Fumarolic activity of Avachinsky and Koryaksky volcanoes, Kamchatka, from 1993 to 1994
Abstract
Volcanic gas and condensate samples were collected in 1993-1994 from fumaroles of Koryaksky and Avachinsky, basaltic andesite volcanoes on the Kamchatka Peninsula near Petropavlovsk-Kamchatsky. The highest-temperature fumarolic discharges, 220 °C at Koryaksky and 473 °C at Avachinsky, are water-rich (940-985mmol/mol of H2O) and have chemical and isotopic characteristics typical of Kamchatka-Kurile, high- and medium-temperature volcanic gases. The temperature and chemical and water isotopic compositions of the Koryaksky gases have not changed during the past 11 years. They represent an approximate 2 : 1 mixture of magmatic and meteoric end members. Low-temperature, near-boiling-point discharges of Avachinsky Volcano are water poor ( 880mmol/mol) Their compositions have not changed since the 1991 eruption, and are suggested to be derived from partially condensed magmatic gases at shallow depth. Based on a simple model involving mixing and single-step steam separation, low water and high CO2 contents, as well as the observed Cl concentration and water isotopic composition in low-temperature discharges, are the result of near-surface boiling of a brine composed of the almost pure condensed magmatic gas. High methane content in low-temperature Avachinsky gases and the 220 °C Koryaksky fumarole, low C isotopic ratio in CO2 at Koryaksky (-11.8‰), and water isotope data suggest that the "meteoric" end member contains considerable amounts of the regional methane-rich thermal water discovered in the vicinity of both volcanoes.
- Publication:
-
Bulletin of Volcanology
- Pub Date:
- 1997
- DOI:
- 10.1007/s004450050152
- Bibcode:
- 1997BVol...58..441T