ИСТИНА

Kamchatka is a volcanic arc composed of three volcanic belts corresponding to the subduction of the northern part of the Pacific Plate. One of the volcanic belts, the Sredinny Ridge (SR) in the back arc region, extends north into the aseismic zone. We explored the northern part of SR (N-SR) (fig. 1), and found several Middle-Upper Pleistocene volcanic edifices . In order to understand the geodynamic and magmatic features, we carried out petrological and geochemical studies of the collected lava samples. All basalts and andesites have typical arc signatures such as positive Pb peaks, indicating subduction is involved. Most rocks are medium-K basaltic andesites, although the lavas of the Cone X located 10 km SSE from the Tobel’tsen cone are high-K andesites and dacites. Based on geophysical data and tectonic models, we assume that the relatively young volcanism that we discovered in the N-SR reflects the sequential attenuation of the movement of chips/microplates located between a series of transform zones Aleutian – Bering – Alpha – Beta – Gamma. These results are in good agreement with the geodynamic reconstruction of Seliverstov for time interval 1.8–0.05 Ma. This research was supported by JSPS grant No. JPJSBP120204804, and RFBR grant No. 20-55-50001.