Structural and compositional study of natural chromites of Indian origin

Abstract

Natural chromites taken from three Indian localities, Sukinda, Ladakh and Byrapur, have been studied by Mossbauer spectroscopy. Microscopical and chemical analyses have also been made. Of the four samples studied, three showed normal structure while one showed an inverse spinel structure with small particle size, which indicates that it crystallised at a higher temperature with a faster rate of cooling of the magma. This fourth sample had also suffered hydrothermal alterations. The Fe3+/Fe2+ ratio demonstrates a high oxygen fugacity at the time of formation of all the samples. The Mg/Fe2+ and Cr/Fe ratios suggest that the chromite from Sukinda was the earliest to be crystallised and that the samples from Byrapur were the latest.

Petrogenetic implication of the Mössbauer hyperfine parameters of Fe3+-chromites from Sukinda (India) ultramafites

“…To reach a better assignment a low-temperature (110 K) spectrum of this sample was taken and the better resolved M6ssbauer spectrum showed a doublet of 6 = (Galvao Da Silva et al, 1976, 1980Fatseas et al, 1976;Singh et al, 1978) had assigned this hyperfine parameter to Fe 2+ (A). Recent work on spinels, however, assign the doublet with 6 i> 1.02 mm/s to FeZ+(B) (Marshall and Dollase, 1984;Dyar et al, 1989).…”

Fe2+?Fe3+ ordered distribution in chromite spinels

“…Since the mid-seventies Mossbauer spectroscopy has been successfully used to characterize the oxidization state and the coordination environment of iron in chromites and to estimate quantitatively the amount of iron in T-and M-sites (Da Silva et al 1976;Fatseas et al 1976;Singh et al 1978). Yet, iron bearing chromites are still a subject of investigation (Li and Stevens 1986).…”