MODES OF GOLD OCCURRENCE IN CRYSTALLIZATION PRODUCTS OF HIGH-TEMPERATURE GAS FLUIDS IN THE KUDRYAVYI VOLCANO, THE KURIL ISLANDS

Abstract

The study of condensates of high-temperature volcanic gases from different volcanoes showed the presence of up to 10 g/t Au [1]; however, the findings of mineral forms of gold are very scarce. Native gold was observed as flat hexagonal crystals up to 0.3 mm in size in sublimates of Tolbachik Volcano [2]. At Colima Volcano, Mexico [1], crystals of native cold 5-40 μm in size were discovered in artificial sublimates in a silica tube inserted into a volcanic gas vent. Gold precipitates as trigonal and pentagonal plates in association with V-bearing sulfates within a narrow temperature range of 550-600°C. The tiny aerosol particles of high-purity gold were documented in the gas of Erebus Volcano [3]. The micrometer-sized gold particles associated with sodium and potassium chlorides, wolframite, and complex potassium-rhenium oxide were previously found in artificial sublimates of fumaroles from the Kudryavyi Volcano [4]. However, their chemical composition was not determined. Numerous differently sized particles of natural Cu-Au-Ag alloys were detected both in natural crystallization conditions of the Kudryavyi Volcano gas fluid and in artificial sublimates in silica tubes inserted in fumarole channels with a fixed temperature regime. Temperatures were measured in cavities and tubes with a chromel-alumel thermocouple. Each tube was sampled for gas and gas condensate.