Estimation of CO2 content in the gas phase of melt inclusions using Raman spectroscopy: Case study of inclusions in olivine from the Karymsky volcano (Kamchatka).

Mironov, Nikita, Tobelko, D. P., Smirnov, S. Z., Portnyagin, Maxim V. and Krasheninnikov, S. P. (2020) Estimation of CO2 content in the gas phase of melt inclusions using Raman spectroscopy: Case study of inclusions in olivine from the Karymsky volcano (Kamchatka). Russian Geology and Geophysics, 61 (5-6, Special issue SI). pp. 600-610. DOI 10.15372/RGG2019169.

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Abstract

Carbon dioxide (CO2) is one of the main volatile components of natural magmas, but estimation of its initial contents remains a challenge. Study of melt inclusions in minerals permits a direct estimation of the content of CO2 in the melts. For the precise determination of its content in melt inclusions, it is necessary to analyze the contents of CO2 both in glass and in the fluid daughter phase of the inclusions. In this work we constructed a calibration dependence of the density of CO2 in the range 0.01-0.22 g/cm3 on the distance between its characteristic peaks in Raman spectra (Fermi diads). The accuracy of density determination is ±0.03 g/cm3. The calibration was used to estimate the density of CO2 in the gas phase of melt inclusions in magnesian olivine (Fo84.8-88.5) from basalts of the Karymsky Volcano, eastern Kamchatka. The estimated density was 0.03-0.21 g/cm3. Using these values, we evaluated the minimum initial content of CO2 in the parental magmas of the Karymsky Volcano, 0.45 wt.%. These data, along with the known initial content of water (~4.5 wt.%), indicate that the parental magmas began to crystallize at a pressure of at least 7 kbar (depth of >25 km). To increase the reliability of the above method of estimation of the CO2 content in olivine-hosted melt inclusions, we propose to carry out preliminary experimental reheating of inclusions for complete homogenization of the fluid phase and determination of the 3D size of melt inclusions. The performed study provides a reliable evaluation of the content of CO2 in parental magmas, the depth of crystallization, and the degree of magma degassing and permits a comparison of the compositions of magmatic fluids and high-temperature volcanic gases.

Document Type: Article
Keywords: olivine-hosted melt inclusions, gas bubble, Raman spectroscopy, CO2, parental magmas, subduction zones
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
Publisher: Siberian Branch of the RAS
Date Deposited: 20 Jul 2020 07:36
Last Modified: 08 Feb 2023 09:28
URI: https://oceanrep.geomar.de/id/eprint/49984

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