A high-pressure granulite facies complex in north-west Payers Land, East Greenland fold belt

Abstract

Aeromagnetic, geological and geochemical data demonstrate the presence of a high-pressure, granu­Iite-facies gneiss complex about 400 km2 in area within a previously almost unexplored nunatak region between latitudes 74°30 and 75°N in northern East Greenland. The gneiss complex is surrounded and in part overthrust by supracrustal rocks of very high amphibolite facies, including garnet-clinopyroxene rocks of eclogitic affinity. A magnetically anomalous area is related to exposures of granulite facies rocks, whereas the surrounding supracrustals give rise to a magnetic smooth zone. Several, independent sets of observations indicate that the granulite facies metamorphism and the high amphibolite facies metamor­phism were related to the same metamorphic event. Maximum temperatures of about 740°C and maximum pressures of about 12.5 kb were reached (kyanite formation) later decreasing to about 10 kb (sillimanite formation). Comparisons with other parts of the East Greenland fold belt suggest a probable Archaean origin for the central gneiss complex and an early or middle Proterozoic age for the granulite and amphibolite facies metamorphism. There are no indications of Caledonian metamorphic events, in contrast to the previously assumed Caledonian origin for the area.