ИСТИНА

This paper describes engineering geological features of rocks in active hydrother-mal systems of the Kuril-Kamchatka island arc. The initial host rocks of studied hydrothermal systems are volcanic complex of Neogene-Quaternary age. Thermal fluids intensely alter them and transform to hydrothermal rocks such as secondary quartzites, propylites, zeolitic rocks, argillic rocks, clays, opalites, and quartz-feldspar metasomatites. Mineralogical alteration of rocks causes the changes in their physical and mechanical properties. The relationship between hydrothermal alterations and properties of rocks is considered. Special attention is given to near-surface alteration zone which affects the selection of sites for geothermal power plants constructions.