Institute of Volcanology and Seismology
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Amphibole record of 1964 plinian and following dome-forming eruptions of Shiveluch volcano, Kamchatka
No full textShiveluch is one of the most active explosive volcanoes worldwide. During the last рlinian eruption in 1964 and the following (1980-current time) dome-forming eruptions Shiveluch has produced andesites and dacites (SiO2~60-64 wt.%) containing variably zoned, compositionally and texturally diverse amphibole phenocrysts. In this work, we attempt to decode the complex zoning of the amphibole crystals in the 55-year series of pumice, dome rocks and mafic enclaves in order to reconstruct the most recent evolution of the volcano plumbing system.
The amphibole zoning in Shiveluch andesites reveals correlation with the style and date of eruption. High-Al cores mantled by low-Al rims in amphiboles from the 1964 plinian eruption record a drastic decrease of pressure and rapid magma ascent from the lower crust to the shallow magma chamber. Typically unzoned and often opacitized low-Al crystals from the early dome-building episodes in 1980-1981 and 1993-1995 reflect magma crystallization in the shallow magma chamber. Complexly zoned amphiboles from andesites erupted in 2000s indicate replenishment of the shallow magma chamber with mafic magma and syn-eruptive mixing processes. Amphibole-based barometric calculations obtained by different approaches indicate that the Shiveluch plumbing system is complex and comprises two, mafic and silicic magma storage zones at ~15-20 km and ~5-6 km depths. We suggest that both episodes of the plinian eruption in 1964 and the extensive dome growth in 2001-2016 were driven by influx of mafic magma in the shallow storage zone beneath Shiveluch. The mafic replenishment likely preceded the 1964 plinian eruption and repeatedly occurred during the period of extensive dome growth in 2001-2016. The variable styles of the recent Shiveluch eruptions may be controlled by the relative volume of the mafic recharges and their thermal and viscosity effects on the efficiency of magma mixing
Hydrogeological Earthquake Precursors: A Case Study From the Kamchatka Peninsula
Get PDFThe relevance of hydrogeological precursors (HGPs) study is justified by the need to obtain reliable information about the spatio-temporal manifestations and the relationships of HGPs with the parameters of subsequent earthquakes for seismic forecasting. In the review the data on repeated manifestations of HGPs before strong earthquakes obtained from long-term observations in five deep wells on the Kamchatka Peninsula (Far East of Russia) are presented. The analysis of the correlation of HGPs occurring in several wells is carried out in comparison with earthquake parameters characterizing both earthquake sources (magnitude, linear size of the source) and the impact of earthquakes in the area of wells (specific energy density in wave, intensity of shaking). It is shown that the manifestation of HGPs in several wells is observed before earthquakes with Mw = 6.6–7.8 at epicentral distances up to the first hundreds of km to observation wells in the near and intermediate zones of the sources with the ratio of the epicentral distances and the source sizes no more than 1–5. A feature of our study was the use of certain types of HGPs in water-level changes for predictive assessments of the strong earthquakes in the Kamchatka Peninsula. The review presents precursors in water-level changes detected in real time and the corresponding earthquake forecasts, which were recognized as successful according to the conclusions of the expert council on earthquake prediction
Высокая пойма р. Камчатка: возраст и особенности формирования отложений
Get PDFИзучены отложения высокой поймы реки Камчатка в ее среднем течении. Выделены два типа обстановок накопления пойменных отложений: стабильная (зарастание стариц, удаленных от основного русла) и динамичная (берега центральной части долины, подверженные регулярным затоплениям полыми водами). Проведено радиоуглеродное датирование погребенной органики. Наиболее древний торф образовался около 3200 14С лет (3460 cal BP), в это время зафиксирован период пониженного стока, который мог быть вызван климатическими изменениями. Формирование пойменно–старичного аллювия началось не позднее 3.8 тыс. л.н. Изменение гидрологического режима и крупная перестройка русла реки, приведшие к образованию новой поверхности, возможно, были обусловлены сейсмическими процессами. Возраст этой поверхности может быть на несколько сотен лет древнее, чем начало субаэрального осадконакопления на высокой пойме в среднем течении р. Камчатки
Походы Семёна Дежнёва
Get PDFНа основе ландшафтно-ситуационного анализа основных обстоятельств похода С. Дежнёва и Ф. Попова к реке Анадырь показывается, что, скорее всего, коч С. Дежнёва был выброшен на юго-западный берег Чукотского полуострова восточнее залива Креста, откуда его отряд пешком вышел на берег Анадырского лимана. Летом сле-дующего года 12 выживших во время трудной зимовки казаков, на выстроенных из плавника лодках поднялись на 480 километров вверх по реке Анадырь и поставили в её среднем течении Анадырское зимовье.Высказывается предположение о том, что коч Ф. Попова, унесённый к юго-востоку от горла Анадырского ли-мана, после блуждания по центральной и юго-западной части Берингова моря, достиг берега Азиатского материка в районе северного побережья Олюторского моря (нынешнего залива Корфа). Здесь, во время зимовки, Ф. Попов и Г. Анкудинов умерли от цинги, а оставшиеся в живых казаки и промышленные люди в последующем на лодках доплыли до нынешней реки Русакова, откуда пешком ушли на реку Еловка, а затем на Тигиль
Geochemical Characteristics of Volcanogenic Deposits and Exhalation Mineralization in the Crater Part of the Active Kudryavy Volcano (Iturup Island of the Kuril Arc)
