Geophysical evidence for doming during the Pan-African/Brasiliano orogeny in the Seridó belt, Borborema Province, Brazil

Domingos, Nitzschia Regina Rodrigues; Medeiros, Walter E.; Oliveira, Roberto Gusmão de

doi:10.1016/j.precamres.2020.105870

Cited by 10 publications

(3 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The eastern termination of the PaSZ displays a complex geometry. The mylonitic foliation curves, forming a horsetail structure that connects the shear zone with the dextral transpressional deformation of the NE-trending Seridó Belt [18,58,[86][87][88]. The connection between the two structures is clearly recorded by anatexites delimited by metasedimentary formations in the southern Seridó belt, which are dragged over several km into the PaSZ, with clear boudinage of the stiffer layers (quartzites).…”

Section: Patos Shear Zonementioning

confidence: 95%

The Borborema Strike-Slip Shear Zone System (NE Brazil): Large-Scale Intracontinental Strain Localization in a Heterogeneous Plate

et al. 2021

View full text Add to dashboard Cite

Large-scale strike-slip faults are fundamental tectonic elements of the continental lithosphere. They constitute plate boundaries (continental transforms), separate terranes with contrasting geological histories within accretionary orogens, or accommodate heterogeneous deformation in intracontinental settings. In ancient orogens, where deeper levels of the crust are exposed, these faults are expressed as shear zones materialized by up to tens of km-wide mylonitic belts. The Borborema shear zone system in northeastern Brazil is one of the largest and best-exposed intracontinental strike-slip shear zone systems in the world, cropping out over 250,000 km2. Here, we review its main geophysical, structural, petrologic, and geochronologic characteristics and discuss the factors controlling its development. This complex continental scale shear zone system is composed of a set of NE- to NNE-trending dextral shear zones from which there are two major E-trending dextral shear zones with horse-tail terminations into the transpressional belt branch, as well as several smaller E-trending dextral and NE-trending dextral and sinistral shear zones. The major shear zones are marked by extensive linear or curvilinear magnetic gradients, implying their continuation at depth. The major shear zones are materialized by migmatite to amphibolite-facies mylonites, but the entire system shows evidence of late deformation at lower temperatures. The system developed during the late stages of the Neoproterozoic Brasiliano (Pan-African) orogeny (mainly from 590 to 560 Ma), postdating by more than 20 Ma the main stage of contractional deformation. Localization of strike-slip shearing in this intraplate setting was controlled by rheological contrasts between blocks with distinct Paleoproterozoic histories, the presence of preorogenic Neoproterozoic rifts, the craton geometry, and zones of enhanced magmatic activity, highlighting the importance of rheological heterogeneity in controlling shear zone nucleation and evolution.

show abstract

Section: Patos Shear Zonementioning

confidence: 95%

The Borborema Strike-Slip Shear Zone System (NE Brazil): Large-Scale Intracontinental Strain Localization in a Heterogeneous Plate

et al. 2021

View full text Add to dashboard Cite

show abstract

“…Considering all nuclei, the residual Bouguer anomaly of the Archean units is 5 mGal higher than that of the Proterozoic terranes (Figure 6E). This general trend is not easily explained, because Archean nuclei are predominantly formed from orthoderived rocks and large volumes of migmatized rocks, which do not seem to be the sources of these positive gravity anomalies (see, for example, the density profile across a migmatitic dome shown in figure 7 of Domingos et al 2020). In addition, evidence for high pressure and high temperature metamorphism (granulite facies) that may favor an increase in rock density (e.g., Bourne et al 1993) is rare in the Borborema Province.…”

Section: Gravity Signatures Of the Archean Units And Their Sourcesmentioning

confidence: 99%

Gamma-ray spectrometry, magnetic and gravity signatures of Archean nuclei of the Borborema Province, Northeastern Brazil

