Temperature and Permeability Structure of Low Enthalpy Geothermal Field, Paratunsky, Kamchatka

Abstract

The Kamchatka Peninsula has the world's highest density of andesitic volcanoes. It also has both high- and low-temperature geothermal systems that are assumed to be powered by subduction-related magmatism. Although high-enthalpy hydrothermal circulation is at time observed close to the surface, we believe that extensive low-enthalpy systems may overly and receive thermal input from higher temperature systems. Our hypothesis is that the thermal regimes are stacked: -Magmatic hydrothermal represented by magmas and steep temperature and physical gradients including the brittle-ductile transition and supercritical fluids that have been demonstrated in the Iceland Deep Drilling program. Magmatic fluids may represent a large component of the fluids present. - High-enthalpy hydrothermal circulation systems that are present in fracture systems overlying the magmatic environment. Fluids are typical NaCl brines as represented by the Mutnovsky geothermal field. Fracture permeability is related to tectonic as well as magmatic processes. - Low-enthalpy geothermal systems (T less than 150o C at less than 1 Km depth) that are present as both fracture and stratigraphic permeability and are represented by the Paratunsky geothermal field.