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Geochemical and geo-electrical study of mud pools at the Mutnovsky volcano (South Kamchatka, Russia): Behavior of elements, structures of feeding channels and a model of origin (2012)
Bessonova E.P., Bortnikova S.B., Gora M.P., Manstein Yu.A., Shevko A.Ya., Panin G.L., Manstein A.K. Geochemical and geo-electrical study of mud pools at the Mutnovsky volcano (South Kamchatka, Russia): Behavior of elements, structures of feeding channels and a model of origin // Applied Geochemistry. 2012. V. 27. № 9. P. 1829 - 1843. doi: 10.1016/j.apgeochem.2012.02.018.    Аннотация
This study presents data on the geochemical composition of boiling mud pools at the Mutnovsky volcano. The physicochemical characteristics of the pools and the concentrations of major, minor and trace elements in pool solutions vary widely. A comparison of the geochemical compositions of host rocks and solutions indicates that leaching from rocks is not the only source of chemicals in thermal solutions. Geophysical studies reveal the inner structure of thermal fields, which reflect the shapes of the underground reservoirs and feed channels. Using geophysical methods (electrical resistivity tomography and frequency domain investigations), it was shown that the vertical structure and complex geochemical zonation of the feed channels leads to a high contrast in the compositions of the mud solutions. These findings answer questions about the origin and composition of surface manifestations. To elucidate the mechanisms of solution formation, an attempt was made to describe the magmatic fluid evolution and the resulting mixing of waters by physical and mathematical models. The model illustrates fluid migration from a magma chamber to the surface. It is shown that the formation of brines corresponding to the mud pool composition is possible during secondary boiling.
Geochemical characterization of marker tephra layers from major Holocene eruptions, Kamchatka Peninsula, Russia (2011)
Kyle Philip R., Ponomareva Vera V., Rourke Schluep Rachelle Geochemical characterization of marker tephra layers from major Holocene eruptions, Kamchatka Peninsula, Russia // International Geology Review. 2011. V. 53. № 9. P. 1059-1097. doi:10.1080/00206810903442162.    Аннотация
Kamchatka Peninsula is one of the most active volcanic regions in the world. Many Holocene explosive eruptions have resulted in widespread dispersal of tephra-fall
deposits. The largest layers have been mapped and dated by the 14C method. The tephra provide valuable stratigraphic markers that constrain the age of many geological
events (e.g. volcanic eruptions, palaeotsunamis, faulting, and so on). This is the first systematic attempt to use electron microprobe (EMP) analyses of glass to characterize
individual tephra deposits in Kamchatka. Eighty-nine glass samples erupted from 11 volcanoes, representing 27 well-identified Holocene key-marker tephra layers, were analysed. The glass is rhyolitic in 21 tephra, dacitic in two, and multimodal in three.
Two tephra are mixed with glass compositions ranging from andesite/dacite to rhyolite. Tephra from the 11 eruptive centres are distinguished by their glass K2O,
CaO, and FeO contents. In some cases, individual tephra from volcanoes with multiple eruptions cannot be differentiated. Trace element compositions of 64 representative
bulk tephra samples erupted from 10 volcanoes were analysed by instrumental neutron activation analysis (INAA) as a pilot study to further refine the geochemical haracteristics; tephra from these volcanoes can be characterized using Cr and Th contents and La/Yb ratios.
Unidentified tephra collected at the islands of Karaginsky (3), Bering (11), and Attu (5) as well as Uka Bay (1) were correlated to known eruptions. Glass compositions and
trace element data from bulk tephra samples show that the Karaginsky Island and Uka Bay tephra were all erupted from the Shiveluch volcano. The 11 Bering Island tephra
are correlated to Kamchatka eruptions. Five tephra from Attu Island in the Aleutians are tentatively correlated with eruptions from the Avachinsky and Shiveluch volcanoes.
