Paleo- and Neoproterozoic magmatic and tectonometamorphic evolution of the Isla Cristalina de Rivera (Nico Pérez Terrane, Uruguay)

Abstract

The Isla Cristalina de Rivera crystalline complex in northeastern Uruguay underwent a multistage magmatic and metamorphic evolution. Based on SHRIMP U-Pb zircon, Th-U-Pb monazite (CHIME-EPMA method) and K-Ar age data from key units several events can be recognized: (1) multistage magmatism at 2,171-2,114 Ma, recorded on zircon of the granulitic orthogneisses and their 2,093-2,077 Ma overgrowths; (2) a distinct amphibolite facies metamorphism at *1,980 Ma, recorded by monazite; (3) greenschist facies reworking and shearing at ca. 606 Ma (monazite and K-Ar on muscovite) along the Rivera Shear Zone, and finally (4) intrusion of the post-tectonic Sobresaliente and Las Flores granites at around 585 Ma. Lithological similarities, geographic proximity and coeval magmatic and metamorphic events indicate a similar tectonometamorphic evolution for the Isla Cristalina de Rivera, the Valentines Block in Uruguay and the Santa María Chico Granulitic Complex in southern Brazil, since at least 2.1 Ga.

The Nico Pérez Terrane (Uruguay): From Archean crustal growth and connections with the Congo Craton to late Neoproterozoic accretion to the Río de la Plata Craton

“…2.18-2.11 Ga (Table 1). However, ages between 2.10 and 2.05 Ga were alternatively interpreted as the result of high-grade metamorphism (Santos et al, 2003) or multistage magmatism (Oyhantçabal et al, 2012). Similar U-Pb zircon ages were obtained in this work, further supporting Paleoproterozoic ages for the Valentines-Rivera Granulitic Complex, although Archean inheritance is also recorded.…”

“…The Pavas Block is dominantly characterized by orthogneisses, amphibolites, migmatites, mafic-ultramafic igneous rocks and Oyhantçabal et al (2012) metasediments with ages between 3.0 and 2.7 Ga (Preciozzi et al, 1979;Hartmann et al, 2001;Gaucher et al, 2011). Hartmann et al (2001) separated the Pavas Block into the La China and Las Tetas complexes, which are constituted by amphibolite facies metaigneous and metasedimentary rocks, respectively.…”

“…In the case of the Valentines-Rivera Granulitic Complex, Santos et al (2003) and Oyhantçabal et al (2012) reported ages of magmatism of ca. 2.18-2.11 Ga (Table 1).…”

“…1). The basement of the Nico Pérez Terrane includes the Archean Pavas Block (Preciozzi et al, 1979) as well as two Paleoproterozoic units, namely the ValentinesRivera Granulitic Complex and the Campanero Unit (Sánchez Bettucci, 1998;Oyhantçabal et al, 2011a), which are intruded by the Paleoproterozoic Illescas granite and several Neoproterozoic intrusions (Campal and Schipilov, 1995;Oyhantçabal et al, 2011aOyhantçabal et al, , 2012. A summary of the available geochronological data for the Nico Pérez Terrane is presented in Table 1.…”

Lithologies, structure and basement-cover relationships in the schist belt of the Dom Feliciano Belt in Uruguay

“…The Santa Maria Chico complex is defined in Rio Grande do Sul and contains ortho-and paragneisses reaching granulite facies at ~ 2.4 Ga (Hartmann 2008). The Valentines-Rivera complex is constituted by mafic and felsic orthogneisses, yielding multistage magmatic ages of ~ 2.17 -2.11 Ga and reaching granulite facies at ~ 2.08 Ga (Oyhantçabal et al 2012). This block is separated from the Pavas block by the Sierra de Sosa Shear Zone (Preciozzi 1987, Oriolo et al 2016a, 2016cFig.…”