Geology, Geochemistry, and Geochronology (U-Pb) of the Rio Fortuna Gneiss - Serra do Baú Intrusive Suite - Paraguá Terrane - SW Amazonian Craton

The Rio Fortuna Gneiss crops out in the Serra Santa Barbara, near the Fortuna military headquarters, on the Brazil-Bolivia border. These orthogneisses are located in a portion of the Paragua terrain affected by the Sunsas Orogeny (1.0-0.9 Ga.). They are classified as monzo to granodiorite orthogneisses and underwent at least three episodes of deformation. The U-Pb zircon age of 1,711 +/- 13 Ma obtained by laser ablation MC-ICP-MS is interpreted as the crystallization age of this orthogneiss. Geochemically, these rocks form a sequence comprising acidic sub-alkaline magmatism, calc-alkalic-type high-K, and metaluminous to peraluminous.