Geochemical evolution of Bolshaya Udina, Malaya Udina, and Gorny Zub volcanoes, Klyuchevskaya Group (Kamchatka) (2017)
Churikova Tatiana, Gordeychik Boris, Wörner Gerhard, Flerov Gleb, Hartmann Gerald, Simon Klaus Geochemical evolution of Bolshaya Udina, Malaya Udina, and Gorny Zub volcanoes, Klyuchevskaya Group (Kamchatka) // Geophysical Research Abstracts. 2017. V. 19. P. EGU2017-10691.    Аннотация
The Klyuchevskaya group of volcanoes (KGV) located in the northern part of Kamchatka has the highest magma production rate for any arc worldwide and several of its volcanoes have been studied in considerable detail [e.g. Kersting & Arculus, 1995; Pineau et al., 1999; Dorendorf et al., 2000; Ozerov, 2000; Churikova et al., 2001, 2012, 2015; Mironov et al., 2001; Portnyagin et al., 2007, 2015; Turner et al., 2007]. However, some volcanoes of the KGV including Late-Pleistocene volcanoes Bolshaya Udina, Malaya Udina, Ostraya Zimina, Ovalnaya Zimina, and Gorny Zub were studied only on a reconnaissance basis [Timerbaeva, 1967; Ermakov, 1977] and the modern geochemical studies have not been carried out at all. Among the volcanoes of KGV these volcanoes are closest to the arc trench and may hold information on geochemical zonation with respect to across arc source variations. We present the first major and trace element data on rocks from these volcanoes as well as on their basement. All rocks are medium-calc-alkaline basaltic andesites to dacites except few low-Mg basalts from Malaya Udina volcano. Phenocrysts are mainly olivine, pyroxene, plagioclase and magnetite, Hb-bearing andesites and dacites are rarely found only in subvolcanic intrusions at Bolshaya Udina volcano. Lavas are geochemically similar to the active Bezymianny volcano, however, individual variations for each volcano exist in both major and trace elements. Trace element geochemistry is typical of island arc volcanism. Compared to KGV lavas all studied rocks form very narrow trends in all major element diagrams, which almost do not overlap with the fields of other KGV volcanoes. The lavas are relatively poor in alkalis, TiO2, P2O5, FeO, Ni, Zr, and enriched in SiO2 compared to other KGV volcanics and show greater geochemical and petrological evidence of magmatic differentiation during shallow crustal processing. Basement samples of the Udinskoe plateau lavas to the east of Bolshaya Udina volcano have similar geochemical composition (trace element enriched high-K basaltic andesites and andesites) and similar eruption age of 274 ka [Calkins et al., 2004] as typical plateau lavas below the northern KGV. This research was supported by RFBR-DFG grant # 16-55-12040.
Geochemical features of the rocks of the Great Tolbachik Fissure Eruption 1975–1976 in relation to petrogenesis (1983)
Volynets O.N., Flerov G.B., Andreyev V.N., Popolitov E.I., Abramov V.A., Petrov L.L., Shcheka S.A., Selivanova G.I. Geochemical features of the rocks of the Great Tolbachik Fissure Eruption 1975–1976 in relation to petrogenesis // The Great Tolbachik Fissure Eruption. Cambridge: Cambridge University Press. 1983. P. 116-140.
Geochemical studies of volcanic rocks from the northern part of Kuril-Kamchatka arc: Tectonic and structural constraints on the origin and evolution of arc magma (2015)
Bergal-Kuvikas Olga Geochemical studies of volcanic rocks from the northern part of Kuril-Kamchatka arc: Tectonic and structural constraints on the origin and evolution of arc magma. 2015. Дисс. канд. геол.-мин. наук.
Geochemistry and solute fluxes of volcano-hydrothermal systems of Shiashkotan, Kuril Islands (2015)
Kalacheva Elena, Taran Yuri, Kotenko Tatiana Geochemistry and solute fluxes of volcano-hydrothermal systems of Shiashkotan, Kuril Islands // Journal of Volcanology and Geothermal Research. 2015. V. 296. P. 40-54. doi:10.1016/j.jvolgeores.2015.03.010.    Аннотация
Shiashkotan Island belongs to the Northern Kuril island arc and consists of two joined volcanoes, Sinarka and
Kuntomintar, with about 18 km of distance between the summits. Both volcanoes are active, with historic
eruptions, and both emit fumarolic gases. Sinarka volcano is degassing through the extrusive domewith inaccessible
strong and hot (N400 °C) fumaroles. A large fumarolic field of the Kuntomintar volcano situated in a wide
eroded caldera-like crater hosts many fumarolic vents with temperatures from boiling point to 480 °C. Both
volcanoes are characterized by intense hydrothermal activity discharging acid SO4-Cl waters, which are drained
to the Sea of Okhotsk by streams. At least 4 groups of near-neutral Na-Mg-Ca-Cl-SO4 springs with temperatures in
the range of 50–80 °C are located at the sea level,within tide zones and discharge slightly altered diluted seawater.
