The nature of the Paleoproterozoic orogen in the Jacobina Range and adjacent areas, northern Sao Francisco Craton, Brazil, based on structural geology and gravimetric modeling

摘要

Defintion of the geometry and tectonic style of Paleoproterozoic mobile belts at the Paleoarchean cratonic margin of the Gaviao Block brings new insights into the early evolution of the Sao Francisco Craton. This paper presents the regional structural framework and tectonic stratigraphic 3D models made from geological mapping and gravimetric modeling of the Jacobina Range. The Jacobina Range is composed of an Archean greenstone belt, Au-U detrital pyrite-bearing sedimentary rocks and Paleoproterozoic granite-gneissic terranes deformed between 2.1 and 1.9 Ga as the result of collision of the Archean Gaviao, Serrinha, and Jequie blocks. Two deformational phases and three subdomains were described in the field area. The deformational phases include (i) a compressional phase with a westward tectonic convergence that built an imbricated fault system and (ii) a sinistral transpressional phase with a northwestward tectonic convergence, which forms a subvertical fault system with sinistral-oblique to lateral displacement. The southern subdomain is characterized by an imbricated tectonic system overprinted by transpressional faults. The central subdomain contains western-verging meso- to megascopic, slightly asymmetric folds, preserved as evidence of high strain. The northern subdomain is characterized as a fold and thrust system that was tilted by the intrusion of late granitic bodies. The modeling of two gravimetric sections identified deep structures that suggest sutures between the Gaviao and Serrinha crustal blocks. Here, we propose a model for the Archean evolution of the Mundo Novo Greenstone Belt and the subsequent deposition of sediments in the Jacobina Basin, followed by intrusion of mafic-ultramafic sills and dikes and Paleoproterozoic deformation.