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Records: 2604
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
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]
Nishizawa Tatsuji, Nakamura Hitomi, Churikova T., Gordeychik B., Ishizuka Osamu, Iwamori Hikaru Genesis of Quaternary volcanism of high-Mg andesitic rocks in the northeast Kamchatka Peninsula // Japan Geoscience Union Meeting. 22-26 May 2016, Makuhari, Messe. 2016. P. SVC48-02.
島弧火成活動はサブダクションファクトリーの産物で, それは沈み込んだスラブ(物質のインプット)-マン
トルウェッジ(加工工場)間の熱的・物質的相互作用を含む. 島弧マグマの組成は, その物質インプットと相
互作用について非常に貴重な情報をもたらす. カムチャツカ半島北東部はそのような相互作用と関係性を調べ
るうえで理想的な場所である, それは次のような特徴を有する為だ(1)天皇海山列の沈み込み(Davaille and
Lees, 2004)(2)沈み込んだスラブ, マントルウェッジと太平洋スラブエッジにかけてのサブスラブマントル
との物質的・熱的相互作用の可能性(Portnyagin and Manea, 2008). この地域の東海岸沿いに, 高-Mg安山岩
と比較的初生的な玄武岩を産出する単成火山群が確認されている(East Cones, EC(Fedorenko, 1969)).
我々はこのEC溶岩について全岩主要-微量元素組成分析とK-Ar, Ar-Ar年代測定を含む地球化学的研究を行い,
EC溶岩の組成は, 火山ごとに独立したソースに由来しており, そのソースの違いはスラブ起源流体の量および
またはその組成の違いによることを示す. マスバランス, 含水量, 相関係に基づき, 我々は溶融温度-圧力条
件を推定した, 溶融温度・圧力~1200℃, 1.5 GPa, スラブ表面温度 620-730℃(深度50-80 km). カム
チャツカ南部に沈み込むスラブ表面温度と比較すると, EC直下のスラブ表面温度は高く, これは天皇海山列に
えられる(Davaille and Lees, 2004; Manea and Manea, 2007).
K-Ar, Ar-Ar年代測定値は中期更新世で, これはテフラ層序学からの推定年代と一致し(Uspensky and
Shapiro, 1984), 2Ma以降現在のテクトニックセッティングに変化したこととも矛盾しない(Lander and
Shapiro, 2007). 最もSiO2含有量が高い高Mg安山岩は最古の年代を示し(0.73 ±0.06 Ma), これはECのみな
らずカムチャツカ北東部においても最も古いとみられる(e.g., Churikova et al., 2015, IAVCEI). 一方他
のECはより若い年代を示す(~0.18 ±0.07 Ma). これらの結果は以下のことを示す: 高Mg安山岩, 玄武岩を
ラックス溶融によりもたらされた(西澤他, 2014, JpGU; 2015, JpGU).
Ovsyannikov A.A., Khrenov A.P., Muravyev Y.D. Recent Fumarole Activity on Dal'nii Ploskii Volcano // Volcanology and Seismology. 1989. Vol. 7. № 5. P. 815-817.
Ozerov A. Gas-hydrodynamic model of basalt explosions (based on experimental data) // 33rd International Geological Congress. Oslo, Norway. Abstracts. 2008.
Ozerov A. Types and Mechanisms of Basaltic Explosions: Environmental Observations and Experimental Data // IAVCEI 2008 - General Assembly, Reykjavik, Iceland. Abstracts. 2008. P. 7
Ozerov A. Yu. Experimental modeling of the explosion mechanism of basaltic magmas // Petrology. 2009. Vol. 17. № 7. P. 653-668. doi:10.1134/S0869591109070029.
Ozerov A., Ispolatov I., Lees J. Modeling Strombolian eruptions of Karymsky volcano, Kamchatka, Russia // Journal of Volcanology and Geothermal Research. 2003. Vol. 122. № 3–4. P. 265 - 280. doi: 10.1016/S0377-0273(02)00506-1.
A model is proposed to explain temporal patterns of activity in a class of periodically exploding Strombolian-type andesite volcanoes. These patterns include major events (explosions) which occur every 3–30 min and subsequent tremor with a typical period of 1 s. This two-periodic activity is thought to be caused by two distinct mechanisms of accumulation of the elastic energy in the moving magma column: compressibility of the magma in the conduit and viscoelastic response of the almost solid magma plug on the top. A release of the elastic energy occurs during a stick–slip dynamic phase transition in a boundary layer along the walls of the conduit; this phase transition is driven by the shear stress accumulated in the boundary layer. The intrinsic hysteresis of this first-order phase transition explains the long periods of inactivity in the explosion cycle. Temporal characteristics of the model are found to be qualitatively similar to the acoustic and seismic signals recorded at Karymsky volcano in Kamchatka.
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.
Ozerov A.Yu. A New Cluster Regime Of Gas-Liquid Flow In Vertical Columns (Physical Modeling) // Сборник тезисов Международной конференции «Потоки и Структуры в Жидкостях: Физика Геосфер». М.: ИПМех РАН. 2009. Vol. 1. P. 178-181.
Ozerov A.Yu. Cluster Regime – The New Regime Of Flowing Of Gas-Liquid Mixture In Vertical Columns (Based On Experimental Data) // 6th International Symposium on Multiphase Flow, Heat Mass Transfer and Energy Conversion. Xi’an, China, 11-15 July 2009. 2009. P. FG-30.