浅成低温热液型金矿床研究的某些进展

Some Advances in the Research of Epithermal Gold Deposis

浅成低温热液型金矿床成矿流体在较深处(3～4km)发生相分离的同时导致不同成矿元素和载矿元素进入不同的相态,从而形成不同性质流体,其中富挥发S的气水相在高压下有很强的载矿能力,对特定矿化类型形成具有决定性意义。流体在向浅成低温环境演化过程中,携带大量成矿物质的气水相必须转化成液相才可能导致浅成低温成矿(深度<1～2km),这个过程与含水的岩浆房冷却密切相关。通过冷却加压,富挥发S的气体在水盐体系的两相界面以上可转变为液体,将成矿元素Au等运移至浅部。浅成低温热液矿床与卡林型矿床均可形成于大陆裂谷环境,前者的高硫化类型与后者在流体性质、蚀变特征、成矿特征等方面具有明显的相似性和可比性。富碲型矿床的Te很可能是在相分离过程中以Te2(g)和H2Te(g)的形式进入气相,并在浅部被地下水吸收,形成Ag(HTe)2-和Au(HTe)2-络合物,伴随着流体的冷却和环境变化,使得碲化物沉淀。少硫(碲)化物特富金的浅成低温热液型矿床金可能以金硅络合物或是金硅合金氢化物形式进行搬运,在浅部SiO2和Au沉淀形成特富金矿。

Studies on epithermal gold deposits showed that during the evolution of ore-forming fluids and in the deeper crustal region（3-4 km）,different ore-forming elements and ore-loading elements changed into different phases due to fluid phase separation.This caused the formation of different types of fluids,in which the vapor phases in volatile S-rich had a strong ability to set mine under high pressures.This particular fluid had decisive significance in generating specific types in mineralization.Only when it transported to liquid phase could much ore-bearing vapor phase migrate to epithermal depth（〈 1-2 km）,which nearly linked to the cooling of hydrous magma chambers.By cooling at elevated pressure above the critical curve of the salt-water fluid system,the vapor could contract directly to an aqueous liquid,and Au and other ore-forming elements would be migrated to shallow environment.Epithermal deposits and Carlin-type deposits could be formed in a continental rift environment.There were obvious similarities and comparability between high-sulfide types of the former and those of the latter,in the fluid source and the evolution,altered characteristics,contents and enrichments of trace elements and ^34S‰.The element Te in Te-rich telluride deposit was likely to access to gas phase in the formation of Te2（g） and H2Te（g） during phase separations,and absorbed by groundwater in shallow,forming Ag（HTe） 2^-and Au（HTe） 2^-complex compounds,accompanied by fluid cooling,environmental changing and telluride precipitating.Gold in epithermal deposit characterized by special goldrich and less sulfur（tellurium） compounds might be transported in the form of gold-silicon complex compounds or gold-silicon alloy hydrides,and the precipitation of silicon and gold formed a special gold-rich ore deposit.