Age and origin of Caledonian granites in the Grandjean Fjord - Bessel Fjord region (75°–76°N), North-East Greenland

Abstract

The Grandjean Fjord – Bessel Fjord region (75°–76°N) contains the northernmost occurrences of Caledonian granites in North-East Greenland. Most of them have been emplaced along the margins of a sequence of late Proterozoic sediments, the Eleonore Bay Supergroup, or occur within middle Proterozoic metasediments of the Smallefjord sequence. Most granites are undeformed, but granite sheets within the Smallefjord sequence may be foliated. Zircon U-Pb dates indicate that they were emplaced about 400 Ma ago. Sm-Nd, Rb-Sr, and major and trace element analyses suggest that the granites are of mixed origin. Components of crustal origin and juvenile mantle-derived material are present, and occur in variable proportions. Under these circumstances precise dating of the rocks is difficult: Rb-Sr whole-rock errorchrons yield erroneous 'ages' and zircon U-Pb data are not always easily interpreted.