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Revisão estratigrafica e faciologia do Grupo Cuiabá no alinhamento Cangas-Poconé, baixada Cuiabana, Mato Grosso

2008; Sociedade Brasileira de Geologia; Volume: 38; Issue: 4 Linguagem: Inglês

10.5327/rbg.v38i4.1426

2317-4889

Cláudia do Couto Tokashiki, Gerson Souza Saes,

Paleontology and Stratigraphy of Fossils

The Cuiaba Group comprises a thick netasedimentary pile accumulated at the southeastern margin of Amazon Craton and affected by the Brasiliano-Panafrican Orogenic Cycle (~600Ma). The study of outcrops in regional profiles, open pits for gold exploration and drilling cores at Cangas-Pocone Alignment provides the basis for proposing a lithostratigraphic division of the Cuiaba Group into the Campina de Pedras, Acorizal and Coxipo formations. Along this alignment is recognized a facies association with predominance of metaritmites with dropstones, with a very strong magnetic signature denominated here as Cangas Facies on the midlle portion of the Acorizal Formation, encompassing a probable chronocorrelation with the glacially influenced Engenho Facies. This lithofacies ocurrs associated with (meta) conglomerates, sandstones and pellites and subordinated horizons of massive diamictites. This sucession is suggestive of a accumulation on a glacially influenced marine setting. The metarimite are interpreted as deposited during a long period of deglaciation, eustatic rise of sea level and liberation of coarse clasts from floating icemassas (icebergs). The sedimentary pile was affected by regional metamorphism at the greenschist facies reaching the Biotite Zone, deformed in recumbent folds and submitted to intensely hydrothermal activity during the last phases of deformation, with remobilization of quartz veins, sericitization, sulfetation and gold bearing fluids. The gold mineralization is supposed to be the product of a combination of diverse factors all contributing to the trapping of hydrothermal fluid flux, such as the very low permeability of host rocks, it's structural transverse position to the hydrothermal fluid flow path and a reworking of a fertile granite-greeenstone basement terrain of the border of southeastern Amazon Craton