Solubility and solution mechanisms of C–O–H volatiles in silicate melt with variable redox conditions and melt composition at upper mantle temperatures and pressures

Mysen, Bjørn O.; Kumamoto, Kathryn M.; Cody, George D.; Fogel, Marilyn L.

doi:10.1016/j.gca.2011.07.035

Cited by 65 publications

(64 citation statements)

References 84 publications

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“…4). This transition in dissolved carbon species occurs at much more reducing conditions in our basaltic composition than previously observed for a simplified silicate system (15). The observation that carbonate is dissolved in haplobasaltic melts and synthetic Martian basalts down to IW+1 (20,21) is consistent with the fO 2 range we observe (Fig.…”

supporting

confidence: 92%

“…4). Previous studies (14)(15)(16) found methane as the only dissolved carbon species within the fO 2 range of our reduced experiments (fO 2 < IW−0.55), but these prior studies used Fe-free basaltic composition and obviously did not contain dissolved iron carbonyl. Therefore, carbon speciation is a function of melt composition as well as fO 2 .…”

mentioning

confidence: 78%

“…Previous experimental studies on the speciation of carbon in Fe-free silicate systems under reducing conditions or at fO 2 < IW show carbon is dissolved as methane (14)(15)(16). However, under more oxidizing conditions in basaltic melt compositions, carbon is dissolved as carbonate (17)(18)(19), and the transition in speciation from methane to carbonate has long been debated as either occurring at more reducing conditions than IW+1 (20,21) or at more oxidizing conditions (15).…”

mentioning

confidence: 99%

“…However, under more oxidizing conditions in basaltic melt compositions, carbon is dissolved as carbonate (17)(18)(19), and the transition in speciation from methane to carbonate has long been debated as either occurring at more reducing conditions than IW+1 (20,21) or at more oxidizing conditions (15). Another study (22) shows that a significant amount of C 4+ (carbonate) can be incorporated at extremely low fO 2 (IW−4.5) if Fe and alkalis are present in the melt.…”

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confidence: 99%

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Degassing of reduced carbon from planetary basalts

Wetzel

Rutherford

Jacobsen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Degassing of planetary interiors through surface volcanism plays an important role in the evolution of planetary bodies and atmospheres. On Earth, carbon dioxide and water are the primary volatile species in magmas. However, little is known about the speciation and degassing of carbon in magmas formed on other planets (i.e., Moon, Mars, Mercury), where the mantle oxidation state [oxygen fugacity (fO 2 )] is different from that of the Earth. Using experiments on a lunar basalt composition, we confirm that carbon dissolves as carbonate at an fO 2 higher than -0.55 relative to the iron wustite oxygen buffer (IW-0.55), whereas at a lower fO 2 , we discover that carbon is present mainly as iron pentacarbonyl and in smaller amounts as methane in the melt. The transition of carbon speciation in mantle-derived melts at fO 2 less than IW-0.55 is associated with a decrease in carbon solubility by a factor of 2. Thus, the fO 2 controls carbon speciation and solubility in mantle-derived melts even more than previous data indicate, and the degassing of reduced carbon from Fe-rich basalts on planetary bodies would produce methane-bearing, CO-rich early atmospheres with a strong greenhouse potential.hydrogen | iron carbonyl | magmatic volatiles | experimental petrology M agmas formed through igneous processes on parent bodies in the early solar system span 12 log units in oxidation state, from 6.3 log units of oxygen fugacity (fO 2 ) below the iron wustite oxygen buffer (IW) to 6 log units above the IW (IW−6.3 to IW+6) (1-4). Over the wide range of basalt fO 2 observed in these planetary bodies, thermodynamic data for the C-O-H gas system indicate that there are significant changes in gas phase speciation (5). These differences should be reflected in how volatiles are dissolved in magmas, but carbon speciation experiments for basaltic systems are limited, particularly at low fO 2 . The developing evidence for volatiles in magmas erupted on the Moon (6, 7) as well as on Earth (3,8), Mars (9-12), and Mercury (13) is a strong incentive to improve our understanding of C-O-H speciation and solubility in planetary basaltic magmas.Previous experimental studies on the speciation of carbon in Fe-free silicate systems under reducing conditions or at fO 2 < IW show carbon is dissolved as methane (14-16). However, under more oxidizing conditions in basaltic melt compositions, carbon is dissolved as carbonate (17)(18)(19), and the transition in speciation from methane to carbonate has long been debated as either occurring at more reducing conditions than IW+1 (20, 21) or at more oxidizing conditions (15). Another study (22) shows that a significant amount of C 4+ (carbonate) can be incorporated at extremely low fO 2 (IW−4.5) if Fe and alkalis are present in the melt. Additional experiments on Fe-bearing basalt are clearly required to resolve the conflicts in existing data. The results are important in understanding the residence time of carbon in the mantle and the rate of carbon degassing during the early evolution of terrestrial planets ...

