Room temperature 57Fe Mössbauer spectra have been recorded for six hornblendes and seven biotites from the Sierra Nevada Batholith, California. The hornblende spectra have been resolved into three Fe2+ doublets due to Fe 2+ in M1, M2, and M3; and one Fe3+ doublet due to Fe3+ mainly in M2. The biotite spectra have been resolved into two Fe2+and two Fe3+ doublets due to Fe2+ and Fe3+ in both Ml and M2. Using the areas of the peaks, Fe3+/Fe2+ ratios have been derived. For biotites, these are found to be in good agreement with the chemical analysis values; for hornblendes, the constant relating the chemical and Mössbauer Fe3+ /Fe2+ values is 1.13 ± 0.02. The accuracy of the non-destructive Fe3+/Fe2+ analysis is within 2 to 4 percent for most samples. Saturation corrections for such analyses are shown to be negligible

The ferrous site populations show that Fe2+ orders in the Ml and M3 positions in hornblendes. There is a small amount of ferrous ordering on M2 in biotites, which increases as the ferrous content decreases.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page of A Mössbauer study of coexisting hornblendes and biotites: quantitative Fe<sup>3+</sup>/Fe<sup>2+</sup> ratios
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.