TY - JOUR

T1 - Solubility of H2O- and CO2-bearing fluids in tholeiitic basalts at pressures up to 500MPa

AU - Shishkina, T. A.

AU - Botcharnikov, R. E.

AU - Holtz, Francois

AU - Almeev, R. R.

AU - Portnyagin, M. V.

N1 - Funding Information: We thank H. Behrens for his advises, O. Diedrich for preparation of samples for infra-red spectroscopy and microprobe analyses, A. Wegorzewski for determinations of redox state of Fe. We appreciate two anonymous reviewers for their constructive comments of the manuscript. This research has been supported by the German Science Foundation (DFG project Ho1337/21 ) and by the Russian-German project KALMAR funded by BMBF . Copyright: Copyright 2011 Elsevier B.V., All rights reserved.

PY - 2010/10

Y1 - 2010/10

N2 - The solubility of H2O- and CO2-bearing fluids in tholeiitic basalts has been investigated experimentally at temperature of 1250°C and pressures of 50, 100, 200, 300, 400 and 500MPa. The concentrations of dissolved H2O and CO2 have been determined using FTIR spectroscopy with an accurate calibration of the absorption coefficients for hydrogen- and carbon-bearing species using synthesized standards of the same tholeiitic composition. The absorption coefficients are 0.65±0.08 and 0.69±0.08L/(molcm) for molecular H2O and OH groups by Near-Infrared (NIR), respectively, and 68±10L/(molcm) for bulk H2O by Mid-Infrared (MIR). The carbonate groups determined by MIR have an absorption coefficient of 317±23L/(molcm) for the band at 1430cm-1.The solubility of H2O in the melt in equilibrium with pure H2O fluid increases from about 2.3±0.12wt.% at 50MPa to about 8.8±0.16wt.% at 500MPa, whereas the concentration of CO2 increases from about 175±15 to 3318±276ppm in the melts which were equilibrated with the most CO2-rich fluids (with mole fraction of CO2 in the fluid, XflCO2, from 0.70 to 0.95). In melts coexisting with H2O- and CO2-bearing fluids, the concentrations of dissolved H2O and CO2 in basaltic melt show a non-linear dependence on both total pressure and mole fraction of volatiles in the equilibrium fluid, which is in agreement with previous studies. A comparison of new experimental data with existing numerical solubility models for mixed H2O-CO2 fluids shows that the models do not adequately predict the solubility of volatiles in basaltic liquids at pressures above 200MPa, in particular for CO2, implying that the models need to be recalibrated.The experimental dataset presented in this study enables a quantitative interpretation of volatile concentrations in glass inclusions to evaluate the magma storage conditions and degassing paths of natural island arc basaltic systems. The experimental database covers the entire range of volatile compositions reported in the literature for natural melt inclusions in olivine from low- to mid-K basalts indicating that most melt inclusions were trapped or equilibrated at intermediate to shallow levels in magmatic systems (< 12-15 km).

AB - The solubility of H2O- and CO2-bearing fluids in tholeiitic basalts has been investigated experimentally at temperature of 1250°C and pressures of 50, 100, 200, 300, 400 and 500MPa. The concentrations of dissolved H2O and CO2 have been determined using FTIR spectroscopy with an accurate calibration of the absorption coefficients for hydrogen- and carbon-bearing species using synthesized standards of the same tholeiitic composition. The absorption coefficients are 0.65±0.08 and 0.69±0.08L/(molcm) for molecular H2O and OH groups by Near-Infrared (NIR), respectively, and 68±10L/(molcm) for bulk H2O by Mid-Infrared (MIR). The carbonate groups determined by MIR have an absorption coefficient of 317±23L/(molcm) for the band at 1430cm-1.The solubility of H2O in the melt in equilibrium with pure H2O fluid increases from about 2.3±0.12wt.% at 50MPa to about 8.8±0.16wt.% at 500MPa, whereas the concentration of CO2 increases from about 175±15 to 3318±276ppm in the melts which were equilibrated with the most CO2-rich fluids (with mole fraction of CO2 in the fluid, XflCO2, from 0.70 to 0.95). In melts coexisting with H2O- and CO2-bearing fluids, the concentrations of dissolved H2O and CO2 in basaltic melt show a non-linear dependence on both total pressure and mole fraction of volatiles in the equilibrium fluid, which is in agreement with previous studies. A comparison of new experimental data with existing numerical solubility models for mixed H2O-CO2 fluids shows that the models do not adequately predict the solubility of volatiles in basaltic liquids at pressures above 200MPa, in particular for CO2, implying that the models need to be recalibrated.The experimental dataset presented in this study enables a quantitative interpretation of volatile concentrations in glass inclusions to evaluate the magma storage conditions and degassing paths of natural island arc basaltic systems. The experimental database covers the entire range of volatile compositions reported in the literature for natural melt inclusions in olivine from low- to mid-K basalts indicating that most melt inclusions were trapped or equilibrated at intermediate to shallow levels in magmatic systems (< 12-15 km).

KW - Basalt

KW - Carbon dioxide

KW - CO

KW - Fluid

KW - HO

KW - Kamchatka

KW - Magma

KW - Mutnovsky volcano

KW - Solubility

KW - Tholeiite

KW - Water

UR - http://www.scopus.com/inward/record.url?scp=77956616295&partnerID=8YFLogxK

U2 - 10.1016/j.chemgeo.2010.07.014

DO - 10.1016/j.chemgeo.2010.07.014

M3 - Article

AN - SCOPUS:77956616295

VL - 277

SP - 115

EP - 125

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

IS - 1-2

ER -