Mineralogy of volcanic rocks in Gusev Crater, Mars: Reconciling Mössbauer, Alpha Particle X-ray Spectrometer, and Miniature Thermal Emission Spectrometer spectra

Citation

McSween HY, Ruff SW, Morris RV, Gellert R, Klingelhoefer G, Christensen PR, McCoy TJ, Ghosh A, Moersch JM, Cohen BA, Rogers AD, Schröder C, Squyres SW, Crisp JA & Yen AS (2008) Mineralogy of volcanic rocks in Gusev Crater, Mars: Reconciling Mössbauer, Alpha Particle X-ray Spectrometer, and Miniature Thermal Emission Spectrometer spectra. Journal of Geophysical Research: Planets, 113 (E6), Art. No.: E06S04. https://doi.org/10.1029/2007JE002970

Abstract
Complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in Gusev Crater have been determined by modeling Mössbauer subspectral areas as mineral weight percentages, and combining those percentages with the proportions of iron-free minerals not detected by Mössbauer (normative plagioclase, apatite, and chromite, as calculated from Alpha Particle X-Ray Spectrometer (APXS) chemical analyses). Comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured Miniature Thermal Emission Spectrometer (Mini-TES) spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic plagioclase compositions or unmodeled sulfate, glass, or pigeonite. The normative compositions of olivine, pyroxene, and feldspar calculated from APXS data are consistent with spectroscopic constraints on mineral compositions. Systematic variations between olivine abundances in APXS norms (which sample tens of micrometers depth) and olivine proportions measured by Mössbauer (which sample hundreds of micrometers depth) support the hypothesis that dissolution of olivine by acidic fluids has occurred on weathered rock surfaces.

Keywords
Mars; mineralogy; Gusev Crater

Journal
Journal of Geophysical Research: Planets: Volume 113, Issue E6

People

Dr Christian Schroeder

Senior Lecturer, Biological and Environmental Sciences