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Title: Oxygen fugacity of mare basalts and the lunar mantle application of a new microscale oxybarometer based on the valence state of vanadium

Abstract

Using the valence state of vanadium on a microscale in lunar volcanic glasses we have developed another approach to estimating the oxygen fugacity of mare basalts. The 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 fO{sub 2}. Still, these approaches have been helpful and indicate that mare basalts crystallized at fO{sub 2} between the iron-wuestite 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 fO{sub 2} among mare basalts or mantle sources. One promising approach to determining the fO2 of mare basalts is using the mean valencemore » 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 fO{sub 2}, temperature, V coordination, and melt composition. Here, we report the initial results of this approach applied to lunar pyroclastic glasses.« less

Authors:
; ; ;  [1];  [2]
  1. (UofC)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE
OSTI Identifier:
1008909
Resource Type:
Conference
Resource Relation:
Conference: Lunar and Planetary Science XXXV;March 15-19, 2004;Houston, Texas
Country of Publication:
United States
Language:
ENGLISH
Subject:
43 PARTICLE ACCELERATORS; ABSORPTION; BREAKDOWN; BUFFERS; FINE STRUCTURE; ILMENITE; IRON; OXYGEN; RUTILE; SPECTROSCOPY; SYNCHROTRONS; THERMODYNAMICS; TRANSPORT; VALENCE; VANADIUM

Citation Formats

Shearer, C.K., Karner, J., Papike, J.J., Sutton, S.R., and Univ. of New Mexico). Oxygen fugacity of mare basalts and the lunar mantle application of a new microscale oxybarometer based on the valence state of vanadium. United States: N. p., 2004. Web.
Shearer, C.K., Karner, J., Papike, J.J., Sutton, S.R., & Univ. of New Mexico). Oxygen fugacity of mare basalts and the lunar mantle application of a new microscale oxybarometer based on the valence state of vanadium. United States.
Shearer, C.K., Karner, J., Papike, J.J., Sutton, S.R., and Univ. of New Mexico). Tue . "Oxygen fugacity of mare basalts and the lunar mantle application of a new microscale oxybarometer based on the valence state of vanadium". United States.
@article{osti_1008909,
title = {Oxygen fugacity of mare basalts and the lunar mantle application of a new microscale oxybarometer based on the valence state of vanadium},
author = {Shearer, C.K. and Karner, J. and Papike, J.J. and Sutton, S.R. and Univ. of New Mexico)},
abstractNote = {Using the valence state of vanadium on a microscale in lunar volcanic glasses we have developed another approach to estimating the oxygen fugacity of mare basalts. The 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 fO{sub 2}. Still, these approaches have been helpful and indicate that mare basalts crystallized at fO{sub 2} between the iron-wuestite 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 fO{sub 2} 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 fO{sub 2}, temperature, V coordination, and melt composition. Here, we report the initial results of this approach applied to lunar pyroclastic glasses.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2004},
month = {5}
}

Conference:
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