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Manganese incorporation in synthetic hercynite

DOI: 10.1180/minmag.2015.079.3.09 DOI Help

Authors: Geoffrey Bromiley (University of Edinburgh) , G. D. Gatta (Universita degli Studi Milano) , Thomas Stokes (University of Edinburgh)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Mineralogical Magazine , VOL 79 (3) , PAGES 635 - 647

State: Published (Approved)
Published: June 2015
Diamond Proposal Number(s): 9094

Abstract: Manganese incorporation in synthetic hercynite, and partitioning between hercynite and silicate melt synthesized at 1.0 GPa, 1250°C, and at an fO2 buffered by Fe–FeO, has been studied by X-ray absorption spectroscopy and single-crystal X-ray structure refinement. Spectra indicate the presence of both Mn2+ and Mn3+ (and possibly also Mn4+) in synthetic hercynite and partitioning of Mn2+ into the melt phase, and Mn3+ into hercynite, respectively, under run conditions. X-ray refinement is consistent with partial disorder of Fe and Al across tetrahedral and octahedral sites. A higher than expected degree of Fe-Al disorder in the Mn-bearing hercynite can be explained by preferential incorporation of Mn2+ onto the tetrahedral site, and indicates that Fe-Al disorder in pure, stoichiometric hercynite cannot necessarily be used to determine closure temperatures in natural spinel. However, partitioning of Mn2+ and Mn3+ between melt and hercynite suggests that Mn incorporation in hercynite could be used as a measure of fO2 conditions in magmas during spinel crystallization.

Journal Keywords: Crystal Chemistry; Disorder; Hercynite; Manganese; Oxygen Fugacity; Spinel

Subject Areas: Earth Science, Chemistry

Instruments: I18-Microfocus Spectroscopy

Added On: 02/09/2015 14:15

Discipline Tags:

Earth Sciences & Environment Mineralogy Geology Geochemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) X-ray Absorption Near Edge Structure (XANES)