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Записей: 2521
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Native gold from volcanic gases at Tolbachik 1975–76 and 2012–13 Fissure Eruptions, Kamchatka (2015)
Chaplygin Ilya, Yudovskaya Marina, Vergasova Lidiya, Mokhov Andrey Native gold from volcanic gases at Tolbachik 1975–76 and 2012–13 Fissure Eruptions, Kamchatka // Journal of Volcanology and Geothermal Research. 2015. Vol. 307. P. 200 - 209. doi: 10.1016/j.jvolgeores.2015.08.018.    Аннотация
Abstract Aggregates and euhedral crystals of native gold were found in sublimates formed during New Tolbachik Fissure Eruption in 2012–2013 (NTFE). Gold-bearing sublimate samples were taken from a red-hot (690 °C) degassing fracture in the roof of an active lava tunnel 1.5 km from active Naboko cinder cone in May 2013. The gas condensate collected at 690 °C in this site contains 16 ppb Au, 190 ppb Ag and 1180 ppm Cu compared to 3 ppb Au, 39 ppb Ag and 9.7 ppm Cu in the condensate of pristine magmatic gas sampled at 1030 °C. The 690 °C volcanic gas is most likely a mix of magmatic gas and local snow buried under the lava flows as indicated by oxygen and hydrogen isotope compositions of the condensate. The lower-temperature gas enrichment in gold, copper and chlorine is resulted from evaporation of the 690 °C condensate during forced gas pumping at sampling. Native gold was also found in fumarolic encrustations collected from caverns in basalt lava flows with temperature up to 600 °C in June 2014, in a year after eruption finished. The native gold precipitation in newly formed Cu-rich sublimates together with the well known gold occurrences in cinder cones of 1975–1976 Large Tolbachik Fissure Eruption manifest a transport capability of oxidized volcanic gas.
New data on Holocene monogenetic volcanism of the Northern Kamchatka: ages and space distribution (2004)
Pevzner M.M. New data on Holocene monogenetic volcanism of the Northern Kamchatka: ages and space distribution // Abstracts. 4rd Biennial Workshop on Subduction Processes emphasizing the Kurile-Kamchatka-Aleutian Arcs (JKASP-4). Linkages among tectonics, seismicity, magma genesis, and eruption in volcanic arcs. August 21-27, 2004. Petropavlovsk-Kamchatsky: Institute of Volcanology and Seismology FEB RAS. 2004. С. 72-76.
New discovered Late Miocene Verkhneavachinsksya caldera on Eastern Kamchatka (2016)
Bergal-Kuvikas Olga, Leonov V., Rogozin A., Bindeman Ilya, Klyupitsky E. New discovered Late Miocene Verkhneavachinsksya caldera on Eastern Kamchatka // 9th Biennial Workshop on Japan-Kamchatka-Alaska Subduction Processes (JKASP-2016). 2016, Fairbanks, Alaska University. 2016.
Numerical modeling of a rockslide avalanche at Koryakskiy volcano, Kamchatka (1996)
Adushkin V.V., Zykov Yu.N., Ivanov B.A. Numerical modeling of a rockslide avalanche at Koryakskiy volcano, Kamchatka // Volcanology and Seismology. 1996. Vol. 17. № 6. P. 705-717.    Аннотация
A numerical model is proposed for the mechanism of a rockslide avalanche on the slope of Koryakskiy volcano caused by the emplacement of sheeted intrusive bodies. The model of non-stationary geomechanical processes with abnormally low internal friction is used to calculate an avalanchelike movement during a potential collapse of the cone.
Numerical simulation of a tsunami event during the 1996 volcanic eruption in Karymskoye lake, Kamchatka, Russia (2010)
Torsvik T., Paris R., Didenkulova I., Pelinovsky E., Belousov A., Belousova M. Numerical simulation of a tsunami event during the 1996 volcanic eruption in Karymskoye lake, Kamchatka, Russia // Natural Hazards and Earth System Science. 2010. Vol. 10. № 11. P. 2359-2369. doi:10.5194/nhess-10-2359-2010.
