西藏加多捕勒铁铜矿床硫、铅同位素组成及成矿物质来源

Sulfur and lead isotope composition and tracing of ore-forming material sources in Jiaduobule Fe-Cu deposit of Tibet

加多捕勒铁铜矿床位于念青唐古拉成矿带西段。综合研究围岩、岩体与矿石的硫、铅同位素组成,发现其矿石硫化物的δ^(34)S值变化范围为-2.1‰～6.2‰,δ^(34)S_(ΣS)值为2.16‰,总体具有岩浆硫的特征。矿石硫化物的δ^(34)S值与石英闪长岩、板岩中硫化物的δ^(34)S值相近,表明矿石的硫源可能部分由板岩与石英闪长岩提供。矿石铅同位素组成比较均一,^(206)Pb/^(204)Pb、^(207)Pb/^(204)Pb和^(208)Pb/^(204)Pb的变化范围分别为18.27～18.842、15.653～15.899和38.793～39.703,与冈底斯成矿带北亚带矿床矿石硫化物的铅同位素组成相近,具有上地壳铅源的特征。矿石铅同位素组成与黑云母二长花岗岩、大理岩的铅同位素组成一致,显示铅可能主要来源于黑云母二长花岗岩和大理岩。综合分析表明,加多捕勒铁铜矿床硫、铅同位素的研究显示其成矿物质可能主要来源于黑云母二长花岗岩,部分来源于中二叠统下拉组岩石,少量由石英闪长岩提供,它们为深入研究该矿床的成矿模式提供了资料。

The Jiaduobule Fe-Cu deposit is located in the western Nyainqentanglha metallogenic belt. Based on S-Pb isotopic geochemical analysis of country rocks, magmatite and ores, the authors reveal that the δ34S values of the ores range from -2.1‰ to 6.2‰ with the estimated δ34SΣS being 2.16‰, showing typical characteristics of magmatic sulfur. The similar δ34S values of sulfide of ores to pyrite in quartz diorite and slate indicates that sulfur of the ores was possibly partly derived from quartz diorite and slate. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of the ores range from 18.27 to 18.842, 15.653 to 15.899 and 38.793 to 39.703, respectively, similar to features of the ore sulfides from the deposits in the north subzone of Gangdise metallogenic belt. On the whole, the lead was almost derived from the upper crust. The lead isotopic compositions of ores are similar to those of biotite monzonite and the marble. It is indicated that lead was possibly mainly derived from biotite monzonite and marble. In a word, the study of sulfur and lead isotopes indicates that the major source was possibly derived from biotite monzonite, with the addition of minor materials from Xiala Formation of Middle Permian and quartz diorite. The results achieved by the authors provide basic data for the mineralization model.