Structure and tectonic significance of high- and low-temperature deformation along the lateral escape-related Guaçuí and Batatal shear zones, southern Araçuaí Orogen (southeastern Brazil)

Marcos Eduardo Hartwig,Marilane Gonzaga De Melo,César Augusto Moreira

doi:10.1590/0370-44672020730043

Marcos Eduardo Hartwig, Marilane Gonzaga De Melo + Show 1 more

Open Access

https://doi.org/10.1590/0370-44672020730043

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Abstract

The Guacuí and Batatal lineaments in the southern region of the state of Espírito Santo (southeastern Brazil) can be traced from satellite images for tens of kilometers. They are considered shear zones associated to the final tectonic stages of the Araçuaí-West Congo (A-WC) Orogen during the Ediacaran-Cambrian period. In order to understand their nature and tectonic implications for the development of the orogeny, we integrated geological and structural data based on fieldwork and detailed microstructural analysis. Data was collected along two profiles located at the central segments of both structures. The results demonstrated that the Guaçuí shear zone (GSZ) is a typical ductile transpressive shear zone with approximately 9 km width that shows numerous dextral kinematic indicators and records metamorphism of upper amphibolite facies. The GSZ shows different levels of intensity of dynamic deformation. The Batatal shear zone (BSZ) is a narrow brittle shear zone that shows essentially brittle microstructures (intercrystalline microfractures) revealing deformation at low-grade conditions (frictional regime). Based on their characteristics and the level of erosion of the rocks exposed in the region, we interpret that GSZ developed prior to BSZ.

Highlights

Shear zones are linear to curvilinear strips of strained rocks that exist in all scales, whose length is much greater than width
Ductile deformation is dominated by crystal-plastic mechanisms and diffusion creep which produces rocks with foliation while brittle deformation is dominated by grain fracture, frictional sliding and grain rotation (Blenkinsop, 2000, Stipp et al, 2002a,b, Vernon, 2004, Passchier and Trouw, 2005, Law, 2014)
The Guaçuí and Batatal lineaments are two of the most strikingly geological features in the southern region of the Espírito Santo State and can be traced from satellite images and aerogeophysical data for tens to hundreds of kilometers. These lineaments developed in the final tectonic stages of the Neoproterozoic Araçuaí-West Congo orogen (Alkmim et al 2006)

Summary

Introduction

Shear zones are linear to curvilinear strips of strained rocks that exist in all scales, whose length is much greater than width These geological features may be formed in different tectonic settings and involve components of both simple and pure shear. The Guaçuí and Batatal lineaments are two of the most strikingly geological features in the southern region of the Espírito Santo State (southeastern Brazil) and can be traced from satellite images and aerogeophysical data for tens to hundreds of kilometers. The study of shear zones usually involves petrographic and geological field descriptions coupled with geochronological and geochemical data (Passarelli et al 2011, Phillips and Searle, 2007, Campanha 1981) In this sense, the aim of this study is to characterize and compare the geological and the structural features of the Guaçuí and Batatal lineaments. We integrated geological, macro- and microstructural data

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