Structure and lithogenesis of hydrothermal clays from Nizhne-Koshelevo geothermal anomaly (Southern Kamchatka)
On the basis of well drilling and prospect-hole digging and detailed level-by-level approbation the lithological structure of hydrothermal clays of Nizhne-Koshelevo geothermal anomaly, one of the largest on Kamchatka, is investigated. The hydrothermal clays forms a uniform geological body, which have layered structure, thickness from 1.5 up to 3.0 m and extent ≥500 m. On active thermal ground (unloadings of hydrotherms) the vertical displacement of clays layers take place, apparently, owing to formation of large cavities inside clays - as a result of intensive gas and solution circulation. Also the landslips processes in deep V-shaped valley of Gremuchii stream are wide display. The mineralogical-geochemical criteria of allocation of three horizons of hydrothermal clays are received: 1) zones of sulphuric leaching - in the field of superficial unloading of thermal waters; 2) intensively sulfidization “blue clays” - in the middle part of sections; 3) siliceous and metalliferous deposits - in the basis of clays horizons. Other clays layers are diagnosed less precisely. The hydrothermal clays of Nizhne-Koshelevo geothermal anomaly differ, as a whole, the high contents of pyrite and other sulfides, which concentrate noble, rare, and other metals. The model of transformation of rocks to hydrothermal clays, as reflection of influence of deep metalliferous fluids on hypergenesis zone of modern hydrothermal systems is offered.