scholarly journals RELAÇÕES ENTRE CISALHAMENTO, MAGMATISMO E ANATEXIA: EXEMPLO DA ZONA DE CISALHAMENTO CRUZEIRO DO NORDESTE, PROVÍNCIA BORBOREMA, BRASIL

2021 ◽  
Vol 31 (1) ◽  
pp. 27-43
Author(s):  
Salviano da Silva ◽  
Andres Bustamante
Keyword(s):  
Shear Zone ◽  
Thermal Anomaly ◽  
Shear Zones ◽  
Northeastern Brazil ◽  
Spatial Proximity ◽  
Oblique Collision ◽  
Shear Structures ◽  
Borborema Province ◽  
Tectonic Transport ◽  
Escape Tectonics

The Borborema Province, northeastern Brazil, exhibit an extensive framework of shear zones in spatial proximity with syn-tectonic magmatism that makes it a perfect place to understand their relationship. In the eastern portion of this province an important dextral shear zone, that divides into two terranes, was originated during an escape tectonics after an oblique collision after a tectonic transport to NW. The recrystallization of quartz and feldspar shows a remarkable increase towards the shear zone, interpreted as a temperature increase during deformation. Thermodynamic modelling coupled with field relationship shows that high strain migmatitic textures such as stromatic structure was formed at ~650 °C and ~0.9 GPa prior to the shear development. Whereas low strain migmatites with schollen texture was formed at ~750 °C and ~0.7 GPa. We propose that the presence of melt during an oblique collision facilitated the emplacement of shear structures due to a thermal anomaly during the emplacement of syn-tectonic plutons.

scholarly journals Lithospheric and sublithospheric deformation under the Borborema Province of northeastern Brazil from receiver function harmonic stripping

Solid Earth ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 893-905 ◽  
Author(s):  
Gaelle Lamarque ◽  
Jordi Julià
Keyword(s):  
Lithospheric Mantle ◽  
Seismic Anisotropy ◽  
Receiver Function ◽  
Seismic Station ◽  
Atlantic Coast ◽  
Shear Zones ◽  
Receiver Functions ◽  
Azimuthal Anisotropy ◽  
Northeastern Brazil ◽  
Borborema Province

Abstract. The depth-dependent anisotropic structure of the lithosphere under the Borborema Province in northeast Brazil has been investigated via harmonic stripping of receiver functions developed at 39 stations in the region. This method retrieves the first (k=1) and second (k=2) degree harmonics of a receiver function dataset, which characterize seismic anisotropy beneath a seismic station. Anisotropic fabrics are in turn directly related to the deformation of the lithosphere from past and current tectonic processes. Our results reveal the presence of anisotropy within the crust and the lithospheric mantle throughout the entire province. Most stations in the continental interior report consistent anisotropic orientations in the crust and lithospheric mantle, suggesting a dominant northeast–southwest pervasive deformation along lithospheric-scale shear zones developed during the Brasiliano–Pan-African orogeny. Several stations aligned along a northeast–southwest trend located above the (now aborted) Mesozoic Cariri–Potiguar rift display large uncertainties for the fast-axis direction. This non-azimuthal anisotropy may be related to a complex anisotropic fabric resulting from a combination of deformation along the ancient collision between Precambrian blocks, Mesozoic extension and thermomechanical erosion dragging by sublithospheric flow. Finally, several stations along the Atlantic coast reveal depth-dependent anisotropic orientations roughly (sub)perpendicular to the margin. These results suggest a more recent overprint, probably related to the presence of frozen anisotropy in the lithosphere due to stretching and rifting during the opening of the South Atlantic.

scholarly journals The Timing of Strike-Slip Deformation Along the Storstrømmen Shear Zone, Greenland Caledonides: U–Pb Zircon and Titanite Geochronology

2014 ◽  
Vol 41 (1) ◽  
pp. 19 ◽  
Author(s):  
Benjamin W. Hallett ◽  
William C. McClelland ◽  
Jane A. Gilotti
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Strike Slip ◽  
Fault System ◽  
Oblique Collision ◽  
Plate Convergence ◽  
Ion Probe ◽  
Slip Displacement ◽  
Land Deformation ◽  
Lateral Escape

