The northern boundary of the Proterozoic (Nagssugtoqidian) mobile belt of South-East Greenland

Abstract

The Proterozoic mobile belt of South-East Greenland has been regarded as a classic example of amphibolite facies reworking of an Archaean granulite facies gneiss terrain. Its northern boundary has been interpreted as a transcurrent shear zone in which reworking was associated with major basic dyke emplacement. A re-examination of the northern boundary shows it to be a diffuse region more than 50 km wide in which retrogression, unrelated to dykes or shear zones, gradually intensifies southwards. Superimposed on this are discrete belts of retrogression associated with dykes and shear zones. The sense of displacement on the latter is compatible with thrusting of the northern Archaean block southwards over the reworked terrain of the mobile belt.