【作 者】L. Feng,Y. Lin,S. Hu,L. Xu,and B. Miao
【摘 要】A combined Raman spectroscopy and electron probe microanalysis study of the heavily shocked Grove Mountains (GRV) 052049 meteorite revealed the largest chemical fractionation of natural ringwoodite, and cmposition-dependent variation of the intensities and/or wavenumbers of Raman bands. With Fa content [atomic ratio of Fe/(Fe+Mg)] of ringwoodite varying from 27.8 to 81.6 mol%,the peak position of the single band around 290 cm–1 (SB1), which relates to the SiO4 translation mode, shifts from 296.0 to 284.6 cm–1, and one of the doublets around 790 cm–1 (DB1), which relates to the symmetric stretching of SiO4, shifts from 796.3 to 782.7 cm–1. In addition, the relative intensities of SB1 and the other band of the doublet around 840 cm–1 (DB2), which relates to asymmetric stretching of SiO4, increases with Fa content. Based on the paired Raman-EPMA data, single-peak and two-peak calibrations were established, which can be used to derive Fa contents of ringwoodite from the Raman spectra. The accuracy of Raman-derived Fa content of ringwoodite is better than ±5 mol%. The correlation of SB1 intensity with the Fa content of ringwoodite suggests that the vibration of SB1 is enhanced with the substitution of Mg2+ by Fe2+. The correlation between Raman spectra and the chemical composition of ringwoodite have potential applications in on-line measurement of high-pressure experiments and in situ mineralogical determination in future planetary explorations.
【关键词 】Raman spectroscopy, ringwoodite, chemical compositions, shocked meteorite