The powerful eruption in the Akademii Nauk caldera on January 2, 1996, marked a new activity phase of Karymsky volcano and became a noticeable event in the history of modern volcanism in Kamchatka. The paper reports data obtained by studying more than 200 glassy melt inclusions in phenocrysts of olivine (Fo82-72), plagioclase (An92-73), and clinopyroxene (Mg# 83-70) in basalts of the 1996 eruption. The data were utilized to estimate the composition of the parental melt and the physicochemical parameters of the magma evolution. According to our data, the parental melt corresponded to low magnesian, highly aluminous basalt (SiO2 = 50.2 wt %, MgO = 5.6 wt %, Al2O3 = 17 wt %) of the mildly potassic type (K2O = 0.56 wt %) and contained much dissolved volatile components (H2O = 2.8 wt %, S = 0.17 wt %, and Cl = 0.11 wt %). Melt inclusions in the minerals are similar in chemical composition, a fact testifying that the minerals crystallized simultaneously with one another. Their crystallization started at a pressure of approximately 1.5 kbar, proceeded within a narrow temperature range of 1040 +/- 20 degrees C, and continued until a near-surface pressure of approximately 100 bar was reached. The degree of crystallization of the parental melt during its eruption was close to 55%. Massive crystallization was triggered by H2O degassing under a pressure of less than 1 kbar. Magma degassing in an open system resulted in the escape of 82% H2O, 93% S, and 24% Cl (of their initial contents in the parental melt) to the fluid phase. The release of volatile compounds to the atmosphere during the eruption that lasted for 18 h was estimated at 1.7 x 10(6) t H2O, 1.4 x 10(5) t S, and 1.5 x 10(4) t Cl. The concen-trations of most incompatible trace elements in the melt inclusions are close to those in the rocks and to the expected fractional differentiation trend. Melt inclusions in the plagioclase were found to be selectively enriched in Li. The Li-enriched plagioclase with melt inclusions thought to originate from cumulate layers in the feeding system beneath Karymsky volcano, in which plagioclase interacted with Li-rich melts/ brines and was subsequently entrapped and entrained by the magma during the 1996 eruption.

Item Type:	Refereed Article
Keywords:	melt inclusions, volcano, eruption
Research Division:	Earth Sciences
Research Group:	Geology
Research Field:	Volcanology
Objective Division:	Mineral Resources (excl. Energy Resources)
Objective Group:	Mineral Exploration
Objective Field:	Mineral Exploration not elsewhere classified
UTAS Author:	Belousov, IA (Dr Ivan Belousov)
ID Code:	87370
Year Published:	2011
Web of Science® Times Cited:	3
Deposited By:	Centre for Ore Deposit Research - CODES CoE
Deposited On:	2013-11-13
Last Modified:	2014-04-29
Downloads:	0