Data are presented about the chemical and isotopic composition of fumarolic gases and thermal water collected in the crater of the Mutnovskiy volcano from 1963 to 1989. A thermodynamic approach, balance estimates and information on the hydrogeological characteristics of the Mutnovskiy geothermal field and volcanic structure were used in the interpretation of the data. Three groups of fumarolic vents in the craters of the volcano have been active for many years (the Aktivnaya cone, the Verkhneye field and the Donnoye field) and differ in the composition of their gases, the isotopic composition of the water, a activity and He ratios. It was shown that the composition of the fumarolic gases is formed as a result of the interaction between the magmatic fluid, the surface and thermal waters and also the boiling of ultra-acidic brines-the mixed waters that form the local hydrothermal system of the Donnoye field in the crater of the Mutnovskiy volcano.

During 1988 gas samples were collected by one technique from the following volcanic fumaroles within the Pacific ocean ring: Momotombo (Nikaragua), the White Island and Raul (New Zealand), Sheveluch (Kamchatka) and Ebeko (the Ku-rile Islands). Gas temperature of fumaroles varied between 92° and 882° C. In this connection, oseveral types of fumaroles were distinguished: magmatic - high temperature (850° C), .mean temperature (300-500° C), low temperature (100-120° C), and aqueous carbon dioxide low temperature (100°C). Independently of the state of activity, location and evolution stage of volcanoes, the atomic composition beeing similar, the molecular ratios of volcanic gases are controlled by mineral buffers of partial oxygen pressure!. The paper is of interest in searching for eruption precur-sors in the change of gas composition when visible variations of fumarole temperature are lacking

Based on the data of field studies in different years, the macro- and microcomponent composition of the waters of the Zelenoe Lake in the crater of the Troitsky active volcano Maly Semyachik were considered. It is shown that the lake contains ultra-acidic (pH < 1) water of sulfate-chloride composition with mineralization from 8 to 42 g/L, depending on the state of the volcano. The anion composition of the lake is formed by the inflow and subsequent dissolution of acidic volcanic gases in the aquifer located directly under the lake. The cation composition of water is formed by the almost congruent dissolution of the host rocks. After a long period of dormancy, in 2008 a new stage of hydrothermal activation of the volcano began. The activity is ongoing. Against the background of a constantly increasing volume, there is an increase in the concentrations of the main macro components (SO4, Cl, Al, Fe) and in the salinity of water in general.

Изучены петро- и геохимические особенности пород Карымского вулканического центра (КВЦ), который является наиболее крупным в Восточном вулканическом поясе Камчатки. Формирование КВЦ происходило ритмично, начиная с конца плиоцена, с образованием последовательных дифференцированных комплексов пород. Закономерное изменение макро- и микроэлементов в вулканических породах КВЦ объясняется процессами фракционирования минеральных фаз из исходного расплава. При этом происходило обогащение остаточных расплавов щелочами, литофильными элементами (Rb, Ba, Sr, Pb, Th, U, РЗЭ) и истощение когерентными элементами (Ni, Cr, Sc, Ti). Результаты геохимического исследования вулканических пород КВЦ указывают на принадлежность их к типичным островодужным образованиям. Отношения несовместимых элементов предполагают двухкомпонентную систему магмообразования: обедненный мантийный источник (N-MORB) и надсубдукционные флюиды (островодужный компонент). Вероятны процессы контаминации расплава в кровле промежуточного очага метасоматизированным субстратом, добавка кумулусных кристаллических фаз (и расплавов) более ранних этапов магмообразования в КВЦ.