Evolução estrutural e metamórfica da porção sul do Domínio São José do Campestre, Província Borborema, NE do Brasil: do Arqueano ao Neoproterozoico

Abstract

The São José do Campestre Domain, Borborema Province, northeastern Brazil was built by a long tectono-magmatic evolution. Inside this domain, outcrops the São José do Campestre Archean Core, composed by archean orthogneisses and metasupracrustal rocks (~3.4 to 2.7 Ga). The core is surrounded by paleoproterozoic orthogneisses (~2.3 to 2.0 Ga). These two units compose the basement of the study area, being cross-cut by intense plutonism during the Neoproterozoic. Based on remote sensing, bibliography, geophysics, geological mapping and petrography, the boundary between these units has been investigated, as well its tectono-metamorphic evolution and its correlation with geodynamic processes. The lithostratigraphy of the archean core in the study area is composed by: orthogneisses with biotite or clinopyroxene of Serra Caiada Complex (~3.36 Ga), serpentinites and pyroxenites of Riacho das Telhas Complex (~3.1 to 3.06 Ga), biotite-garnet paragneisses (~3.0 Ga?), including dolomitic marble lenses, hornblende-syenogranite São José do Campestre (~2.7 Ga). Surrounding the archean nuclei, paleoproterozoic orthogneisses (~2.3 to 2.0 Ga) are cross-cut by intense Neoproterozoic plutonism (granitoids, diorites and carbonatites), as well E-W Mesozoic basaltic dikes. The structural framework of the study area is characterized by five deformational events, which took place from Archean to Neoproterozoic. The first two events, exclusive of the archean units, are responsible for a high temperature tangential deformation, generating recumbent folding (Sn+1) parallel to S¬n. The third event (Dn+2), affecting paleoproterozoic units too, is marked by low temperature recumbent folding (Sn+2). The fourth deformational event, which likely took place in Ediacaran, is characterized by antiforms and sinforms with NW-SE axial plane (Sn+3). The last deformational event (Dn+4) is marked by sinforms and antiforms with subvertical N-S axial plane. Two metamorphic events related to these deformational events where identified. The first (Mn+1) is related to Dn+1, reaching low pressure granulite facies. The presence of metamorphic spinel in metasedimentary rocks attest this condition. The second metamorphic event reached amphibolite facies, being related to high temperature shear zones. The tectonic context of this domain, previously interpreted as a paleoproterozoic continental collision, cannot be attested by the observed deformation and metamorphic conditions. Instead, they likely represent crustal block movements along dextral shear zones during the Neoproterozoic.