Institute of Volcanology and Seismology
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Особенности вещественного состава осадочных и вулканогенно-осадочных пород островов группы Фу-Куй – Катуик (шельф Вьетнама)
No full textИзучен вещественный состав осадочных и вулканогенно-осадочных пород из естественных обнажений на вулканических островах группы Фу-Куй – Катуик (шельф Вьетнама). По минералого-петрохимическим характеристикам песчаные породы о. Фу-Куй являются петрогенными и относятся к субаркозам. Судя по преобладанию среди породообразующих компонентов песчаников кварца и полевого шпата, доминированию в тяжелой фракции минералов сиалических пород, а также характеру распределения главных, редких и редкоземельных элементов, основными источниками кластики были кислые интрузивные и метаморфические породы зрелой континентальной земной коры, а геодинамическая обстановка в области питания соответствует пассивной континентальной окраине. Среднеплейстоценовые вулканогенно-осадочные породы островов группы Фу-Куй – Катуик сложены пирокластическим материалом основного состава близкого к базальтам трахибазальт-трахитовой и щелочно-базальтовой серий Вьетнама, имеющим внутриплитные характеристики и связанным с существующими здесь обстановками растяжения. Формирование вулканогенных отложений происходило в субаэральных условиях вблизи от центров вулканических извержений
Особенности состава меловых вулканитов Алазейского плоскогорья (Северо-Восточная Якутия)
No full textНовые данные по составу меловых вулканитов, развитых в пределах Алазейского плоскогорья, Колымо-Индигирской складчатой области северо-востока Якутии, указывают на существенные различия в их составе, что позволяет говорить о различных геодинамических режимах при формировании этих пород. Изученные магматические породы разделяются на две группы: образования первой группы относятся к дифференцированной серии (от андезибазальтов до дацитов и риолитов), формировавшихся в пределах вулканического пояса; вулканиты второй группы, относятся к толеитовой серии и формировались в геодинамической обстановке, связанной с режимом растяжения и рифтообразования
A multi-sensor satellite assessment of SO2 emissions from the 2012–13 eruption of Plosky Tolbachik volcano, Kamchatka
No full textAbstract Prolonged basaltic effusive eruptions at high latitudes can have significant atmospheric and environmental impacts, but can be challenging to observe in winter conditions. Here, we use multi-sensor satellite data to assess sulfur dioxide (SO2) emissions from the 2012–2013 eruption of Plosky Tolbachik volcano (Kamchatka), which lasted ~ 9–10 months and erupted ~ 0.55 km3 DRE. Observations from the Ozone Monitoring Instrument (OMI), the Ozone Mapping and Profiler Suite (OMPS), the Atmospheric Infrared Sounder (AIRS), and the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to evaluate volcanic activity, SO2 emissions and heat flux associated with the effusion of lava flows. Gaps in the primary OMI SO2 time-series dataset occurred due to instrument limitations and adverse meteorological conditions. Four methods were tested to assess how efficiently they could fill these data gaps and improve estimates of total SO2 emissions. When available, using data from other {SO2} observing instruments was the most comprehensive way to address these data gaps. Satellite measurements yield a total SO2 loading of ~ 200 kt SO2 during the 10-month Plosky Tolbachik eruption, although actual SO2 emissions may have been greater. Based on the satellite SO2 measurements, the Fast Fourier Transform (FFT) multi-taper method (MTM) was used to analyze cyclical behavior in the complete data series and a 55-day cycle potentially attributable to the eruptive behavior of Plosky Tolbachik during the 2012 – 2013 eruption was identified
Геодинамическая позиция мезозойских мантийных пород Стрельцовской кальдеры (Восточное Забайкалье), мантийные домены Центральной Азии и Китая
No full textНовые изотопно-геохимические данные по юрско-меловым вулканическим породам Стрельцовской кальдеры позволили установить существование нескольких источников расплавов, из которых были образованы магматические породы кальдеры. Мантийные расплавы (базальтовые и трахибазальтовые) выплавлялись из гранатовых лерцолитов мантии характеризующихся εNd(T)= -0.9 – 3.4, ISr(T)=0.7056-0.707, Zr/Nb=14-30, Nb/U=4-8, Th/Ta=5-15. Магматизм Стрельцовской кальдеры начался 160 млн. лет назад. По-видимому, он был генетически связан с началом процессов растяжения в Китае и Монголии. Области мантии, из которых выплавлялись позднеюрско-раннемеловые расплавы Стрельцовской кальдеры, Большехинганского пояса, Восточного Китая, Южной Монголии по изотопно-геохимическим характеристикам могут быть объединены в единый домен, отличающийся от других мантийных доменов Китая
Chlorine Stable Isotopes to reveal contribution of magmatic chlorine in subduction zones: the case of the Kamchatka-Kuril and the Lesser Antilles Volcanic Arcs
No full text