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confidence: 92%

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confidence: 78%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Degassing of reduced carbon from planetary basalts

Wetzel

Rutherford

Jacobsen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…In addition to molecular water and hydroxyl, silicate melts can also dissolve other H-bearing species, such as molecular hydrogen (Hirschmann et al 2012;Armstrong et al 2015), NH-bearing species (Armstrong et al 2015), and hydrocarbons such as methane (Taylor and Green 1987;Mysen et al 2009;Mysen and Yamashita 2010;Mysen et al 2011;Ardia et al 2013;Armstrong et al 2015). The H-C-O vapor in our experiments contains negligible N, and, under the conditions of our experiments, CH 4 can also be neglected (Deines et al 1974;Zhang and Duan 2009).…”

Section: The Potential Role Of Other H-bearing Species In Lunar Meltsmentioning

confidence: 99%

Solubility of water in lunar basalt at low pH2O

Newcombe

Brett

Beckett

et al. 2017

Geochimica et Cosmochimica Acta

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractWe report the solubility of water in Apollo 15 basaltic 'Yellow Glass' and an iron-free basaltic analog composition at 1 atm and 1350 °C. We equilibrated melts in a 1-atm furnace with flowing H 2 /CO 2 gas mixtures that spanned ~8 orders of magnitude in fO 2 (from three orders of magnitude more reducing than the iron-wüstite buffer, IW−3.0, to IW+4.8) and ~4 orders of magnitude in pH 2 /pH 2 O (from 0.003 to 24). Based on Fourier transform infrared spectroscopy (FTIR), our quenched experimental glasses contain 69-425 ppm total water (by weight). Our results demonstrate that under the conditions of our experiments: (1) hydroxyl is the only H-bearing species detected by FTIR; (2) the solubility of water is proportional to the square root of pH 2 O in the furnace atmosphere and is independent of fO 2 and pH 2 /pH 2 O; (3) the solubility of water is very similar in both melt compositions; (4) the concentration of H 2 in our iron-free experiments is <~4 ppm, even at oxygen fugacities as low as IW−2.3 and pH 2 /pH 2 O as high as 11; (5) Secondary ion mass spectrometry (SIMS) analyses of water in iron-rich glasses equilibrated under variable fO 2 conditions may be strongly influenced by matrix effects, even when the concentration of water in the glasses is low; and (6) Our results can be used to constrain the entrapment pressure of lunar melt inclusions and the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads. We find that the most water-rich melt inclusion of Hauri et al.(2011) would be in equilibrium with a vapor with pH 2 O ~3 bar and pH 2 ~8 bar. We constrain the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads to be 0.0005 bar and 0.0011 bar respectively. We calculate that batch degassing of lunar magmas containing initial volatile contents of 1200 ppm H 2 O (dissolved primarily as hydroxyl) and 4-64 ppm C would produce enough vapor to reach the critical vapor volume fraction thought to be required for magma 2 fragmentation (~65-75 vol. %) at a total pressure of ~5 bar (corresponding to a depth beneath the lunar surface of ~120 m). At a fragmentation pressure of ~5 bar, the calculated vapor composition is dominated by H 2 , supporting the hypothesis that H 2 , rather than CO, was the primary propellant of the lunar fire fountain eruptions. The results of our batch degassing model suggest that initial melt compositions with >~200 ppm C would be required for the vapor composition to be dominated by CO rather than H 2 at 65-75 % vesicularity.

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Application of the MELTS algorithm to Martian compositions and implications for magma crystallization

Balta

McSween

2013

JGR Planets

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[1] The MELTS algorithm, the most commonly used tool for calculating crystallization of basaltic magmas, uses thermodynamic parameters calibrated by experiments on select compositions, and thus, its use on newly discovered extraterrestrial compositions requires extrapolation across ranges where its applicability has not been evaluated in detail. To apply MELTS to Martian compositions, we undertook a systematic examination of the original MELTS calibration and the pMELTS revision as applied to Martian magmas. We find that the algorithm is effective in predicting the crystallization paths and conditions of Martian magmas, with some issues. The algorithm consistently overestimates the stability of spinel and underestimates pressures of multiple saturation compared to experiments. The pMELTS calibration comes close to fitting multiple-saturation pressures but cannot be used at low pressures. Both calibrations model crystallization temperatures with similar variances to those observed for terrestrial compositions. Both calibrations reproduce important compositional details of crystallizing magmas and coexisting minerals with errors similar to those observed on terrestrial compositions. We calculate several crystallization paths which predict high-FeO, high-density magma compositions that could be a mechanism for cumulate formation. Low-FeO compositions in recent Mars volcanism may be an expression of this density barrier. However, the composition of a high-FeO rock called "Et-Then" discovered by the rover Curiosity is strikingly similar to compositions calculated by the MELTS algorithm and could represent one of these high-FeO volcanic rocks.

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Solubility and solution mechanisms of C–O–H volatiles in silicate melt with variable redox conditions and melt composition at upper mantle temperatures and pressures

Cited by 65 publications

References 84 publications

Degassing of reduced carbon from planetary basalts

Degassing of reduced carbon from planetary basalts

Solubility of water in lunar basalt at low pH2O

Application of the MELTS algorithm to Martian compositions and implications for magma crystallization

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