Diaspores and related hydroxides: Spectral-compositional properties and implications for Mars

Edward A. Cloutis, James F. Bell

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Differences in spectral reflectance properties (0.3-26 μm) of a suite of metal hydroxides (gibbsite, böhmite, diaspore, goethite, and manganite) have been found to be a function of both structural and compositional differences between these minerals. The properties of the O-H stretching fundamental bands in particular can be used to identify the presence of these minerals and to discriminate isostructural and heteromorphous species. This is due to the fact that the O-H stretching fundamental bands are very intense in these minerals and occur at longer wavelengths than those of other minerals, and also due to the fact that these metal hydroxides lack strong absorption bands at shorter wavelengths. In the case of dimorphous minerals such as böhmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), differences in the wavelength positions of O-H stretching fundamental bands can be of the order of 0.1-0.3 μm. Reflectance spectra of metal hydroxide-bearing "ores" (bauxites) and impure samples indicate that accessory phases, in particular iron-bearing minerals, have a more pronounced effect on spectral reflectance toward shorter wavelengths. Intimate mixtures of diaspore + orthopyroxene indicate that diaspore abundances as low as 5 wt % (or less) can be detected by the appearance of characteristic absorption bands at 3.33 and 3.41 μm. This finding has particular relevance to the study of near-infrared spectra of Mars, in that the conditions which favor diaspore formation on the Earth may have also been prevalent early in Mars' history. If diaspore did form on Mars in the past, it is likely to have persisted to the present.

Original languageEnglish (US)
Article number1999JE001188
Pages (from-to)7053-7070
Number of pages18
JournalJournal of Geophysical Research E: Planets
Volume105
Issue numberE3
DOIs
StatePublished - Mar 25 2000
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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