Федотов С.А., Уткин И.С., Уткина Л.И. Оценка размеров коровых очагов вулканов и изменения их размеров во времени по данным о количестве, составе изверженных продуктов и глубине очага // Вулканология и сейсмология. 2000. № 3. С. 3-14.
Проведено математическое моделирование динамики роста коровых магматических очагов вулканов за счет плавления вмещающих пород и выноса выплавленного материала на поверхность в процессе извержений. Получены оценки размеров магматических очагов вулканов Камчатки: Ключевского, Шивелуча, Ильинского, Желтовского и Безымянного, - и изменения, роста и последующего уменьшения этих размеров во времени по данным о количестве, составе изверженных продуктов и глубине очага. Максимальные величины радиусов очагов находятся в пределах от 0.5 до 6.0 км. Оценено время достижения очагами указанных вулканов своих максимальных размеров, а также продолжительность времени их пребывания в квазистационарном состоянии, когда температура в очаге почти постоянна, а его размеры близки к максимальным. Время нахождения в квазистационарном состоянии достигает нескольких десятков тысяч лет у крупных вулканов.
Belousov Alexander, Belousova Marina, Voight Barry Multiple edifice failures, debris avalanches and associated eruptions in the Holocene history of Shiveluch volcano, Kamchatka, Russia // Bulletin of Volcanology. 1999. Vol. 61. № 5. P. 324-342. doi:10.1007/s004450050300.
Dirksen O.V., Melekestsev I.V. Chronology, evolution and morphology of plateau basalt eruptive centers in Avacha River Area, Kamchatka, Russia // Volcanology and Seismology. 1999. Vol. 21. № 1. P. 1-27.
Nineteen Holocene eruptive centers (cinder cones with lava flows and maars) were located and described in the Avacha horst and anticline zone west of the East Kamchatka volcanic area. A tephrochronological study and the carbon-14 dating of soil and plant remains ranked the eruptive centers into three age groups: 11 000-7700, 3000-2500, and 1200-600 carbon-14 years B. P. The eruptive centers of these groups are believed to have been operating roughly synchronously with the periods of active magma injection in the East Kamchatka volcanic area. Eruptive histories were reconstructed for some of the volcanic centers. The structural and tectonic settings, geographical positions, and elevations of the centers were analyzed. The volume (1.1 km3) and weight (1.8 X 10^9 metric tons) of the erupted rocks were evaluated. The productivity of the plateau basalt volcanism was found to be 10-100 times lower than the plateau basalt productivity in the area of grabens and synclines, possibly, because of the more shallow basement in the horsts and because of the fact that the compression of the crust under uplifting conditions hampered the magma rise toward the surface. Most of the lavas and pyroclastics are basalts of the medium-potassic series, some having medium (54-62) and some elevated (65-70) Kmg values.
Melekestsev I.V., Dirksen O.V., Girina O.A. A giant landslide-explosion circue and debris avalanche at Bakening volcano, Kamchatka // Volcanology and Seismology. 1999. Vol. 20. № 3. P. 265-279.
This study revealed that the giant cirque of Bakening Volcano had been produced by its eruption ca. 8000-8500 carbon-14 year ago. The eruption is supposed to have been heralded by a large earthquake (M > 7) resulting in the collapse and slide of the SE sector of the cone. The landslide unroofed the hydrothermal system and triggered an explosion which was followed by an ash-and-block pyroclastic flow. A rockslide avalanche rolled down into the valley of the Srednyaya Avacha River and travelled as far as 10-11 km along it. The avalanche deposited its debris material over an area of 18-20 km2 measuring 0.4-0.5 km3 in volume. These deposits dammed the river, produced two lakes (Bezymyannoe and Verkhneavacha), and gave birth to a large lahar which traveled along the valley much farther.
Ozerov A., Lees J., Ispolatov J. Long and Short Term Periodic Activity at Karymsky Volcano // AGU Spring Meeting 1999. Eos Trans. AGU, xx (xx), Spring Meet. Suppl., Abstract. Boston, Massachusetts: AGU. 1999. P. V11D-09.
