The role of intracratonic crustal reworking in the tectonic compartmentalization of the Juruena Terrane, SW Amazonas Craton: the Roosevelt-Guariba Transpressive Belt

Ano: 2021 | Volume: 4 | Número: 2

Autores: A. C. da S. Oliveira, M. E. Almeida

Palavras-chave: lithospheric shear zone, intracontinental deformation, structural geophysics, multiscale, juruena terrane, amazon craton

Resumo Inglês:

The multiscale structural analysis carried out in the NNW sector of the Juruena Terrane, SE of the State of Amazonas combines structural mapping, microtectonic analysis and aeromagnetic data analysis. The terrane shows a complex structural and metamorphic history composed of successive deformation events, responsible by the formation of its tectonic framework. Event D2 (1520-1460 Ma) is responsible for the main structure of the NNW sector of the Juruena Terrane, and it generates a dextral transpressive NW-SE-trending shear zone, called Roosevelt-Guariba Transpressive Belt (RGTB). This is an intracontinental high-temperature, medium-pressure tectono-thermal event, compatible with the conditions of the upper amphibolite to granulite facies. The RGTB controls the tectonic compartmentation of the region, particularly affecting the Granitic Gneiss Domain (1760-1750 Ma). Other sectors, such as the Supracrustal Rock Domain (1800-1730 Ma) and the Pre-Juruena geological-structural association (>1830 Ma), are subordinately affected. Event D2 overlaps the regional structure E-W (ENE-WSW) attributed to D1 (1690-1630 Ma), which is restricted to the deep basement in the NNW sector, but dominant in the south central sector of the Juruena Terrane. There are also two late brittle-ductile to brittle deformation events (D3 and D4). Event D3 (1320-1300 Ma) is represented by NE-SW cataclastic and shear zones, commonly serving as conduits for hydrothermal fluids relative to gold mineralization. Event D4 is comprised of normal faults and fractures that reactivate RGTB shear zones, limiting Neoproterozoic and Paleozoic-Mesozoic sedimentary exposures. The tectonic structural model proposed in this study reinforces the interpretation that the Juruena Terrane evolved from a foreland basin, which was formed during the Juruena Orogen and whose basement is the Orosirian Tapajós Crust. This basin was preserved from the tectono-thermal effects of the end of the Statherian (D1), and it was only during event D2, after emplacement of the RGTB, that it underwent high-grade deformation and metamorphism, whose driving force is attributed to the stress propagation in pericratonic regions, associated with Calymmian orogens. The successive events are related to the cratonization of the Juruena Terrane, represented by late crust reactivation (D3) and neotectonic events (D4).