The Río de la Plata Craton of Argentina and Uruguay

Abstract

The geology and the tectonic evolution of the Río de laPlata Craton is reviewed, taking into account geochronological,isotopic and geophysical data. The craton consistsof voluminous granite-gneissic terrains (2.2?2.1 Ga) thatrepresent magmatism during the accretional stage of theorogeny. Coeval volcano-sedimentary basins are preservedas relics of supracrustal rocks, deformed andmetamorphosed during a collisional event that occurred atca. 2.1 Ga. Sm?Nd and Hf model ages between 2.7 and2.2 Ga, and positive to slightly negative eNd(t) valuesindicate a Neoarchean to Paleoproterozoic juvenile crustwhich underwent a short period of crustal recycling.Undeformed granitoids, gabbros and dolerite swarms withcalc-alkaline signature intruded at ca. 2.07 Ga correspondto the late- to post-tectonic stages of the orogeny.Exhumation, cooling and cratonization occurred duringthe Orosirian (2050?1800 Ma) and later anorogenicextension is recorded in tholeiitic dyke swarms intrudedat ca. 1.8 Ga in Uruguay and at ca. 1.6 Ga in the BuenosAires province of Argentina. There is no evidence ofMeso- or Neoproterozoic orogenic reworking and onlyone shallow granite intrusion in Uruguay andlow-temperature hydrothermal alteration in theNeoproterozoic cover of the Tandilia System can beascribed to far-field effects of the Brasiliano orogeny.