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The Río de la Plata craton and the assembly of SW Gondwana

Rapela, Carlos W. and Pankhurst, R.J. and Casquet, César and Fanning, C.M. and Baldo, Edgardo G. and González Casado, José Manuel and Galindo Francisco, Mª del Carmen and Dahlquist, Juan A. (2007) The Río de la Plata craton and the assembly of SW Gondwana. Earth-science reviews, 83 . pp. 49-82. ISSN 0012-8252

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Abstract

The extent and nature of the Archaean–Palaeoproterozoic craton of Río de la Plata of southern South America, a major but
poorly understood crustal component in Neoproterozoic plate reconstructions, as well as the depositional, metamorphic and
magmatic history of the surrounding orogenic belts, are reviewed and reassessed, in part through the analysis of material recovered
from deep boreholes in western Argentina that penetrated Palaeozoic cover into basement. U–Pb SHRIMP zircon ages for these
samples of 2162±6 Ma (diorite), 2189±14 Ma (amphibolitic schist) and 2088±6 Ma (granite) encompass the range of ages
determined for the major Palaeoproterozoic orogenic events in the exposed parts of the craton close to the Atlantic coasts of
Uruguay and Argentina. Taken together with the geochemical and Nd-isotope characteristics of these samples and an olivine
gabbro from a further borehole that failed to yield zircon, these results strongly suggest that the Río de la Plata craton is extremely
uniform in its dominant chrono-tectonic and lithological make-up, and that it extends westwards as far as the 535–520 Ma
Pampean 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 in
the Tandilia belt of eastern Argentina, and from the Pampean (Cambrian) and Famatinian (Ordovician) belts to the west of the
craton. Whereas the oldest cover rocks in Tandilia clearly show material derived from the underlying craton, such detritus only
appears in the younger (Ordovician) units to the west. Sedimentary protoliths in the Pampean belt were dominated by
Neoproterozoic (broadly ∼600 Ma) and late Mesoproterozoic (broadly ∼1100 Ma) provenance, and derivation from the Río de la
Plata craton is highly unlikely. Regional considerations, including previously published zircon data, palaeocurrent and structural
data, suggest that these rocks must have had an origin within Gondwana-forming blocks, for which the closest identifiable sources
are ‘Brazilian’ and ‘African’ (Namaqua–Natal). Consequently, the preferred model for the Pampean orogeny is that the Río de la
Plata craton reached its present position by large-scale dextral strike-slip movement against fore-arc sedimentary sequences that
had developed on the southern and western margins of the Kalahari craton during the Early Cambrian. In the final stage the
displaced 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 and
Río Apa. Protracted relative displacement of the RPC after the Pampean Orogeny led to its final position.


Item Type:Article
Uncontrolled Keywords:Río de la Plata craton; Gondwana assembly; Palaeoproterozoic; Neoproterozoic; Cambrian; Brasiliano orogeny; Pampean orogeny; U–Pb zircon dating
Subjects:Sciences > Geology > Petrology
ID Code:12028
Deposited On:17 Jan 2011 13:16
Last Modified:01 Sep 2011 12:03

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