Abstract:
Based on allostratigraphic criteria used during geological mapping of an area of approximately 1,600 km2, it was interpreted that the structural framework of the Serra do Espinhaço in Minas Gerais consists of a duplex thrust system of regional importance. The two main shear zones of the duplex (roof- and sole-shear zones) are connected one to another by a system of minor subsidiary thrusts, forming a system of tectonic horses. Above the roof-shear zone, deformation is represented by an array of embricated tectonic fans, where thrusts converge below into the main roof-shear zone. Heterogeneous, progressive in character, brittle/ductile, simple-shear deformation, with tectonic transport directed towards the west, developed the duplex thrust system, during an initial phase of deformation (D1). A second deformational phase (D2) caused crustal shortening by generalized asymmetric folding and reactivation of D1 thrust-planes and shear-zones. Syntectonic progressive metamorphism produced the crystallization of a mineral association typical of lower greenschist facies conditions.
Keywords:
geological mapping; structural analysis of Proterozoic terrains; duplex thrust system