Geologia e geocronologia do Complexo Uvá, Bloco Arqueano de Goiás

Abstract

The Uva complex is the southernmost orthgneiss assemblage of the Archean terrain of Goias. It is limited to the north by the Serra de Santa Rita anf Faina greenstone belts, to south and southeast by Proterozoic metasedimentary rocks, to the east by Terciary-Quaternary units represented by lateritic plateaux and fluvial deposits. One for one hundred thousand scale geologic mapping revealed that the complex consists of an infrastructure that contains two domains: the Rio do Indio domain comprises banded and polydeformed dioritic, tonalitic and granodioritic gneisses of 2.9 Ga, and the Rio Vermelho domain, made up of tabular, variably foliated metatonalite, metamonzonite and metagranodiorite bodies of ca . 2.75 Ga. The compositional banding of the largest tonalitic body of the Rio do Indio domain has an average orientation N25 o -35 o W,20 o -60 o SW, whilst the foliation of the adjacent Rio Vermelho metaplutonic rocks follows the contact between both units, being N25 o W,20 o SW in the southeast and N70 o W,65 o SW in the west, which reproduces a dome-shaped structure. The granodioritic gneisses of the Rio do Indio domain probably occur as a large imbricated body whithin the metaplutonic rocks of the Rio Vermelho domain. Both domains have a Sm- Nd model age between 3.0 and 3.2 Ga, but their igneous protoliths differ in U-Pb zircon age of about 175 m.y., which indicated repeated crustal anatexy. The gneiss and metaplutonic infrastructure is extensivelly covered by a nappe suprastructure mostly composed of metaultramafic, subordinately metamafic rocks of probably komatiite and basalt protolith, with minor iron formation intercalations. A body of muscovite granite (Davinopolis Granite), with several facies including subvolcanic and xenolith-rich facies, and a syenite (Serra das Araras Syenite) intrude the infrastructure and suprastructure, and are probably related to the Neoproterozoic Brasiliano Cycle.