Río de la Plata Craton

The Río de la Plata Craton (RPC) is a medium-sized continental block found in Uruguay, eastern Argentina and southern Brazil. During its complex and protracted history it interacted with a series other blocks and is therefore considered important for the understanding of the amalgamation of West Gondwana. Two orogenic cycles have been identified in the RPC: a 2000 Ma-old western domain representing the old craton and a 700–500 Ma-old eastern domain assigned to the Brasiliano Cycle. It is one of the five cratons (ancient nuclei) of the South American continent. The other four cratons are: Amazonia, São Francisco, Río Apa and Arequipa–Antofalla.

Three shear zones divides the Precambrian basement of Uruguay and southern Brazil into four terranes.

Along the Uruguayan east coast (reaching into Brazil) is the Cuchilla Dionisio Terrane, an allochthonous African block juxtaposed to the RPC along the Sierra Ballena Shear Zone (SBSZ).

West of Cuchilla Dionisio, the Nico Pérez Terrane is delimited by two longitudinal shear zones: the SBSZ and the Late Mesoporterozoic Sarandí del Yí Shear Zone (SYSZ). In the Nico Pérez Terrane, Neoproterzoic sedimentary successions crop out, probably deposited on an Atlantic-style continental shelf. The terrane hosts a swarm of NEE-SSW oriented dykes that date to the Neoproterozoic.

East of the SYSZ, the latitudinal Colonia Shear Zone (CSZ) separates the Palaeoproterozoic (2000±100 Ma) Piedra Alta Terrane to the north from the Tandilia Terrane to the south. A period of extensional tectonics in the Late Paleoproterozoic coincided with the formation and intrusion of the Piedra Alta mafic dike swarm and the rapakivi granites of Illescas Batholith. The 1790±5 Ma-old Late Palaeoproterozoic Piedra Alta mafic dike swarm was subsequently affected by the 8 km (5.0 mi)-wide Mesoproterozoic SYSZ and its eastern end bends along the dextral megashear zone.

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