藏南马扎拉金-锑矿床:成矿流体性质和成矿物质来源

马扎拉金-锑矿床是藏南巨型金-锑成矿带的重要组成部分,其矿床成因目前仍存在不同认识.通过主要矿石和蚀变围岩的岩相学、矿相学、流体包裹体和稳定同位素分析,探讨了马扎拉金-锑矿床的成矿流体性质、矿质迁移和沉淀机制.结果表明,马扎拉金-锑矿床成矿流体主要来自岩浆水,主成矿期流体为中温(约255℃)、低盐度(2.8%~3.5%NaCleqv)、富CO2流体,成矿压力约150 MPa,流体演化过程中的CO2与水的不混溶是造成矿质沉淀的主要原因,成矿金属主要来源于地层,特别是区域广泛分布的海相火山岩地层.

Mazhala Gold-Antimony Deposit in Southern Tibet: The Characteristics of OreForming Fluids and The Origin of Gold and Antimony

The genesis of Mazhala Au-Sb deposit, which is one of the most important Au-Sb deposits in South Tibet Au-Sb metallogenic belt, is still open to debate. Based on field observation, petrography, microscopy, fluid inclusions, and stable isotopic results, in this paper, it discusses the characteristics of ore-forming fluid, the transportation, and the precipitation mechanism of Au and Sb. It can be concluded that the ore-formng fluid has a dominant magmatic origin, and is of moderate temperature (ca.255℃), low salinity (ca.2.8%-3.5% NaCleqv) and rich in CO₂. The estimated ore-forming pressure is about 150 MPa. The unmixing between CO₂ and aqueous during the fluid evolution leads to the ore precipitation. The Au, Sb may have been sourced from wall rocks, especially the submarine volcanic rock of them.