Transition from contractional to transpressive tectonics: evidence from the Feira Nova Region, Rio Capibaribe Domain, Borborema Province, NE Brazil

Sérgio Pacheco Neves,Valdielly Larisse Silva

doi:10.1590/2317-4889202120200049

Sérgio Pacheco Neves, Valdielly Larisse Silva

Open Access

https://doi.org/10.1590/2317-4889202120200049

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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.

Highlights

In protracted tectonic events, the transposition of structures formed during progressive deformation is common (e.g., Gray and Mitra 1999, Baird and Shrady 2011)
In the Borborema Province (Fig. 1A), formed during the Brasiliano Orogeny (650–550 Ma), a flat-lying foliation related to thrusting precedes development of a transcurrent shear zone system (e.g., Guimarães et al 2004, Neves et al 2006b, Viegas et al 2014, Araújo et al 2014)
The results of this study indicate that the structural evolution of the Feira Nova region resulted from a progressive sequence of events (Fig. 6): Figure 6

Summary

Introduction

The transposition of structures formed during progressive deformation is common (e.g., Gray and Mitra 1999, Baird and Shrady 2011). Strain partitioning into pure and simple shear components in orogenic belts may result in domains with flat-lying fabrics alternating with domains with steep fabrics in transpressive or transtensive regimes (e.g., Tikoff and Greene 1997, Goscombe and Gray 2008). Transcurrent shear zones may develop later in the orogenic evolution, representing a separate deformation phase from that responsible for the development of a regional flat-lying foliation. In the Borborema Province (Fig. 1A), formed during the Brasiliano Orogeny (650–550 Ma), a flat-lying foliation related to thrusting precedes development of a transcurrent shear zone system (e.g., Guimarães et al 2004, Neves et al 2006b, Viegas et al 2014, Araújo et al 2014). Whether there is partial overlap of the contractional and transpressional regimes or if they resulted from separate deformation phases is a major issue in the tectonic evolution of the region (Neves et al 2005), and constitutes the aim of the present study

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Discussion

Conclusion