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  • Controls on Iron‐Redox State in Martian Magmas Quantified by Mössbauer Spectroscopy, Colorimetric Wet Chemistry, and XANES Spectroscopy
Title: Controls on Iron‐Redox State in Martian Magmas Quantified by Mössbauer Spectroscopy, Colorimetric Wet Chemistry, and XANES Spectroscopy
Abstract To elucidate the relationship between oxygen fugacities (fO2) recorded in martian basalts and redox processes in the martian interior, superliquidus 100‐kPa furnace experiments on a composition similar to Humphrey (Adirondack basalt) were conducted at variablefO2and temperature. Quenched glasses were analyzed by EPMA, Mössbauer spectroscopy, colorimetric wet chemistry, and microbeam X‐ray absorption near edge structure (XANES) spectroscopy. The experiments reveal Mössbauer and wet chemical determinations of silicate glass Fe3+/FeTagreeing within uncertainty, supporting the accuracy of extended‐Voigt‐based fitting of Mössbauer spectra when recoil‐free fraction is considered. Fe3+/FeTratios determined from Mössbauer spectroscopy from Humphrey and previously studied martian‐relevant glass compositions are combined to calibrate models that characterize the relationship between Fe3+/FeT,fO2, temperature, and composition in martian silicate liquids. The models demonstrate, similar to previously investigated silicate liquids, that the correlation between and logfO2in martian magmas has a slope less than the value (0.25) expected if ferric and ferrous iron oxide mixed ideally. Martian magma Fe3+/FeTratios are more temperature‐sensitive compared to non‐martian compositions, suggesting that temperature variations may contribute to comparatively largefO2variations in martian basalt. The models are applied to demonstrate that the Fe3+/FeTincreases required to explain multiple‐log unit changes infO2in shergottite magma would not increase terrestrial magmafO2as effectively. To aid in future investigations of martian magma redox, a XANES technique that allows for non‐destructive, microanalytical characterization of Fe3+/FeTin natural martian materials and martian‐relevant experiments is introduced.  more » « less
Award ID(s):
2153786
PAR ID:
10671827
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
American Geophysical Union
Date Published:
Journal Name:
Journal of Geophysical Research: Planets
Volume:
131
Issue:
3
ISSN:
2169-9097
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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