Fieldworks at Alaid volcano in 2018, Atlasov Island, the Kuriles

The article presents a discussion of contaminants in nickeliferous magmas of various composition and phase as metamorphic rocks and fluids. It describes distribution of different solid-phase contaminants (xenoliths) in intrusions and compositionally different accumulative rocks. Xenogenic material is represented both by host rocks with intrusions and deeper rocks with no surface outcropping. In order to estimate contamination effect on the variety of accumulative rock series and location of sulphide ores as a benchmark standard we use similar data on a ore-bearing intrusive rocks formed by nearly non-contaminated high-magnesian (parental) magma. Besides, the article describes contamination of magma by high-alumina coal slates as well as variety of forming series of its cumulative rocks and exotic floatation graphite-sulphide ores in aluminous granodiorites in one of the intrusive bodies.

The paper presents data on identified and described short-term local (1955−1976) enhanced volcanic activity within the Northern Group at the Central Kamchatka Depression and regional disasters (1907-1976), clearly revealed within Kamchatka Peninsular and the Kurile Islands. In scale (volume is about 9 km3, weight of erupted and replaced productswas calculated to be about 16×109 t), the local volcanic disaster was the most powerful in Kamchatka and Kurile Islands over the period of the last 2000 years. This volume exceeds 80% of ~19×109 t totally erupted by all volcanoes over the same period of time. Over the period 1907−1976, the Kamchatka and Kurile volcanoes erupted and transported about 29.5×109 t of juvenile and resurgent material while other volcanoes in the world erupted about 122×109 t.

This is the final article that describes various for petro- and oreogenesis consequences of the contamination of nickel-bearing magma with siliceous material (quartzites), which led to the replacement of ultrabasic ore-hosting rocks (cortlandites) with ultramafic (amphibole orthopyroxenites). Besides, the paper describes the products of metamagmatic variations of pyroxene ore cumulates in biotite-amphibole rocks inported by water-potassium fluid. The author shows the unconventional results of fluid influence on similar cumulates with relics of quartzite xenoliths accompanied by the formation of ore granophyric autobreccies, as well as ore-bearing derivatives from the process of magma mixing (auto-contamination). We introduce an intraformational classification of copper-nickel ores by their associations with host rocks of different composition and origin — from juvenile magmatic ultrabasites, contaminated and ultramafites and melanodiorites to hybrid granitoids. The dynamics of the formation of intrusive ore-magmatic systems and the plausible reason of differences in the ore content of large and small intrusions are discussed.

Based on visual and satellite data, the authors provide information that characterizes the volcanic activity in the Kuril Islands in 2018. Ebeko (Paramushir Island, the Northern Kurile Islands) and Sarychev Peak (Matua Island, the Central Kurile Islands) volcanoes were active in the Kuril Islands. Ebeko Volcano produced a weak (to moderate) explosive eruption in form of steam and ash-gas emissions (about 800 emissions at a height from 2 to 5.5 km). Sarychev Peak activity was characterized by a weak (to moderate) explosions (over the period from September till October the volcano produced at least 10 emissions that reached a height of 2 to 4.5 km). Due to the relatively low emission height and low ash concentration, the activity on Ebeko and Sarychev Peak in 2018 did not pose a serious threat to the international air routes, but could have a certain impact on the local airlines.

The article presents the methods and results of the magnetotelluric sounding within the Avacha-Koryaksky group of volcanoes. Geoelectrical section was studied within the period range from 0.0001 to 1000 seconds and above. The authors performed a numerical two-dimensional modeling. Initially, we used test models for possible distortions of curves. The analysis of the magnetotelluric parametres allowed us to characterize the geoelectrical inhomogenuities. Curves along the strike and across the strike were used as main curves. Since longitudinal curves are less prone to coast effect, they were used with transverse curves in order to create a geoelectrical model based on a 2D magnetotelluric field numerical modeling. The created geolectrical model has a conductive bed in the upper part of the section that is connected with an igneous-sedimentary cover. The deep part of the model includes near-vertical conductive zones, which denote a zone with deep faults. The paper describes possible nature of the revealed anomalies and provides rough estimation of rock porosity in the conductive zones.

В работе даны краткая характеристика динамики извержения вулкана Кизимен от начала активизации до апреля 2012 г. и первые результаты петрохимического и минералогического изучения твердых продуктов извержения в 2011 г.

The number of explosive eruptions at Shiveluch Volcano has significantly increased over the past years, which requires close volcanic monitoring using all available techniques. In order to implement a new monitoring technique into integrated methods of volcano monitoring, the authors analyze response to the intensity of the vertical component in the atmospheric electrical field (EZ AEF) during the movement of ash clouds. Two eruptions of different intensity that occurred December 16, 2016 and June 14, 2017 at Shiveluch were selected for study. We used a combination of satellite, seismic, and infrasound data to select signals in the EZ AEF field. Signals with negative polarity that accompanied ashfalls in the EZ AEF dynamics were registered for both eruptions within the closest area (< 50 km). In the former case, the ash cloud was “dry” and thus it caused aerial-electrical structure of the negatively charged cloud. In the latter case, a strong explosion sent into the atmosphere the large volume of ash and volcanic gases (98% in form of vapour) that resulted in the formation of a dipolar aerial-electrical structure caused by eolian differentiation within the closest area. At the distance of more than 100 km we registered a positivegoing signal that is attributive to the aerial-electrical structure of the positively charged type of the cloud.