A review of Antarctic granulite-facies rocks

Abstract

Precambrian granulite-facies rocks occur in significant proportion in the East Antarctic Precambrian shield. Ages of metamorphic and deformational events range from 2500 m.y. to about 500 m.y., but some rocks are much older, notably the approximately 3500 m.y. ages for crust formation in Enderby Land. Mineral assemblages over most of the area are typical of the hornblende granulite facies, and sparse temperature pressure estimates indicate metamorphism at 700–800°C and 5–8 kbar at reduced water pressures. A terrane of exceptional interest is the Napier complex of Enderby Land, where sapphirine-quartz ± garnet, sillimanite-orthopyroxene, osumilite, and inverted pigeonite are associated with pyroxene-granulite-facies rocks. Metamorphic conditions are estimated to have reached 900°–980°C, 7–9 kbar, and p H 2 O < 0.5 kbar. Metamorphism in the Napier complex, and possibly in other parts of East Antarctica, may be associated with large loss of fluid rather than massive influx of CO 2.