Ph.D. student FENG Lu and her teacher LIN Yangting estimate compositions of natural ringwoodite in Grove Mountains from Raman spectra.

They present a method of calibration between Raman spectra and chemical composition of ringwoodite and discuss its potential application to high-pressure experiments and space exploration.

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 ±5mol%. 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.

Figure 8. Two-dimensional projections of the peak positions from (a) the selected data set and (b) the full data set onto the plane of SB1 and DB1 peak positions. Fayalite values derived from the two-peak calibration plotted against the Fa content determined by EMPA. (c) Selected data set. Solid black line is linear regression and solid gray lines are 95% confidence intervals. The error bars are less than the size of symbols. (d) Full data set. The range of ±5 Fa units is outlined. (Image by FENG)

Feng et al. Estimating compositions of natural ringwoodite in the heavily shocked Grove Mountains 052049 meteorite from Raman spectra. American Mineralogsit. 2011, 96: 1480-1489 （Download Here）