Eh-pH相图在玉龙铜矿床次生富集作用研究中的应用

THE APPLICATION OF Eh-pH DIAGRAM TO SECONDARY ENRICHMENT OF YULONG COPPER DEPOSIT

玉龙铜矿床表生成矿过程中成矿物质主要呈碳酸盐络合物的形式迁移。以孔雀石、蓝铜矿组合为主的次生富集带是在碱性(pH= 7.15～11.55)、氧化(Eh> 0.14)的环境中形成的,所以它们相对靠近氧化带的上部及碳酸盐岩发育的地区分布。以赤铜矿、自然铜组合为主的次生氧化物富集带形成环境为弱氧化-还原(Eh< 0.16),它们常靠近氧化带的中、下部分布。表生成矿环境中CO2 含量高是玉龙铜矿床氧化带中黑铜矿极不发育的根本原因。pH值升高与氧化-还原电位(Eh 值)的降低是造成矿质沉淀(次生富集)的两种机制。

Ore forming material was transported in the form of carbonate complex in supergene metallogenic processes of Yulong copper deposit. The enrichment zone consisted mainly of malachite and azurite was formed under basic(pH=7.15～11.55) and oxidizing(Eh>0.14) conditions, which explain why malachite and azurite occur at the upper part of oxided zone where carbonate rock is well developed. The secondary oxide enrichment zone consisted mainly of cuprite and native copper was formed under weak oxidizing to reducing(Eh<0.16) conditions, which explain why cuprite and native copper always appear in the middle to lower part of oxidized zone. The rare occurrence of tenorite in oxidized zone was resulted from high CO 2 content of supergene ore forming environment in Yulong copper deposit. The increase of pH value and the decrease of redox potential(Eh) are two mechanisms giving rise to deposition of ore forming materials.