The cation distribution in synthetic and natural (Fe,Mn) olivines has been investigated by use of Mössbauer spectroscopy. A partially ordered distribution with Mn2+ entering the M2 site and Fe2+ entering the M1 site was observed which, however, becomes more disordered at higher temperature of quenching. Gibbs free energy of exchange for the reaction

at 1000°C is −3.5 kcal/mole. The observed variations in the a and b parameters of the solid solution series are in general agreement with the expected order–disorder behavior (Lumpkin et al., 1983) but would suggest a higher degree of Fe order into M1 than the results we obtained from Mössbauer spectra.

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

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.