A combined zircon SHRIMP and Sm-Nd isotope study of high-grade paragneisses from the Mid-German Crystalline Rise: evidence for northern Gondwanan and Grenvillian provenance

Abstract

SHRIMP analyses of detrital zircon cores from high-grade metasediments from the Mid-German Crystalline Rise, which is situated between Eastern Avalonia in the NW and Saxo-Thuringia in the SE, yield mostly ages of c. 550 Ma and c. 2.06 Ga, with minor c. 1.0 and 2.4-2.9 Ga components. The sedimentary protoliths were deposited during the Late Proterozoic to Early Cambrian, probably prior to the break up of the northern Gondwana margin at 460-500 Ma. These data are consistent with the sediments' high εNd values (0.9 to -3.0), which are comparable to those of well-documented Late Proterozoic sediments from other parts of Europe. The combined isotopic data suggest derivation of the sediments from at least three distinct crustal source regions. Dominant sources were the Avalonian-Cadomian orogenic belt (c. 45%), situated at the northern margin of Gondwana during the Neo-proterozoic, and the West African and/or eastern Amazonian cratons (c. 45%). The Grenvillian belt was a minor source (c. 10%). Show more