PALAEOPROTEROZOIC BASEMENT PROVINCE IN THE CALEDONIAN FOLD BELT OF NORTHEAST GREENLAND

Rb-Sr and Sm-Nd model ages of basement gneisses in the Caledonian fold belt of North-East Greenland show that most of these rocks are relate d to a Palaeoproterozoic event of crust formation around 2000 Ma ago. U-Pb within-zircon (SHRIMP) analyses on three samples yield ages of 19 74 +/- 17, 1764 +/- 20, and 1739 +/- 11 Ma (2sigma values). Archaean r ocks (approximately 3000 Ma) are also present, but do not appear to be common. However, Sm-Nd analyses demonstrate that the Proterozoic gnei sses may contain substantial proportions of older (probably Archaean) crustal material. The discovery of a major province of mainly juvenile Palaeoproterozoic crust, which extends some 900 km along the coastal outcrops of North-East Greenland, implies that as much as one third of the whole of the Greenland shield may have been generated in the Pala eoproterozoic.