Institute of Volcanology and Seismology
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Происхождение термальных вод вулканических областей
No full textИсследуется природа источников тепла и вещества гидротерм вулканических регионов: являются ли они разными (и тогда гидротермы – это нагретые метеорные воды) или источник тепла и вещества – общий (и тогда гидротермы имеют в составе теплоноситель, или флюид). Выводы получены на основе комплексного подхода к проблеме с учетом баланса вод Земли, связи воды и вулканизма на планетах земного типа, закономерностей формирования состава гидротерм, выявленных на основе Камчатского материала с привлечением данных по выносу тепла. Согласно выводам источником, как тепла, так и вещества гидротерм является мантийный флюид. Гидротермы представлены либо им самим, либо продуктами его рассеяния. Но прежде этот флюид выступает инициатором кислого вулканизма, который предваряет гидротермальный процесс. Места дифференциации флюида в коре перспективны как участки гидротермального минералоо и рудообразования. Работа представляет интерес для геологов, изучающих воду как действующее вещество высокотемпературных процессов
Testing of the Titanomagnetite Method to Detect Magmatic Chamber Depth at Avachinsky Stratovolcano and Tolbachik Fissure Eruption
No full textTwo volcanoes were tested using the titanomagnetite method in order to detect the magma chamber depth. Curie temperature of andesite tephra shows that the magmatic chamber was situated on the depth of 18±7 km under Avachinsky Volcano ~5 Ka ago, but one of the basalt-andesite tephra from Avachinsky results the chamber depth of 32±6 km ~3 Ka ago. This method applied to the lava from Tolbachik Fissure Eruption (TFE) shows a chamber depth of 47±5 km. This result is inconsistent slightly with the depth of 35±6 km obtained by our microzond analysing of element composition of titanomagnetite grains into lava sample from earlier phase of the same eruption. This two different results between TFE lava samples may occur from magma differentiation or this is a methodical or occasional error. To know true it needs a sample statistics. At present, more microzond data from Tolbachik Fissure Eruption are being analyzed
Evolution and genesis of volcanic rocks from Mutnovsky Volcano, Kamchatka
No full textThis study presents new geochemical data for Mutnovsky Volcano, located on the volcanic front of the southern portion of the Kamchatka arc. Field relationships show that Mutnovsky Volcano is comprised of four distinct stratocones, which have grown over that past 80 ka. The youngest center, Mutnovsky IV, has produced basalts and basaltic andesites only. The three older centers (Mutnovsky I, II, III) are dominated by basalt and basaltic andesite (60–80 by volume), but each has also produced small volumes of andesite and dacite. Across centers of all ages, Mutnovsky lavas define a tholeiitic igneous series, from 48–70 SiO2. Basalts and basaltic andesites have relatively low K2O and Na2O, and high FeO* and Al2O3 compared to volcanic rocks throughout Kamchatka. The mafic lavas are also depleted in the light rare earth elements (REEs), with chondrite-normalized La/Sm < 1.0. Andesites have generally higher REE abundances and are more enriched in light REEs, some showing negative Eu anomalies. All samples are depleted in field strength elements (HFSEs) relative to similarly incompatible REEs (e.g., low La/Ta, Nd/Hf compared to MORB), similar to island arc volcanic rocks worldwide. Radiogenic isotope ratios (Sr, Nd, Pb, Hf) are similar for samples from all four eruptive centers, and indicate that all samples were produced by melting of a similar source mixture. No clear age-progressive changes are evident in the compositions of Mutnovsky lavas. Mass balance and assimilation-fractional crystallization (AFC) modeling of major and rare earth elements (REEs) indicate that basaltic andesites were produced by FC of plagioclase, clinopyroxene and olivine from a parental basalt, combined with assimilation of a melt composition similar to dacite lavas present at Mutnovsky. This modeling also indicates that andesites were produced by FC of plagioclase from basaltic andesite, combined with assimilation of dacite. Dacites erupted from Mutnovsky I and II have low abundances of REEs, and do not appear to be related to mafic