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The Rio de la Plata craton and the adjoining Pan-African/brasiliano terranes: Their origins and incorporation into south-west Gondwana

Rapela, Carlos W. and Fanning, C.M. and Casquet, César and Pankhurst, R.J. and Spalletti, Luis and Poiré, Daniel and Baldo, Edgardo G. (2011) The Rio de la Plata craton and the adjoining Pan-African/brasiliano terranes: Their origins and incorporation into south-west Gondwana. Gondwana research, 20 . pp. 673-690. ISSN 1342-937X

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Abstract

The Neoproterozoic to Early Cambrian amalgamation of SW Gondwana through the Brasiliano/Pan-African
orogeny is reviewed with emphasis on the role of the Río de la Plata craton of South America in the light of
new evidence from a borehole at the eastern end of the Tandilia belt (38°S). U–Pb, Hf and O isotope data on
zircon indicate that this un-reworked Palaeoproterozoic craton abuts against a distinct continental terrane to
the east (Mar del Plata terrane). The craton is bounded everywhere by transcurrent faults and there is no
evidence to relate it to the Neoproterozoic mobile belts now seen 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 N6.5‰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 38°S. A new geodynamic scenario for West Gondwana assembly includes at least
two major oblique collisional 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. Assembly of this part of South-West Gondwana was accomplished before the Ordovician (to Silurian?)
siliciclastic platform sediments of the Balcarce Formation in the Tandilia Belt covered the southern sector of
Río de la Plata craton.

Item Type:Article
Uncontrolled Keywords:Palaeoproterozoic, Cratons, U–Pb provenance, Neoproterozoic rifting, Southwestern Gondwana assembly
Subjects:Sciences > Geology > Stratigraphic geology
ID Code:14729
Deposited On:27 Mar 2012 10:24
Last Modified:27 Mar 2012 10:24

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