Geochronological constraints on the evolution of the southern Dom Feliciano Belt (Uruguay)

Abstract

New U–Pb sensitive high-resolution ion microprobe, K–Ar and Ar–Ar data from the southernmost Dom Feliciano Belt allow the identification of four major events. Orthogneisses from the Punta del Este Terrane indicate a magmatic episode at c . 770 Ma and high-grade metamorphism at 641 ± 17 Ma. Granitoid emplacement at 627 ± 23 Ma was roughly coeval with peak metamorphism. Volcaniclastic rocks of the Las Ventanas Formation dated at 573 ± 11 Ma can be correlated with the peripheral foreland basin (571 ± 8 Ma). Transpression and coeval high-K calc-alkaline magmatism is recorded in the Maldonado granite dated at 564 ± 7 Ma. The following events are postulated: (1) magmatism at 850–750 Ma related to rifting; (2) metamorphism and granite emplacement at 650–600 Ma; (3) molasse sequences and foreland basins at c . 573 Ma; (4) late magmatism at 580–560 Ma associated with transpression. The data indicate that (1) the Punta del Este Terrane could be a portion of the Coastal Terrane of the Kaoko Belt, (2) granitoid emplacement at 650–600 Ma in the Punta del Este and Nico Pérez terranes favours westward subduction, and (3) widespread post-collisional synkinematic magmatism occurred in the Dom Feliciano and Kaoko belts between 580 and 550 Ma. Supplementary material: Analytical methods and data are available at http://www.geolsoc.org.uk/SUP18369 .

The Río de la Plata Craton: a review of units, boundaries, ages and isotopic signature

“…Two main belts have been recognized: (1) the San José belt (Bossi Fig. 1 The main outcrop areas of the Río de la Plata Craton and the new boundary proposed in this contribution (after Preciozzi et al 1985;Bossi and Ferrando 2001;Oyhantçabal et al 2007b;Rapela et al 2007;Sánchez Bettucci et al 2010) Int J Earth Sci (Geol Rundsch) ) 100:201-220 203 et al 1993bOyhantçabal et al 2003Oyhantçabal et al , 2007bSánchez Bettucci et al 2010) located in southernmost Uruguay and (2) the Arroyo Grande Belt (Bossi and Ferrando 2001), which crops out in the northern part of the terrane (Fig. 2).…”

“…The Fig. 2 Geological map of the Piedra Alta Terrane, Uruguay (after Preciozzi et al 1985;Bossi and Ferrando 2001;Oyhantçabal et al 2007b) name San José Belt is preferred due to the better exposure in the surroundings of the City of San José (Oyhantçabal et al 2007b). The Montevideo Formation (Fig.…”

“…2) comprises amphibolites, paragneisses and garnet and staurolite-bearing micaschists. The San José Formation-probably the continuation of the former-is almost exclusively composed of paragneisses and garnet and staurolite-bearing micaschists (Preciozzi 1993;Oyhantçabal et al 2003Oyhantçabal et al , 2007b.…”

“…The metavolcanic rocks include metabasalts and metaandesites, metadacites and metatuffs. At least two deformation events are recognized in the belt (Campal 1990;Preciozzi 1993;Oyhantçabal et al 2007b). The last event is associated with syn-tectonic granites and the above-mentioned conjugate shear system.…”

“…Several post-tectonic granites also intrude the central granitic gneiss belt. U-Pb age determinations are not available, but Rb-Sr whole-rock ages (2,015 ± 40 Ma, Piedra Alta granodiorite; 2,030 ± 75 Ma, Carmelo granodiorite and 1,970 ± 55 Ma, Conchillas granitic gneiss; Umpierre and Halpern 1971) and field relationships (Oyhantçabal et al 2007b) indicate that the late-to postorogenic intrusions correspond to the same magmatic event responsible for the 2.08-2.05 Ga post-orogenic plutons that intruded into the Arroyo Grande and San José Belts.…”