Tectonic inversion of compressional structures in the Southern portion of the Paramirim Corridor, Bahia, Brazil

Cruz, Simone Cerqueira Pereira; Alkmim, Fernando Flecha de; Barbosa, Johildo Salomão Figueirêdo; Dussin, Ivo; Gomes, Luiz César Corrêa

doi:10.1590/2317-488920150030240

Cited by 20 publications

(11 citation statements)

References 49 publications

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“…The external fold‐and‐thrust belt and its structural grain trends N‐S in both Brazil and Congo (from Vitoria/Luanda and northward; Figure ), curving east‐southeastward around latitude 15°S toward the present Brazilian coastline, but with a northward extension into and across the craton along the reactivated Paramirim aulacogen (Figure ) (Cruz & Alkmim, ). This modified aulacogen represents a long‐lived pre‐Brasiliano extensional rift basin that was inverted (shortened) during the Brasiliano orogenic evolution, but also with evidence of extensional and transcurrent kinematics interpreted as late or postorogenic (Cruz et al, ). The amount of late Proterozoic shortening across this aulacogen decreases northward, but the structure clearly crosscuts the entire São Francisco craton.…”

Section: The Araçuaí‐west Congo Orogenmentioning

confidence: 99%

Hot Versus Cold Orogenic Behavior: Comparing the Araçuaí‐West Congo and the Caledonian Orogens

2017

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Observations and modeling show that temperature controls crustal rheology and therefore also the orogenic evolution of continent‐continent collision zones and the associated tectonic style. In order to explore the effect of temperature in a natural environment, we compare eroded sections through the unusually cold lower Paleozoic North Atlantic Caledonian (Scandian) collision zone and the very hot Brasiliano/Pan‐African Araçuaí‐West Congo orogen. A cold and stiff subducting Caledonian continental margin was able to subduct as a rather coherent unit to ultrahigh‐pressure conditions, twice as deep as the Pan‐African/Brasiliano crust that was quickly heated and softened and got involved in partial melting. Furthermore, the Caledonian collision developed large coherent thrust sheets that were transported hundreds of kilometers toward the foreland. This was never achieved in the hot Araçuaí‐West Congo orogen, where much of the tectonic stress was absorbed by the partially molten central part of the orogen through magmatic state deformation. Major mylonite zones (thrusts) such as those seen in the Caledonides are therefore less common in the Araçuaí‐West Congo orogen. Further, the deep continental subduction in the Caledonides developed a strongly asymmetric collision zone, with rapid variations in pressure and temperature. In contrast, the Araçuaí‐West Congo orogen soon developed into a more symmetric geometry due to its easily flowing hot crust, with a relatively flat base and a corresponding plateau in its upper part. Deformation of the cold Caledonian crust was controlled by plate‐tectonic stress, while gravitational forces more strongly influenced the hot Brasiliano/Pan‐African example.

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Section: The Araçuaí‐west Congo Orogenmentioning

confidence: 99%

Hot Versus Cold Orogenic Behavior: Comparing the Araçuaí‐West Congo and the Caledonian Orogens

2017

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“…Typical shear zones that reactivate these structures are related to the collapse of the Araçuaí-West Congo Orogen (Cruz et al 2015).…”

Section: Geological Contextmentioning

confidence: 99%

Deformational sequence of inversion in the Paramirim Aulacogen, northern region of the intracontinental sector of the Araçuaí Orogen

Bitencourt

Cruz

2023

Braz. J. Geol.

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The Paramirim Aulacogen was filled by the Espinhaço and São Francisco supergroups in the period from 1.75 to 0.69 Ga, and suffered partial inversion during the Ediacaran. In the northern sector of the intracontinental domain of the Araçuaí-WestCongo Orogen, six compressive deformational phases were interpreted and associated with the frontal inversion of the Paramirim Aulacogen. Three structural domains were identified: Jacaraci Fold-Thrust Belt, Caetité Nappe, and Transpressive Domain. The nucleation of deformational structures is related to a maximum stress field with general WSW-ENE orientation. The first deformational phase (D 1 ), found in the Jacaraci Fold-Thrust Belt and the Transpressional Domain, is related to the evolution of the Rio Pardo Salient. A dextral transpressional system nucleated the Caetité Nappe. This system also juxtaposed amphibolite facies rocks over lower temperature facies, as well as Statherian over Tonian rocks. Furthermore, this system was responsible for deformation in the transpressional domains and late deformation in the Jacaraci Fold-Thrust Belt. The region presents a variety of structures and is, therefore, an excellent natural laboratory for studying positive inversion in aulacogens.

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“…This region has a complex geological evolution, overlapped by orogenic events and riftings inserted in a tectonic context of the northern portion of the Araçuaí intracontinental orogen (Figure 1) (Borges et al., 2015; Cruz & Alkmim, 2017; Cruz et al., 2015). The granitoids and orthogneiss vary from paleoarchean to neoarchean which were generically inserted in the so‐called Gavião and Caraguataí Complex (Figure 2) (Barbosa et al., 2020; Medeiros et al., 2017).…”

Section: Geological Settingsmentioning

confidence: 99%

Magnetic modelling and physical properties of magnesite deposits and regional sequences of Serra das Éguas, Brumado, Brazil

Sena

Vasconcelos

Cruz

et al. 2022

Geophysical Prospecting

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The Serra das Éguas Complex, in Brumado, state of Bahia, located in the northeastern region of Brazil, is a geological structure comprising volcanochemical, siliciclastic and carbonate units that contain layers and lenses of magnesite, important as a refractory in steel, cement, glass and copper and other applications. Considering the importance of such sort of deposit, this work aims to (i) study the physical properties of magnesite deposits via direct measurements of radiometric spectrometry and magnetic susceptibility associated with chemical analysis of the available borehole core samples; (ii) analyse the magnetic and radiometric data acquired by the combined airborne survey over the area with known magnesite deposits; (iii) estimate the magnetic response of the magnesite deposits and surrounding rock formations via 2D forward and 3D inverse magnetic modelling; (iv) evaluate and, if necessary, reconsider the stratigraphic sequences of the identified geological units of the Complex using the results of the 2D and 3D magnetic modelling. Through forward/inverse models, we noted an expressive magnetic signature likely related to the iron formations and metamafic and meta‐ultramafic rocks. The radiometric data analysis on the drill cores showed that the reddish magnesite has a well‐defined U/Th signature. Furthermore, the results show that the carbonate unit, which contains the magnesite deposits, has the lowest amplitude of magnetization values, and both signatures might be helpful for their identification. Additionally, the magnetic models show that the carbonate unit lies in the upper part of the stratigraphic sequence of the Serra das Éguas Complex. This conclusion drives us to propose a new stratigraphy sequence, where the volcanochemical unit that includes the iron formations lies at the bottom of this stratigraphic sequence.

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Tectonic inversion of compressional structures in the Southern portion of the Paramirim Corridor, Bahia, Brazil

Cited by 20 publications

References 49 publications

Hot Versus Cold Orogenic Behavior: Comparing the Araçuaí‐West Congo and the Caledonian Orogens

Hot Versus Cold Orogenic Behavior: Comparing the Araçuaí‐West Congo and the Caledonian Orogens

Deformational sequence of inversion in the Paramirim Aulacogen, northern region of the intracontinental sector of the Araçuaí Orogen

Magnetic modelling and physical properties of magnesite deposits and regional sequences of Serra das Éguas, Brumado, Brazil

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