Volcanic gas of Kuntomintar as well as all types of hydrothermal manifestations of both volcanoes were collected
and analyzed for major and trace elements and water isotopes. Volcanic gases are typical for arc volcanoes
with 3He/4He corrected for air contamination up to 6.4 Ra (Ra=1.4 ×10−6, the air ratio) and δ13C (CO2) within
−10‰to−8‰VPDB. Using a saturation indices approach it is shown that acid volcanic waters are formed at a
shallow level, whereas waters of the coastal springs are partially equilibrated with rocks at ~180 °C. Trace
element distribution and concentrations and the total REE depend on the water type, acidity and Al+Fe concentration.
The REE pattern for acidic waters is unusual but similar to that found in some acidic crater lake waters.
The total hydrothermal discharge of Cl and S from the island associated with volcanic activity is estimated at
ca. 20 t/d and 40 t/d, respectively, based on the measurements of flow rates of the draining streams and
their chemistry. The chemical erosion of the island by surface and thermal waters is estimated at 27 and 140
ton/km2/year, respectively, which is 2–3 times lower than chemical erosion of tropical volcanic islands.
Geochemistry of high-Mg andesitic rocks in NE Kamchatka (2016)
Nishizawa T., Nakamura Hitomi, Churikova T., Gordeychik B., Ishizuka Osamu, Haraguchi Satoru, Miyazaki Takashi, Vaglarov Bogdan S., Ueki K., Toyama C., Iwamori Hikaru Geochemistry of high-Mg andesitic rocks in NE Kamchatka // V.M. Goldschmidt Conference, Yokohama, Japan, 26 June - 1 July 2016. Program and Abstracts. 2016. P. 2295    Аннотация
The northeast Kamchatka Peninsula is characterized by unique tectonic regimes: (i) the triple junction ~30 km off the east coast [1], (ii) subduction of the Emperor Seamount Chain [2], and (iii) possible asthenospheric flow between the mantle wedge and the sub-slab mantle via the edge of subducted Pacific slab [3]. Within this area, a monogenetic volcanic group occurs along the east coast, including high-Mg andesitic rocks and relatively primitive basalts (East Cones, EC [4]). We have conducted geochemical studies of the EC lavas, with bulk rock major and trace elements, Sr-Nd isotopic compositions, and K-Ar and Ar-Ar ages, based on which a possible contribution of subducted seamounts and its relation to the tectonic setting are discussed.
The elemental and isotopic compositions indicate that the lavas from individual cones have distinct mantle sources with different amounts and/or compositions of slab-derived fluids. Based on mass balance, water content and melting phase relations, we estimate the melting P-T conditions to be ~1200 ℃ at 1.5 GPa, while the slab surface temperature is 620 – 730 ℃ (at 50-80 km depth). The Sr-Nd isotopic compositions is close to Late Cretaceous Emperor Seamount Chain, especially Detroit [5]. The K-Ar and Ar-Ar ages of the Middle to Late Pleistocene are consistent with the present tectonic setting after 2 Ma [6].
