2003/02/01 by Daniel J. Frost, D. J. Frost · 6 citations
Earth and Planetary Sciences · Materials Science · #Geological and Geochemical Analysis #High-pressure geophysics and materials #Clay minerals and soil interactions
paper · doi:10.2138/am-2003-2-315
The partitioning of Fe and Mg between garnet coexisting with olivine, wadsleyite, ringwoodite and magnesiowüstite solid solutions has been measured between 9 and 19 GPa and 1400-1700 ℃. In addition to studying exchange reactions involving the pyrope-almandine garnet solid solution, majoritic garnets forming in a natural peridotite bulk composition have been also examined. Metallic Fe was added to all bulk compositions to buffer the Fe3+ concentration at its lowest possible level. Partitioning data between pyrope-almandine garnet and ringwoodite were combined with data for garnet-magnesiowüstite and ringwoodite-magnesiowüstite partitioning to refine thermodynamic mixing properties for these solid solutions at 18 GPa and 1400 ℃. A multiple non-linear regression employing cation exchange data between these 3 solid solutions yielded the following well-constrained values for the differences in symmetric solid-solution interaction parameters: WmwFeMg - WringFeMg = 8.8(2) kJ/mol, WmwFeMg - WgtFeMg = 12.8(5) kJ/mol,WringFeMg - WgtFeMg = 4.0(4) kJ/mol.