Precambrian Research 172 (2009) 67–79 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Neoproterozoic magmatism and high-grade metamorphism in the Goiás Massif: New LA-MC-ICMPS U–Pb and Sm–Nd data and implications for collisional history of the Brasília Belt Maria Emilia Schutesky Della Giustina ∗ , Claudinei Gouveia de Oliveira, Márcio Martins Pimentel, Bernhard Buhn Instituto de Geociências, Campus Universitário Darcy Ribeiro, Universidade de Brasília (UnB), CEP 70910-900, Brasília, DF, Brazil article info Article history: Received 27 March 2008 Received in revised form 13 March 2009 Accepted 18 March 2009 Keywords: Neoproterozoic Brasiliano orogen Uruac ¸ u Complex U–Pb LA-MC-ICPMS Metamorphic core Delamination abstract This paper presents the first U–Pb and Sm–Nd data for the gneisses of the high-grade Uruac ¸ u Complex, exposed in the northern part of the Neoproterozoic Brasília Belt, central Brazil. Previous studies have interpreted this complex as the exposure of Archaean or Paleoproterozoic continental crust, included, therefore, in the so-called Goiás Massif, a small Archaean/Paleoproterozoic allochthonous (?) block. The complex is located in the northern Brasília Belt, adjacent to the eastern limit of the Goiás Magmatic Arc, and comprises a variety of para- and orthogneisses metamorphosed under amphibolite to granulite facies. New U–Pb LA-MC-ICPMS data for zircon grains from felsic and mafic orthogneisses reveal ages ranging from ca. 690 to 650Ma, interpreted as representative of the original igneous crystallization. Zircon overgrowths indicate metamorphic ages around 650Ma, suggesting that the metamorphism was partly concomitant or only slightly younger than the intrusion of granitoids and mafic bodies, as well as with the closure of the ocean between the Amazon and São Francisco continents at the end of the Neoproterozoic. The main geological characteristics of the Uruac ¸ u Complex, as well as the new U–Pb crystallization and provenance ages discussed in this work, are analogous to those observed in the Anápolis–Itauc ¸ u Complex, exposed in the southern Brasília Belt. This may suggests the correlation between both complexes, result- ing in a long granulitic belt developed to the east of the Goiás Magmatic Arc during the main collisional stage of evolution of the Brasília Belt. High-grade metamorphism and associated igneous intrusions rep- resented mainly by metagabbros and metagranites are, therefore, a conspicuous feature of the final stages of evolution of the Brasília Belt and might be related to delamination, uplift and extension following ocean closure and continental collision. © 2009 Elsevier B.V. All rights reserved. 1. Introduction High-grade rocks are common in several Pan-African/Brasiliano orogenic belts. Their significance is still a matter of controversy. They have been interpreted as: (i) exposure of older continental crust; (ii) the result of crustal thickening due to continental colli- sion; or (iii) being formed during extension and uplift following continental collision. In the Brasília Belt, large areas of Neopro- terozoic granulitic rocks are exposed and have been investigated in detail in recent years (Moraes et al., 2002; Piuzana et al., 2003) and the new field, petrological, geochronological and isotopic data have been instrumental for the understanding of their role in the tectonic evolution of the Brasília Belt. Located in the northern part of the belt, the Uruac ¸ u Complex (UC) is one of the least studied high-grade ∗ Corresponding author. Fax: +55 61 32724286. E-mail address: maria emilia@unb.br (M.E.S. Della Giustina). areas in Brazil. It comprises a variety of para- and orthogneisses, metamorphosed under amphibolite to granulite facies. The Uruac ¸ u Complex is exposed in the central part of the so- called Goiás Massif, which is interpreted as a microcontinent or exotic terrain accreted to the Neoproterozoic Tocantins Province during the Brasiliano Orogeny (Pimentel et al., 2000). Early stud- ies have attributed Archean or Paleoproterozoic ages to the Uruac ¸u Complex (Ribeiro Filho et al., 1978; Lacerda Filho et al., 1999). On the other hand, it has been suggested that the Uruac ¸ u Complex may be correlated with the large, high-grade, mafic–ultramafic Barro Alto, Cana Brava and Niquelândia Complexes due to their similar aero- magnetic signature. Oliveira et al. (2006), during a recent mapping project and based on field relationships, suggested a Neoprotero- zoic age for the Uruac ¸ u Complex. This controversy led to the detailed investigation of this unit, aiming to constrain the crystallization and metamorphic ages, to identify the sources involved in the origin of the paragneiss pro- tholiths, as well as to investigate the tectonic significance of these 0301-9268/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.precamres.2009.03.012