Abstract Differences in tectonic style and kinematics in orogenic belts can result from either multiphase or progressive deformation. In eastern Borborema Province, a regional shallow dipping foliation is multiply folded and crosscut by transcurrent shear zones. Here, we investigate if these fabrics resulted from diachronous deformational events or from a single-phase progressive deformation. The study area, the Feira Nova region, mostly comprises metasedimentary rocks from the Surubim Complex, and is bounded by the NE-trending sinistral Gloria do Goitá (GGSZ) and the sinistral contractional Paudalho (PSZ) shear zones, which separate it from Paleoproterozoic basement rocks. Structures can be grouped into a contractional and a transpressional stage, both related to the Brasiliano Orogeny. The contraction-related structures are represented by a gently dipping foliation (S2) related to a top-to-the-NW tectonic transport. The contact between the metasedimentary and basement rocks is parallel to S2, indicating the fabrics in both lithotypes are of Brasiliano age, with strain localization having produced the PSZ. NW-verging macroscopic folds are consistent with this regime. The following transpression generated steep mylonitic foliation (S3) mainly along the GGSZ, and caused refolding. The data here presented are consistent with a progressive deformation history comprising a gradual transition from contraction to transpression.

ABSTRACT: The recent proposition for a long-lived (635-580 Ma) magmatic arc in the central portion of the Borborema Province is critically evaluated. Evidence favoring subduction include: low-T, high-P metamorphism; local occurrence of retroeclogites; and the probable participation of juvenile material in the genesis of 630-620 Ma-old plutons. However, several factors argue against the existence of a large ocean separating the Northern and Central subprovinces. First, early Tonian detrital zircons (1.0-0.9 Ga) in the Northern Subprovince indicate derivation from the Central Subprovince, and thus a connection between them until the time of deposition (ca. 660 Ma). Second, the age of peak metamorphism in the Northern Subprovince implies concomitant deformation in the upper and lower plates at 630-610 Ma. Third, 630-620 Ma-old granites have characteristics (e.g., high δO 18 values, low magnetic susceptibility) unlike plutons emplaced in continental active margins. Fourth, 590-580 Ma-old granites are clearly syn-transcurrent, i.e., post-collisional. Finally, the Patos shear zone, proposed to be a boundary transform between the two plates, is younger than 570 Ma, and thus cannot represent a suture zone. Therefore, if a magmatic arc existed, it had short duration and was developed at the end of the Cryogenian.