Geochemistry, Sm-Nd isotopes and SHRIMP U-Pb geochronology of the Morro do Coco Granite (RJ, Brazil): another piece of the post-collisional magmatism of the Ribeira Belt

Abstract

The Morro do Coco granite (MC) is a post-collisional intrusive body that was emplaced at Ribeira Belt, in the Cambro-Ordovician, succeeding the final stages of the Gondwana supercontinent amalgamation. This unit requires more studies, contrasting with similar best investigated occurrences of the central Ribeira Belt. This work presents a detailed investigation of such unit using petrography, Inductively Coupled Plasma (ICP), X-Ray Fluorescence (XRF) whole-rock geochemistry, U-Pb (SHRIMP) geochronology and Sm-Nd isotopes. The rock is a nearly undeformed syenogranite, geochemically classified as a high-K calc-alkaline magnesian, with metaluminous to slightly peraluminous affinity. Strongly light rare earth elements (LREE)-enriched patterns with significant negative Eu anomalies, typical of post-collisional granites, are identified. Similarly to other post-collisional granites of the central Ribeira Belt, U-Pb zircon data provide crystallization age of 496 ± 3 Ma. Sm-Nd isotopic data suggest crustal magma source as indicated by εNd (496) of-9, 143 Nd/ 144 Nd ratios between 0.511747 and 0.511752 and Mesoproterozoic TDM ages of 1.3 Ga. Based on its geochemical characteristics, morphology and geochronology, this unit is considered here as a member of Nova Friburgo Suite. Geochronological data defined three pulses of magmatism in this part of the orogen during the Cambro-Ordovician (515, 490 and 460 Ma).

A Juvenile Component in the Pre- and Post-Collisional Magmatism in the Transition Zone between the Araçuaí and Ribeira Orogens (SE Brazil)

“…This magmatic bimodality is mainly observed in the bodies of the G5 super suite in the transition zone between the Araçuaí and Ribeira orogens [10]. The presence of mantle components is restricted in the post-collision units of the northern sector of the Araçuaí orogen and the segment of the Ribeira orogen [10,12,39,40,45,56,57].…”

Sana Granite, a post-collisional S-type magmatic suite of the Ribeira Belt (Rio de Janeiro, SE Brazil)

“…Journal Pre-proof Mambucaba, Favela, Andorinha, Teresópolis, Nova Friburgo, Frades, Conselheiro Paulino, Itaoca, São José do Ribeirão, Morro do Coco and Sana units (Valeriano et al, 2011;Tupinambá et al, 2012;Valeriano et al, 2016;Potratz and Valeriano, 2017;Bione et al, 2019). Based on geochronological, compositional, and structural criteria, Valeriano et al (2011) considered that the bodies of this suite are mainly composed of titanite, I-type, leucocratic and calc-alkaline granites.…”