The Storstrømmen shear zone (SSZ) in the Greenland Caledonides is widely interpreted to have formed in a transpressional regime during sinistral, oblique collision between Baltica and Laurentia in the Silurian to Devonian. New mapping of the SSZ at Sanddal documents a 100 m thick, greenschistfacies mylonite zone cutting the eclogite to amphibolite-facies gneiss complex. We present U–Pb ion probe geochronology on zircon and titanite from a variety of lithologies that shows the SSZ was active from late Devonian to the Carboniferous (at least until 350 Ma). The age of thrusting in the foreland is not well known, but must be younger than the age of eclogite-facies metamorphism at ~400 Ma. It is, therefore, possible that contraction is the same age as strike-slip motion, and that transpression is a viable model. The timing of the SSZ is synchronous with dextral strike-slip displacement on the Germania Land deformation zone. Simultaneous displacement on sinistral and dextral, conjugate shear zones suggests that the SSZ is part of a strikeslip fault system that led to lateral escape of material northward (present day coordinates) during the waning stages of plate convergence between Laurentia and Baltica.SOMMAIRELa zone de cisaillement de Storstrømmen (SSZ) dans les Calédonides du Groenland est généralement comprise comme ayant été formée durant un régime de transpression sénestre lors de la collision oblique entre Baltica et Laurentie, du Silurien au Dévonien.  Une nouvelle cartographie de la SSZ à Sanddal décrit une zone de 100 m d’épaisseur de mylonite au faciès des schistes verts qui recoupe un complexe de gneiss au faciès éclogite à amphibolite.  Notre analyse géochronologique par sonde ionique U-Pb sur zircon et titanite sur diverses lithologies, montre que la SSZ a été active de la fin du Dévonien jusqu’au Carbonifère (au moins jusqu’à 350 Ma).  L’âge du chevauchement dans l’avant-pays n’est pas bien connue, mais il doit être plus jeune que le métamorphisme au faciès d’éclogite à ~400 Ma.  Il est donc possible que la contraction soit du même âge que le mouvement de coulissage, et que la transpression soit un modèle viable.  La chronologie de la SSZ est synchrone au mouvement de coulissage dextre de la zone de déformation de Germania Land.  Les déplacements simultanés, sénestre et dextre, sur des zones de cisaillement conjuguées permettent de penser que la SSZ fait partie d’un système de décrochement qui a engendré une éjection latérale de matériau vers le nord (selon les coordonnées actuelles) durant les stades de convergence des plaques Laurentie et Baltica.

scholarly journals Zippered Shear Zone Model for Interacting Shear Zones in the Borborema Province, Brazil, as Constrained by U‐Pb Dating

Tectonics ◽  
2019 ◽  
Vol 38 (11) ◽  
pp. 3959-3974 ◽  
Author(s):  
Carlos F. Ávila ◽  
Carlos J. Archanjo ◽  
Haakon Fossen ◽  
Maria Helena B. M. Hollanda
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Zone Model ◽  
Borborema Province

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

2021 ◽  
Vol 51 (2) ◽  
Author(s):  
Carlos José Archanjo ◽  
Maria Helena Bezerra Maia de Hollanda ◽  
Luis Gustavo Ferreira Viegas
Keyword(s):  
Shear Zone ◽  
Borborema Province ◽  
Escape Tectonics ◽  
Lateral Escape

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

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 6) ◽  
Author(s):  
Sergio P. Neves ◽  
Andréa Tommasi ◽  
Alain Vauchez ◽  
Thais Andressa Carrino
Keyword(s):  
Shear Zone ◽  
Large Scale ◽  
Shear Zones ◽  
Strike Slip ◽  
Northeastern Brazil ◽  
Main Stage ◽  
Plate Boundaries ◽  
Deformation Localization ◽  
Continental Scale ◽  
Dextral Shear

Abstract 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.

scholarly journals Integration of remote sensing and airborne geophysical data applied to geological mapping: a case study of the Vieirópolis region (Paraíba), Rio Grande do Norte Subprovince, Borborema Province