Volynets O.N., Melekestsev I.V., Ponomareva V.V., Yogodzinski G.M. Kharchinsky and Zarechnyi volcanoes - unique centers of late Pleistocene magnesian basalts in Kamchatka: Structural setting, morphology, geologic structure and age // Volcanology and Seismology. 1999. Vol. 20. № 4-5. P. 383-399.
This paper presents the results of studying the spatial distribution and structural setting of magnesian basalts and andesites in the Northern group of Kamchatkan volcanoes and in the junction zone of the Kuril-Kamchatka and Aleutian island arcs. The morphology and geologic structure of unique Kamchatkan magnesian basalt stratovolcanoes are described: Kharchinsky, Zarechnyi, and the Kharchinsky regional zone of cinder cones. The reported evidence includes the ages and eruptive histories, and productivities of the volcanoes and the volumes and weights of their edifices. The magnesian basalts were erupted 40-50 thousand years ago, for the first time during the Holocene.
Volynets O.N., Melekestsev I.V., Ponomareva V.V., Yogodzinski J.M. Kharchinskii and Zarechnyi volcanoes, unique centers of Late Pleistocene magnesian basalts in Kamchatka: Composition of erupted rocks // Volcanology and Seismology. 1999. Vol. 21. № 1. P. 45-66.
Most of the Kharchinskii and Zarechnyi products, as well as those of the Kharchinskii cinder cones, are magnesian rocks. Mineralogical data suggest that both the basaltic and the andesitic magma were rich in water (≥3-4 and >6-7 wt., respectively) and crystallized at high oxygen fugacity (2.0-2.5 orders of magnitude higher than the NNO buffer). These features, coupled with the geochemical characteristics of these basalts and andesites, indicate that they are similar to the rocks of Shiveluch, a volcano also located on the northern flank of the Northern volcanic group, but differ from the rocks of the other volcanoes of this group which are located further south. The Kharchinskii, Zarechnyi, and Shiveluch magnesian basalts differ from the rocks of the Klyuchevskoi volcano and Tolbachik lava field by their higher K, Ba, Sr and lower Ca, Sc, Yb contents at higher La/Yb, Ni/Sc, and La/Ta ratios, while their initial magmas were more hydrous and more oxidized.
Volynets O.N., Ponomareva V.V., Braitseva O.A., Melekestsev I.V., Chen Ch.H. Holocene eruptive history of Ksudach volcanic massif, South Kamchatka: evolution of a large magmatic chamber // Journal of Volcanology and Geothermal Research. 1999. Vol. 91. P. 23-42. doi: 10.1016/S0377-0273(99)00049-9.
The combination of geological, tephrochronological and geochemical studies is used to reconstruct the Holocene eruptive history of Ksudach volcanic massif, South Kamchatka and to trace the evolution of its magma. Ksudach is located in the frontal volcanic zone of Kamchatka. From Early Holocene till AD 240, the volcano had repetitive voluminous caldera-forming eruptions. Later they gave way to frequent moderate explosive–effusive eruptions that formed the Shtyubel' stratovolcano inside the nested calderas, and then to frequent larger explosive eruptions. Holocene eruptive products are low-K2O two pyroxene–plagioclase basaltic andesite to rhyodacite. Mineralogical, geochemical and isotopic data suggest that all the rock varieties originated as a result of fractionation of an initial mafic melt, with insignificant contamination and assimilation. Intensive mixing of the fractionating melts prior to, and during the course of the eruptions, is ubiquitous. The eruptions might have been triggered by repetitive injections of new mafic melt into the silicic chamber. Crystallization of the andesitic and rhyodacitic melts is estimated to have occurred at temperatures of 970–1010°C and 890–910°C, respectively, PH2O 1.5–2.0 kbar and fO2 close to the NNO buffer. According to the experimental data, such PH2O corresponds to 4.5%–5.5% of water in the melt, that is close to the content of water in the silicic hornblende-bearing magmas of the rear zone of the Kuril–Kamchatka arc. Hence, we suggest that the transition from pyroxene phenocryst associations of the frontal zone to the hornblende-bearing ones of the rear zone might be interpreted as reflecting higher temperatures of crystallization of the melts from the frontal zone rather than increasing water content in the rear zone magmas.