulfur was multi-sourced. The δ34s value of pyrite ranges from -1.4‰ to 4.9‰ with a mean value of 1.8‰ and the δ34s value of chaleopyrite ranges from -5.9‰to 9‰ with a mean value of 1.5‰. Together with sulfide formation analysis and comparison with some type IOCG deposits worldwide, these data demonstrate that sulfur from seawater evaporate is important to precipitation of pyrite and ehalcopyrite. But there is no evidence to support that the variation of sulfur isotope composition is reduced during metamorphism in the Lala deposit.