2018 ◽  
Vol 18 (3) ◽  
pp. 89-103 ◽  
Author(s):  
José Ferreira de Araújo Neto ◽  
Glenda Lira Santos ◽  
Igor Manoel Belo de Albuquerque e Souza ◽  
Sandra De Brito Barreto ◽  
Lauro Cézar Montefalco de Lira Santos ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Shear Zone ◽  
Gamma Ray ◽  
Rio Grande ◽  
Shear Zones ◽  
Geological Mapping ◽  
Gamma Ray Spectrometry ◽  
Borborema Province ◽  
Geological Map

The integration of geological data obtained through fieldwork, remote sensing and airborne geophysics has been shown to be efficient in creation of precise geological maps. The Vieirópolis region, sited in the west of the Rio Grande do Norte Subprovince of the Borborema Province, is characteristically made up of rocks intensely deformed by transcurrent shear zones and late brittle structures which control the mineralization of gemmological and industrial minerals. ASTER GDEM and airborne geophysical images (magnetometry and gamma-ray spectrometry) were used in order to enhance the geological knowledge of this region and to facilitate the identification and delimitation of structures and lithologies mapped during stages of fieldwork. Thus, a geological map on a scale of 1:50,000 was achieved, made up of six main lithological units and three new shear zones (Vieirópolis, Lastro and São Pedro), as well as the NE-SW-trending Portalegre Shear Zone. Within the newly mapped structures, the Vieirópolis Shear Zone stands out due to its expressiveness. Aeromagnetometry data suggest that this zone originated on the edge of the Brejo das Freiras Subbasin, part of the Portalegre Shear Zone System. NW-SE, ESE-WNW and E-W lineaments were correlated to lesser extent brittle structures which sometimes transversely cut the regional foliation, allowing pegmatite fluids to rise. The RGB ternary composition map (K, eTh, eU) also corroborates the presence of these structures, besides helping to determine lithological units. In this case study, the integration of direct and indirect data showed to be essential for the understanding and producing of local geological map.

scholarly journals ANÁLISE TECTÔNICA DA PORÇÃO NORDESTE DA FAIXA SERGIPANA, PROVÍNCIA BORBOREMA: DUPLA VERGÊNCIA EM RESPOSTA A COLISÃO OBLÍQUA ENTRE O CRÁTON DO SÃO FRANCISCO E O TERRENO PERNAMBUCO-ALAGOAS

2018 ◽  
Author(s):  
Haroldo Monteiro Lima ◽  
Márcio Martins Pimentel ◽  
Lauro Cezar Montefalco de Lira Santos ◽  
Vanildo Almeida Mendes
Keyword(s):  
Geometric Analysis ◽  
Shear Zones ◽  
Strain Partitioning ◽  
Fold Belt ◽  
Oblique Collision ◽  
Borborema Province ◽  
Thrust Tectonics ◽  
Late Neoproterozoic ◽  
Orogenic Belts ◽  
Belo Monte

