Multiple meso-scale shear zones, Negar multiple meso-scale shear zones, south of Iran

2021 ◽  
Author(s):  
Raana Razavi-Pash ◽  
Moslem Ghavam-Abadi ◽  
Farhad Mohammadi ◽  
Ali Sholeh
Keyword(s):  
Shear Zones ◽  
Meso Scale ◽  
Scale Shear

Chapter 14 Regional context and lithotectonic framework of the 1.1–0.9 Ga Sveconorwegian orogen, southwestern Sweden

2020 ◽  
Vol 50 (1) ◽  
pp. 337-349 ◽  
Author(s):  
Michael B. Stephens ◽  
Ulf Bergström ◽  
Carl-Henric Wahlgren
Keyword(s):  
High Pressure ◽  
Tectonic Evolution ◽  
Shear Zones ◽  
Crustal Extension ◽  
Frontal Part ◽  
Eastern Segment ◽  
Mountain Belts ◽  
Sveconorwegian Orogen ◽  
Scale Shear ◽  
Early Neoproterozoic

AbstractThe 1.1–0.9 Ga Sveconorwegian orogen in southwestern Scandinavia belongs to the global system of mountain belts established during the assembly of the supercontinent Rodinia. An overall north–south structural trend and five lithotectonic units bounded by crustal-scale shear zones characterize this orogen. In Sweden, the Eastern Segment abuts the orogen's cratonic foreland eastwards and is separated from the Idefjorden terrane westwards by a ductile shear zone, up to 5 km thick, displaying a sinistral transpressive component. These two lithotectonic units differ on the basis of their pre-Sveconorwegian accretionary tectonic evolution, and the timing of Sveconorwegian high-pressure metamorphism, anatexis and polyphase deformation. High-pressure granulites and migmatites formed at c. 1.05–1.02 Ga in the Idefjorden terrane; eclogites, high-pressure granulites and migmatites at c. 0.99–0.95 Ga in the Eastern Segment. Magmatic activity and crustal extension progressed westwards at c. 0.98–0.92 Ga. Prior to or at 0.93–0.91 Ga, greenschist facies shear deformation with top-to-the-foreland movement affected the frontal part of the orogen. Geodynamic uncertainties concern the affinity of the Idefjorden terrane relative to Fennoscandia (Baltica), the character of the Sveconorwegian orogenesis, and the contiguous or non-contiguous nature of the erosional fronts of the late Mesoproterozoic–early Neoproterozoic orogens in Sweden and Canada.

The role of regional-scale shear zones in paleogeographic reconstructions: the case study of the Variscan belt in the Mediterranean area

2021 ◽  
Author(s):  
Matteo Simonetti ◽  
Rodolfo Carosi ◽  
Chiara Montomoli ◽  
Salvatore Iaccarino
Keyword(s):  
Earth Sciences ◽  
Shear Zone ◽  
Regional Scale ◽  
Shear Zones ◽  
Mediterranean Area ◽  
Variscan Belt ◽  
Metamorphic Evolution ◽  
The Mediterranean ◽  
Scale Shear

<p>Paleogeographic reconstruction and recognition of the tectono-metamorphic evolution of ancient orogenic belt is often complex. The combination of an adequate amount of paleomagnetic, metamorphic, structural and geochronological data is necessary. Fundamental data derive from the study of regional-scale shear zones, that can be directly observed, by combining detailed field work with structural analysis, microstructural analysis and petrochronology. The Southern European Variscan Belt in the Mediterranean area was partially overprinted by the Alpine cycle (Stampfli and Kozur, 2006) and correlations are mainly based on lithological similarities. Little attention has been paid to the compatibility of structures in the dispersed fragments. A main debate is the connection among the Corsica-Sardinia Block (CSB), the Maures-Tanneron Massif (MTM) and the future Alpine External Crystalline Massifs (ECM) (Stampfli et al., 2002; Advokaat et al., 2014) and if these sectors were connected by a network of shear zones of regional extent, known as the East Variscan Shear Zone (EVSZ).</p><p>We present a multidisciplinary study of shear zones cropping out in the CSB (the Posada-Asinara shear zone; Carosi et al., 2020), in the MTM (the Cavalaire Fault; Simonetti et al., 2020a) and in the ECM (the Ferriere-Mollières and the Emosson-Berard shear zones; Simonetti et al., 2018; 2020b).</p><p>Kinematic and finite strain analysis allowed to recognize a transpressional deformation, with a major component of pure shear and a variable component of simple shear, coupled with general flattening deformation. Syn-kinematic paragenesis, microstructures and quartz c-axis fabrics revealed that shear deformation, in all the studied sectors, occurred under decreasing temperature starting from amphibolite-facies up to greenschist-facies. A systematic petrochronological study (U-Th-Pb on monazite collected in the sheared rocks) was conducted in order to constrain the timing of deformation. We obtained ages ranging between ~340 Ma and ~320 Ma. Ages of ~340-330 Ma can be interpreted as the beginning of the activity of the EVSZ along its older branches while ages of ~320 Ma, obtained in all the shear zones, demonstrate that they were all active in the same time span.</p><p>The multidisciplinary approach revealed a similar kinematics and tectono-metamorphic evolution of the studied shear zones contributing to better constrain the extension and timing the EVSZ and to strength the paleogeographic reconstructions of the Southern Variscan belt during Late Carboniferous time, with important implications on the evolution of the Mediterranean area after the Late Paleozoic. This case study demonstrates how paleogeographic reconstructions could benefit from datasets obtained from large-scale structures (i.e., shear zones) that can be directly investigated.</p><p> </p><p>Advokaat et al. (2014). Earth and Planetary Science Letters 401, 183–195</p><p> </p><p>Carosi et al. (2012). Terra Nova 24, 42–51</p><p> </p><p>Carosi and Palmeri (2002). Geological Magazine 139.</p><p> </p><p>Carosi et al. (2020). Geosciences 10, 288.</p><p> </p><p>Simonetti et al (2020a). International Journal of Earth Sciences 109, 2261–2285</p><p> </p><p>Simonetti et al. (2020b). Tectonics 39</p><p> </p><p>Simonetti et al. (2018). International Journal of Earth Sciences. 107, 2163–2189</p><p> </p><p>Stampfli and Kozur (2006). Geological Society, London, Memoirs 32, 57–82</p><p> </p><p>Stampfli et al. (2002). Journal of the Virtual Explorer 8, 77</p>