magmas by FC or AFC processes. These dacites are modeled as the products of dehydration partial melting at mid-crustal levels of a garnet-free, amphibole-bearing basaltic rock, which itself formed in the mid-crust by emplacement of magma that originated from the same source as all Mutnovsky magmas. Lead isotope data indicate that subducted sediment is likely present in the source beneath Mutnovsky and most Kamchatka volcanoes, but uniformly radiogenic Hf and Nd in mafic samples (εNd = 8.7–9.3, εHf = 15.4–15.9), and significant variation in trace element ratios at nearly constant εNd and εHf, indicate that sediment plays a minor roll in controlling subduction trace element patterns in Mutnovsky lavas. Mafic lavas with Ba/Th > 450 require an aqueous fluid source component from subducting oceanic crust, but mixing patterns in isotope versus trace element ratio plots for Hf and the REEs (εNd and εHf vs. ratios with Ce, Nd and Hf) demonstrate that a source component with radiogenic Nd and Hf, and fractionated (arc-type) trace element ratios must be present in the source of Mutnovsky lavas. This source component, which is interpreted to be a partial melt of subducted basalt in the eclogite facies (eclogite melt source component), appears to be present in the source of all Kamchatka volcanoes. Cross-arc geochemical patterns at Mutnovsky and in other arc systems (Isu-Bonin, Tonga-Kermadec) suggest that the aqueous fluid component diminishes and the eclogite melt component is increased from volcanoes at the arc front compared to those in rear-arc positions
Seismicity observed during the precursory process and the actual eruption of Kizimen Volcano, Kamchatka in 2009-2013
No full textKizimen Volcano began to erupt in December 2010. The eruption was preceded by a precursory period of seismicity that lasted for 20 months. This paper discusses the space-time features of the precursory seismicity. We provide a brief description of this explosive and effusive eruption between December 2010 and March 2013. The eruption started with some explosive activity followed by extrusion of a viscous lava flow. The extrusion of viscous andesitic magma and the motion of the lava flow down the slope were accompanied by unusual seismicity in the form of the quasiperiodic occurrence of microearthquakes, the so-called drumbeat phenomenon. It is shown that the occurrence of a drumbeat was first recorded during the extrusion process at the volcano's summit. Subsequently, the drumbeat mode of activity was caused by the front of the viscous lava flow as it was moving down the slope. The dynamic parameters of the microearthquakes varied in accordance with the dimensions of the lava flow front. The motion of the main tongue of the lava flow (March to September 2011) gave rise to drumbeat I with energy classes of microearthquakes K = 3-5.5, while the second tongue, which was smaller than the first, produced drumbeat II with microearthquakes of K < 3 during its motion down the slope. In January 2013 we saw a phenomenon similar to the drumbeat that was recorded at the start of the eruption. This was caused by an obelisk being extruded at the volcano's summit. В© 2014 Pleiades Publishing, Ltd
Содержание кальция в кристаллах оливина, выросших из экспериментальных расплавов. Часть 1
No full textВ статье представлены выявленные закономерности содержаний кальция в кристаллах оливина в системе основной-ультраосновной расплав–оливин в широком диапазоне условий, полученные по результатам обработки экспериментальных данных, заимствованных из базы данных “ИНФОРЕКС”. Были выделены две группы параметров системы расплав–оливин, ответственных за увеличение, или уменьшение содержаний кальция в оливине. Появление в экспериментах низкокальциевых разностей оливинов в системе расплав–оливин, независимо от давления и температуры, в первую очередь обязано низким содержаниям кальция в расплаве
Первые данные по геохимии магнезиальных андезитов палеовулкана г. Шиш (хребет Кумроч, Восточная Камчатка)
Get PDFВ сообщении приведены первые краткие данные о составе пород палеовулкана г. Шиш в хребте Кумроч. Показано, что по содержаниям главных элементов, хрома, никеля, а также по степени обогащения легкими PЗЭ и обеднения тяжелыми РЗЭ и иттрием породы г. Шиш близки к магнезиальным андезитам северного фланга Центрально-Камчатской депрессии
