Earth Planets Space, Vol. 54 (No. 3), pp. 337-347, 2002
Mikhail A. Korzhinsky1, Roman E. Botcharnikov1, Sergey I. Tkachenko1, and Genrikh S. Steinberg2
1Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka 142432, Russia
2Institute of Volcanology and Geodynamics, Russian Academy of Natural Sciences, Yuzhno-Sakhalinsk 693008, Russia
(Received May 29, 2000; Revised September 11, 2001; Accepted September 20, 2001)
Abstract: A high-temperature (up to 940°C) fumarolic activity at Kudriavy volcano had been studied during 1990-1999. The maximum gas temperatures of the fumaroles were measured in 1992 as 940°C, then gradually decreased with time and reached to 907°C in 1999. Gas composition of the high-temperature fumarole became enriched in H2O and depleted in other gas components, in particular in CO2. Hydrogen isotopic compositions of the high-temperature fumarolic gases were gradually depleted in deuterium. The gradual and continuous decrease in temperature and changes in gas composition observed during the last 10-year suggest that a magmatic melt have been degassing in a relatively steady-state manner from a single magma chamber. The detail investigations in 1998 and 1999 revealed short-term changes in gas composition characterized by sporadic increases in H2, CO2, and Stotal after intense precipitations. Small-scale eruptions occurred on October 7, 1999 at the summit. The ratios of major gas components (C/S, C/Cl, S/Cl, C/F, S/F, and Cl/F) significantly increased just prior to the eruption. The eruption at the Kudriavy volcano in 1999 was likely a phreatic eruption as a result of the intense precipitations after unusually long dry period. Meteoric water penetrated into the hot zone of volcano edifice and rapidly boiled causing the eruption.