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

Ribeiro, Bruno Vieira; Faleiros, Frederico Meira; Campanha, Ginaldo Ademar da Cruz; Lagoeiro, Leonardo Evangelista; Weinberg, Roberto F.; Hunter, Nicholas J.R.

doi:10.1016/j.tecto.2018.12.025

Cited by 27 publications

(21 citation statements)

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“…605 Ma, UePb TIMS zircon; ) igneous suites. In contrast with the São Roque Group, the Votuverava Group is composed of distal turbidites with significant basic magmatism represented by concordant lenses of metamorphosed mafic rocks (Campanha et al, 2019). It displays a principal NNW-SSE structural trend orthogonal to the TSZ and shows an east to west transition from low-grade to medium-grade metamorphism.…”

Section: Study Areamentioning

confidence: 99%

“…Detrital zircons show an important Riacian contribution (ca. 2200 Ma, UePb LA-ICP-MS; Campanha et al, 2019;Henrique-Pinto et al, 2015 and with younger grains at ca. 2000 Ma.…”

Section: Study Areamentioning

confidence: 99%

“…Detrital zircon data show Orosirian-Riacian contribution (ca. 1800-2200 Ma, UePb LA-ICP-MS; Campanha et al, 2019) with minor Archean ages (ca. 2800-3200 Ma, UePb LA-ICP-MS; Campanha et al, 2019) and include zircon with minimum age of ca.…”

Section: Study Areamentioning

confidence: 99%

“…1300 Ma crystallization age and a Neoproterozoic metamorphic overprint ca. 600-700 Ma (zircon UePb SHRIMP data; Campanha et al, 2019), while metabasites from its southernmost portion display older ages of 1475-1490 Ma (Campanha et al, 2015).…”

Section: Study Areamentioning

confidence: 99%

“…Since shear zones play an important role in the deformation history of the crust unrevealing not only the thermo-tectonic history of the deformation, but often the tectonic evolution of orogenic belts as a whole, it is highly important to proper comprehend this shear zone system in order to broadly understand the Neoproterozoic RB evolution. This shear zone system has been studied throughout the time (Campanha, 2002;Ebert et al, 1996;Ebert and Hasui, 1992;Faleiros, 2003;Faleiros et al, 2010;Ribeiro et al, 2019). Due to its neglected importance in regional tectonic studies, there is still a significant lack of data regarding mechanisms of deformation, well established deformation conditions based on quantitative analyses (e.g., thermodynamic modelling), tectonic system and the timing of development of these shear zones.…”

Section: Introductionmentioning

confidence: 99%

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Deformational, crystallographic and petrochronological analyses of the mylonites from Taxaquara shear zone in Ribeira Belt (São Paulo)

Ribeiro¹

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The Taxaquara Shear Zone (TSZ) is a major transcurrent structure in the Ribeira Belt (RB), SE Brazil. In the study area, around Pilar do Sul city in the countryside of São Paulo, the TSZ display a strong NE-SW mylonitic foliation preferentially dipping to W and stretching lineation with variable plunge. It separates the Votuverava and the São Roque Groups and cross-cut granitic rocks from the Pilar do Sul and Piedade Suits giving rise to quartz-feldspathic mylonitic rocks with newformed matrix assemblage composed of quartz + oligoclase + Kfeldspar + biotite + muscovite + rutile + magnetite. Pseudosection with Si (p.f.u) in muscovite and sodium molar number in plagioclase (XNa) isopleths, couple with muscovite-biotite geothermometer, indicates that the mineral assemblage constrains the deformation condition at 513-525°C and 3.9-4.4 kbar. Microstructures and crystallographic preferred orientation (CPO) indicate that quartz from monomineralic ribbons accommodates deformation through dislocation creep achieving the transition between subgrain rotation and grain boundary migration, at a mean strain rate of 10-12 to 10-12 s-1 , with monoclinic CPO patterns and activation of 'basal-' + 'rhomb-' slip system during deformation. CPO from fine-grained quartz and feldspar from polyphase matrix, however, indicate a switch in deformation mechanism from dislocation to diffusion creep. Vorticity and three-dimensional finite strain data indicate that the TSZ was developed under moderate to high strain within a transpressional sub-simple shear environment. Petrochronological analyses using muscovite 40 Ar/ 39 Ar (step heating) and apatite, titanite and zircon U-Pb ages (LASS-ICP-MS) indicates that the TSZ was active from 544 ± 4.0 Ma to 534 ± 1.5 Ma, continuously or not. These ages, coupled with closure temperature estimates, suggest a cooling rate of ~5°C/Ma as indicated by regional studies. The geochronological data from the TSZ contrast with those from other shear zones in the RB, generally constrained by single mineral dating lacking textural and chemical data between the mineral and deformation. Thus, a detailed revision using multi-mineral method approach is required to improve the understanding the tectonic significance of the shear zones in the RB.

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Section: Study Areamentioning

confidence: 99%

“…Detrital zircons show an important Riacian contribution (ca. 2200 Ma, UePb LA-ICP-MS; Campanha et al, 2019;Henrique-Pinto et al, 2015 and with younger grains at ca. 2000 Ma.…”

Section: Study Areamentioning

confidence: 99%