These results suggest that the EC lavas including high-Mg andesite and basalt were generated by mantle flux-melting induced by dehydration of a subducted seamount inheriting a local thermal anomaly [7, 8]
Geochemistry of magmatic gases from Kudryavy volcano, Iturup, Kuril Islands (1995)
Taran Yu.A., Hedenquist J.W., Korzhinsky M.A., Tkachenko S.I., Shmulovich K.I. Geochemistry of magmatic gases from Kudryavy volcano, Iturup, Kuril Islands // Geochimica et Cosmochimica Acta. 1995. V. 59. № 9. P. 1749 - 1761. doi: 10.1016/0016-7037(95)00079-F.    Аннотация
Volcanic vapors were collected during 1990–1993 from the summit crater of Kudryavy, a basaltic andesite volcano on Iturup island in the Kuril arc. The highest temperature (700–940°C) fumarolic discharges are water rich (94–98 mole% H2O and have δD values of −20 to −12%o. The chemical and water isotope compositions of the vapors (temperature of thirteen samples, 940 to 130°C) show a simple trend of mixing between hot magmatic fluid and meteoric water; the magmatic parent vapor is similar in composition to altered seawater. The origin of this endmember is not known; it may be connate seawater, or possibly caused by the shallow incorporation of seawater into the magmatic-hydrothermal system. Samples of condensed vapor from 535 to 940°C fumaroles have major element trends indicating contamination by wall-rock particles. However, the enrichment factors (relative to the host rock) of many of the trace elements indicate another source; these elements likely derive from a degassing magma. The strongest temperature dependence is for Re, Mo, W, Cu, and Co; highly volatile elements such as Cl, I, F, Bi, Cd, B, and Br show little temperature dependence. The Re abundance in high-temperature condensates is 2–10 ppb, sufficient to form the pure Re sulfide recently discovered in sublimates of Kudryavy. Anomalously high I concentrations (1–12 ppm) may be caused by magma-marine sediment interaction, as Br/I ratios are similar to those in marine sediments.

The high-temperature (>700°C) fumaroles have a relatively constant composition (∼2 mol% each C and S species, with SO2/H2S ratio of about 3:1, and 0.5 mol% HCl); as temperature decreases, both St and CI are depleted, most likely due to formation of native S and HCl absorption by condensed liquid, in addition to the dilution by meteoric water. Thermochemical evaluation of the high-temperature gas compositions indicates they are close to equilibrium mixtures, apart from minor loss of H2O and oxidation of CO and H2 during sampling. Calculation to an assumed equilibrium state indicates temperatures from 705 to 987°C. At high temperature (≈900°C), the redox states are close to the overlap of mineral (quartz-fayalite-magnetite and nickel-nickel oxide) and gas (H2OH2SO2H2S) buffer curves, due to heterogeneous reaction between the melt and gas species. At lower temperatures (<800°C), the trend of the redox state is similar to the gas buffer curve, probably caused by homogeneous reaction among gas species in a closed system during vapor ascent.
Geochemistry of the late Holocene rocks from the Tolbachik volcanic field, Kamchatka: Quantitative modelling of subduction-related open magmatic systems (2015)
Portnyagin Maxim, Duggen Svend, Hauff Folkmar, Mironov Nikita, Bindeman Ilya, Thirlwall Matthew, Hoernle Kaj Geochemistry of the late Holocene rocks from the Tolbachik volcanic field, Kamchatka: Quantitative modelling of subduction-related open magmatic systems // Journal of Volcanology and Geothermal Research. 2015. V. 307. P. 133 - 155. doi: 10.1016/j.jvolgeores.2015.08.015.    Аннотация
Abstract We present new major and trace element, high-precision Sr–Nd–Pb (double spike), and O-isotope data for the whole range of rocks from the Holocene Tolbachik volcanic field in the Central Kamchatka Depression (CKD). The Tolbachik rocks range from high-Mg basalts to low-Mg basaltic trachyandesites. The rocks considered in this paper represent mostly Late Holocene eruptions (using tephrochronological dating), including historic ones in 1941, 1975–1976 and 2012–2013. Major compositional features of the Tolbachik volcanic rocks include the prolonged predominance of one erupted magma type, close association of middle-K primitive and high-K evolved rocks, large variations in incompatible element abundances and ratios but narrow range in isotopic composition. We quantify the conditions of the Tolbachik magma origin and evolution and revise previously proposed models. We conclude that all Tolbachik rocks are genetically related by crystal fractionation of medium-K primary magmas with only a small range in trace element and isotope composition. The primary Tolbachik magmas contain ~ 14 wt. of MgO and ~ 4 wt. of {H2O} and originated by partial melting (~ 6) of moderately depleted mantle peridotite with Indian-MORB-type isotopic composition at temperature of ~ 1250 °C and pressure of ~ 2 GPa. The melting of the mantle wedge was triggered by slab-derived hydrous melts formed at ~ 2.8 {GPa} and ~ 725 °C from a mixture of sediments and MORB- and Meiji-type altered oceanic crust. The primary magmas experienced a complex open-system evolution termed Recharge-Evacuation-Fractional Crystallization (REFC). First the original primary magmas underwent open-system crystal fractionation combined with periodic recharge of the magma chamber with more primitive magma, followed by mixing of both magma types, further fractionation and finally eruption. Evolved high-K basalts, which predominate in the Tolbachik field, and basaltic trachyandesites erupted in 2012–2013 approach steady-state {REFC} liquid compositions at different eruption or replenishment rates. Intermediate rocks, including high-K, high-Mg basalts, are formed by mixing of the evolved and primitive magmas. Evolution of Tolbachik magmas is associated with large fractionation between incompatible trace elements (e.g., Rb/Ba, La/Nb, Ba/Th) and is strongly controlled by the relative difference in partitioning between crystal and liquid phases. The Tolbachik volcanic field shows that open-system scenarios provide more plausible and precise descriptions of long-lived arc magmatic systems than simpler, but often geologically unrealistic, closed-system models.
