Изложены данные по вулканическим сериям пород Белоголовского массива в Срединном хребте Камчатки. Рассмотрены новые геохронологические данные, особенности распределения в породах массива редких элементов, элементов платиновой группы и приведены изотопные характеристики вулканических серий нормальной и умеренной щелочности. Показано, что позднеплиоцен-раннеплейстоценовые породы умеренно-щелочной серии вулканического массива Белоголовский отличаются от пород нормально-щелочной серии позднемиоцен-среднеплиоценового вулканогенного фундамента повышенными концентрациями HFSE и LILE компонентов. Предложена модель образования умеренно-щелочных магм с участием гетерогенных деплетированного и обогащенного источников вещества. По изотопным данным одним из источников могла быть субдуцируемая океаническая литосфера Тихоокеанского или Командорского типа, тогда как другим источником был рециклированный материал Индийского MORB типа.

Abstract—This study is concerned with the petrographic, mineralogic, and geochemical features in the K-high basaltic trachyandesites that were discharged by the 2012–2013 parasitic eruption on Ploskii Tolbachik Volcano. These K-high basaltic trachyandesites exhibit some obvious characteristics that testify to their suprasubduction origin. They are deeply differentiated rocks with strongly fractionated plagioclase.A study of the Sr, Nd, and Pb radiogenic isotope ratios in the K-high basaltic trachyandesites provided evidence of their mantle origin and of the fact that the crust has exerted no influence on their compositions. We performed a comparative analysis of the ratios of the concentrations for some incoherent elements in the K-high basaltic trachyandesites, as well as in intraplate, riftogenic, and island-arc moderate potassium basalts and basaltic andesites in relation to the concentrations of these elements in the primitive mantle. The geochemical features of these K-high basaltic trachyandesites classify them as belonging to the suprasubduction subalkaline formation of the potassium series.

Abstract We use both regional and local infrasound data to investigate the dynamics of the 2012–2013 eruption of Tolbachik Volcano, Kamchatka, Russia during select periods of time. Analysis of regional data recorded at the {IMS} array {IS44} in southern Kamchatka, ~ 384 km from the vent focuses on the eruption onset in November 2012, while analysis of local data focuses on activity in February and August 2013. Signals recorded from Tolbachik suggest a change in eruptive intensity possibly occurred from November 27–30, 2012. Local infrasound data recorded at distances of 100–950 m from the vent are characterized primarily by repeated, transient explosion signals indicative of gas slug bursts. Three methods are employed to pick slug burst events in February and August. The nature of slug bursts makes a monopole acoustic source model particularly fitting, permitting volume outflux and slug radius calculations for individual events. Volume outfluxes and slug radii distributions provide three possible explanations for the eruption style of Tolbachik Volcano from mid-February to late August. Cumulative outflux for slug bursts (i.e. mass of emissions from individual bursts) derived by infrasound for both February and August range from < 100 to ~ 3000 kg. These values are greater than infrasound-derived emissions calculated at Pacaya Volcano, but less than those calculated at Mt. Erebus Volcano. From this, we determine slug bursts at Tolbachik Volcano in February and August were larger on average than those at Pacaya Volcano in 2010, but smaller on average than those at Mt. Erebus in 2008. Our overall emissions estimates are in general agreement with estimates from satellite observations. This agreement supports the monopole source inversion as a potential method for estimating mass of emissions from slug burst events.

Abstract We present a broad overview of the 2012–13 flank fissure eruption of Plosky Tolbachik Volcano in the central Kamchatka Peninsula. The eruption lasted more than nine months and produced approximately 0.55 km3 {DRE} (volume recalculated to a density of 2.8 g/cm3) of basaltic trachyandesite magma. The 2012–13 eruption of Tolbachik is one of the most voluminous historical eruptions of mafic magma at subduction related volcanoes globally, and it is the second largest at Kamchatka. The eruption was preceded by five months of elevated seismicity and ground inflation, both of which peaked a day before the eruption commenced on 27 November 2012. The batch of high-Al magma ascended from depths of 5–10 km; its apical part contained 54–55 wt. SiO2, and the main body 52–53 wt. SiO2. The eruption started by the opening of a 6 km-long radial fissure on the southwestern slope of the volcano that fed multi-vent phreatomagmatic and magmatic explosive activity, as well as intensive effusion of lava with an initial discharge of > 440 m3/s. After 10 days the eruption continued only at the lower part of the fissure, where explosive and effusive activity of Hawaiian–Strombolian type occurred from a lava pond in the crater of the main growing scoria cone. The discharge rate for the nine month long, effusion-dominated eruption gradually declined from 140 to 18 m3/s and formed a compound lava field with a total area of ~ 36 km2; the effusive activity evolved from high-discharge channel-fed 'a'a lavas to dominantly low-discharge tube-fed pahoehoe lavas. On 23 August, the effusion of lava ceased and the intra-crater lava pond drained. Weak Strombolian-type explosions continued for several more days on the crater bottom until the end of the eruption around 5 September 2013. Based on a broad array of new data collected during this eruption, we develop a model for the magma storage and transport system of Plosky Tolbachik that links the storage zones of the two main genetically related magma types of the volcano (high-Al and high-Mg basalts) with the clusters of local seismicity. The model explains why precursory seismicity and dynamics of the 2012–13 eruption was drastically different from those of the previous eruption of the volcano in 1975–76.