Vulkanologiâ i sejsmologiâ

The paper contains the data on volume of erupted products from both lateral and summit eruptions over the period 1932–1989. The paper shows that over that period the volume of the erupted products from lateral eruptions prevailed over that ones from summit eruptions. We also examined further changes of the volcano eruptive nature. From 1932 to 1989 the volcano was producing both summit and lateral eruptions, but over the period 1993–2016 Klyuchevskoy was only producing summit eruptions. In 2016, the volcano resumed lateral eruptions on its slopes. It was revealed that each summit eruption caused formation of pits in the volcano’s central crater. The paper provides specific features of those pits. The collapsed crater’s formation is associated with changes in the magma density and volume as it rises to the surface. The article provides the data on the 2019–2021 summit eruptions and the 2021 lateral eruption named after G.S. Gorshkov. The paper also contains the updates on morphological evolution of both the summit crater during the eruptions and the pits inside the crater after the eruptions.

Identification of a large number of quasi-linear chains of earthquakes in the epicentral seismicity field of the Baikal region and their study showed that among these chains there may be not only chains of “migration” earthquakes, but also chains formed during a random spatio-temporal distribution of earthquakes. In this work, using a statistical analysis of the distribution of distances between epicenters, the possibility of forming chains of “migrations” within groups of seismic events is shown and their distribution is studied. It is noted that chains in groups of earthquakes are distinguished not only by the distribution of distances, but also by the time between them. The formation of chains of earthquakes was established in the areas of the following groups of earthquakes: Busiyingol and 1976 and 1991. in the same area, the South Baikal, Kyakhtinsky, Kichersky earthquakes of the Tompudinsky series, Oldongsinsky and Charudinsky groups. It is shown that these chains were formed during the implementation of these groups. In the identified areas of concentration of chains of grouping seismicity, a connection can be traced between the location and direction of the chains with the strike of fault zones, near-fault cracks and the orientation of nodal planes in earthquake sources.

The Evevpenta epithermal low-sulfidation ore occurrence is located in the northeastern part of the Central Kamchatka volcanic belt (Kamchatka Peninsula, Russia). It is hosted by andesitic lavas and pyroclastic rocks of the Middle Miocene-Early Pliocene. The ore bodies are comprised of quartz and adularia-quartz veins and stockworks, as well as hydrothermal breccias. Ore bodies are accompanied by argillic wall-rock alteration and peripheral propylitic alteration. Gold-silver mineralization was formed as a result of hypogenic (hydrothermal) and supergen stages of ore-forming processes. Two hypogenic mineral assemblages were documented: gold-telluride-quartz in the Central flank and telluride-sulfide-quartz in the Northern flank. Supergenic mineral assemblage with native (mustard) gold is detected only within the Central flank. The Evevpenta ore occurrence is a typical member of the reducing-alkaline (low-sulfidation) epithermal deposits of Kamchatka, which is based on the study of the material composition of ores.

Sublimates tested in 2013–2020 were studied. in the near-crater zone and on the slopes of the Alaid volcano, located in the Kuril Island arc. It has been established that in the near-crater zone there are native metals confined to zones of acid leaching, within which the original lavas and tuffs have been transformed into opal-like formations or rocks sharply enriched in ferric hydroxides. In these zones, the presence of native gold, palladium, silver, chromium, copper, zinc and alloys of gold and palladium, copper and zinc, copper and tungsten has been established. On the slopes of the Alaid volcano, the range of minerals in sublimates is wider, while the temperature of their formation is lower. Of the ore minerals, copper-containing ones predominate, and sublimates with vanadium-containing minerals belonging to hydrous oxides and vanadate-silicates are established. Two genetic types of slope sublimates have been identified: 1) minerals crystallizing from hydrothermal or steam-hydrothermal solutions near the outcrops of near-surface fumaroles and 2) copper and ferruginous colomorphic formations formed as a result of sedimentation from colloidal solutions in the shallow waters of drying up reservoirs, including small and large puddles.