A REVISION OF THE GARNET-CLINOPYROXENE FE2-MG EXCHANGE GEOTHERMOMETER()

A comprehensive experimental dataset was used to analyse the compositi onal dependence of the garnet-clinopyroxene Fe2+/Mg partition coeffici ent (K(d)). The Mg no. of garnet was found to have a significant effec t on the K(d), in addition to calcium content of garnet. An empirical model was developed to relate these effects with equilibrium temperatu re and pressure in the form of a conventional geothermometer, T(K) = { -1629[X(Ca)Gt]2 + 3648.55[X(Ca)Gt] -6.59[Mg no. (Gt)] + 1987.98 + 17.6 6P(kbar)}/(ln K(d) + 1.076). Application of this thermometer produced reasonable temperature estimates for rocks from the lower crust (garne t amphibolites, granulites and eclogites) and the upper mantle (eclogi te and lherzolite xenoliths in kimberlites, mineral inclusions in diam onds).