Numerical simulation of plagioclase rim growth during magma ascent at Bezymianny Volcano, Kamchatka (2013)
Gorokhova N.V., Melnik O.E., Plechov P.Yu., Shcherbakov V.D. Numerical simulation of plagioclase rim growth during magma ascent at Bezymianny Volcano, Kamchatka // Journal of Volcanology and Geothermal Research. 2013. Vol. 263. P. 172 - 181. doi: 10.1016/j.jvolgeores.2013.03.020.    Аннотация
Slow CaAl-NaSi interdiffusion in plagioclase crystals preserves chemical zoning of plagioclase in detail, which, along with strong dependence of anorthite content in plagioclase on melt composition, pressure, and temperature, make this mineral an important source of information on magma processes. A numerical model of zoned crystal growth is developed in the paper. The model is based on equations of multicomponent diffusion with diagonal cross-component diffusion terms and accounts for mass conservation on the melt–crystal interface and growth rate controlled by undercooling. The model is applied to the data of plagioclase rim zoning from several recent Bezymianny Volcano (Kamchatka) eruptions. We show that an equilibrium growth model cannot explain crystallization of naturally observed plagioclase during magma ascent. The developed non-equilibrium model reproduced natural plagioclase zoning and allowed magma ascent rates to be constrained. Matching of natural and simulated zoning suggests ascent from 100 to 50 MPa during 15–20 days. Magma ascent rate from 50 MPa to the surface varies from eruption to eruption: plagioclase zoning from the December 2006 eruption suggests ascent to the surface in less than 1 day, whereas plagioclase zoning from March 2000 and May 2007 eruptions are better explained by magma ascent over periods of more than 30 days). Based on comparison of diffusion coefficients for individual elements a mechanism of atomic diffusion during plagioclase crystallization is proposed.
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Observations on lava, snowpack and their interactions during the 2012–13 Tolbachik eruption, Klyuchevskoy Group, Kamchatka, Russia (2015)
Edwards Benjamin R., Belousov Alexander, Belousova Marina, Melnikov Dmitry Observations on lava, snowpack and their interactions during the 2012–13 Tolbachik eruption, Klyuchevskoy Group, Kamchatka, Russia // Journal of Volcanology and Geothermal Research. 2015. Vol. 307. P. 107 - 119. doi: 10.1016/j.jvolgeores.2015.08.010.    Аннотация
Abstract Observations made during January and April 2013 show that interactions between lava flows and snowpack during the 2012–13 Tolbachik fissure eruption in Kamchatka, Russia, were controlled by different styles of emplacement and flow velocities. `A`a lava flows and sheet lava flows generally moved on top of the snowpack with few immediate signs of interaction besides localized steaming. However, lavas melted through underlying snowpack 1–4 m thick within 12 to 24 h, and melt water flowed episodically from the beneath flows. Pahoehoe lava lobes had lower velocities and locally moved beneath/within the snowpack; even there the snow melting was limited. Snowpack responses were physical, including compressional buckling and doming, and thermal, including partial and complete melting. Maximum lava temperatures were up to 1355 K (1082 °C; type K thermal probes), and maximum measured meltwater temperatures were 335 K (62.7 °C). Theoretical estimates for rates of rapid (e.g., radiative) and slower (conductive) snowmelt are consistent with field observations showing that lava advance was fast enough for `a`a and sheet flows to move on top of the snowpack. At least two styles of physical interactions between lava flows and snowpack observed at Tolbachik have not been previously reported: migration of lava flows beneath the snowpack, and localized phreatomagmatic explosions caused by snowpack failure beneath lava. The distinctive morphologies of sub-snowpack lava flows have a high preservation potential and can be used to document snowpack emplacement during eruptions.
