¹Colin R.M. Jackson et al. (>10)*
¹Geological Sciences, Brown University, 324 Brook Street, Providence, Rhode Island 02912, U.S.A.
*Find the extensive, full author and affiliation list on the publishers website

Remote sensing observations have identified aluminate spinel, in the absence of measureable olivine and pyroxene, as a globally distributed component of the lunar crust. Earlier remote sensing observations and returned samples did not indicate the presence of this component, leaving its geologic significance unclear. Here, we report visible to mid-infrared (V-IR) reflectance (300–25 000 nm) and Mössbauer spectra of aluminate spinels, synthesized at lunar-like oxygen fugacity (fO2), that vary systematically in Fe abundance. Reflectance spectra of particulate (6 Fe#. Although the 2000 and 2800 nm bands are assigned to Fe2+IV electronic transitions, spectra of aluminate spinels with excess Al2O3 demonstrate that the strengths of the 1000 nm bands are related to the abundance of Fe2+VI. The abundance of Fe2+VI depends on bulk Fe content as well as factors that control the degree of structural order-disorder, such as cooling rate. Consequently the strength of the 1000 nm bands are useful for constraining the Fe content and cooling rate of remotely sensed spinel. Controlling for cooling rate, particle size, and fO2, we conclude that spinels with >12 Fe# (

Reference
Jackson CRM et al. (2014) Visible-infrared spectral properties of iron-bearing aluminate spinel under lunar-like redox conditions. American Mineralogist October 99, 1893-1910
Link to Article [doi:10.2138/am-2014-4793]

Copyright: The Mineralogical Society of America