Hydrothermal clays of the geothermal fields of South Kamchatka: A new approach and study results

Using the Pauzhetka and Nizhnee Koshelevskoe geothermal deposits (South Kamchatka), we studied physical-chemical characteristics of hydrothermal clays that form thick (on average, 1.5–1.8 m) and spacious (up to few km² in area) subsurface horizon with peculiar petrophysical and mineralogical-geochemical properties. It was established that the properties of hydrothermal clays are determined by their micro- and nanostructure, which is made up of nanoparticles of aluminosilicates, sulfates, accessory and ore minerals (primarily, sulfides and iron oxides), and amorphous phases. The subsurface horizon of hydrothermal clays represents a long-lived (up to 10 ka and more) highly dynamic colloidal-dispersed mineralogical-geochemical system, which reflects the interaction of deep-seated metalliferous fluids with geological medium in the supergene zone of geothermal deposits.