Análise geométrica e cinemática dos metassedimentos da Klippe de Ijaci, Sul de Minas Gerais / não informado pelo autor.

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

18/06/1996

RESUMO

The present work was undertaken in the Ijaci region, southern Minas Gerais state, and involved geological maping, emphasizing geometric and kinematic analysis of the structures in the meta-sedimentary cover. Two litostructural domains were distinguished: the basement domain, composed by granitic and granodioritic orthogneisses, with a steep plunging EW tectonic foliation; and the meta-sedimentary cover domain, composed by marbles at the base, and pelites and quartzites at the top. The meta-sedimentary cover is characterized by a sub-horizontal tectonic foliation, that plunges gentlly to the south. In the plane of tectonic foliation of the metasediments, a down plunge mineral-streching lineation was recognized with shear sense indicators, such as S-C foliations planes, assymetrical folds and sheath folds, that indicates top to NNW sense of shear. Microtectonic data suggest that the S and C foliation planes formed at the same time, under greenschist metamorphic conditions ( biotite zone ). This structural style is absent from in the basement rocks. This fact and the ductility contrast between the two lithostructural domains suggest a allocthonous character for the meta-sedimentary cover. In the late stage of the compressive evolution, folds with sub-horizontal hinge lines, plunging to the WSW direction were developed. After the compressive evolution, conjugated assymetrical extensional shear bands, with NE-SW general trend, and open folds, with hinge lines plunging gently to the south were developed. Probably the youngest structures observed in the cover are ductil-ruptil shear zones, subparallel to the old structural trend of the basement domain. Finally, it is concluded that the meta-sedimentary cover forms a klippe, and that it was affected by thin-skin tectonics, with thrust movements vergent to the foreland. Hence, the studied rocks may be localized in the extemal parts of a orogen, with internal parts localized in the south.

ASSUNTO(S)

geologia não informadas pelo autor. sedimentologia

ACESSO AO ARTIGO

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