Original paper

Experimental data on Fe and Mg partitioning between coexisting sapphirine and spinel: an empirical geothermometer and its application

Das, Kaushik; Fujino, Kiyoshi; Tomioka, Naotaka; Miura, Hiroyuki

Abstract

Specially designed experiments were carried out in the temperature range 950-1100 °C at 800 MPa to grow coexisting sapphirine and spinel-bearing metapelitic assemblages in the KFMASH system. Equilibrium phase assemblages contain these two phases with stoichiometric compositions. Compositional data obtained from the two coexisting phases indicate a strong dependence of the Mg-Fe distribution coefficient on temperature. An empirical thermometric expression has been formulated from the experimentally constrained relationship, lnKD = -6277/T(°K) + 6.4202, where KD = (XMg/XFe)Spr.(XFe/XMg)Spl. Application of this thermometer to natural mineral pairs indicate that earlier temperature estimates based on sapphirine-spinel need to be revised upward by 120-160 °C.

Keywords

sapphirine-spinel granulitesfe-mg exchange thermometerapplication to natural rocksuht metamorphism