The mineralogical evidence for the formation of gold-bearing pyrite through the metasomatism of siderite by the Au-As-S multicomponent fluids
The reaction between ore-forming fluids and iron-bearing wallrocks can generate a large amount of pyrite accompanied by efficiently precipitated gold.However,the mineralogical process for the formation of gold-bearing pyrite through the replacment of iron-bearing carbonate wallrocks by the Au-As-S-bearing multicomponent fluids remains to be revealed.In this study,hydrothermal experiments were conducted to simulate the ore-forming process of gold-bearing pyrite through the metasomatism of siderite by the Au-As-S multicomponent fluids,and mineralogical characteristics of siderites before and after the hydrothermal alteration are investigated by using the X-ray diffraction(XRD),Raman spectroscopy(Raman),Scanning electron microscopy(SEM),and Electron probe microanalysis(EPMA)methods.The results show that the gold-bearing pyrite can be formed through the metasomatism of siderite by the Au-As-S-bearing multicomponent fluids,and the average particle size of formed pyrites is controlled by the arsenic(As)concentration of the initial solution.When the As concentration of the solution was increased from 0 to 100× 10-6,the average particle size of pyrites was decreased by approximately 56％.The higher the As concentration of the initial solution,the more As entered into the pyrite structure.This is more conducive to the entry of Au of the fluid into the pyrite in the form of invisible gold.The Au and As contents of the formed gold-bearing pyrites are significant positively correlated,indicating that there is an As-Au coupling relationship which is consistent with the phenomenon observed in previously reported gold-bearing pyrites.This study not only provides an in-depth analysis of the mineralogical evolution characteristics of siderite before and after alteration by the Au-As-S-bearing multicomponent fluids,but also contributes to the good understanding of the genesis of the Au-As coupling relationship in gold-bearing pyrites.
万方数据
维普
