Variability in the sources of North Gondwana Cadomian basins tracked by Nd isotopic systematics (Iberian Massif)

Abstract

The Cadomian Orogeny encompassed the opening and closure of oceanic domains and associated sedimentary basins in the northern margin of Gondwana from Ediacaran to Early Cambrian time. In the Iberian Massif, these Cadomian basins are included in autochthonous and allochthonous (far-travelled) terranes of the Variscan Orogen. A compilation of Nd isotope information of Ediacaran-Lower Cambrian siliciclastic series supports previous proposal for variability in the sources along the North Gondwanan margin that continued during the Early Paleozoic. Older TDM model ages ranging from 1361 to 2357 Ma of the Variscan allochthonous Ediacaran-Lower Cambrian siliciclastic series indicate proximity to Archean and Paleoproterozoic old crustal sources of the West African Craton and represent deposition on a western Cadomian basin. In turn, the autochthonous Ediacaran-Lower Cambrian siliciclastic series show relatively younger TDM values ranging from 1179 to 2114 Ma, suggesting derivation from more juvenile magmatic rocks that are well represented further east. The Ediacaran-Lower Cambrian siliciclastic series of the autochthonous terranes formed in an eastern Cadomian basin located near the Sahara Metacraton, the Trans-Saharan Orogen and the Tuareg and Arabian-Nubian shields.