Avachinsky and Koryaksky Group of Volcanoes: Geophysical Inhomogeneity of the Lithosphere and Deep Processes (Kamchatka)

The article presents the results of our gravimetric, seismic and electromagnetic research, as well as the data on deep seismicity of the lithosphere in the area of the active Avachinsky and Koryaksky group of volcanoes, which is the part of the East Kamchatka volcanic belt. We managed to develop the comprehensive geophysical model of the Earth’s crust and lithospheric mantle of this area. Based on the distribution scheme of the Earth’s crust geophysical inhomogeneities in general, and particularly beneath Avachinsky Volcano, we revealed specific features for both intracrustal fluid saturation and conduits through which deep fluids rise to the upper part of the crust. According to the comprehensive model, stresses arising at the margins of zones with different defluidisation conditions, in particular, in the lower part of the crust, and characterizing by contrasting electrical conductivity values, are one of the most important reasons for active seismicity beneath active volcanoes. The general scheme of the deep lithospheric processes and the volcanoes magma feeding system specific features are based on the obtained results and the data on the local seismic tomography. It is assumed that Avachinsky Volcano, being a part of the active Avachinsky and Koryaksky group of volcanoes, is connected with the asthenospheric layer at a depth of ~70–120 km, from which fluid/melts enter into the magma chamber located in the lower crust and then, under the influence of the heat from the lower crustal source, the peripheral chamber is formed in the upper crust beneath the volcano’s cone.