Geobarometry in granulites.

Abstract

The experimental data and results for the application of various geobarometers to granulite-facies terrains are reviewed. The solution model for garnet is being actively studied and further data are given for the development of the garnet geobarometer. One useful assemblage in pelitic rocks is that containing garnet + rutile + Al2SiO5+ ilmenite (with excess quartz implied), which is referred to as GRAIL. A geobarometer based on coexisting orthopyroxene + plagioclase + garnet + quartz is also presented. Inferred P for upper amphibolite grade and transitional amphibolite-granulites does not differ much from that inferred in granulite and garnet-granulite terrains, suggesting that the formation of granulites is dependent on increasing T with only a modest increase in P.-R.A.H.