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新西兰怀特岛的火山热水系统与形成强硫化Cu-Au矿床的化学条件非常接近。据计算,1万多年间火山活动带出的Cu和Au(主要来自岩浆脱气)分别为1百万吨和45吨。从近期喷口中喷出的蚀变安山岩块含有明矾石、硬石膏和黄铁矿。其硫同位素组成表明,矿脉充填温度约为380℃。在此温度下,Cu、Au在酸性溶液中易于溶解。这可以解释喷发物中Cu亏损、Au缺失的原因。然而,质量平衡计算表明,Cu、Au在酸性溶液释放到地表之前就在冷却带中沉淀下来了。
The volcanic hot water system on the Isle of Wight, New Zealand, closely resembles the chemical conditions for the formation of strongly Cu-Au deposits. It is calculated that more than 10,000 years of volcanic activity brought Cu and Au (mainly from the magma degassing) were 1 million tons and 45 tons. The altered andesite from recent spouts contains alunite, anhydrite and pyrite. Its sulfur isotopic composition shows that the vein filling temperature is about 380 ℃. At this temperature, Cu, Au is easily dissolved in an acidic solution. This can explain the Cu loss in the eruption, the reason for the lack of Au. However, mass balance calculations show that Cu and Au precipitate in the cooling zone before the acid solution is released to the surface.