An evaluation of garnet-clinopyroxene geothermometry in granulites

Abstract

Four new formulations of the garnet-clinopyroxene geothermometer (Ellis and Green 1979; Ganguly 1979; Saxena 1979; Dahl 1980) have been evaluated in the Adirondacks and five other granulite terranes using results from 94 mineral pairs. The Saxena and Ganguly formulations give temperatures that are generally 100–150° C above those constrained by phase equilibria and other independent thermometry while the empirical calibration of Dahl gives widely scattered, erratic results. Despite some scatter in the data, the Ellis and Green calibration appears to be more accurate and precise than the others and is the most useful garnet-clinopyroxene thermometer currently available for quantitative thermometry in granulites. All four formulations are sensitive to large variations (>70–80° C) in temperature suggesting that problems with accuracy and precision can be improved with further refinement of model-based aspects of the thermometers.