广西珊瑚钨锡矿床伴生银的迁移沉淀机制

The mechanism of migration and precipitation of associated silver in the Shanhu tungsten-tin deposit, Guangxi

关键词:  钨锡矿床  伴生银  迁移  沉淀机制

Key words:  tungsten-tin deposit  associated silver  migration  mechanism for precipitation

摘要:

珊瑚钨锡矿床具垂直逆向分带特征,上部富锡,中部富钨锡,下部富钨、硫化物和银。成矿流体的盐度、密度较低,属于弱还原、弱酸性的体系。伴生银以氯络合物和硫络合物形式迁移。银络合物的迁移与沉淀取决于热液中[S^2-]的浓度。随成矿温度的降低、Ca²⁺浓度增大、pH值增大,成矿流体中S^2-浓度增大,导致大量硫化物和含银硫盐沉淀。由于向深部成矿温度逐渐降低,故伴生银主要以含银硫盐形式赋存于矿脉的中下部。

Abstract:

The Shanhu tungsten-tin deposit in Guangxi displays vertical inverse zoning:tin enrichment in the upper part, tungsten and tin enrichment in the middle part, and tungsten enrichment in the lower part of the deposit. The lower salinity and density of the ore-forming fluids suggest slightly reduction and acidic systems. The associated silver tends to be migrated as chlorine complexes and sulfur complexes. The migration and precipitation of silver complexes depend on the S^2- concentration in the hydrothermal solution. The S^2- concentration increases with the decrease of mineralization temperatures and the increase of Ca²⁺ concentration and pH values, resulting in the precipitation of abundant sulfides and silver-bearing sulfosalts. The associated silver tends to occur in the lower and middle parts of ore veins due to lower ore-forming temperatures in the deeper parts.