Rb-Sr and K-Ar Caledonian ages from the Upper Eleonore Bay Group and Cambrian metasediments of the East Greenland Caledonian fold belt

Abstract

Fine sediment fractions < 2 u extracted from various formations of Upper Proterozoic and Cambrian age in Canning Land and Segelsällskapet Fjord in East Greenland are anchimetamorphic to strongly diagenetic. Rb-Sr and K-Ar isotopic analyses indicate that the metamorphic and diagenetic changes correspond to the main Caledonian event at c. 450 Ma while some of the data are consistent with ayounger event at nearly 400 Ma, possibly connected to late Caledonian tectonics. The study also shows the peculiar features of the isotopic diagrams often observed in such conditions: parallel isotopic lines, discordant behaviour of the Rb-Sr and K-Ar chronometers, and the necessity of collecting sets of samples from small homogeneous areas.