IUGS Zumaia Declaration
← View all Geoheritage Sites

The Patos Shear Zone

Brazil

Migmatitic rocks from the high-temperature part of the Patos shear zone near Patos where melt formed during late Proterozoic shearing.

Migmatitic rocks from the high-temperature part of the Patos shear zone near Patos where melt formed during late Proterozoic shearing.

Geological Period

Neoproterozoic (Cryogenian to Ediacaran)

Main geological interest

Tectonics

Location

Borborema Province, States of Paraíba and Ceará, Brazil
07°02’19”S, 037°16’35”W

Migmatitic rocks from the high-temperature part of the Patos shear zone near Patos where melt formed during late Proterozoic shearing.

Impressive example of an exhumed mid-crustal strike-slip intracontinental shear zone.

Strain localization into crustal-scale shear zones is an important process during crustal deformation, and the Patos Shear Zone in the Borborema Province is an outstanding example of the role of shearing during the Neoproterozoic Brasiliano–Pan-African orogeny. This tens of kilometers wide and hundreds of kilometers long shear zone offers locations that expose the fundamental crustal processes related to strike-slip dominated movement of continental blocks: the role of partial melting, kinematic indicators, strike-slip duplexing, strain, mylonitic structures from the grain scale to tens of kilometers. This is also a superb area for studying reactivation of shear zone fabrics during the Cretaceous.

Looking east along the southern margin of the Patos SZ, where deformed Ediacaran granitic plutons form hills in the semi-arid landscape of NE Brazil.

Looking east along the southern margin of the Patos SZ, where deformed Ediacaran granitic plutons form hills in the semi-arid landscape of NE Brazil.

  • Geological description

In NE Brazil, rocks of Archean to Ediacaran age are dragged in and out of an impressive network of continental shear zones. The largest one is the Patos Shear Zone, where the older igneous, metamorphic and metasedimentary rocks are transformed into sheared rocks with mylonitic and gneissic fabrics. This transcurrent shear zone transects NE Brazil from the Atlantic coast and 700 km westwards until being covered by the Paleozoic-Mesozoic Parnaiba basin (Fossen et al., 2022). Pre-Atlantic Ocean reconstructions indicate that the shear zone continues on the African side as part of a network of intracontinental shear zones.
More than three hundred kilometers of dextral offset on this shear zone reflect the forces involved during completion of the late Neoproterozoic Gondwana supercontinent. Today we can study the processes that occurred at mid-crustal levels in well-exposed migmatitic rocks and lower temperature (ultra) mylonites (e.g., Cavalcante et al., 2016, 2022). Teh shear zone exposes an impressive large-scale strike-slip duplex. There are spectacular examples of brittle reactivation during Cretaceous pre-Atlantic rifting, where shear zone fabrics acted as guides for fault nucleation during the rifting. Publicly available seismic data combined with field examples gives good control on this reactivation behavior.

  • Scientific research and tradition

The Patos and related Borborema Province shear zones have been studied by mainly Brazilian and French researchers, particularly since the 1980s (e.g., Corsini et al., 1996; Archanjo et al., 2021). This has resulted in a series of Master and PhD theses and around 30 international research articles so far.

Magnetic anomaly model of the Patos SZ. Colors indicate lithologies with different magnetic properties. Cretaceous rift basins with margins controlled by basement structure are shown.

Magnetic anomaly model of the Patos SZ. Colors indicate lithologies with different magnetic properties. Cretaceous rift basins with margins controlled by basement structure are shown.

  • Reference

Archanjo, C.J., Hollanda, M.H.B.M.D. and Viegas, L.G.F. (2021) ‘Late Ediacaran lateral-escape tectonics as recorded by the Patos shear zone (Borborema Province, NE Brazil)’, Brazilian Journal of Geology, 51(2), p. e20200132. Available at: https://doi.org/10.1590/2317-4889202120200132.

Cavalcante, C. et al. (2022) ‘TitaniQ temperatures and textural analysis as a record of the deformation history in a major continental shear zone system, Borborema Province, Brazil’, Tectonophysics, 841, p. 229548. Available at: https://doi.org/10.1016/j.tecto.2022.229548.

Cavalcante, G.C.G. et al. (2016) ‘The influence of partial melting and melt migration on the rheology of the continental crust’, Journal of Geodynamics, 101, pp. 186–199. Available at: https://doi.org/10.1016/j.jog.2016.06.002.

Corsini, M., Vauchez, A. and Caby, R. (1996) ‘Ductile duplexing at a bend of a continental-scale strike-slip shear zone: example from NE Brazil’, Journal of Structural Geology, 18(4), pp. 385–394. Available at: https://doi.org/10.1016/0191-8141(95)00102-J.

Fossen, H. et al. (2022) ‘The Patos-Pernambuco shear system of NE Brazil: Partitioned intracontinental transcurrent deformation revealed by enhanced aeromagnetic data’, Journal of Structural Geology, 158, p. 104573. Available at: https://doi.org/10.1016/j.jsg.2022.104573.

  • Author(s)

Carolina Cavalcante.
Departamento de Geologia, Universidade Federal do Paraná, Av. Cel. Francisco Heráclito dos Santos, 100, Centro Politécnico, Curitiba (PR), 81531-980, Brazil.

Haakon Fossen.
Museum of Natural History/Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway.

View all Geoheritage Sites →

Contact us

IUGS Zumaia Declaration