Geofisica

Revista Brasileira de Geociências

28(4):503-512, dezembro de 1998

A MODELAGEM DE SISTEMAS DE FALHAS EXTENSIONAIS, NUCLEADOS EM ZONAS DE FRAQUEZA PREEXISTENTES, E SUA APLICAÇÃO À BACIA MINAS NO QUADRILÁTERO FERRÍFERO, MINAS GERAIS
CAROLINE JANETTE SOUZA GOMES*, MARCELO A. MARTINS-NETO**, GESNER J. L SANTOS*** & LUIZ MARCELO R. MARTINS
ABSTRACT ANALOGUE MODELLING OF EXTENSIONAL BASINS CONTROLLED BY PREEXISTENT BASEMENT FAULTS, WITH APPLICATION TO THE MINAS BASIN IN THE IRON QUADRANGLE, MINAS GERAIS Analogue models were used to investigate the development of extensional basins above reactivated basement faults. All the experiments were set up with a fault system configured both oblique and orthogonal to the extension direction. In one sequence of eight sand models, the simple-shear model simulated the lithospheric stretching. The extension was applied on diverse fault dip angles in different extension directions. In a second sequence, the rift systems were simulated by homogeneous pure-shear acting on a brittle crust (sand) and on a brittle-ductile system (a silicone layer above the sand layer). The 3-D analysis of the resulting structures revealed that the geometry of basins controlled by preexistent basement faults depends essentially on two factors: the angle between extension direction and fault-strike, and the involvement of the ductile crust. In map-view, the structures were correlated to the Minas Basin, in the Quadrilátero Ferrífero, and ari ENE extension direction was proposed. Keywords: physical modelling of faults; reactivated basement faults; extensional basins; Quadrilátero Ferrífero RESUMO Com o objetivo de se estudar a geometria de bacias extensionais, nucleadas a partir de antigas zonas de fraqueza, foram montados treze modelos físicos. Todos os modelos continham um sistema de descontinuidades, em sua base. Em uma sequência de oito modelos, simulou-se a extensão litosférica pelo modelo do cisalhamento simples e em outra, de cinco modelos, a