Crystallographic orientation-dependence of Raman spectrum of Fo₈₉Fa₁₁ olivine

Abstract

The relationship between Raman spectra and crystallographic orientation was examined for single crystals of Fo₈₉Fa₁₁ olivine [(Mg_0.89Fe_0.11)₂SiO₄]. Raman spectra were obtained for chemically homogeneous olivine grains with various orientations on a thin section of dunite using micro-Raman equipment and an unpolarized exciting laser. Crystallographic orientations of each olivine grain were determined using an electron backscattered diffraction (EBSD) method. Five apparent peaks at 822 (p1), 854 (p2), 880 (p3), 917 (p4), and 959 cm^-1 (p5) were observed in the spectral range of 700- 1050 cm^-1. Intensity ratios of p-i to p2 , Ii/I2, for i = 1, 4, and 5 were formulated empirically as functions of crystallographic orientations. These empirical equations well describe the relationships between Ii/I2 and crystallographic orientation and enable Raman spectroscopic determination of the crystallographic orientation of olivine.