%0 Journal Article
%A Rapela, Carlos W.
%A Pankhurst, R.J.
%A Casquet Martín, César
%A Fanning, C.M.
%A Baldo, Edgardo G.
%A González Casado, José Manuel
%A Galindo Francisco, María Del Carmen
%A Dahlquist, Juan A.
%T The Río de la Plata craton and the assembly of SW Gondwana
%D 2007
%@ 0012-8252
%U https://hdl.handle.net/20.500.14352/49519
%X The extent and nature of the Archaean–Palaeoproterozoic craton of Río de la Plata of southern South America, a major butpoorly understood crustal component in Neoproterozoic plate reconstructions, as well as the depositional, metamorphic andmagmatic history of the surrounding orogenic belts, are reviewed and reassessed, in part through the analysis of material recoveredfrom deep boreholes in western Argentina that penetrated Palaeozoic cover into basement. U–Pb SHRIMP zircon ages for thesesamples of 2162±6 Ma (diorite), 2189±14 Ma (amphibolitic schist) and 2088±6 Ma (granite) encompass the range of agesdetermined for the major Palaeoproterozoic orogenic events in the exposed parts of the craton close to the Atlantic coasts ofUruguay and Argentina. Taken together with the geochemical and Nd-isotope characteristics of these samples and an olivinegabbro from a further borehole that failed to yield zircon, these results strongly suggest that the Río de la Plata craton is extremelyuniform in its dominant chrono-tectonic and lithological make-up, and that it extends westwards as far as the 535–520 MaPampean orogenic belt, against which it probably has a fault contact.U–Pb SHRIMP zircon detrital age patterns are presented for representative metasedimentary samples from the craton cover inthe Tandilia belt of eastern Argentina, and from the Pampean (Cambrian) and Famatinian (Ordovician) belts to the west of thecraton. Whereas the oldest cover rocks in Tandilia clearly show material derived from the underlying craton, such detritus onlyappears in the younger (Ordovician) units to the west. Sedimentary protoliths in the Pampean belt were dominated byNeoproterozoic (broadly ∼600 Ma) and late Mesoproterozoic (broadly ∼1100 Ma) provenance, and derivation from the Río de laPlata craton is highly unlikely. Regional considerations, including previously published zircon data, palaeocurrent and structuraldata, suggest that these rocks must have had an origin within Gondwana-forming blocks, for which the closest identifiable sourcesare ‘Brazilian’ and ‘African’ (Namaqua–Natal). Consequently, the preferred model for the Pampean orogeny is that the Río de laPlata craton reached its present position by large-scale dextral strike-slip movement against fore-arc sedimentary sequences thathad developed on the southern and western margins of the Kalahari craton during the Early Cambrian. In the final stage thedisplaced sedimentary sequences outboard of the RPC collided with the Mesoproterozoic Western Sierras Pampeanas terrane, which was at the time attached to the large Amazonia craton and other smaller continental blocks, such as Arequipa–Antofalla andRío Apa. Protracted relative displacement of the RPC after the Pampean Orogeny led to its final position.
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