Strain localization at the frictional-viscous transition in the middle crust: examples from the Pernambuco shear zone (Borborema Province, NE Brazil)

• Grant number: 14/01114-2
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: May 18, 2014
• End date: May 03, 2015
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Carlos José Archanjo
• Grantee: Luís Gustavo Ferreira Viegas
• Supervisor: Luca Menegon
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Plymouth University, England
• Associated to the scholarship: 13/11866-9 - Strain localization in the Pernambuco shear zone (Borborema Province, NE Brazil): Implications for the rheology of the continental crust, BP.PD

Abstract

The Pernambuco shear zone, one of the main structures of the Borborema Province, consists of two sheared branches in which high- to low-temperature mylonites are deformed in distinct ways: the western branch involves partial melting and coarse-grained amphibolite facies mylonites, while the eastern branch was developed in the vicinities of two granitic batholiths. In the eastern branch, medium- to low-grade mylonites outcrop in the outer regions away from the batholiths, displaying several microstructures indicative of deformation at the frictional-viscous transition. Although restricted to the eastern portion of the shear zone, these mylonites represent outstanding natural laboratories to investigate crustal rheology under brittle-ductile conditions. However, their structural characteristics are poorly constrained so far. The main goal of the project is to combine microstructures, crystallographic preferred orientations, chemical analyses and temperature estimates to investigate the processes that control the rheology of the Pernambuco shear zone during fluid-assisted strain localization at medium- to low-grade metamorphic conditions. These data are important to understand the rheological behaviour of the continental crust, as well as to contribute to the study of the evolution of the Borborema Province during the Neoproterozoic. (AU)

Scientific publications

(4)

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

CARLOS JOSÉ ARCHANJO; MARIA HELENA BEZERRA MAIA DE HOLLANDA; LUIS GUSTAVO FERREIRA VIEGAS. Late Ediacaran lateral-escape tectonics as recorded by the Patos shear zone (Borborema Province, NE Brazil). BRAZILIAN JOURNAL OF GEOLOGY, v. 51, n. 2, 2021-05-28. (14/01114-2)

VIEGAS, GUSTAVO; HIDAS, KAROLY; CASTELLAN, PAULO. Structural relationships between ultramylonite, pseudotachylyte and cataclasite in the East Pernambuco shear zone (Borborema Province, NE Brazil). JOURNAL OF STRUCTURAL GEOLOGY, v. 147, p. 17-pg., 2021-04-16. (14/01114-2)

CASTELLAN, PAULO; VIEGAS, GUSTAVO; FALEIROS, FREDERICO M.. Brittle-ductile fabrics and P-T conditions of deformation in the East Pernambuco shear zone (Borborema Province, NE Brazil). JOURNAL OF THE GEOLOGICAL SOCIETY, v. 178, n. 1, NOV 2020. (14/01114-2)

VIEGAS, GUSTAVO; MENEGON, LUCA; ARCHANJO, CARLOS. Brittle grain-size reduction of feldspar, phase mixing and strain localization in granitoids at mid-crustal conditions (Pernambuco shear zone, NE Brazil). SOLID EARTH, v. 7, n. 2, p. 375-396, 2016. (13/11866-9, 14/01114-2)