Oliveira,

Domingos,

Medeiros

et al. 2024

JGSB

View full text Add to dashboard Cite

Gamma-ray spectrometry, as well as magnetic and gravity data, are used to investigate the geophysical signatures of the Archean nuclei of the Borborema Province. Natural radioactivity, magnetic anomalies, and residual Bouguer gravity anomalies of the Archean nuclei exhibit distinct signatures in relation to adjacent Proterozoic domains. Gamma-ray spectrometry data reveal eTh enrichment in relation to K and eU contents in Archean units. Assuming that K and U were the dominant isotopes, this relative enrichment of eTh can be explained by the fact that Th radioisotopes have a longer half-life than the other two radionuclides and that 4.56 Ga has elapsed since Earth's formation. The intensity of the total magnetic gradient in Archean units is greater than in Proterozoic units in most nuclei. The Archean units underwent deformation and metamorphism in the Brasiliano/Pan-African Orogeny; therefore, the magnetic characteristics now observed in Archean mafic-ultramafic rocks, iron formations and gneissmigmatite complexes are the joint result of their primary properties and the superposed effects of the orogeny. All Archean nuclei of the Borborema Province show positive residual Bouguer gravity anomalies. This could be due to the conservation of the main petrophysical properties of the Archean lithosphere, and their preservation during the intense granitization that occurred in the Brasiliano/Pan-African Orogeny. As magnetic and gravity methods provide information from depth, it is possible to infer the continuity of some Archean nuclei beyond the limits established by surface geological data. Based on these results, it will be possible to use geophysical signatures to investigate the possible existence of unknown Archean units in the province.

show abstract

“…The Patos shear zone is an important tectonic corridor mostly consisting of E-to NE-trending mylonites and migmatites. The E-trending central segment consists of gneissic mylonites, metatexites and diatexites that can be traced in structural and geophysical continuity to the NE-trending Seridó belt (Corsini et al 1991, Domingos et al 2020, whereas to the West these rocks form imbricated slices that define the Lavras da Mangabeira strike-slip duplex. Available U-Pb zircon ages for the basement rocks situated between the Patos and Seridó belts are Siderian to Rhyacian (Hollanda et al 2011, Viegas et al 2014, whereas the metasedimentary units disrupted along the E-trending shear zone branch were deposited in the Neoproterozoic (Hollanda et al 2015).…”

Section: The Patos Mylonite Belt and Granjeiro Complexmentioning

confidence: 99%

Late Ediacaran lateral-escape tectonics as recorded by the Patos shear zone (Borborema Province, NE Brazil)

2021

View full text Add to dashboard Cite

Lateral escape tectonics mediated by strike-slip fault zones are an efficient mechanism of rock deformation in the continental crust of collision zones. The Borborema shear zone system, which shows dimensions comparable to the Cenozoic extrusion of Indochina, defines a lateral escape setting of the Brasilano orogeny in Northeastern Brazil. In this paper, the timing of high-grade metamorphism and compositions of the terranes involved in the shear deformation were investigated. The Patos shear corridor deforms the Siderian to Neoarchean rocks of the Granjeiro Complex that, in turn, form the basement of Seridó-Lavras da Mangabeira metapelites. U-Pb zircon ages and Sm-Nd whole-rock isotopic compositions indicate that the 2.80 -2.35 Ga basement sequences mainly include juvenile material, whereas zircons from synkinematic migmatites indicate that the partial melting occurred in the Late Ediacaran (ca. 565 Ma). Cooling rates provided by 40 Ar/ 39 Ar range from 12 to 17°C/Ma, indicating a differential shear zone exhumation, in agreement with a transpressive setting. The presence of allochthonous Siderian sequences dismembered along the shear zone suggests that the Seridó-Granjeiro corridor defines a major tectonic boundary connected to the collisional front defined by the convergence of São Francisco-Congo and Amazonian cratons.

show abstract

Geophysical evidence for doming during the Pan-African/Brasiliano orogeny in the Seridó belt, Borborema Province, Brazil

Cited by 10 publications

References 74 publications

The Borborema Strike-Slip Shear Zone System (NE Brazil): Large-Scale Intracontinental Strain Localization in a Heterogeneous Plate

The Borborema Strike-Slip Shear Zone System (NE Brazil): Large-Scale Intracontinental Strain Localization in a Heterogeneous Plate

Gamma-ray spectrometry, magnetic and gravity signatures of Archean nuclei of the Borborema Province, Northeastern Brazil

Late Ediacaran lateral-escape tectonics as recorded by the Patos shear zone (Borborema Province, NE Brazil)

Contact Info

Product

Resources

About