Structural analysis of the Rio Preto fold belt (northwestern Bahia / southern Piauí), a doubly-vergent asymmetric fan developed during the Brasiliano Orogeny

Abstract

The Rio Preto fold belt borders the northwestern São Francisco craton and shows an exquisite kilometric doubly-vergent asymmetric fan structure, of polyphasic structural evolution attributed exclusively to the Brasiliano Orogeny (~600-540 Ma). The fold belt can be subdivided into three structural compartments: The Northern and Southern compartments showing a general NE-SW trend, separated by the Central Compartment which shows a roughly E-W trend. The change of dip of S 2 , a tight crenulation foliation which is the main structure of the fold belt, between the three compartments, characterizes the fan structure. The Central Compartment is characterized by sub-vertical mylonitic quartzites, which materialize a system of low-T strike slip shear zones (Malhadinha -Rio Preto Shear Zone) crosscutting the central portion of the fold belt. In comparison to published analog models, we consider that the unique structure of the Rio Preto fold belt was generated by the oblique, dextral-sense interaction between the Cristalândia do Piauí block to the north and the São Francisco craton to the south.

Toward an integrated model of geological evolution for NE Brazil-NW Africa: The Borborema Province and its connections to the Trans-Saharan (Benino-Nigerian and Tuareg shields) and Central African orogens

“…The RP belt at the western end of this system seems to represent a simple inverted rift basin (aulacogenic structure) that would provide the link between the RdP (Monte Orebe)-Se-Yaoundé-Central African ocean, here called Transnordestino-Central African Ocean, to the east, and the much larger Goiás-Pharusian Ocean to the west, similar to the link between the Mediterranean and Atlantic oceans today. The RP basin would later be inverted in a doubly-vergent fan-like structure during the Brasiliano Orogeny, similar to the structure of the present-day Pyrenees (Caxito et al 2014c).…”

Orosirian (ca. 1.96 Ga) mafic crust of the northwestern São Francisco Craton margin: Petrography, geochemistry and geochronology of amphibolites from the Rio Preto fold belt basement, NE Brazil

“…In effect, the Rio Preto fold belt displays a doublyvergent structural style (Fig. 2), as the result of the inversion of a classic intra-continental fold belt (Egydio-Silva et al, 1989;Caxito, 2010;Caxito et al, 2014b).…”

Análise Tectônica Da Porção Nordeste Da Faixa Sergipana, Província Borborema: Dupla Vergência Em Resposta a Colisão Oblíqua Entre O Cráton Do São Francisco E O Terreno Pernambuco-Alagoas

“…Na região oriental do Brasil, registros de dupla vergência em zonas de cisalhamento dúcteis foram documentados nas faixas adjacentes do Cráton do São Francisco, incluindo Riacho do Pontal, Brasília, Rio Preto, Ribeira e Araçuaí demonstrando a importância de processos de colisões oblíquas na construção crustal de parte do orógeno Brasiliano/Pan-Africano (Alkmim et al, 2007;Caxito & Uhlein 2013;Uhlein et al, 2004;Caxito et al,2014).…”