Tracing the history from Rodinia break-up to the Gondwana amalgamation in the Embu Terrane, southern Ribeira Belt, Brazil

Abstract

The Mantiqueira Province (MP) is the major tectonic unit of southern Brazil, resulting from the closure of the Adamastor Ocean during Gondwana assembly. The Ribeira Belt (RB), the largest domain of the MP, has developed in several episodes of convergence during the Brasiliano-Pananafricano Orogeny and is subdivided into several terranes. One of them is the Embu Terrane (ET) that hosts metasedimentary successions and granitic bodies of different tectonic contexts. A combined study of petrography, geochemistry, LA–ICP–MS zircon U—Pb dating, and Hf isotope geology was carried out on the Juquiá (JG) and Sete Barras (SBG) granites of the southeastern ET, hosted by metasupracrustal rocks. The JG yielded U—Pb zircon ages of 799 ± 5 Ma and 755 ± 3 Ma, while the SBG U—Pb zircon and monazite ages of 602 ± 2 Ma and 598 ± 2 Ma respectively. Both granites have Neoarchean/Paleoproterozoic Hf(TDM) model ages and strongly negative εHf(t) values in zircon. Whole rock isotopic data support an evolved crustal signature, pointing to sources of long-lived crustal residence. The JG is a ferroan calc-alkalic peraluminous two-mica granite, while the SBG is a ferroan alkali-calcic peraluminous two-mica granite. The acquired data disclose two distinct magmatic episodes in ET: the Tonian Juquiá magmatism took place during the final stages of the Rodinia break-up or initial stages of expansion of one of the hypothetical oceans in the region and the Ediacaran Sete Barras magmatism might have been formed at the local transtensional area during final West Gondwana amalgamation. The data presented here and the wide-ranging geochronological data assemblage from the RB allowed a new paleogeographic reconstruction of the West Gondwana assembly.