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DEFORMAÇÃO E METAMORFISMO DAS SEQÜÊNCIAS JUSCELÂNDIA E SERRA DA MALACACHETA, COMPLEXO BARRO ALTO, GOIÁS

1994; Sociedade Brasileira de Geologia; Volume: 24; Issue: 3 Linguagem: Inglês

10.25249/0375-7536.1994189197

2177-4382

RENATO DE MORAES, Reinhardt A. Fuck,

Fish biology, ecology, and behavior

SEQUENCES, BARRO ALTO COMPLEX, GOIÁS.The Juscelândia volcanosedimentary and the Serra da Malacacheta gabbro-anorthositic sequences are part of the Barro Alto Complex, central Goiás, Brazil.In a geological section from south to north, the following tectonic-stratigraphic succession is recognized: i) mafic to felsic granulites, ii) sillimanite-garnet quartzite, iii) banded garnet amphibolite, iv) fine grained (garnet) amphibolite (metabasalt) with intercalations of metachert and calcsilicate rocks, v) biotite granite gneiss (metagranitoid) cut by fine grained (garnet) amphibolite dykes, vi) biotite-muscovite gneiss, feldspathic schist and micaschist (felsic volcanics, tuffs), vii) schist and phyllite with minor amphibolite and biotite-muscovite gneiss.Units i and ii represent the Serra de Santa Bárbara sequence, unit iii represents the Serra da Malacacheta sequence, whereas units iv to vii are included in the Juscelândia sequence.Four phases of deformation were recognized, the first two generated in a progressive event, while the last phases are represented by open folds and associated with retrometamorphic greenschist facies recristallization.The main foliation (Sn), formed by amphibolite facies minerals, strikes EW and dips 55° to the N.The associated stretching lineation is parallel to the strike of the main foliation and plunges slightly to the west.Along with kynematic indicators, this relationship indicates that the structures were formed in a lateral ramp of a major thrust structure, with tectonic transport from west to east.Garnet, staurolite and kyanite porphyroblasts overgrow the main foliation in micaschists, indicating that the peak of metamorphism post-dates the main deformation.The metamorphism of the Juscelândia sequence occurred at 520°C and 5.5 kbar, while in the Serra da Malacacheta sequence metamorphic conditions reached 720°C and 8.5 kbar.Textural relationships in micaschists of the Juscelândia sequence indicate a clockwise PT path of metamorphism.