Provenance of the Ediacaran-Early Palaeozoic Arroyo Del Soldado Group (Uruguay) and the Nama Group (Namibia): Geodynamic Implications for the SW- Gondwana amalgamation

the petrographic, heavy mineral analyses and geochemical results from the nama group indicate a recycled upper crust composition characterized mainly by metamorphic and granitic and minor mafic rocks sources. paleocurrent analyses of the chromian spinel bearing sandstones of the nama basin point to a volcanic island arc source located in the damara belt. detrital zircon dating of the nama group display major peaks of neoproterozoic and mesoproterozoic ages suggesting a provenance from the damara/gariep belts and their basements. paleocurrents from the west and the dominance of neoproterozoic-cambrian detrital u-pb zircon ages (76%) in the "molasse" stage of the foreland evolution probably indicate exhumation of the felsic volcanic arc root which probably occurred after the time indicated by the younger zircon dated at 531 ±9 ma. the petrographic and geochemical results from the arroyo del soldado group indicate a recycled upper crust composition characterized by source diversity composed of granite-gneissic and mafic-metamorphic rocks. on average, nd isotopes account for negative end values and tdm ages in a range of variation found elsewhere within sw gondwana. detrital u-pb zircon dating indicate sources dominated by paleoproterozoic (1.7-2.0-2.2 ga) and subordinate archaean ages (2.5-2.9-3.5 ga). the scarcity of mesoproterozoic and neoproterozoic zircons and paleocurrent directions towards the east indicate that the arroyo del soldado group was fed by detritus from the río de la plata craton favouring a passive margin tectonic setting for their deposition. deformation of the arroyo del soldado group took place ca. 530 ma, after strike-slip collision.