Discrimination of annealed and dynamic fabrics: Consequences for strain localization and deformation episodes of large-scale shear zones

2008 ◽  
Vol 276 (1-2) ◽  
pp. 52-61 ◽  
Author(s):  
Marco Herwegh ◽  
Alfons Berger ◽  
Andreas Ebert ◽  
Sabine Brodhag
Keyword(s):  
Strain Localization ◽  
Large Scale ◽  
Shear Zones ◽  
Scale Shear

A dimensional analysis to quantify the thermal budget around lithospheric-scale shear zones

Terra Nova ◽  
2015 ◽  
Vol 27 (3) ◽  
pp. 163-168 ◽  
Author(s):  
Sylvia Duprat-Oualid ◽  
Philippe Yamato ◽  
Stefan M. Schmalholz
Keyword(s):  
Dimensional Analysis ◽  
Shear Zones ◽  
Thermal Budget ◽  
Scale Shear

Age constraints on terrane-scale shear zones in the Gawler Craton, southern Australia

2005 ◽  
Vol 139 (3-4) ◽  
pp. 164-180 ◽  
Author(s):  
G SWAIN ◽  
M HAND ◽  
J TEASDALE ◽  
L RUTHERFORD ◽  
C CLARK
Keyword(s):  
Shear Zones ◽  
Age Constraints ◽  
Scale Shear

Thermo-mechanical model for the finite strain gradient in kilometer-scale shear zones

Geology ◽  
2013 ◽  
Vol 41 (5) ◽  
pp. 567-570 ◽  
Author(s):  
Arthur Bauville ◽  
Stefan M. Schmalholz
Keyword(s):  
Strain Gradient ◽  
Mechanical Model ◽  
Finite Strain ◽  
Shear Zones ◽  
Scale Shear

scholarly journals The Alps-Apennines Interference Zone: A Perspective from the Maritime and Wester Ligurian Alps

Geosciences ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 185
Author(s):  
Fabrizio Piana ◽  
Luca Barale ◽  
Carlo Bertok ◽  
Anna d’Atri ◽  
Andrea Irace ◽  
...  
Keyword(s):  
Shear Zones ◽  
Western Alps ◽  
Structural Systems ◽  
Early Oligocene ◽  
Ligurian Alps ◽  
Tectonic Transport ◽  
The Alps ◽  
Southwestern Alps ◽  
Transfer Zone ◽  
Scale Shear

In SW Piemonte the Western Alps arc ends off in a narrow, E-W trending zone, where some geological domains of the Alps converged. Based on a critical review of available data, integrated with new field data, it is concluded that the southern termination of Western Alps recorded the Oligocene-Miocene activity of a regional transfer zone (southwestern Alps Transfer, SWAT) already postulated in the literature, which should have allowed, since early Oligocene, the westward indentation of Adria, while the regional shortening of SW Alps and tectonic transport toward the SSW (Dauphinois foreland) was continuing. This transfer zone corresponds to a system of deformation units and km-scale shear zones (Gardetta-Viozene Zone, GVZ). The GVZ/SWAT developed externally to the Penninic Front (PF), here corresponding to the Internal Briançonnais Front (IBF), which separates the Internal Briançonnais domain, affected by major tectono-metamorphic transformations, from the External Briançonnais, subjected only to anchizonal metamorphic conditions. The postcollisional evolution of the SW Alps axial belt units was recorded by the Oligocene to Miocene inner syn-orogenic basin (Tertiary Piemonte Basin, TPB), which rests also on the Ligurian units stacked within the adjoining Apennines belt in southern Piemonte. The TPB successions were controlled by transpressive faults propagating (to E and NE) from the previously formed Alpine belt, as well as by the Apennine thrusts that were progressively stacking the Ligurian units, resting on the subducting Adriatic continental margin, with the TPB units themselves. This allows correlation between Alps and Apennines kinematics, in terms of age of the main geologic events, interference between the main structural systems and tectonic control exerted by both tectonic belts on the same syn-orogenic basin.

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