Deformation, thermochronology and tectonic significance of the crustal-scale Cubatao Shear Zone, Ribeira Belt, Brazil

Author(s)

Cabrita, Dina I. G. ; Faleiros, Frederico M. ; Ribeiro, Bruno, V ; Menegon, Luca ; Cawood, Peter A. ; Campanha, Ginaldo A. C.

• Document type: Journal article
• Source: TECTONOPHYSICS; v. 828, p. 16-pg., 2022-03-09.

Abstract

Crustal-scale shear zones are key structures in orogenic belts linked to the assembly of West Gondwana. The Cubatao Shear Zone (CSZ) represents a significant segment of a crustal-scale transcurrent shear zone system that cuts Paleoproterozoic to Neoproterozoic units in the Ribeira Belt (SE Brazil). Despite its tectonic importance, the relationship between transcurrent deformation and orogenesis is still controversial. This work aims to understand this relationship by integrating the transcurrent deformation history of the CSZ with regional orogenic processes through structural analyses, phase-equilibria modelling, and zircon and apatite U-Pb-REE analyses. The results indicate that the CSZ developed within a transpressional setting with a dominant subhorizontal stretching lineation at medium-temperature conditions of 460-520 degrees C and 4.5-9.5 kbar, consistent with quartz recrystallisation microstructures indicative of subgrain rotation recrystallisation. Igneous-type apatite from the mylonites of the CSZ record ages of ca. 610-570 Ma, which are interpreted as reset ages due to ductile deformation at medium-temperature conditions. Zircon U-Pb geochronology indicates that mylonites are sourced from the Juquin Granite and the Atuba Complex. The CSZ activity is coeval with the main period of activity of other ductile shear zones from the Ribeira Belt, as indicated by available geochronological data. This age interval coincides with the main period of other regional shear zones activity, voluminous granitic magmatism, regional metamorphism and convergence of the cratons surrounding the Ribeira Belt, indicating active participation of the transcurrent shear zones in the orogenic processes that built up West Gondwana. (AU)

• FAPESP's process: 19/10457-4 - Isotope dating coupled to trace element characteristics in igneous and metamorphic minerals from the Embu Terrane, and their implications for the reconstruction of the Ribeira Belt tectonic evolution
• Grantee: Dina Isabel Guerreiro Cabrita
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 15/04487-7 - Metamorphism and tectonic evolution of the southern Ribeira Belt: relationships between the Embu, Apiaí and Curitiba terranes
• Grantee: Frederico Meira Faleiros
• Support Opportunities: Regular Research Grants
• FAPESP's process: 15/26645-3 - Tectonometamorphic evolution of the Embu Terrane and relationships with adjacent terranes in the Southern Ribeira Belt (São Paulo, Brazil)
• Grantee: Dina Isabel Guerreiro Cabrita
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 18/10012-0 - Fluid flow, deformation and tectonic significance of regional shear zones from the southern Ribeira Belt
• Grantee: Frederico Meira Faleiros
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/21824-5 - Deformation regimes and fabrics in lower to mid-crustal large-scale transcurrent shear zones: the Lancinha-Cubatão shear system, Ribeira belt, Brazil
• Grantee: Dina Isabel Guerreiro Cabrita
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate