Abstract

The native gold in the Woxi Au–Sb–W deposit is characterized by remarkably high purities (99.9%), called as super-pure native gold. The deposit can thus be used as the suitable application example for analyzing ore-forming conditions by using the thermodynamic calculation of Au_xAg_1 – x-fluid equilibria. According to experimental results of minerals and fluid inclusions, some physicochemical conditions are assumed in the thermodynamic calculation of the fluids equilibrated with Au–Ag solid solutions of X_Au = 0.999. Calculated results in log fO₂-pH diagrams show dissolved gold and silver concentrations, as well as stability fields of pyrite and sericite associated with the super-pure native gold. On the other hand, LA-ICP-MS analysis indicates that both Au and Ag concentration are determined in the fluid inclusions of scheelite, showing varied Au/Ag ratios with different homogenization temperatures. The calculated results assumed by different data of inclusions in scheelite, indicate two fluid inclusions showing higher homogenization temperatures (303°C and 356°C) and higher Au/Ag ratios are possible for precipitation of the super-pure native gold coexisting with pyrite and sericite, whereas one fluid inclusion showing a lower homogenization temperature (198°C) and a lower Au/Ag ratio is impossible for the super-pure native gold. Therefore, the super-pure native gold in the Woxi deposit was probably formed by the hydrothermal fluid with higher Au/Ag ratios and high temperatures in the mineralization stage of scheelite.

中文翻译：

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Au x Ag 1 – x-流体平衡的热力学计算中的应用：湘西沃西Au–Sb–W矿床中的超纯天然金

摘要

沃西金–锑–钨矿床中的原生金的特征在于纯度极高（99.9％），被称为超纯原生金。因此，通过使用Au _x Ag _{1 –  x-}流体平衡的热力学计算，该矿床可以用作分析成矿条件的合适应用实例。根据矿物和流体包裹体的实验结果，在以X _Au = 0.999的Au-Ag固溶体平衡的流体的热力学计算中，假定了一些理化条件。计算结果以log  f O _2表示-pH图显示了溶解的金和银浓度，以及与超纯天然金有关的黄铁矿和绢云母的稳定性场。另一方面，LA-ICP-MS分析表明，白钨矿流体包裹体中的Au和Ag浓度都是确定的，显示出均质温度不同时Au / Ag的比例也不同。白钨矿中夹杂物的不同数据所得出的计算结果表明，两种流体夹杂物显示出较高的均质温度（303°C和356°C），并且较高的Au / Ag比可能沉淀出与黄铁矿和铁矿共存的超纯天然金。绢云母，而对于超纯天然金而言，一种流体包裹体显示出较低的均质温度（198℃）和较低的Au / Ag比是不可能的。所以，