A Raman spectroscopic study of shocked forsterite

Abstract

The profiles of Raman spectra below 670 cm-1 of synthetic single crystals of forsterite shocked up to 82 GPa were analyzed. Up to the shock pressure of 46.2 GPa, Raman bands of Si-O external vibrations of translational and rotational modes are linearly shifted without band broadening to higher frequencies with the increase of the residual strain caused by shock pressure. The Mg(M2)-O translational band is not shifted, but broadens linearly with the strain increase. Normalized band shift and broadening are used to compare the variation. These variations show that differential residual stress and strain still remain within cation polyhedra. The dependence of the normalized broadening on the pressures less than 46.2 GPa is formulated, and this relation can be used to estimate the shock pressure of chondritic olivne. Many extra Raman bands are found in this region, implying that the forsterite may be partly transformed into unknown phases.