Age and tectonothermal record of Laurentian basement, Caledonides of NE Greenland

Abstract

Isotope mineral ages provide constraints on the age and tectonothermal record of Laurentian basement in Dronning Louise Land, NE Greenland Caledonides. West of the Caledonian thrust zone, U-Pb dates for detrital zircon grains within late Proterozoic–early Palaeozoic foreland cover sequences define an age range of detritus between 3001 Ma and 1700 Ma. Detrital muscovites record 40 Ar/ 39 Ar mineral cooling ages of c. 1700–1600 Ma. A reworked granitic orthogneiss east of the Caledonian thrust zone yields a U-Pb zircon age of 1909 +6 −5 Ma which is interpreted as dating emplacement of the protolith. A lower concordia intercept of 422 +28 −25 Ma dates Caledonian reworking. The data indicate that the Pre-cambrian basement in NE Greenland forms part of an early Proterozoic (c. 1900–1700 Ma) mobile belt comprising, in part, reworked Archaean rocks. In contrast to central E Greenland, there is no isotopic evidence for regional tectonothermal activity of late Proterozoic age (c. 1000 Ma).