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GEOLOGIA DA PORÇÃO NORTE DO GREENSTONE BELT DE GUARINOS, GOIÁS

1995; Sociedade Brasileira de Geologia; Volume: 25; Issue: 1 Linguagem: Inglês

10.25249/0375-7536.19955160

2177-4382

Hardy Jost, Raul Minas Kuyumjian, ANA LUIZA SABÓIA DE FREITAS, André Luiz Lima Costa, CARLOS TADEU C. NASCIMENTO, FLÁVIO DE MORAIS VASCONCELOS, LUIZ GALOTTI NETO, MARIA CEICILENE ARAGÃO MARTINS, MOISÉS NAVES CARVALHO, VALERIA CERQUEIRA CONDE,

Geochemistry and Geologic Mapping

The Guarinos greenstone belt is one of the three Archaean volcano-sedimentary rock assemblages of Crixás, Goiás, and its northern half was maped by the authors in 1992. The belt was intruded by a tonalite of the Caiamar Complex in the west, has a transcurrent fault contact with gneisses of the Moquém Block in the east and north, and is tectonically covered by Late Proterozoic metassedimentary rocks of the Araxá Group in the south. Its northeastern portion was intruded by a trondhjemite. Rocks of the belt (Guarinos Group) are grouped, from base to top, into the Serra do Cotovelo Formation (metakomatiites), Serra Azul Formation (tholeiitic metabasalts), São Patricinho Formation (detrital metassedimentary rocks), Aimbé Formation (banded iron formations, metaconglomerates and metahydrothermalites), and the Cabaçal Formation, which is further subdivided into a lower sub-unit (carbonaceous phyllites, locally metachert and banded iron and manganese formations), and an upper sub-unit (rythmic metashales and metasiltites). The supracrustais are folded into a normal and horizontal antiform in the south, which gives place to westerly dipping inverse antiforms in the north and east. The trondhjemite intrusion in the northeastern portion of the belt deformed the supracrustal rocks into a dome. Primary structures in metavolcanic and metasedimentary rocks indicate that the stratigraphic sequence of the greenstone belt is overturned, due to early northward verging nappes, followed by Late Proterozoic, easterly verging folding. Regional metamorphism took place under greenschist facies conditions. Contact metamorphic parageneses formed under hornblende hornfels and albite-epidote hornfels facies, respectively in contact with the western tonalite and the northeastern trondhjemite. Mylonites are of greenschist to lower amphibolite facies. Mineral resources in the area comprise gold and banded iron and manganese formations, under several modes of occurrence.