--> Abstract: Reduced C-O-H Volatiles Dissolved in Lunar Volcanic Glasses, by Diane T. Wetzel, Malcolm J. Rutherford, Steven D. Jacobsen, Erik H. Hauri, Alberto E. Saal, and Sylvia-Monique Thomas; #90181 (2013)

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Reduced C-O-H Volatiles Dissolved in Lunar Volcanic Glasses

Diane T. Wetzel1, Malcolm J. Rutherford1, Steven D. Jacobsen2, Erik H. Hauri3, Alberto E. Saal1, and Sylvia-Monique Thomas4
1Brown University, Providence, RI
2Northwestern University, Evanston, IL
3Carnegie Institution of Washington, Washington, DC
4University of Nevada Las Vegas, Las Vegas, NV

The Moon had long been considered dry, until recently, when up to 40 ppm H2O was measured in the lunar volcanic glasses. Before this discovery, carbon was considered the primary volatile element. The formation of a CO-rich gas phase by graphite oxidation was thought to drive fire fountain eruptions on the Moon that produced spherical glass beads found on the lunar surface. These natural lunar glasses do not contain enough dissolved carbon to be detected by FTIR spectroscopy. Therefore, we used the Apollo 15 green glass composition to experimentally determine the solubility and speciation of carbon in water-bearing, graphite-saturated melts. Our experiments show carbon dissolves in reduced lunar melts as mainly Fe(CO)5 and to a lesser extent CH4. Under more oxidizing conditions, we find carbon is dissolved as carbonate in lunar basaltic melts. We also determine that twice as much carbon can be dissolved in oxidized melts compared to the reduced melts. The hydrogen content of the natural lunar glasses, in contrast to the carbon content, is dissolved in large enough quantities to be detectible by FTIR spectroscopy. We used Raman and FTIR spectroscopy to study the speciation of hydrogen in the natural orange, yellow, and green lunar glasses. With this work, we are able to determine the abundance and speciation of dissolved volatiles in lunar and other reduced high FeO melts and the effect of planetary degassing on the evolution of an early atmosphere.

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013