Problems in oxygen isotope geothermometry in mafic granulite facies rocks from near Einasleigh,northern Queensland

Oxygen isotope geothermometry of coexisting minerals from five mafic granulites does not reflect the peak temperature of metamorphism as determined by other methods. Exchange of ¹⁸O between phases during slow cooling has (a) lowered the δ ¹⁸O of clinopyroxene relative to orthopyroxene in the presence of hornblende, (b) raised the δ ¹⁸O of quartz in a manner which is partly dependent on quartz abundance, and (c) lowered the δ ¹⁸O of plagioclase in some rocks.