The Rio de la Plata craton and the adjoining Pan-African/Brasiliano terranes: the record from Rodinia break-up to West Gondwana assembly.

RAPELA, C.W.; FANNING, C.M.; CASQUET, C.; PANKHURST, R.J.; SPALLETTI, L.A.; POIRÉ, D.G. Y BALDO, E.G.

GONDWANA RESEARCH

ELSEVIER SCIENCE BV

Lugar: Koshi; Año: 2011 vol. 20 p. 673 - 690

1342-937X

U–Pb, Hf and O isotope data on zircon from a borehole at the eastern end of the Tandilia belt (38ºS) indicate that the un-reworked Palaeoproterozoic Río de la Plata craton abuts against a distinct continental terrane (Mar del Plata). The craton is bounded on all sides by transcurrent faults and there is no evidence to relate it to the Neoproterozoic mobile belts on either side. The Punta Mogotes Formation at the bottom of the borehole contains 740–840 Ma detrital zircons that are assigned to a widespread Neoproterozoic rifting event. The data suggest that the Mar del Plata terrane rifted away from the southwestern corner of the Angola block at c.780 Ma. Negative εHft values and δ18O > 6.5‰ suggest derivation by melting of old crust during a protracted extensional episode. Other continental terranes may have formed in a similar way in Uruguay (Nico Pérez) and southeastern Brazil, where the Schist Belt of the Dom Feliciano orogenic belt is probably a correlative of the Punta Mogotes sequence, implying that the Dom Feliciano belt must extend at least as far as 38º S. A new geodynamic scenario for West Gondwana assembly includes at least two major oblique collision transcurrent orogenies: Kaoko–Dom Feliciano (580–680 Ma) and Gariep–Saldania (480–580 Ma) the latter resulting from oblique impingement of the Rio de la Plata craton against the Kalahari craton. Accretion culminated with foreland basins such as the Cambrian (?) to Ordovician Balcarce Formation of the Tandilia belt and the Nama Group in southwestern Africa.