Kinematics, nature of deformation and tectonic setting of the Taxaquara Shear Zone, a major transpressional zone of the Ribeira Belt (SE Brazil)

Author(s)

Ribeiro, B. V. ^{[1, 2]} ; Faleiros, F. M. ^[1] ; Campanha, G. A. C. ^[1] ; Lagoeiro, L. ^[3] ; Weinberg, R. F. ^[2] ; Hunter, N. J. R. ^[2]

Affiliation

^[1] Univ Sao Paulo, Inst Geociencias, Dept Mineral & Geotecton, Rua Lago 562, BR-05508900 Sao Paulo, SP - Brazil

^[2] Monash Univ, Sch Earth Atmosphere & Environm, Clayton, Vic 3800 - Australia

^[3] Univ Fed Parana, Dept Geol, Rua Francisco Heraclito dos Santos 100, Bloco 6, BR-35400000 Curitiba, PR - Brazil

• Document type: Journal article
• Source: TECTONOPHYSICS; v. 751, p. 83-108, JAN 20 2019.
• Web of Science Citations: 0

Abstract

In this paper we have investigated the Taxaquara Shear Zone (TSZ), a major strike-slip structure within the Ribeira Belt (RB, SE Brazil) in order to assess its kinematics, the nature of deformation of rocks affected by the TSZ and its tectonic setting. The TSZ presents a vertical NE-trending mylonitic foliation and ENE- to WSW stretching lineation with variable plunge. Granitic rocks are intensely deformed giving rise to mylonites with newformed matrix assemblage (quartz + oligoclase + K-feldspar + biotite + muscovite + rutile + magnetite). This assemblage within a pseudosection couple with muscovite-biotite thermometer helps to constrain a metamorphic condition during deformation which spans similar to 513-525 degrees C and similar to 3.9-4.4 kbar with mean peak at similar to 520 degrees C and similar to 4.0 kbar. Quartz accommodates deformation through dislocation creep achieving subgrain rotation with minor contribution of grain boundary migration at a mean strain rate of 10(-13) -10(-12) s(-1). Feldspar porphyroclasts record brittle deformation (microfaults) and evidences of dislocation creep (e.g., kink twinning). The CPOs for monomineralic quartz ribbons display monoclinic pattern and activation of `basal< a > ` + `rhomb- < a > ` slip systems during deformation. However, the CPOs for quartz and feldspar from fine-grained polyphase matrix show a switch in deformation mechanism from dislocation creep to diffusion creep. The vorticity and three-dimensional finite strain data results suggest that the TSZ was developed under a moderate to high strain conditions and a transpressional sub-simple shear environment, with predominance of simple over pure shear. Regional correlation with other structures from the Ribeira Belt and African Belts based on finite strain quantification support that a major transpressional system was mainly responsible for the shear zones development during late stages of Braziliano-Pan African orogeny. (AU)

• FAPESP's process: 16/22051-4 - Microstructures, kinematics and thermometry of milonitic rocks of the Western portion of the Taxaquara shear zone - Pilar do sul, SP
• Grantee: Bruno Vieira Ribeiro
• Support type: Scholarships in Brazil - Scientific Initiation
• 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 type: Regular Research Grants
• 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 type: Regular Research Grants
• FAPESP's process: 17/08919-4 - Microstructures, kinematics and thermometry of mylonitic rocks of the western portion of the Taxaquara Shear Zone - Pilar do sul, SP
• Grantee: Bruno Vieira Ribeiro
• Support type: Scholarships abroad - Research Internship - Scientific Initiation
• FAPESP's process: 18/00320-9 - Crystallographic, deformational and thermocronological analysis of mylonites of Taxaquara shear zone (São Paulo)
• Grantee: Bruno Vieira Ribeiro
• Support type: Scholarships in Brazil - Master