Estruturas de dupla vergência são reconhecidas em cinturões orogênicos pré-cambrianos e fanerozoicos em resposta à partição da deformação entre componentes contracionais e transcorrentes em zonas transpressionais. A Faixa Sergipana é um importante segmento crustal localizado no sul da Província Borborema, NE do Brasil. Análise cinemática e geométrica em escala meso e microscópica realizadas na porção Nordeste da Faixa Sergipana revelou a existência de quatro fases deformacionais: Dn, D1, D2 e D3 que resultaram em inversão de transporte tectônico e imbricamento de complexos metavulcanossedimentares abundantes na região. O Domo Jirau do Ponciano representa o embasamento gnáissico migmatítico que preserva a trama mais antiga Dn. As fases posteriores (D1 e D2) representam tectônica contracional manifestada pelas zonas de cisalhamento de Jacaré dos Homens, Belo Monte-Jeremoabo e Palmeira dos Índios, e transcorrente/transpressional, respectivamente. Todo esse conjunto foi deformado por último por um episódio rúptil-dúctil (D3) responsável pela formação de fraturas, falhas e brechas de falhas. A combinação de dados estruturais e análise litoestratigráfica sugere que este arcabouço deve ter se desenvolvido em episódios contracionais distintos e retrabalhado durante o final do Neoproterozoico em resposta à colisão oblíqua entre o Terreno Pernambuco-Alagoas e o Cráton do São Francisco.Palavras Chave: Cinturões orogênicos, dupla vergência, Faixa SergipanaAbstract:TECTONIC ANALYSIS OF THE NORTHEAST SERGIPANA BELT, BORBOREMA PROVINCE: DOUBLE VERGENCE IN RESPONSE TO OBLIQUE COLLISION BETWEEN THE SÃO FRANCISCO CRATON AND PERNAMBUCO-ALAGOAS TERRANE. Double-vergent structures are recognized in Precambrian and Phanerozoic orogenic belts due strain partitioning in thrust and transcurrent components in transpressional sites. The Sergipano Fold Belt is an important crustal segment, located in the southern Borborema Province, NE Brazil. Meso and microscopic kinematic and geometric analysis in the northeastern portion of the Sergipano Fold Belt revealed the presence of four deformation stages (Dn, D1, D2 e D3). They resulted in inversion of tectonic vergence and imbrication of the metavolcanosedimentary sequences. The Jirau do Ponciano Dome represents the gneissic-migmatitic basement, preserving the older fabric. The later stages (D1 and D2), corresponds to thrust tectonics, represented by the Jacaré dos Homens, Belo Monte-Jeremoabo and Palmeira dos Índios shear zones and the transcurrent/transpressional stage, respectively. All this set is later affected by a ductile-brittle phase (D3), responsible for fractures, faults and formation of breccias. The integration of the obtained data suggest that the area framework was developed in distinct contractional episodes and reworked in the Late Neoproterozoic, in response to oblique collision between the Pernambuco-Alagoas terrane/block and the São Francisco Craton.Keywords: Orogenic belts, double vergence, Sergipana belt

Unraveling sedimentary precursors and metal enrichment of high-grade metamorphosed manganese-rich rocks from the Borborema Province, northeastern Brazil

2021 ◽  
pp. 104283
Author(s):  
Felipe Holanda dos Santos ◽  
Wagner da Silva Amaral ◽  
Kurt Konhauser ◽  
Douglas Teixeira Martins ◽  
Marco Paulo de Castro ◽  
...  
Keyword(s):  
Northeastern Brazil ◽  
High Grade ◽  
Metal Enrichment ◽  
Borborema Province

scholarly journals Decratonization by rifting enables orogenic reworking and transcurrent dispersal of old terranes in NE Brazil

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Carlos E. Ganade ◽  
Roberto F. Weinberg ◽  
Fabricio A. Caxito ◽  
Leonardo B. L. Lopes ◽  
Lucas R. Tesser ◽  
...  
Keyword(s):  
Shear Zones ◽  
Boundary Region ◽  
The North ◽  
Pan African ◽  
Juvenile Material ◽  
Oceanic Basin ◽  
Borborema Province ◽  
Isotopic Model ◽  
Late Neoproterozoic

AbstractDispersion and deformation of cratonic fragments within orogens require weakening of the craton margins in a process of decratonization. The orogenic Borborema Province, in NE Brazil, is one of several Brasiliano/Pan-African late Neoproterozoic orogens that led to the amalgamation of Gondwana. A common feature of these orogens is that a period of extension and opening of narrow oceans preceded inversion and collision. For the case of the Borborema Province, the São Francisco Craton was pulled away from its other half, the Benino-Nigerian Shield, during an intermittent extension event between 1.0–0.92 and 0.9–0.82 Ga. This was followed by inversion of an embryonic and confined oceanic basin at ca. 0.60 Ga and transpressional orogeny from ca. 0.59 Ga onwards. Here we investigate the boundary region between the north São Francisco Craton and the Borborema Province and demonstrate how cratonic blocks became physically involved in the orogeny. We combine these results with a wide compilation of U–Pb and Nd-isotopic model ages to show that the Borborema Province consists of up to 65% of strongly sheared ancient rocks affiliated with the São Francisco/Benino-Nigerian Craton, separated by major transcurrent shear zones, with only ≈ 15% addition of juvenile material during the Neoproterozoic orogeny. This evolution is repeated across a number of Brasiliano/Pan-African orogens, with significant local variations, and indicate that extension weakened cratonic regions in a process of decratonization that prepared them for involvement in the orogenies, that led to the amalgamation of Gondwana.

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