Calymmian (1.50-1.45 Ga) magmatic records in Votuverava and Perau sequences, south-southeastern Brazil: Zircon ages and Nd-Sr isotopic geochemistry

The main aim of this work is to present and discuss the U-Pb zircon ages and Nd-Sr isotopic data from the metabasic rocks that occur within the metamorphosed Votuverava and Perau volcano sedimentary sequences, located in the Apiai Terrane, south-southeastern Brazil. The geochemical pattern of most of these metabasic rocks is similar to those of tholeiitic basalts, suggesting an extensional environment. The U-Pb zircon ages obtained around ca. 1480 Ma characterize an important basic magmatism during the Mesoproterozoic in south-southeastern Brazil. Nd model ages and epsilon(Nd)/epsilon(Sr) signatures suggest the Mesoproterozoic as the main period of mantle/crust differentiation for the crustal precursors of these metabasic rocks. It is quite possible that the Mesoproterozoic extentional events that caused the opening of large sedimentary basins in southern-southeastern Brazil have been underestimated. Possible regional correlations between the Votuverava-Perau basin (PR), the Betara and Agua Clara sequences (PR-SP) and the Serra do Itaberaba Group (SP) demonstrate the magnitude of the extensional process associated with the break-up of the preexisting continental masses. (C) 2011 Elsevier Ltd. All rights reserved

The Itaja foreland basin: a tectono-sedimentary record of the Ediacaran period, Southern Brazil

The Itajai Basin located in the southern border of the Luis Alves Microplate is considered as a peripheral foreland basin related to the Dom Feliciano Belt. It presents an excellent record of the Ediacaran period, and its upper parts display the best Brazilian example of Precambrian turbiditic deposits. The basal succession of Itajai Group is represented by sandstones and conglomerates (Bau Formation) deposited in alluvial and deltaic-fan systems. The marine upper sequences correspond to the Ribeiro Carvalho (channelized and non-channelized proximal silty-argillaceous rhythmic turbidites), Ribeiro Neisse (arkosic sandstones and siltites), and Ribeiro do Bode (distal silty turbidites) formations. The Apiuna Formation felsic volcanic rocks crosscut the sedimentary succession. The Cambrian Subida leucosyenogranite represents the last felsic magmatic activity to affect the Itajai Basin. The Brusque Group and the Florianopolis Batholith are proposed as source areas for the sediments of the upper sequence. For the lower continental units the source areas are the Santa Catarina, So Miguel and Camboriu complexes. The lack of any oceanic crust in the Itajai Basin suggests that the marine units were deposited in a restricted, internal sea. The sedimentation started around 600 Ma and ended before 560 Ma as indicated by the emplacement of rhyolitic domes. The Itajai Basin is temporally and tectonically correlated with the Camaqu Basin in Rio Grande do Sul and the Arroyo del Soldado/Piriapolis Basin in Uruguay. It also has several tectono-sedimentary characteristics in common with the African-equivalent Nama Basin. Copyright 2010 Springer-Verlag