No 4 (2019)

Many active volcanoes of the Kuril Islands host hydrothermal systems. Their surface manifestations are represented by numerous thermal springs showing diverse chemical composition and physical-chemical parameters. Four main isotopic shifts relative to the local meteoric water line can be observed in the corresponding δD vs. δ¹⁸O diagrams. For the acid Cl-SO₄ waters there is a clear mixing trend between meteoric water and volcanic vapor. The acid SO₄waters demonstrate trends indicating kinetic fractionation at temperatures close to the boiling-point. Isotopic composition of the coastal springs tend to march the mixing line between meteoric and seawater. The δ¹⁸O-shift for deep thermal water is accounted to of isotopic exchange with host rock. The latitude effect revealed for meteoric waters also observed in the isotopic composition of the thermal waters.

The data are given on the structure, chemical composition, and content of microelements in the ferromanganese and siliceous crusts of Pervenets Rise (the Sea of Japan). The crusts resulted from the cementation of small fragments of green clays (celadonite) with hydroxides of manganese (todorokite and birnessite) or silica. Initial was the formation of celadonite deposited during the eruption of ore-bearing hydrothermal solutions in the volcano caldera or on its slopes.The features of the crust structure show that they were originated through the diffusive infiltration of gas-hydrothermal solutions along the fractures or weakened zones in volcanic rocks and subsequent cementation of the celadonite already formed occurrences with manganese or siliceous oxides. The manganese and siliceous mineralization is separated in time and often in space and demonstrate more local distribution.

A review is given of high-precision measurements of distances by light-rangefinders and elevations from Class I leveling between long-term geodetic centers at local deformation sites laid on the coast of Avacha Bay, in order to detect deformation precursors of a likely strong earthquake (M > 7.0) and to obtain quantitative characteristics of co-seismic deformations. The report in tabular form contains the results of all measurements performed in the period 1984 –1995. These data are necessary for future researchers, since between the preserved centers you can repeat the measurements with any exact methods, compare them with the results of previous years and draw more objective conclusions. During the observations at all sites, no significant changes (exceeding the double accuracy of their determination) exceeded and the distances between the geodetic centers did not occur. The strong (M = 6.8) earthquake that occurred on March 2, 1992, with its epicenter in Avacha Bay did not cause precursors of deformations, and co-seismic deformations did not occur either. Perhaps they were, however, the sensitivity of the method and the remoteness of the sites from the hypocenter of the earthquake did not allow them to be detected.