微细浸染型金矿矿后热液和表生溶液的物理化学条件研究

A STUDY ON PHYSICOCHEMICAL CONDITIONS OF POST MINERALIZATION THERMAL SOLUTION AND EXO SOLUTION IN CARLIN TYPE GOLD DEPOSITS

通过成矿热液、矿后热液和表生溶液形成的冷液矿物的包裹体成分、温度和盐度测定，作了有关的系列热力学参数计算，探讨了溶液的低温地球化学特征和变化规律。研究表明：成矿期和矿后热液均为弱碱性，但进入表生溶液则转为弱酸性；在表生作用过程中，矿后热液和表生溶液的ｌｇｆ（Ｈ２）、ｌｇｆ（ＣＨ４）和ｌｇｆ（ＣＯ）均较成矿期明显下降，尤以ｌｇｆ（ＣＨ４）最显著，相反，ｌｇｆ（Ｓ２）则有明显提高；从含硫原子团的性质看，成矿期热液主要含Ｈ２Ｓ和ＨＳ－，而矿后热液和表生溶液主要含ＳＯ２－４、ＫＳＯ－４和ＮａＳＯ－４。这些特征和变化直接影响和制约金在表生作用过程中的迁移形式以及原生矿石向氧化矿石的转化机理。

Based on composition,temperature and salinity of inclusion of representative minerals to be formed in post mineralization thermal solution and exo solution, the authors calculated a series of thermodynamics parameters and the geochemical charactemistics and studied the change pattern for low temperature solution. The results show that the nature of thermal solution of mineralization and post-mineralization stage is weak alkaline, but the exo-solution is weak acid; The H 2,CH 4 and CO fugacities of post-mineralization thermal solution and exo-solution obviously decrease, especially CH 4 fugacity, comparing with mineralization epoch in exogenic process. Contrarily, S 2 fugacity obviously increase in the exogenic process. For the natures of sulfur-bearing atomic group in solution, H 2S and HS - are main composition in the thermal solution of mineralization stage, but SO 2- 4, KSO - 4 and NaSO - 4 are the most important composition in post-mineralization thermal solution and exo-solution. Migration forms of gold and mechanism of which primary ore transform into oxidized ore are affected or controled by the characteristics and varieties of solution in exogenic process. Hence, the researching results have significance for opening up and using primary ore in Carlin-type gold deposits.