The tectonostratigraphic terrains surrounding the north-central part of the São Francisco Craton

Abstract

This paper focusses the presence of proximal tectonostratigraphic terranes positioned at the- central- north surroundings of the S. Francisco Craton. There are some cases where the high grade basement rocks of these terranes and of the craton show observable continuity, in terms of rock assemblage and structure. Sometimes this continuity cannot be observed because the presence of diferente Fanerozoic .posits. The tectonicstratigraphic terranes are considered as “natives” (they were separated parts of the main craton) . The idea of tectonic and erosional wearing of a previous larger cratonic block (“Paramirim Craton”) was arosed first by Almeida, (1981) with a drastic reduction of the original dimensions of the previous craton. The idea was recently arosen by Dantas et al.(2019) with some good arguments, ,but they were not enough. They were considered as “natives” tectonostratigraphic terranes (they would be parts of the neighboring craton (according the classification of Kearey et al, 2009). In all cases the structural tectonic vergence is toward the present craton. Actually the process of decratonization of the craton is partially viable, but it needs to be discussed in terms of cause, way and time. Rarely we do have clear and undiscussible data. In this paper three domains of the meridional Borborema Province will be considered: a) SE of Piaui and NWt of the São Francisco Province - domain of the Rio Preto Fold belt and surroundings; b) North of Bahia until the Pernambuco Lineament, domains of the Riacho do Pontal folding system; c) NE of the São Francisco Province, from the Pernambuco Lineamento up to Aracaju parallel (south of Sergipe.).So doing, the history of “decratonization” is a viable idea, but is demanding discussion in terms of cause and time. Along this paper, we are going to discuss three áreas, distinct of each other: a) SE of Piauí - NW of S. Francisco craton; b) North of Bahia until the Pernambuco lineament; c) NE of the craton, from the Pernambuco Lineament till the parallel of Aracaju (SE), along the domains of the Sergipano belt. All these areas have been visited and reviwed by the authors more than once, they observed interesting points for an up to date discussion. All these geological domains have been observed by the authors, more than once, and they offered attactive themes for discussion. Some problems do exist and they will be discussed with basis on our present geological knowledge