干旱区生态环境知识资源中心

Naturally occurring Al- Fe3 +- poor magnesiochromite and Fe2+- Fe3 +- rich ferrian chromite solid solutions have been analyzed by micro-Raman spectroscopy. The results reflect a strong positive correlation between the Fe3 + # [Fe3+/(Fe3 ++Cr + Al)] and the positions of all Raman bands. A positive correlation of the Raman band positions with Mg# [Mg/(Mg + Fe2 +)] is less stringent. Raman spectra of magnesiochromite and ferrian chromite show seven and six bands, respectively, in the spectral region of 800 - 100 cm(- 1). The most intense band in both minerals is identified as symmetric stretching vibrational mode, nu (1)(A (1g) ). In the intermediate Raman-shift region (400-600 cm(- 1)), the significant bands are attributed to the nu (3)(F (2g) ) > nu (4)(F (2g) ) > nu (2)(E (g) ) modes. The bands with the lowest Raman shifts (< 200 cm(- 1)) are assigned to F (2g) (trans) translatory lattice modes. Extra bands in magnesiochromite (two bands) and in ferrian chromite (one weak band) are attributed to lowering in local symmetry and order/disorder effects.