| Research Abstract |
On the genesis and formation process of the epithermal Au-Ag deposits related to young volcanic activities in the island arc geologic environ- ment, it is investigated to clarify the formation environment and con- centration process of the elements from the viewpoints of ore geology, geochemistry and petrology based on the field and laboratory works. Basic experiments are also conducted in order to improve and obtain high accuracy in chemical analyses.
Both low- and high-sulfidation types of gold mineralizations in epi- and meso-thermal conditions are investigated on their assemblages of ore and alteration minerals to determine the physicochemical conditions and time-spatial relationships of the both types. Study fields are also extended to the same types in northeast Japan and Indonesia to make comparative study.
As a concluding remarks, it is clarified that the high-sulfidation type gold mineralization is stongly affected by the magmatic fluids, but the low-sulfidations is by meteoric water. The former is prior to the latter and is located closer to the intrusive rock. Both types of gold mineralizations are strongly related to the magmatic acitivity, and the originated high temperature fluids dissolving various metals in the style of sulfide complexes might have effectively precipitated them due to the boiling by pressure decrease and/or mixing with meteoric water to cause cooling, oxidation or dilution in shallow environment.
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