The patterns of fracture and the conditioning tectonics in the region of the Quadrilatero Ferrifero and part of the Migmatitic-Gnanulitic Complex in Minas Gerais (Brazil)

The structural evolution of the SE portion of Minas Gerais State, including the Quadrilatero Ferrifero and adjacent parts of the Migmatitic-Granulitic Complex are described. The area of complex policiclic evolution is composed of pre-Cambrian metamorphic rocks, arquean to upper proterozoic in age. In phanerozoic times basaltic magmatism and related tectonism took place principally in the Mesozoic Era, and restricted lacustric sedimentary basins developed in the tertiary and quaternary periods. This study is based on the interpretation of remote sensing products (MSS, RBV, TM and SLAR images) and geological data form literature and field work. An integrated geological map (1:250.000) and a statistical analysis of the patterns of fracturing show the importance of NNE-SSW and E-W directed events of ruptile and ruptile-ductile tectonics in the Archean and in the conditioning of the younger fracture-generations. Further evidences regarding the structural evolution of the Minas Supergroup in the Quadrilaterio Ferrifero revealed different fracture patterns in the Minas - cover in respect to its underlying basement.