Oil of the volcano Uzon caldera, Kamchatka (1998)
Bazhenova O.K., Arefiev O.A., Frolov E.B. Oil of the volcano Uzon caldera, Kamchatka // Organic Geochemistry. 1998. Vol. 29. № 1–3. P. 421 - 428. doi: 10.1016/S0146-6380(98)00129-6.    Аннотация
There are reported gas chromatography, gas chromatography/mass spectrometry and carbon isotopic data on the oils sampled in caldera of the Uzon volcano (East Kamchatka). The Uzon volcano is located in the west of the eastern Kamchatka basin which is made up of thick Paleogene-Neogene sedimentary rocks. Its caldera is made up of lacustrine volcanogenic-sedimentary formations of Pleistocene age (38–70 thousand years), lying on dense basalts. Two samples studied were heavy oils (0.915 g/ml) and contained 2 sulfur; 2.5 paraffin, 9.3 waxes; 1.4 wt olefinic hydrocarbons. Their gas chromatograms show a mono-modal distribution for n-alkanes with a maximum at C18. Pristane/Phytane concentration ratios were measured to be 0.48–0.52. Olefinic hydrocarbons were interpreted to be of hydrothermal origin. Sterane and triterpane biomarkers indicated a low maturation degree and a lacustrine orgin of the initial organic matter. The Uzon oil was found to be isotopically heavy with a δ13C value of −21‰14C isotope was detected, which indicates that recent plant organic matter was significantly involved in oil generation process.
Olivine zoning in high-Mg basalts of the Shiveluch volcano (Kamchatka) (2017)
Gordeychik Boris, Churikova Tatiana, Kronz Andreas, Simakin Alexander, Wörner Gerhard Olivine zoning in high-Mg basalts of the Shiveluch volcano (Kamchatka) // Geophysical Research Abstracts. 2017. Vol. 19. P. EGU2017-10473.    Аннотация
Shiveluch volcano located in northern Kamchatka erupted mainly high-Mg andesites during Holocene times. However, tephrochronologists found two Holocene tephra layers that are unusual for this volcano: a high-Mg middle-K basalts with an age of 7600 yr BP and high-Mg high-K basalt with an age of 3600 yr BP [Volynets et al, 1997]. The proximal outcrops for these two tephra deposits were discovered just recently [Churikova et al., 2010; Gorbach & Portnyagin, 2011]. Our study of olivines from the high-Mg basalts documents unusual Mg-Fe zonation [Gordeychik et al., 2016]: Inner cores of olivines from both eruptions show Fo87-92, falling to the rim to Fo75-85. In the outer cores of both basalt tephra, forsterite decreases linearly abruptly changing to a steeper gradient towards the rim. Electron microprobe element maps reveal the complex and highly unusual zoning features of these olivines.
The inner cores of the olivines of 7600 yr BP tephra have bell-shaped distributions for forsterite and nickel. The maximum forsterite in their core can be up to Fo92, decreasing outward to the outer core to Fo86. At the same time, the trace elements in the inner core remain constant. Such element distribution is consistent with diffusion of Fe, Mg, and Ni in the initially uniform high Mg cores after the phenocrysts were changed to non-equilibrium in a less mafic melt. The shape of the inner cores suggests partial dissolution after magma mixing. The interfaces between the inner and outer cores are marked by abundant melt/fluid inclusions. The inner cores were overgrown by olivine with Fo90 when the crystals moved to the high-Mg melt. As result some olivine grains have the maximum forsterite values in the outer core. The specific feature of the olivine outer cores from basalt of the 7600 yr BP tephra eruption are concentric zones with higher values of Ca, Cr, Al, P. One of the crystals has five distinct growth zones with high Cr concentrations. The width of these zones can be only a few microns and thus such zones are often missed in typical quantitative point measurements in microprobe profiles.
Inner cores of olivines from the 3600 yr BP tephra are uniform in forsterite and nickel. However, Al and Ca element distribution maps show in inner cores higher concentrations with rather smooth contours. This suggests that initially the olivines were formed from high-Al and high-Ca melt, then were dissolved and the overgrowth zonation has been smoothed out due to faster Mg-Fe diffusion. Only Ca and Al with low diffusivity were conserved. The concentric zones with higher element concentrations are not so well expressed in olivines from the 3600 yr BP tephra, but some distinct growth zones are also shown in Ca, Cr, and P.
Information extraction and decoding of the elemental maps allow seeing highly complex growth-dissolutiondiffusion history of magma mixing processes prior to eruption. This research was supported by RFBR-DFG grant # 16-55-12040.
Om Kamtjatkas vulkaner og Gejserdalen (2012)
Girina O.A. Om Kamtjatkas vulkaner og Gejserdalen // Geografisk orientering. 2012. № 2. P. 470-475.