U-Pb SHRIMP and Sm-Nd geochronology of the Silvânia Volcanics and Jurubatuba Granite: juvenile Paleoproterozoic crust in the basement of the Neoproterozoic Brasília Belt, Goiás, central Brazil

Abstract

U-Pb SHRIMP and Sm-Nd isotopic ages were determined for felsic metavolcanic rocks from the Silvânia Sequence and Jurubatuba Granite in the central part of the Brasília Belt. Zircon grains from a metavolcanic sample yielded 2115 ± 23 Ma and from the granite yielded 2089 ± 14 Ma, interpreted as crystallization ages of these rocks.Six metavolcanic samples of the Silvânia Sequence yielded a six-point whole-rock Sm-Nd isochron indicating a crystallization age of 2262 ± 110 Ma and positive ε Nd (T) = +3.0 interpreted as a juvenile magmatic event.Nd isotopic analyses on samples from the Jurubatuba Granite have Paleoproterozoic T DM model ages between 2.30 and 2.42 Ga and ε Nd (T) values vary between -0.22 and -0.58. The oldest T DM value refers to a sedimentary xenolith in the granite. These results suggest crystallization ages of Silvânia volcanics and Jurubatuba Granite are the first evidence of a ca. 2.14-2.08 juvenile magmatic event in the basement of the central part of the Brasília Belt that implies the presence of arc/suture hidden in reworked basement of the Brasília Belt.

Two neoproterozoic crustal accretion events in the Brasília belt, central Brazil

“…Previous age data from the Goiás magmatic arc document two distinct crustal accretion events Pimentel and Fuck, 1992;Viana et al, 1995;Rodrigues et al, 1999;Fischel et al, 2001b;Dantas et al, 2001;Piuzana et al, 2003a,b;Junges et al, 2002Junges et al, , 2003Laux et al, 2002aLaux et al, ,b, 2003aLaux et al, ,b, 2004Motta-Araújo and Pimentel, 2003). with those discussed herein.…”

The Paleoproterozoic Campinorte Arc: Tectonic evolution of a Central Brazil pre-Columbia orogeny

“…Unlike the Pau de Mel Suite, however, the biotite-muscovite-bearing Aurumina Suite is characterized by extensive peraluminous syn-collisional magmatism (Alvarenga et al, 2007). Silvânia Arc metagranites and felsic metavolcanics, further south, show ages comparable to the Campinorte back arc granulites and are loosely interpreted as part of a magmatic arc (Fischel et al, 2001). Its genetic relationship with the Campinorte Arc deserves further study.…”

“…D'el-Rey published a detailed geological-structural study on the Rio Maranhão Thrust as an intracontinental fault rather than a collisional suture. Aside from their own structural data the authors mention the Araí-Serra da Mesa lateral correlation and the occurrence of Paranoá Group rocks within the Brasília Belt internal zone (Jost et al, 1993Fischel et al, 2001;Fortes et al, 2003;Moraes et al, 2003;Botelho et al, 2006;Queiroz et al, 2008;Giustina et al, 2009a;Marques, 2010). Minimum sedimentation ages are inferred from U-Pb ages of rocks intrusive in the sequence.…”

“…Coeval basement rocks as the Aurumina Suite (Botelho et al, 2006;Alvarenga et al, 2007) and the Silvânia Arc (Fischel et al, 2001) could be somehow related to the Campinorte Arc evolution (Fig. 8).…”

Shrimp and conventional U-Pb age, Sm-Nd isotopic characteristics and tectonic significance of the K-rich Itapuranga suite in Goiás, Central Brazil

“…This sequence has been traditionally correlated with the Silvânia metavolcanics, exposed to the southeast of the area, and dated recently at ca. 2.1 Ga (Fischel et al 2001b). The Araxá Group is formed dominantly by pelitic schists with garnet and thin quartzite layers, and the Serra Dourada Sequence, of unknown age, comprises quartz schist and quartzite.…”