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 40Ar/39Ar 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).

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