Geochronology of the greatest Holocene explosive eruptions in Kamchatka and their imprint on the Greenland glacier shield (1997)
Braitseva O.A., Sulerzhitskii L.D., Ponomareva V.V., Melekestsev I.V. Geochronology of the greatest Holocene explosive eruptions in Kamchatka and their imprint on the Greenland glacier shield // Transactions (Doklady) of the Russian Academy of Sciences. Earth science section. 1997. V. 352. № 1. P. 138-140.
http://repo.kscnet.ru/907/ [связанный ресурс]
Geologic and petrologic study of the Central Kurile Islands, VI - Dzigoku Volcano, Urup Island (1937)
Nemoto T. Geologic and petrologic study of the Central Kurile Islands, VI - Dzigoku Volcano, Urup Island // Bulletin of the Volcanological Society of Japan. 1937. V. 3. № 2.
Geological Effect of 2005 Eruptions of Sheveluch Volcano, Kamchatka, Russia (2006)
Girina O.A., Gorbach N.V., Nuzhdaev A.A. Geological Effect of 2005 Eruptions of Sheveluch Volcano, Kamchatka, Russia // Abstracts. 5rd Biennial Workshop on Subduction Processes emphasizing the Japan-Kurile-Kamchatka-Aleutian Arcs (JKASP-5). 2006. P. 43
Geology, petrology and geochemistry of the Tolbachik volcanic massif, Kamchatka, Russia (2015)
Churikova T., Gordeychik B., Iwamori H., Nakamura H., Ishizuka O., Nishizawa T., Haraguchi S., Yasukawa K., Miyazaki T., Vaglarov B., Ueki K., Toyama C., Chang Q., Kimura J.I. Geology, petrology and geochemistry of the Tolbachik volcanic massif, Kamchatka, Russia // 26th IUGG General Assembly 2015. June 22 - July 2, 2015, Prague, Czech Republic. 2015. P. VS28p-487.    Аннотация
Data on the geology, petrography, and geochemistry of previously geochemically unstudied Middle-Late-Pleistocene rocks from Tolbachik volcanic massif (Central Kamchatka Depression, CKD) are presented. Two volcanic series – middle-K and high-K were erupted. The geochemical history of the massif was started earlier 86 ka (K-Ar dating) with the formation of the Tolbachik pedestal presented by middle-K series. During stratovolcanoes formation both series occur and the role of high-K melts was increasing with time. In Holocene high-K rocks are dominated but some cinder cone lavas are presented by middle-K high-Mg melts which suggest that both volcanic series are still exists. The computer modeling show that both series can be explained by the process of crystal fractionation at different water content from nearly or the same mantle source similar to high-Mg basalts of 1975 Northern Breakthrough. Middle-K rocks could crystallize at water-rich conditions (more than 2% of H2O) while the high-K rock could crystallize at dry conditions at the same pressure. However the existence of different mantle sources and possible magma mixing cannot be excluded. Our data show that fractional crystallization at different P-T-H2O-fO2 conditions can be one of the main processes responsible for rock variations at CKD. Sr-Nd-Pb isotopes suggest 2-4% of crustal assimilation to the magma chamber during pedestal and stratovolcanoes formation while lava-cinder cones are not show evidences of crustal assimilation. Major and trace element data coupled with K-Ar dating provide strong evidence that Povorotnaya mount located in 8 km NE of Plosky Tolbachik is the old block of the Tolbachik massif pedestal and for the moment the oldest known object (306 ka by K-Ar dating) in Klyuchevskaya group.

