Deformational sequence of inversion in the Paramirim Aulacogen, northern region of the intracontinental sector of the Araçuaí Orogen

Abstract

The Paramirim Aulacogen was filled by the Espinhaço and São Francisco supergroups in the period from 1.75 to 0.69 Ga, and suffered partial inversion during the Ediacaran. In the northern sector of the intracontinental domain of the Araçuaí-WestCongo Orogen, six compressive deformational phases were interpreted and associated with the frontal inversion of the Paramirim Aulacogen. Three structural domains were identified: Jacaraci Fold-Thrust Belt, Caetité Nappe, and Transpressive Domain. The nucleation of deformational structures is related to a maximum stress field with general WSW-ENE orientation. The first deformational phase (D₁), found in the Jacaraci Fold-Thrust Belt and the Transpressional Domain, is related to the evolution of the Rio Pardo Salient. A dextral transpressional system nucleated the Caetité Nappe. This system also juxtaposed amphibolite facies rocks over lower temperature facies, as well as Statherian over Tonian rocks. Furthermore, this system was responsible for deformation in the transpressional domains and late deformation in the Jacaraci Fold-Thrust Belt. The region presents a variety of structures and is, therefore, an excellent natural laboratory for studying positive inversion in aulacogens.

KEYWORDS:
aulacogen; orogen; tectonic inversion; craton; deformational phases