Geofluid Systems of Koryaksky-Avachinsky Volcanoes (Kamchatka, Russia)

The Koryaksky-Avachinsky volcanogenic basin, which has an area of 2530 km², is located 25 km from Petropavlovsk-Kamchatsky City and includes five Quaternary volcanoes (two of which, Avachinsky (2750 masl) and Koryaksky (3456 masl), are active), and is located within a depression that has formed atop Cretaceous basement rocks. Magma injection zones (dikes and chamber-like shapes) are defined by plane-oriented clusters of local earthquakes that occur during volcanic activity (mostly in 2008–2011) below Koryaksky and Avachinsky volcanoes at depths ranging from −4.0 to −2.0 km and +1.0 to +2.0 km, respectively. Water isotopic (δD, δ¹⁸O) data indicate that these volcanoes act as recharge areas for their adjacent thermal mineral springs (Koryaksky Narzans, Isotovsky, and Pinachevsky) and the wells of the Bystrinsky and Elizovo aquifers. Carbon δ¹³С data in СО₂ from CO₂ springs in the northern foothills of Koryaksky Volcano reflect the magmatic origin of CO₂. Carbon δ¹³С data in methane CH₄ reservoirs penetrated by wells in the Neogene-Quaternary layer around Koryaksky and Avachinsky volcanoes indicate the thermobiogenic origin of methane. Thermal-hydrodynamic TOUGH2 conceptual modeling is used to determine what types of hydrogeologic boundaries and heat and mass sources are required to create the temperature, pressure, phase, and CO₂ distributions observed within the given geological conditions of the Koryaksky-Avachinsky volcanic geofluid system.