The Río de la Plata Craton of Argentina and Uruguay

The geology and the tectonic evolution of the Rio de la Plata Craton is reviewed, taking into account geochronological, isotopic and geophysical data. The craton consists of voluminous granite-gneissic terrains (2.2–2.1 Ga) that represent magmatism during the accretional stage of the orogeny. Coeval volcano-sedimentary basins are preserved as relics of supracrustal rocks, deformed and metamorphosed during a collisional event that occurred at ca. 2.1 Ga. Sm–Nd and Hf model ages between 2.7 and 2.2 Ga, and positive to slightly negative eNd(t) values indicate a Neoarchean to Paleoproterozoic juvenile crust which underwent a short period of crustal recycling. Undeformed granitoids, gabbros and dolerite swarms with calc-alkaline signature intruded at ca. 2.07 Ga correspond to the late- to post-tectonic stages of the orogeny. Exhumation, cooling and cratonization occurred during the Orosirian (2050–1800 Ma) and later anorogenic extension is recorded in tholeiitic dyke swarms intruded at ca. 1.8 Ga in Uruguay and at ca. 1.6 Ga in the Buenos Aires province of Argentina. There is no evidence of Meso- or Neoproterozoic orogenic reworking and only one shallow granite intrusion in Uruguay and low-temperature hydrothermal alteration in the Neoproterozoic cover of the Tandilia System can be ascribed to far-field effects of the Brasiliano orogeny.