No full textExhalation ore mineralization is developing in the crater part of the active Kudryavy volcano. Lithogeochemical sampling results have revealed that Re, Au, Ag, As, Bi, Cd, Cu, Ge, In, Mo, Pb, S, Sb, Se, Sn, Te, Tl, W, Zn, Rb, and Cs accumulate in solid fumarole formations. These elements are transported by high-temperature volcanic gases and are deposited in mineral phases in the near-surface horizons of fumarole fields under decreasing temperature conditions. The contents of rhenium and other metals in volcanic deposits of fumarole fields locally reach values characteristic of ore deposits. Zoning of lithogeochemical anomalies in ore element associations has been revealed, expressed by the series Re, Mo, W, Au, Cu, Ag, Zn, Cs, Ge → In → Bi, Cd, Pb, Sn, Tl → As, Sb, Se, Te, (Cu, Ag, Au) in the direction from the highest-temperature fumarole fields to less hot, reflecting their temperature zoning. It is demonstrated that lateral geochemical zoning is caused both by the ore element contents in fumarole gases, which depend on temperature, and by differences in the optimal temperature ranges in which various elements precipitate from gases. Signatures for similar exhalation mineral formation processes have been revealed that occurred in the recent geological past at the neighboring extinct Sredny volcano. This suggests the occurrence of similar processes within other volcanic systems of Iturup Island, which increases the prospects for detecting complex exhalation-related manifestations of rare, base, and noble metals
Timing, magnitude and geochemistry of major Southeast Asian volcanic eruptions: identifying tephrochronologic markers
Get PDFWe review the current knowledge about Southeast Asian volcanoes and their eruption histories, and focus on identifying tephrochronologic markers representing major explosive eruptions in order to further future palaeoclimate and volcanological studies. Forty‐one volcanic edifices in Southeast Asia have been classified as large calderas by Whelley et al. (2015) and thus have, or are likely to have, produced large explosive eruptions with a Volcanic Explosivity Index (VEI) of 6–8. Unfortunately, only 20 such eruptions have known ages, spanning from 1.2 Ma to 1991 ad, and fewer have geochemical data that can be used for tephrostratigraphic correlations. Volcanic products from different geodynamic regions and different sources can generally be distinguished on major element plots (e.g. K2O versus CaO) of matrix glass composition. However, the distinction of multiple eruptions from the same source often requires additional data such as trace element compositions of matrix glass and/or mineral compositions. Biotite, but also magnetite compositions (MgO and TiO2 content in particular) appear to be very discriminating. Up to nine tuffs in addition to the three to four Toba tuffs can be utilised as widespread tephrochronologic markers and span a range from 1.2 to 1.6 Ma to recent. As only a few Holocene major eruptions have been well characterised and dated, many large calderas are still unstudied, and many distal tephra layers are still lacking a source, more tephrochronologic markers can certainly be defined in the future
Идентификация разрывных нарушений северной части о. Парамушир (Курильские острова, Россия) и их взаимосвязь с гидротермально-магматическими системами: 3D моделирование тектонической раздробленности
Get PDFThe 2019 Eruption Dynamics and Morphology at Ebeko Volcano Monitored by Unoccupied Aircraft Systems (UAS) and Field Stations
Get PDFLong-lived Volcanic Centers of Kamchatka Geothermal Areas
Get PDFThe current problems of hydrothermal processes and ore-forming systems are volcanic heat sources and mechanisms of heat
transfer. In Pauzhetsky, Semyachik and Mutnovsky geothermal areas in Kamchatka, active long-lived volcanic centers have been
studied, with which high-temperature hydrothermal systems are associated. In the Banno-Paratunsky geothermal area the Paleogene
and Neogene long-lived volcanic centers were identified, with which low-temperature hydrothermal systems are associated. The
geological history of the long-lived volcanic centers development is characterized by changes in their structure as a result of
hydrothermal-magmatic activity. These changes are manifested in the generation and evolution of magma chambers in the mantle
and in the Earth’s crust. Basalt melts of the mantle chambers transport the deep heat to the Earth’s surface through plane magmatic
channels without significant losses. The heat flow of these volcanic centers is short-lived and is characterized by a significant
capacity of ~8,000 kcal/km2s. The long-lived volcanic centers are characterized by the presence of magma chambers in the Earth's
crust. They shield the part of the mantle heat flow. Their thermal capacity on the Earth's surface is estimated from 1000 kcal/km2s
to 5000 kcal/km2s. It is assumed that a significant amount of thermal energy is retained in the long-lived volcanic centers. It is
spent on formation and activity of the chambers as well as the convective hydrothermal ore-forming systems. The evolution of such
centers is accompanied by the formation of complexes of metamorphic rocks which interaction with high-temperature mantle melts
is accompanied by redox reactions like combustion. As a result of these reactions, thermal energy is produced in such magma
chambers. A long-lived jet magmatic system is formed, and it provides the transfer of mantle heat. Heat transfer in the system is
accompanied by minimization of heat losses, accumulation of heat and its additional generation which is necessary for the heat
transfer in the structures with low thermal conductivity. The formation, evolution and extinction of magma chambers and reservoirs
in such heat-conducting structures are controlled by the thermophysical properties of the rocks, their geological structure and redox processes in them
