NTRS - NASA Technical Reports Server

Back to Results
Oxygen Fugacity of Mare Basalts and the Lunar Mantle Application of a New Microscale Oxybarometer Based on the Valence State of VanadiumThe ability to estimate oxygen fugacities for mare basalts and to extend these observations to the lunar mantle is limited using bulk analysis techniques based on buffering assemblages or the valence state of iron. These limitations are due to reequilibration of mineral assemblages at subsolidus conditions, deviations of mineral compositions from thermodynamic ideality, size requirements, and the limits of the iron valence at very low fO2. Still, these approaches have been helpful and indicate that mare basalts crystallized at fO2 between the iron-w stite buffer (IW) and the ilmenite breakdown reaction (ilmenite = rutile + iron). It has also been inferred from these estimates that the lunar mantle is also highly reduced lying at conditions below IW. Generally, these data cannot be used to determine if the mare basalts become increasingly reduced during transport from their mantle source and eruption at the lunar surface and if there are differences in fO2 among mare basalts or mantle sources. One promising approach to determining the fO2 of mare basalts is using the mean valence of vanadium (2+, 3+, 4+, 5+) determined on spots of a few micrometers in diameter using synchrotron x-ray absorption fine structure (XAFS) spectroscopy. The average valence state of V in basaltic glasses is a function of fO2, temperature, V coordination, and melt composition. Here, we report the initial results of this approach applied to lunar pyroclastic glasses.
Document ID
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Shearer, C. K.
(New Mexico Univ. Albuquerque, NM, United States)
Karner, J.
(New Mexico Univ. Albuquerque, NM, United States)
Papike, J. J.
(New Mexico Univ. Albuquerque, NM, United States)
Sutton, S. R.
(Chicago Univ. Chicago, IL, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Publication Information
Publication: Lunar and Planetary Science XXXV: Viewing the Lunar Interior Through Titanium-Colored Glassed
Subject Category
Distribution Limits
Public Use Permitted.
Document Inquiry

Available Downloads

There are no available downloads for this record.
No Preview Available