The garnet-clinopyroxene Fe-Mg geothermometer — a reinterpretation of existing experimental data

Experimental data on the partitioning of Fe²⁺ and Mg between garnet and clinopyroxene (Råheim and Green 1974; Mori and Green 1978; Ellis and Green 1979) have been used to construct a new expression for the garnet-clinopyroxene geothermometer, including a curvilinear relationship between In Kd and X_Ca(ga): T(°C)=((-6173(X_Ca)²+6731 X_Ca+1879 +10 P(kb))/(lnKd+1.393))–273Application of this geothermometer to a suite of samples of eclogites and associated omphacite-garnet-bearing gneisses from the uppermost allochthon within the North Norwegian Caledonides shows that the calculated temperatures do not vary with rather great variations in the mg number of the garnet (0.17–0.54) and Na content of the clinopyroxene (0.11–0.44). Temperatures below 900° C calculated using the present equation are somewhat lower than those obtained by the method of Powell (1985), the difference being larger for lower temperatures and lower values of X_Ca.