Modelagem gravimétrica do Complexo de Cana Brava e Seqüência De Palmeirópolis, GO

Abstract

The tectonic set composed by the Mafic Ultramafic Complex of Cana Brava ( CCB ) and the Volcano Sedimentary Sequence of Palmeiropolis ( SVSP ) is located in the north of Goias state, at the limit with Tocantins state, in Central Brazil. The complex is part of Tocantins Province, that lies between the Amazonian and Sao Francisco cratons. The Bouguer anomaly of the set is a large positive feature, elongated NS like the geological boundaries of the bodies, and does not have any small anomalies that could characterize the two main bodies. 2 ½D and 3D gravity models were used to determine the anomalous mass distribution at depth. The residual Bouguer profiles, for 2 ½D model, were obtained by graphic adjusting of a line, and the Bouguer residual map, for 3D model, was obtained by polynomial fitting of order 1. At both models, the major thickness is at the center of the exposed body and the contacts between the studied geological units are dipping westward. The SVSP unit has a depth of 15.5km at the north and 4.5km at the south. The denser CCB unit is thicker at the south (6.5km) than at the north (4km). The 2 ½D model suggests a triangular vertical section for the body ( CCB+SVSP ) with a broader area close to the surface. Small residual positives east of the geological boundary can be modeled by a small buried body of CCB , disconnected of the main one.