Magma migration at the onset of the 2012–13 Tolbachik eruption revealed by Seismic Amplitude Ratio Analysis
No full textAbstract In contrast of the 1975–76 Tolbachik eruption, the 2012–13 Tolbachik eruption was not preceded by any striking change in seismic activity. By processing the Klyuchevskoy volcano group seismic data with the Seismic Amplitude Ratio Analysis (SARA) method, we gain insights into the dynamics of magma movement prior to this important eruption. A clear seismic migration within the seismic swarm, started 20 hours before the reported eruption onset (05:15 UTC, 26 November 2012). This migration proceeded in different phases and ended when eruptive tremor, corresponding to lava flows, was recorded (at ~ 11:00 UTC, 27 November 2012). In order to get a first order approximation of the magma location, we compare the calculated seismic intensity ratios with the theoretical ones. As expected, the observations suggest that the seismicity migrated toward the eruption location. However, we explain the pre-eruptive observed ratios by a vertical migration under the northern slope of Plosky Tolbachik volcano followed by a lateral migration toward the eruptive vents. Another migration is also captured by this technique and coincides with a seismic swarm that started 16–20 km to the south of Plosky Tolbachik at 20:31 {UTC} on November 28 and lasted for more than 2 days. This seismic swarm is very similar to the seismicity preceding the 1975–76 Tolbachik eruption and can be considered as a possible aborted eruption
Dike model for the 2012–2013 Tolbachik eruption constrained by satellite radar interferometry observations
No full textAbstract A large dike intrusion and fissure eruption lasting 9 months began on November 27, 2013, beneath the south flank of Tolbachik Volcano, Kamchatka, Russia. The eruption was the most recent at Tolbachik since the Great Tolbachik Eruption from 1975 to 1976. The 2012 eruption was preceded by more than 6 months of seismicity that clustered beneath the east flank of the volcano along a NW–SE trend. Seismicity increased dramatically before the eruption, with propagation of the seismicity from the central volcano conduit in the final hours. We use interferometric synthetic aperture radar (InSAR) to compute relative displacement images (interferograms) for {SAR} data pairs spanning the eruption. We use satellite {SAR} data from the Canadian Space Agency's RADARSAT-2 and from the Italian Space Agency's COSMO-SkyMed missions. Data are modeled first through a Markov Chain Monte Carlo solution for a single tensile dislocation (dike). We then use a boundary element method that includes topography to model a distributed dike-opening model. We find the best-fitting dike dips 80° to the {WNW} with maximum opening of 6–8 m, localized in the near surface and more broadly distributed in distinct regions up to 3 km beneath the surface, which varies from 1 to 2 km elevation for the eruptive fissures. The distribution of dike opening and its correspondence with co-diking seismicity suggests that the dike propagated radially from Tolbachik's central conduit
Petrology and volatile content of magmas erupted from Tolbachik Volcano, Kamchatka, 2012–13
No full textAbstract We report petrography, and bulk rock, mineral and glass analyses of eruptive products of the 2012–13 eruption of Tolbachik volcano, Central Kamchatka Depression, Russia. Magmas are shoshonitic in composition, with phenocrysts of olivine and plagioclase; clinopyroxene phenocrysts are scarce. Samples collected as bombs from the active vent, from liquid lava at the active lava front, and as naturally solidified “toothpaste” lava allow us to quantify changes in porosity and crystallinity that took place during 5.25 km of lava flow and during solidification. Olivine-hosted melt inclusions from rapidly-cooled, mm-size tephra have near-constant {H2O} contents (1.19 ± 0.1 wt) over a wide range of {CO2} contents (< 900 ppm), consistent with degassing. The groundmass glasses from tephras lie at the shallow end of this degassing trend with 0.3 wt {H2O} and 50 ppm CO2. The presence of small saturation, rather than shrinkage, bubbles testifies to volatile saturation at the time of entrapment. Calculated saturation pressures are 0.3 to 1.7 kbar, in agreement with the depths of earthquake swarms during November 2012 (0.6 to 7.5 km below the volcano). Melt inclusions from slowly-cooled and hot-collected lavas have {H2O} contents that are lower by an order of magnitude than tephras, despite comparable {CO2} contents. We ascribe this to diffusive {H2O} loss through olivine host crystals during cooling. The absence of shrinkage bubbles in the inclusions accounts for the lack of reduction in dissolved {CO2} (and S and Cl). Melt inclusions from tephras experienced < 3 wt post-entrapment crystallisation. Melt inclusion entrapment temperatures are around 1080 °C. Compared to magmas erupted elsewhere in the Kluchevskoy Group, the 2012–13 Tolbachik magmas appear to derive from an unusually H2O-poor and K2O-rich basaltic parent