Geology, petrology and geochemistry of the Tolbachik volcanic massif, Kamchatka, Russia. Available from: https://www.researchgate.net/publication/282656425_Geology_petrology_and_geochemistry_of_the_Tolbachik_volcanic_massif_Kamchatka_Russia [accessed Jun 19, 2017].
Geomagnetic and Bathymetric Study of the Okhotsk Sea - (1) (1967)
Yasui M., Hashimoto Y., Ueda S. Geomagnetic and Bathymetric Study of the Okhotsk Sea - (1) // Oceanographical Magazine. 1967. V. 19. № 1. P. 73-85.
Gigantic Eruption of the Volcano Bezymianny (1959)
Gorshkov G.S. Gigantic Eruption of the Volcano Bezymianny // Bulletin Volcanologique. 1959. V. 20. № 2. P. 77-109.
Gigantic directed blast at Shiveluch volcano (Kamchatka) (1970)
Gorshkov G.S., Dubik Y.M. Gigantic directed blast at Shiveluch volcano (Kamchatka) // Bulletin Volcanologique. 1970. V. 34. P. 261-288.
Granulometric composition of pyroclastics from andesite volcanoes of Kamchatka (1995)
Girina O.A. Granulometric composition of pyroclastics from andesite volcanoes of Kamchatka // 5 Zonenshain conference on plate tectonics. Moscow. 1995. P. 11
Great explosive eruptions on Kamchatka during the last 10,000 years: Self-similar irregularity of the output of volcanic products (2003)
Gusev A.A., Ponomareva V.V., Braitseva O.A., Melekestsev I.V., Sulerzhitsky L.D. Great explosive eruptions on Kamchatka during the last 10,000 years: Self-similar irregularity of the output of volcanic products // Journal of Geophysical Research. 2003. V. 108. № B2. doi:10.1029/2001JB000312.    Аннотация
Temporal irregularity of the output of volcanic material is studied for the sequence of large (V ≥ 0.5 km3, N = 29) explosive eruptions on Kamchatka during the last 10,000 years. Informally, volcanic productivity looks episodic, and dates of eruptions cluster. To investigate the probable self-similar clustering behavior of eruption times, we determine correlation dimension Dc. For intervals between events 800 and 10,000 years, Dc ≈ 1 (no self-similar clustering). However, for shorter delays, Dc = 0.71, and the significance level for the hypothesis Dc < 1 is 2.5%. For the temporal structure of the output of volcanic products (i.e., for the sequence of variable-weight points), a self-similar “episodic” behavior holds over the entire range of delays 100–10,000 years, with Dc = 0.67 (Dc < 1 at 3.4% significance). This behavior is produced partly by the mentioned common clustering of event dates, and partly by another specific property of the event sequence, that we call “order clustering”. This kind of clustering is a property of a time-ordered list of eruptions, and is manifested as the tendency of the largest eruptions (as opposed to smaller ones) to be close neighbors in this list. Another statistical technique, of “rescaled range” (R/S), confirms these results. Similar but weaker-expressed behavior was also found for two other data sets: historical Kamchatka eruptions and acid layers in Greenland ice column. The episodic multiscaled mode of the output of volcanic material may be a characteristic property of a sequence of eruptions in an island arc, with important consequences for climate forcing by volcanic aerosol, and volcanic hazard.
