Table 5 Parameters used in calculating of the force constants for each mineral site.

Parameters used in calculating of the force constants for each mineral site.. All other constants are as used in (13). The ionicity is set to 0.36. For each equilibrium calculation, KT is calculated for each mineral using the molar proportions of Fe2+ and Fe3+ on each site, as determined using THERMOCALC.

MineralSpeciesSiteCation
coord.
Bond lengthOxygen
coord.
No. in formulaKf
(N m−1)
KT
(N m−1)
SpinelFe2+M62.154243178
SpinelFe2+T42.004179221
SpinelFe3+M62.0254276319
SpinelFe3+T41.87541145401
GarnetFe2+M182.2914326147
GarnetFe3+M262.0244277319
OlivineFe2+M62.16854142173
OrthopyroxeneFe2+M162.1353.66148198
OrthopyroxeneFe3+M162.1183.66173304
OrthopyroxeneFe2+M262.2283.33146192
ClinopyroxeneFe2+M162.143.66147197
ClinopyroxeneFe3+M162.0333.66183344
ClinopyroxeneFe2+M262.5263.75128117