Resumo

BLANCO, Gonzalo. Provenance of the Ediacaran-Early Palaeozoic Arroyo Del Soldado Group (Uruguay) and the Nama Group (Namibia): Geodynamic Implications for the SW- Gondwana amalgamation. Ser. correl. geol. [online]. 2010, vol.26, n.1, pp.9-26. ISSN 1666-9479.

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 e_Nd values and T_DM 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.

Palavras-chave : Ediacaran; Nama Group; Arroyo del Soldado Group; Provenance; SW Gondwana.

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