scholarly journals Metamorphic evolution of the Great Slave Lake shear zone

2020 ◽  
Author(s):  
Brendan Dyck ◽  
Rellie M. Goddard ◽  
David Wallis ◽  
Lars N. Hansen ◽  
Edith Martel
Keyword(s):  
Shear Zone ◽  
Metamorphic Evolution ◽  
Great Slave Lake

Structure of the crust and upper mantle of the Great Slave Lake shear zone, northwestern Canada, from teleseismic analysis and gravity modelling

2003 ◽  
Vol 40 (9) ◽  
pp. 1203-1218 ◽  
Author(s):  
David W Eaton ◽  
Jacqueline Hope
Keyword(s):  
Shear Zone ◽  
Upper Mantle ◽  
Receiver Function ◽  
Function Analysis ◽  
Crustal Material ◽  
S Wave ◽  
Crust And Upper Mantle ◽  
Fast Axis ◽  
Great Slave Lake ◽  
Basic Features

The Great Slave Lake shear zone (GSLsz) exposes lower crustal rocks analogous to deep-seated segments of modern strike-slip fault zones, such as the San Andreas fault. Extending for 1300 km beneath the Western Canada Sedimentary Basin to the southern margin of the Slave Province, the GSLsz produces one of the most prominent linear magnetic anomalies in Canada. From May to October 1999, 13 three-component portable broadband seismograph stations were deployed in a 150-km profile across a buried segment of the shear zone to investigate its lithospheric structure. Splitting analysis of core-refracted teleseismic shear waves reveals an average fast-polarization direction (N49°E ± 19°) that is approximately parallel to the shear zone. Individual stations near the axis of the shear zone show more northerly splitting directions, which we attribute to interference between regional anisotropy in the upper mantle (fast axis ~N60°E) and crustal anisotropy within the shear zone (fast axis ~N30°E). At the location of our profile, the shear zone is characterized by a 10-mGal axial gravity high with a wavelength of 30 km, superimposed on a longer wavelength 12-mGal low. This gravity signature is consistent with the basic features of the crustal model derived from receiver-function analysis: a Moho that dips inward toward the shear-zone axis and a mid-crustal zone with high S-wave velocity (ΔVs = 0.6 ± 0.2 km/s). The axial gravity high may be related to uplift of deeper crustal material within the shear zone, or protolith-dependent compositional differences between the shear zone and surrounding wall rocks.

scholarly journals Electrical resistivity structure of the Great Slave Lake shear zone, northwest Canada: implications for tectonic history

2014 ◽  
Vol 199 (1) ◽  
pp. 178-199 ◽  
Author(s):  
Yaotian Yin ◽  
Martyn Unsworth ◽  
Mitch Liddell ◽  
Dinu Pana ◽  
James A. Craven
Keyword(s):  
Electrical Resistivity ◽  
Shear Zone ◽  
Resistivity Structure ◽  
Tectonic History ◽  
Great Slave Lake

scholarly journals Tectono-Metamorphic Evolution of the Grenville-Aged Jahazpur Shear Zone, in Northwest India

2020 ◽  
Author(s):  
Shikha Gupta ◽  
Lopamudra Saha ◽  
A Prakash ◽  
N Alfimova ◽  
E Bogomolov
Keyword(s):  
Shear Zone ◽  
Metamorphic Evolution ◽  
Northwest India

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>

The electrical resistivity structure of Archean to Tertiary lithosphere along 3200 km of SNORCLE profiles, northwestern Canada

2005 ◽  
Vol 42 (6) ◽  
pp. 1257-1275 ◽  
Author(s):  
Alan G Jones ◽  
Juanjo Ledo ◽  
Ian J Ferguson ◽  
Colin Farquharson ◽  
Xavier Garcia ◽  
...  
Keyword(s):  
Shear Zone ◽  
North American ◽  
Three Dimensional ◽  
Thickness Variation ◽  
Resistivity Structure ◽  
Seismic Reflection Data ◽  
Lithospheric Thickness ◽  
The North ◽  
Reflection Data ◽  
Great Slave Lake

Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure of the North American continent from an Archean core to a region of Tertiary assembly were recorded at almost 300 sites along 3200 km of profiles on the Lithoprobe Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) transect in northwestern Canada. At the largest scale, the MT results indicate significant lithospheric thickness variation, from 260 km at the southwest margin of the Slave craton to significantly < 100 km at the southwestern end of the SNORCLE transect in the Cordillera. At intermediate scale, the resistivity results allow broad terrane subdivisions to be made. Several anomalously conductive zones along the SNORCLE transect, in rocks ranging in age from Archean to Tertiary, are attributed to the introduction of either water or carbon into the crust and mantle during subduction processes. At the local scale, the MT data image two major faults crossing the study area, the Great Slave Lake shear zone and the Tintina Fault. The resistivity images show that both the Tintina Fault and Great Slave Lake shear zone form crustal-scale features, and that the Tintina Fault has a remarkably uniform resistivity signature over a 400 km strike length in the study area. Arguably the most controversial conclusion reached is that the MT data do not support the western extension of North American autochthonous basement suggested from interpretation of the seismic reflection data.

scholarly journals Geoelectric structure of the Great Slave Lake shear zone in northwest Alberta: implications for structure and tectonic history

2018 ◽  
Vol 55 (3) ◽  
pp. 295-307
Author(s):  
Enci Wang ◽  
Martyn Unsworth ◽  
Thomas Chacko
Keyword(s):  
Shear Zone ◽  
Electrical Anisotropy ◽  
Plate Boundaries ◽  
Western Canada Sedimentary Basin ◽  
Low Resistivity ◽  
The North ◽  
Tectonic History ◽  
Tectonic Processes ◽  
Great Slave Lake ◽  
Seismic Reflectivity

The study of ancient plate boundaries can provide insights into the past and present-day tectonic processes. Here, we describe a magnetotellurics (MT) study of the Precambrian basement of the Hay River Fault (HRF) in northwest Alberta, which is the southwest segment of the Great Slave Lake shear zone. New broadband MT data were collected to give a clearer image of the crustal structure. The Western Canada Sedimentary Basin was imaged as a low-resistivity layer above the resistive crystalline basement. Four basement conductors were defined, and correlate with the terrane boundaries delineated with aeromagnetic data. These are (1) a major conductor in the Kiskatinaw domain, (2) a conductor on the boundary of the Ksituan and Chinchaga domains, (3) a conductor on the boundary of the Chinchaga and Buffalo Head domains, and (4) a conductor near the HRF. Both (1) and (2) correspond to areas of high seismic reflectivity. The low resistivity can be explained by interconnected grain boundary graphite or sulfide phases deposited by metamorphic fluid migration. The HRF was not definitively located in previous studies. The new data show that the HRF could be thin (1 km) or wide (10 km) and located at the boundary of the contrasting aeromagnetic anomalies or further to the north. Various tectonic processes are proposed to interpret the possible locations of the HRF. No electrical anisotropy structure is required to interpret the MT data in this study.

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