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Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An UpdateWe have been developing an oxygen barometer based on the valence state of V (V(2+), V(3+), V(4+), and V(5+)) in solar system basaltic glasses. The V valence is determined by synchrotron micro x-ray absorption near edge structure (XANES), which uses x-ray absorption associated with core-electronic transitions (absorption edges) to reveal a pre-edge peak whose intensity is directly proportional to the valence state of an element. XANES has advantages over other techniques that determine elemental valence because measurements can be made non-destructively in air and in situ on conventional thin sections at a micrometer spatial resolution with elemental sensitivities of approx. 100 ppm. Recent results show that fO2 values derived from the V valence technique are consistent with fO2 estimates determined by other techniques for materials that crystallized above the IW buffer. The fO2's determined by V valence (IW-3.8 to IW-2) for the lunar pyroclastic glasses, however, are on the order of 1 to 2.8 log units below previous estimates. Furthermore, the calculated fO2's decrease with increasing TiO2 contents from the A17 VLT to the A17 Orange glasses. In order to investigate these results further, we have synthesized lunar green and orange glasses and examined them by XANES.
Document ID
20040085441
Document Type
Conference Paper
Authors
Karner, J. M.
(New Mexico Univ. Albuquerque, NM, United States)
Sutton, S. R.
(Chicago Univ. Chicago, IL, United States)
Papike, J. J.
(New Mexico Univ. Albuquerque, NM, United States)
Shearer, C. K.
(New Mexico Univ. Albuquerque, NM, United States)
Jones, J. H.
(NASA Johnson Space Center Houston, TX, United States)
Newville, M.
(Chicago Univ. Chicago, IL, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Publication Information
Publication: Workshop on Oxygen in the Terrestrial Planets
Subject Category
Lunar And Planetary Science And Exploration
Distribution Limits
Public
Copyright
Public Use Permitted.
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