Fault damage zones width: Implications for the tectonic evolution of the northern border of the Araripe Basin, Brazil, NE Brazil

Abstract

Fault zones commonly have spatially variable fault rocks and brittle structures. Differing fault-rock attributes may retard or increase cross- and along-fault permeability. Our work analyzed brittle deformation of a segment of the Patos shear zone, Triunfo Fault, which is located in the northern border of the Araripe Basin, NE Brazil. We investigated the structural evolution and tectonic implications of the Triunfo Fault by mapping damage zone width patterns and the types and distributions of breccia and brittle structure arrays within the fault zone using scanline fracture analysis techniques and topographic and aeromagnetometric data. Fractured rocks of the damage zone mainly comprise: mylonitic orthogneiss (footwall); and sandstone and carbonate rocks (hangingwall). The fault core is composed of tectonic breccia and cataclasites occurring as lenses, with calcite-filled veins. Due to fault sinuosity and rheology heterogeneities, the width of the damage zone ranges from 240 to 290m (footwall), and 372–610m (hangingwall). Our analysis obtained from the topographic and gravimetric data combined with field data indicate the following sequential deformation phases: a) Dn, Brasiliano Orogeny, dextral shear zone; b) Dn+1, Paleozoic time, brittle-ductile deformation; and c) Dn+2, Lower Cretaceous time, brittle deformation.