Sedimentary and volcanic-sedimentary rocks from natural exposures on the Phu-Qui and Katuik volcanic islands (Vietnam Shelf) have been analyzed for their elemental composition. Mineralogically and petrochemically, sandstone rocks of Phu-Qui Island are petrogenic compounds and refer to subarkose. Judging by the prevalence of quartz and feldspar, by the dominance of sialic association in the heavy mineral fraction as well as by the pattern of major, minor and rare-earth element distribution, the main sources of clasts were intrusive and metamorphic rocks of the mature continental crust, and sedimentation settings correspond to passive continental margins. The Middle Pleistocene volcanic-sedimentary rocks of the Phu-Qui – Katuik group of islands are composed of pyroclastic material of mafic composition close to the basalts from trachybasalt-trachytic and alkaline basaltic series of Vietnam, which possess intraplate characteristics and relate to the existing here extension settings. The sedimentation occurred in subaerial environment near the centers of volcanic eruptions.

A lineament analysis of the relief was made using a detailed bathymetry map of the region drawn according to the results of multi-beam echo-sounding. The authors separated linear objects of the relief, measured their course azimuths, plotted the rose diagram of the lineament directivities of the region, and built the models of the surface and subsurface deformation field of the region at separating the blocks of dominant stress and strain. The blocks travel along the lines of alternation of stress sign (block borders). The directivities
of the block borders were compared with the lineaments directivities resulting in conclusion that they both have spatial and generic relations. The systems of linear forms directivities of the relief and the borders of surface and subsurface blocks partially correspond to the four main systems of the global disjunctive network (planetary fracturing), which suggests a considerable influence of the latter on the structural plan of the region.Redistribution of stresses is associated with the modern geological processes leading to the formation of new
configurations of seabed relief and partial destruction of the old surfaces of guyots.

Предложен новый вариант геолого-геоморфологического строения и истории формирования массива Вулканологов (МВ), расположенного в Командорской котловине Берингова моря. Основой для него послужили батиметрическая карта, созданная в 2009 г. по результатам многолучевого эхолотирования с борта экспедиционного судна «Зонне», и частично ревизованные материалы более ранних геолого-геофизических исследований этого района. Показано, что МВ перед началом формирования вулкана Пийпа был кардинально преобразован и разрушен катастрофическими магмо-тектоническими и обвально-взрывными процессами. Определены параметры МВ, активного вулкана Пийпа и открытого автором магматического суперпотока, оценен их возраст.

With the use of the method of low-frequency microseismic sounding, the configuration of the magmatic feeding system of the Tolbachinsky Dol—a regional zone of areal basaltic volcanism in the southern part of the Klyuchevskoy volcano group in Kamchatka—is studied. The initial data are obtained by a step-by-step recording of the background microseismic noise in 2010–2015 within a thoroughly marked-out survey area covering the zones of fissure eruptions in 1975–1976 and 2012–2013 and, partly, the edifice of thePloskii (flat) Tolbachik volcano. The depth sections ref lecting the distributions of the relative velocities of seismic waves in the Earth’s crust are constructed. For a more reliable interpretation of the revealed deep anomalies, the results of independent geological and geophysical studies are used. The ascertained low-velocity structures are closely correlated to the manifestations of present-day volcanism. It is shown that the feeding structure of the Tolbachinsky Dol is spatially heterogeneous, incorporating subvertical and lateral pipe-shaped magma conduits, closely spaced magma feeding channels, and shallow magma reservoirs. A long-lived local transcrustal magma conducting zone is revealed, and regularities in the deep structure of the feeding systems of fissure eruptions are identified. The configuration of the established subvertical magma conduits permits basalts moving to rise to the surface by different paths, which, inter alia, explains the contrasting magma compositions observed during a single eruption. Thus, based on the instrumental data, it is shown that the magmatic feeding structure of the Tolbachinsky Dol has a number of specific peculiarities and is significantly more complicated than has been previously thought about the areal volcanic fields.