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]

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,
沈み込んだ海山からの寄与の可能性とテクトニックセッティングとの関係について議論する.
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
沿ったプレートの薄化およびまたは沈み込む直前のプルームからの熱的効果による若返り効果によるものと考
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
含むEC溶岩は沈み込んだ海山による局所的な温度異常がスラブ起源流体の脱水を強めそれによって生じたフ
ラックス溶融によりもたらされた（西澤他, 2014, JpGU; 2015, JpGU）.

Compositional zonation in olivine phenocrysts and diffusion modelling have been used in the last ten years to estimate magma residence times and the duration of magma ascent. The fundamental assumption is that mixing with newly injected magma into a reservoir triggers diffusional exchange between mafic olivine crystals and more evolved magma and that this magma mixing eventually triggers eruption. If depth of mixing is known, this translates to ascent rates of magmas to the surface. We applied this approach to a series of different arc basalt lavas from Kamchatka to constrain the rates of magma ascent and magma resident in what is one of the most active subduction zones in the world that is also dominated by an abundance of unusually mafic magmas. Our sample collection cover the principal modes of arc magmatism in Kamchatka: from different volcanic complexes (stratovolcano, dikes, summit eruptions, monogenetic cones), of different age (from Late-Pleistocene to Holocene and recent eruptions), from different magmatic regimes (long-lived volcanoes vs. monogenetic eruptions) and different major element composition (from basalt to basaltic andesite of different geochemical character including LILE enrichments). We analyzed and modelled zonation profiles for a range of elements with different diffusivities (e.g. Mg-Fe, Ca, Ni, Mn, Cr) to assess the role of variable diffusivities as a function of major and trace elements in the olivines from different P-T conditions. First data were obtained on samples from the Klyuchevskoy, Shiveluch and Tolbachik, including recent most eruption in 2012/2013. These data show that for some samples the zonation patterns are much more complex than is usually observed: high-Mg olivines at different volcanoes have very different zonation patterns, including normally, reversely zoned grains or even show highly complex repetitive zonation that indicate large compositional changes in the surrounding magma at very short time scales (years). Thus in some Kamchatka basalts, we observe unusual Mg-Fe zonations that are linked to complex mixing, possibly resorption and subsequent crystal growth processes that are generally not preserved due to fast diffusion of Mg-Fe. Based on a first assessment of our measured profiles, the values for diffusion times in Fo-rich olivines (88 to 92% Fo) vary from only a few months to years and thus magma ascent from deep magma sources must have been fast.

The paper proposes a formalized technique of probabilistic forecast by applying statistical estimation of seismicity level and a number of additional functions that characterize the predictive situation. The possibilities of this method are illustrated by the example of seismic activation before the eruptions of Bezymianny Volcano (Klyuchevskaya group, Kamchatka).
The initial data is the catalog of earthquakes of the Klyuchevskaya group of volcanoes during 1999-2014, compiled by the Kamchatka Branch of the Geophysical Survey, RAS. During this time there were 21 eruptions of Bezymianny Volcano. The precursor is defined as a threshold function associated with the current seismicity level and its characteristic form before the eruption.
The values of parameters characterizing the precursor are given including validity, reliability and efficiency, calculated by two methods. It is shown that the reliability of the precursor decreases with the increase in threshold values, and its validity increases.
The reliability of the method is 0.38–0.95, i.e., from 38 % to 95 % of eruptions had the precursor depending on the threshold level; and the validity is 0.3–0.6, i.e., from 30 % to 60 % of the identified precursors are realized also depending on the threshold level. Values of efficiency confirm the non-random nature of the precursor appearance.
The method includes determination of the probability of the forecast realization. The nomogram for probabilities depending on the duration of the forecast and the values of the prognostic parameter is designed.

По данным микросейсмического зондирования построена глубинная модель среды под районом Узон-Гейзерной вулкано-тектонической депрессии и прилежащего к ней вулканического массива Кихпиныч (Камчатка) до глубины 30 км. Для этого была осуществлена регистрация естественного фонового микросейсмического поля переносными широкополосными сейсмометрами Guralp CMG-6TD в точках специально спланированной наблюдательной сети: в 60-ти точках вдоль трех профилей общей длиной около 28 км. Выявленные структурные неоднородности проинтерпретированы с учетом известных ранее результатов геологических, геолого-морфологических и петрологических исследований. Идентифицирована и пространственно локализована область малоглубинного закристаллизовавшегося магматического очага под депрессией. Выявлены области предположительной концентрации базальтовых расплавов, с которыми может быть связана наблюдающаяся в последние ~ 15 лет локальная геодинамическая активизация исследуемого района: периферический магматический очаг вулканического массива Кихпиныч на глубине 5-12 км, более глубокая (15-20 км) магматическая камера. Получено согласие геометрии обнаруженных глубинных структур с локальной микросейсмичностью и моделью современного магматического внедрения в верхние горизонты коры, разработанной по данным спутниковой интерферометрии.