金是通过什么方式搬运与沉淀的
HOW IS GOLD TRANSPORTED AND DEPOSITED DURING THE GEOLOGIC PROCESS?
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摘要: 数十年来,金在不同的地质作用过程中的迁移与沉淀机理一直是许多矿床地质学家和地球化学家们争论的焦点。根据最近的地质与地球化学研究,对如下几个问题进行了探讨:(1)什么样的含水络合物最有利于金的迁移与搬运;(2)为什么金富集在脉型矿床中;(3)在什么样的物理-化学条件下,金的含水络合物可以得到充分溶解;(4)为什么绝大多数金矿床的形成范围集中在340℃~400℃.在热液成矿流体中,金可能是以AuHS(H2S)30形式进行迁移,温度的降低会使溶液中90%的金沉淀,这能够解释这些含金石英脉为什么形成在一个很窄的温度范围内.Abstract: Transportation and participation of gold during various geological processes has been a controversial subject for several decades, and has attracted attention of numerous economic geologists and geochemists. Based on the most recent geological and geochemical studies,the following subjects are discussed in this short note:(1)which aqueous species dissolves gold?(2)why is gold concentrated in vein-type deposits?(3)under which condition is the aqueous gold species soluble? and (4)why do the majority of gold deposits form over a narrow temperature ranging from 340℃ to 400℃? It is concluded that gold may be transported as AuHS(H2S)30 in hydrothermal ore fluids. Cooling will result in precipitation of 90% of the dissolved gold as metallic gold. This may explain these gold-bearing quartz veins that were formed at a narrow temperature window.