ABSTRACT
The paper focuses on the alteration of volcanic rocks in near-surface zone in geothermal fields of Kuril-Kamchatka arc (Far East, Russia). The mechanism of transformation of hard volcanic rocks with brittle failure into plastic clays with ductile deformation is described in details on macro- and micro-scale. Special attention is given to the variation of the physical and mechanical properties which occur due to geothermal alteration.
