Studies of melt inclusions in minerals of some Kamchatka volcanoes are reported. We studies andesite basalts and andesites in volcanoes situated in the Central Kamchatka Depression (Shiveluch and Bezymyannyi) and in the East Kamchatka Volcanic Belt (Avacha and Karymskii). In addition, we studied the basalts of the 1996 eruption in the Karymskii Volcanic Center and the dacites on Dikiy Greben Volcano, southern Kamchatka. We used homogenization of melt inclusions and the analysis of chilled glass in these inclusions with electron and ion microlog sondes. More than 200 melt inclusions have been studied in minerals from 25 volcanic rock samples. It was found that the compositions of melt inclusions in andesite phenocrysts strongly vary in basicity; the content of SiO 2 varies between 56 and 80% wt, increasing silica percentage going along with decreasing concentrations of Al2O3, FeO, MgO, CaO and increasing concentrations of Na2O and K2O. Most (about 80%) of glass in the inclusions have dacite and rhyolite compositions. However, the compositions of acid melts (SiO2 > 65% wt) which produce the andesites are significantly different from those which produce the dacites and rhyolites as to the content of TiO2, FeO, MgO, CaO and K2O. Comparison between the compositions of melt inclusions from andesite plagioclase on the four volcanoes showed considerable differences. The basic andesites (56-59% SiO2) of Bezymyannyi Volcano exhibit a large scatter in inclusion composition (SiO2 = = 56-81%). The more acid andesites (SiO2 = 61%) of Shiveluch Volcano show a lower scatter in inclusion composition (SiO2 = 67-79%). The melt inclusions in the Karymskii andesites are amore basic. They are enriched with Fe, Ti, Ca, Mg, P, Na and are considerably depleted in K. The melts that produce the Karymskii andesites are probably less differentiated. On the volcanoes under study we also found high-potassium melts (K 2O = 3.8-6.8% wt), independent of the concentrations of SiO2 in them (the range here is between 51.4 and 77.2% wt). The melts differ considerably between volcanoes as to the concentration of volatiles. The greatest concentrations of H2O are found in the Shiveluch melts (3.0 to 7.2% wt with the mean equal to 4.7% wt) and on Avacha (4.7-4.8% wt), lower concentrations being in the melts of Dikiy Greben (0.4-1.8% wt) and Bezymyanyi (<1% wt). Using fluid inclusions of CO2 found in andesite plagioclase of Shiveluch Volcano, we inferred a pressure of 350-1600 bars, which corresponds to the depth of the magma chamber equal to 1.5-6 km. We found the concentrations of 17 admixture elements in glass of melt inclusions sampled from the plagioclase of four volcanoes (Avacha, Bezymyannyi, Dikiy Greben, Shiveluch). Judging by the concentrations of these elements, the melts here studied are similar to the typical island arc magmas.

The geological and geophysical research carried out during the five cruises of R/V/ Vulkanolog in the 1980s and early 1990s provided new evidence of the structure and evolution of the Chernye Bratya volcanic massif. Five phases have been identified in its evolution. The first phase which began in the Early - Middle Pleistocene, or possibly Neogene, involvel the generation of a major shield-shaped, mostly laval, volcanic massif with dimensions 30 km by 35 km. The secondphase seems to have been a catastrophic explosive eruption producing the older caldera (Gorshkov Outer Caldera) of dimensions 15 km by 20 km. It is not younger than the mid-Late Pleistocene. A large volcanic structure formed during the third phase in the north and central parts of the older caldera, filling most of the caldera and overlapping its rim. A major explosive eruption occurred during the fourth phase producing the younger caldera (Gorshkov Caldera) of dimensions 7.5 km by 11.5 km. The generations time of that caldera corresponds to a powerful burst of acid explosive volcanism in the Kuril-Kamchatka region about 45.000 to 30.000 years ago. The final phase involved high volcanic activity within the younger caldera producing the present-day volcanic edifices of Chirpoy and Brat Chirpoev islands near the caldera rim. The total volume of ejecta discharged in the area may be in excess of 1000-1300 km 3; of these, 400-600 km 3 consist of pyroclastic material produced by the caldera-generating eruptions.

During the voyages of R\V Vulkanolog in the eighties of the last century the kamchatkan scientists studied 17 geophysical profiles (about 1100 route kilometres) within the submarine Shokalsky Ridge. The investigation showed that the Shokalsky Ridge is comprised of 4 large volcanic massives. Numerous faults were revealed within the ridge area, including those with traces of recent activity. Shift amplitude along some faults may be as long as several hundreds of meters. Canyons that split the Shokalsky Ridge are chiefly confined to the cross keystone faults.

There has been given a new data regarding morphology of submarine volcanic ridges Gidrographov and Browton (Kurile island arc). Within the limits of this ridges there has been discovered four new submarine volcanoes, that has not been included in the Catalogue of «Submarine volcanoes and mountains of Kurile island arc». Two in the Gidrographov ridge and two in the Browton ridge.