Abstract
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.
Highlights
Avachinsky and Koryaksky volcanoes are located 25–30 km from the city of Petropavlovsk-Kamchatsky, which has a population of approximately 250 thousand people, contains in its interior significant resources of underground heat and groundwater, and represents a potential danger
The results of the model are matched to observations in order to improve the model; we discuss the ability of the model to reproduce the temperature response of hot springs to recent dike injections
The distribution of the temperatures output by the TOUGH2 modeling (Figure 7) is rather symmetrical in shape, but all of the hot springs adjacent to Koryaksky Volcano are located in an area that is 7 to 12 km to the north (Figure 1)
Summary
Avachinsky and Koryaksky volcanoes are located 25–30 km from the city of Petropavlovsk-Kamchatsky, which has a population of approximately 250 thousand people, contains in its interior significant resources of underground heat and groundwater, and represents a potential danger (see Appendix A with Figures). The magma injection zones (i.e., dikes and chamberlike shapes) defined using this method were defined as heat sources for their adjacent hydrogeological reservoirs and surface features (hot springs and fumaroles) in terms of thermal-hydrodynamic models. This paper focuses on the Koryaksky-Avachinsky volcanic cluster and aims to achieve the following objectives: (1) using seismic data to identify dike swarms and magma chambers (i.e., potential heat sources); (2) using deep wells, thermal features, and the geochemistry of cold springs (i.e., water and carbon isotopes and water and gas chemistry) and temperature data to estimate the pressure/temperature/phase parameters of reservoirs and their mass/heat recharge conditions; (3) using TOUGH2-modeling, based on the abovementioned data, to verify and estimate the role of Koryaksky Volcano as an injector of magma and cold water into adjacent structures and the creation of hydrothermal circulation and geothermal and gas reservoirs. It is noteworthy that the rate and extent of water injection into the plumbing systems of active volcanoes are crucial to prevent or trigger catastrophic eruptions (i.e., hundreds of km in size) due to heat overbalance between magma and water injection rates, as was shown earlier by Fournier and Pitt [8] using Yellowstone caldera as an example
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