scholarly journals Great Slave Lake shear zone meets Thelon Tectonic Zone, District of Mackenzie, N.W.T.

1988 ◽  
Author(s):  
S Hanmer ◽  
T Needham
Keyword(s):  
Shear Zone ◽  
Tectonic Zone ◽  
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.

The Cora Lake shear zone, Athabasca granulite terrane, an intraplate response to far-field orogenic processes during the amalgamation of Laurentia

2014 ◽  
Vol 51 (9) ◽  
pp. 877-901 ◽  
Author(s):  
S.P. Regan ◽  
M.L. Williams ◽  
S. Leslie ◽  
K.H. Mahan ◽  
M.J. Jercinovic ◽  
...  
Keyword(s):  
Shear Zone ◽  
Granulite Facies ◽  
Dyke Swarm ◽  
Tectonic Zone ◽  
Metamorphic Peak ◽  
Fine Grain ◽  
Planar Shear ◽  
Mafic Dyke Swarm ◽  
Dextral Shear ◽  
Regional Stresses

The Cora Lake shear zone (CLsz) is a 4–6 km wide localized high-strain zone that bisects the polydeformed Athabasca granulite terrane, northern Saskatchewan. It also coincides with the geophysical trace of the Snowbird tectonic zone. The CLsz represents a major lithotectonic and thermobarometric discontinuity within the exposure of >20 000 km2 of high-pressure granulites. Most rocks have a strong mineral lineation plunging moderately to the southwest. The Northwestern subdomain (hangingwall) is characterized by ca. 2.6 Ga plutonic rocks that contain an early, subhorizontal gneissic layering (ca. 2.57 Ga) that was overprinted by large amplitude folds and a partitioned, but pervasive, axial planar, dextral, shear fabric at ca. 1.9 Ga. Thermobarometry suggests metamorphic conditions of ∼0.9 GPa and ∼750 °C during both of the phases of tectonism. The footwall is predominantly underlain by the ca. 3.3–3.0 Ga Chipman tonalite, layers of intercalated mafic and felsic granulite, and the widespread 1.9 Ga Chipman mafic dyke swarm. Early subhorizontal layering in the footwall was also folded at ca. 1.9 Ga and transposed into a steeply dipping, northeast-striking axial planar shear fabric that corresponds with the metamorphic peak (1.1–1.2 GPa and 800–900 °C). These distinct domains were juxtaposed across the CLsz, which contains a gneissic foliation striking 231° and dipping moderately to steeply to the northwest. Abundant sinistral–normal kinematic indicators are consistent with the distinctly lower pressures to the northwest. The shear zone is characterized by very fine grain sizes, despite its high-temperature assemblages including clinopyroxene and garnet. Thermobarometry from the CLsz displays progressive decompression of reworked footwall rocks with increasing mylonitization. In situ monazite geochronology indicates shearing at 1.89–1.87 Ga shortly after the granulite facies metamorphic peak. The anomalous sinistral kinematics of the CLsz, bracketed in time between periods of dextral shearing, can be explained by changing regional stresses during alternating convergent tectonics to the west and to the southeast of the Athabasca granulite terrane.

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

Striding-Athabasca mylonite zone: Complex Archean deep-crustal deformation in the East Athabasca mylonite triangle, northern Saskatchewan

1994 ◽  
Vol 31 (8) ◽  
pp. 1287-1300 ◽  
Author(s):  
Simon Hanmer ◽  
Randy Parrish ◽  
Michael Williams ◽  
Chris Kopf
Keyword(s):  
Flow Pattern ◽  
Shear Zone ◽  
Crustal Deformation ◽  
Principal Axis ◽  
Shear Zones ◽  
Granulite Facies ◽  
Strike Slip ◽  
Tectonic Zone ◽  
Early Proterozoic ◽  
Lower Deck

The geophysically defined Snowbird tectonic zone is manifested in northernmost Saskatchewan as a deep-crustal, multistage mylonitic structure, the East Athabasca mylonite triangle. The triangle, located at the northeastern apex of a stiff, crustal-scale "lozenge," is composed of mid-Archean annealed mylonites and late Archean ribbon mylonites, formed during two granulite facies events (850–1000 °C, 1.0 GPa). The flow pattern in the mylonites is geometrically and kinematically complex, and corresponds to that expected adjacent to the apex of a stiff elliptical volume subjected to subhorizontal regional extension parallel to its principal axis. The late Archean mylonites are divided into an upper structural deck, entirely occupied by a dip-slip shear zone, and an underlying lower deck. The latter is divided into two upright conjugate strike-slip shear zones, separated by a low-strain septum, which deformed by progressive coaxial flow. The flow pattern in the mid-Archean mylonites is compatible with that of the late Archean mylonites, and suggests that the crustal-scale lozenge influenced deformation since the mid-Archean. In the interval ca. 2.62–2.60 Ga, deformation in the upper and lower decks evolved from a granulite facies pervasive regime to a more localized amphibolite facies regime. With further cooling, deformation was localized within very narrow greenschist mylonitic faults at the lateral limits of the lower deck. By the late Archean, the East Athabasca mylonite triangle was part of a deep-crustal, intracontinental shear zone. This segment of the Snowbird tectonic zone was not the site of an Early Proterozoic suture or orogen.

The Great Falls Tectonic Zone: suture or intracontinental shear zone?

1998 ◽  
Vol 35 (2) ◽  
pp. 175-183 ◽  
Author(s):  
D E Boerner ◽  
J A Craven ◽  
R D Kurtz ◽  
G M Ross ◽  
F W Jones
Keyword(s):  
Shear Zone ◽  
Foreland Basin ◽  
Oceanic Lithosphere ◽  
Plate Edge ◽  
Tectonic Zone ◽  
Magmatic Arc ◽  
Tectonically Active ◽  
Proterozoic Basement ◽  
Wyoming Province ◽  
Remote Sensing Methods

The Great Falls Tectonic Zone is generally considered to be the boundary between the Archean Hearne and Wyoming provinces. Although completely buried beneath the western Canadian sedimentary basin, the zone can be studied indirectly through variations in Phanerozoic sedimentation patterns, faulting, basement geochronology, and xenoliths, and with geophysical remote sensing methods. While tectonically active ca. 1.8 Ga and clearly truncating the potential field fabrics of Wyoming Province and Medicine Hat Block, the Great Falls Tectonic Zone lacks a colinear magmatic arc, suggesting that the Hearne-Wyoming juxtaposition did not involve subduction of oceanic lithosphere. Furthermore, electromagnetic studies fail to detect a response that can be interpreted as a plate-edge foreland basin, typical of exposed Proterozoic suture zones. The only conductivity anomaly associated with the zone is weak and appears at depths exceeding 20 km, well below the top of the Proterozoic basement. Taken together, these observations suggest the Great Falls Tectonic Zone may be better interpreted as a reactivated Archean(?) intracontinental shear zone rather than a Proterozoic age suture between Archean provinces.

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.

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