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新西兰Taupo火山岩带中Waiotapu地热系统的地表和近地表地带,金正在沉淀,品位可达80g/t。这一活动系统的许多特征使它与环太平洋带的浅成低温贵金属矿化环境相似。地热系统的近地表面积大约为17km~2,它是由深处上升的中性pH流体转为侧向流动几公里所造成的。该流体使流纹质火山碎屑岩和火山灰沉积物蚀变为以绿盘岩化为特征的矿物组合,未见主要的脉型矿化。在1100m深处钻孔中测得的温度为300℃,温度沿沸点曲线向地表方向降低。蒸气和H_2S(后来被氧化)在地表(来自深部的沸腾)的冷凝形成酸性硫酸盐热水,进而造成了浅部(50m)的泥质蚀变盖。这种氧化的冷凝物与深部来的中性流体混合可能是造成金从硫代硫酸络合物中沉淀下来的主要原因。金矿化的主要聚集区是在Champagne塘,这是充填几个有900年历史的热液喷发火山口之一的热泉。
The surface and near-surface areas of the Waiotapu geothermal system in the Taupo Volcanic Rock, New Zealand, are precipitating with grades up to 80 g / t. Many features of this activity system make it similar to the epithermal precious metal mineralization in the Pacific Rim. The near-surface area of the geothermal system is about 17 km -2, which is caused by a shift from a neutral pH fluid deep into several kilometers laterally. The fluid altered rhyolitic pyroclastic and volcanic ash sediments into a mineral assemblage characterized by green-plate petrography, with no major vein-type mineralization. The measured temperature in the borehole at a depth of 1100 m is 300 ° C and the temperature decreases along the boiling point curve toward the surface. Condensation of steam and H2S (later oxidized) on the surface (boiling from deep) forms acidic sulphate hot water, which in turn results in a shallow (50 m) muddy altered cap. Mixing this oxidized condensate with a deep neutral fluid may be the primary cause of gold precipitation from the thiosulfate complex. The main gold mineralization is in the Champagne pond, a hot spring filled with one of several 900-year-old hydrothermal vents.