 H
H2O and CO2 in parental magmas of Kliuchevskoi volcano inferred from study of melt and fluid inclusions in olivine (2011)
Mironov N.L., Portnyagin M.V. H2O and CO2 in parental magmas of Kliuchevskoi volcano inferred from study of melt and fluid inclusions in olivine // Russian Geology and Geophysics. 2011. V. 52. № 11. P. 1353 - 1367. doi: 10.1016/j.rgg.2011.10.007.    Аннотация
This paper reports new FTIR data on the H2O and CO2 concentrations in glasses of 26 naturally quenched and experimentally partially homogenized melt inclusions in olivine (Fo85–91) phenocrysts from rocks of the Kliuchevskoi volcano. Measured H2O concentrations in the inclusions range from 0.02 to 4 wt.%. The wide variations in the H2O content of the inclusions, which do not correlate with the host olivine composition and contents of major elements in the melts, are explained by the H2O escape from inclusions via diffusion through the host olivine during the magma eruption and the following cooling. The largest H2O loss is characteristic of inclusions from lava samples which cooled slowly after eruption. The minimal H2O loss is observed for inclusions from rapidly quenched pyroclastic rocks. Parental magmas of the Kliuchevskoi volcano are estimated to contain 3.5 wt.% H2O. The new data imply a 40 °C lower mantle temperatures than that estimated earlier for the Kliuchevskoi primary melts. The concentrations of CO2 in glasses range from <0.01 to 0.13 wt.% and do not correlate with the type of studied inclusions and their composition. The calculated pressures of melt equilibria with H2O–CO2 fluid inside the inclusions are lower than 270 MPa. They are significantly lower than a pressure of 500 MPa calculated from the density (~0.8 g/cm3) of cogenetic fluid inclusions in high-Fo olivine. The significant pressure drop inside the melt inclusions after their trapping in olivine might be due to the H2O loss and redistribution of CO2 from melt to daughter fluid phase. Compared with melt inclusions, cogenetic fluid inclusions provide independent information about the crystallization pressures of olivine and initial CO2 content in the Kliuchevskoi magma, which were estimated to be at least 500 MPa and 0.35 wt.%, respectively. The maximum CO2 concentrations in the primary Kliuchevskoi melts are estimated at 0.8–0.9 wt.%. The decompression crystallization of the Kliuchevskoi magmas starts at depths of 30–40 km and proceeds with a continuous decrease in CO2 content and an increase (up to 6–7 wt.%) and then a decrease (at <300 MPa) in H2O content in melts, which explains the origin of the whole spectrum of rocks and melt inclusions of the Kliuchevskoi volcano.
Highly silicic glasses in peridotite xenoliths from Avacha volcano, Kamchatka arc; implications for melting and metasomatism within the sub-arc mantle (2009)
Ishimaru Satoko, Arai Shoji Highly silicic glasses in peridotite xenoliths from Avacha volcano, Kamchatka arc; implications for melting and metasomatism within the sub-arc mantle // Lithos. 2009. V. 107. № 1–2. P. 93 - 106. doi: 10.1016/j.lithos.2008.07.005.    Аннотация
Silicate glasses in peridotite xenoliths from Avacha volcano have high SiO2 (up to 72 wt.) and highly SiO2-oversaturated characteristics; normative quartz content is up to 50 wt.. The glasses represent secondary melts solidified after interaction with mantle peridotite, i.e. crystallization of secondary orthopyroxene at the expense of olivine. We identified two kinds of silicate glasses in Avacha peridotites; one is higher in K2O and enriched in Rb, Ba, U, and Pb than the other. The glasses show basically similar chemical characteristics to the host basaltic andesite to andesite of the Avacha volcano. These chemical characteristics are inherited from slab-derived fluids/melts, which metasomatize the mantle wedge and induce partial melting. The differences of chemical features among the Avacha glasses are attributed to chemical difference of the slab-derived fluids/melts, possibly due to the difference of sediments/basalt ratio of the relevant slab. The low-degree partial melt of peridotite assisted by these fluids/melts, is primarily SiO2-oversaturated, and can conduct silicate metasomatism, evolving through interaction with surrounding mantle peridotite, i.e. formation of orthopyroxene at the expense of olivine. Highly silicic glasses, also reported from peridotite xenoliths from oceanic hotspots and continental rift zones, mostly result from assimilation of orthopyroxene by SiO2-undersaturated melts, which crystallize clinopyroxene and olivine. The glasses also show similar trace-element patterns to their host alkali basaltic magmas, as in the case of arc glasses/calc-alkali magmas. If the glasses in peridotite xenoliths are of silicate metasomatism origin, they are similar in chemistry to host magmas. Reaction between carbonatite melts and peridotites shows the same petrographical feature as that of SiO2-undersaturated silicate melts with peridotites. The glasses originated from carbonatite metasomatism, however, exhibit clearly different trace-element patterns from their host alkali basaltic magmas.





 

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