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

Yin, Yixing; Unsworth, Martyn; Liddell, M. V.; Pană, D.I.; Craven, John

doi:10.1093/gji/ggu251

Cited by 27 publications

(14 citation statements)

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“…In contrast, high resistivity is associated with the Great Slave shear zone up to 50 km depth (Yin et al, 2014) and with a Neoproterozoic collisional suture in northeast Brazil .…”

Section: Accepted Manuscriptmentioning

confidence: 87%

Heterogeneity and anisotropy in the lithospheric mantle

2015

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International audienceThe lithospheric mantle is intrinsically heterogeneous and anisotropic. These two properties govern the repartition of deformation, controlling intraplate strain localization and development of new plate boundaries. Geophysical and geological observations provide clues on the types, ranges, and characteristic length scales of heterogeneity and anisotropy in the lithospheric mantle. Seismic tomography points to variations in geothermal gradient and hence in rheological behavior at scales of hundreds of km. Seismic anisotropy data substantiate anisotropic physical properties consistent at scales of tens to hundreds of km. Receiver functions imply lateral and vertical heterogeneity at scales < 10 km, which might record gradients in composition or anisotropy. Observations on naturally deformed peridotites establish that compositional heterogeneity and Crystal Preferred Orientations (CPOs) are ubiquitous from the mm to the km scales. These data allow discussing the processes that produce/destroy heterogeneity and anisotropy and constraining the time scales over which they are active. This analysis highlights: (i) the role of deformation and reactive percolation of melts and fluids in producing compositional and structural heterogeneity and the feedbacks between these processes, (ii) the weak mechanical effect of mineralogical variations, and (iii) the low volumes of fine-grained microstructures and difficulty to preserve them. In contrast, olivine CPO and the resulting anisotropy of mechanical and thermal properties are only modified by deformation. Based on this analysis, we propose that strain localization at the plate scale is, at first order, controlled by large-scale variations in thermal structure and in CPO-induced anisotropy. In cold parts of the lithospheric mantle , grain size reduction may contribute to strain localization, but the low volume of fine-grained domains limits this effect

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“…In contrast, high resistivity is associated with the Great Slave shear zone up to 50 km depth (Yin et al, 2014) and with a Neoproterozoic collisional suture in northeast Brazil .…”

Section: Accepted Manuscriptmentioning

confidence: 87%

Heterogeneity and anisotropy in the lithospheric mantle

2015

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“…A variety of different approaches has been used to evaluate the existence of electrical anisotropy within the subsurface, that is, phases exceeding 90° (Heise & Pous, 2003;Weckmann et al, 2003), the coincidence of a large split between phase tensor invariants and small induction arrows (Häuserer & Junge, 2011), and the coincidence of phase differences and induction arrows (Yin et al, 2014). In a MT study by Wannamaker et al (2008), two-dimensional (2-D) isotropic inversion imaged two narrow steep conductors that are separated by steep resistive zones.…”

Section: Introductionmentioning

confidence: 99%

Electrically Anisotropic Crust From Three‐Dimensional Magnetotelluric Modeling in the Western Junggar, NW China

et al. 2019

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An island arc environment related to intraoceanic subduction or ridge subduction from the Late Carboniferous to the Early Permian has been proposed for the formation of Western Junggar, NW China, situated in the southwest of Central Asian Orogenic Belt. However, the details and consequences of the subduction remain controversial. To further identify the relics of the Late Carboniferous subduction at depth, three magnetotelluric profiles were deployed. Phase tensors, real induction arrows, and three‐dimensional (3‐D) isotropic resistivity models indicate the presence of a 3‐D anisotropic resistivity structure in the crust. Consequently, a 3‐D anisotropic resistivity model was constructed by forward modeling. The 3‐D anisotropic resistivity model contains two azimuthally anisotropic middle‐upper crust anomalies with minimum resistivity striking N90°E at depths of 5 to 20 km, and an azimuthally anisotropic lower crust anomaly with minimum resistivity striking N20°E at depths of 20 to 46 km. The electrically anisotropic anomalies are closely related to relatively high shear‐wave velocities with significant negative radial anisotropy. The anisotropies in the middle‐to‐upper crust and the lower crust are related to the oceanic ridge (N90°E) subduction with a slab window in the Late Carboniferous and the remnant oceanic slab, respectively. The magnetotelluric observations support a NW70° subduction with an intraoceanic ridge‐transform system in the Late Carboniferous and a remnant oceanic slab trapped in Western Junggar.

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“…Weckmann et al 2003;Eaton et al 2004;Yin et al 2014). Geological studies of the exposed part of the CLsz by McDonough et al (2000) have mapped high-grade metamorphic mylonites that are strike-lineated in the centre of the shear zone, and dip-lineated to either side, similar to Model 1 in Fig.…”

Section: Discussionmentioning

confidence: 80%

“…Yin et al (2014) were able to characterize the GSLsz in northern Alberta as a resistive feature cut by a dipping anisotropic layer. They used dimensional analysis, phase tensor patterns, as well as 2-D anisotropic and 3-D isotropic inversions of the MT data.…”

Section: E V I D E N C E F O R a N I S O T Ro P Ymentioning

confidence: 99%

Magnetotelluric imaging of anisotropic crust near Fort McMurray, Alberta: implications for engineered geothermal system development

Liddell¹,

Unsworth

Pek

2016

Geophys. J. Int.

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S U M M A R YViability for the development of an engineered geothermal system (EGS) in the oilsands region near Fort McMurray, Alberta, is investigated by studying the structure of the Precambrian basement rocks with magnetotellurics (MT). MT data were collected at 94 broad-band stations on two east-west profiles. Apparent resistivity and phase data showed little variation along each profile. The short period MT data detected a 1-D resistivity structure that could be identified as the shallow sedimentary basin underlain by crystalline basement rocks to a depth of 4-5 km. At lower frequencies a strong directional dependence, large phase splits, and regions of out-of-quadrant (OOQ) phase were detected. 2-D isotropic inversions of these data failed to produce a realistic resistivity model. A detailed dimensionality analysis found links between large phase tensor skews (∼15• ), azimuths, OOQ phases and tensor decomposition strike angles at periods greater than 1 s. Low magnitude induction vectors, as well as uniformity of phase splits and phase tensor character between the northern and southern profiles imply that a 3-D analysis is not necessary or appropriate. Therefore, 2-D anisotropic forward modelling was used to generate a resistivity model to interpret the MT data. The preferred model was based on geological observations of outcropping anisotropic mylonitic basement rocks of the Charles Lake shear zone, 150 km to the north, linked to the study area by aeromagnetic and core sample data. This model fits all four impedance tensor elements with an rms misfit of 2.82 on the southern profile, and 3.3 on the northern. The conductive phase causing the anisotropy is interpreted to be interconnected graphite films within the metamorphic basement rocks. Characterizing the anisotropy is important for understanding how artificial fractures, necessary for EGS development, would form. Features of MT data commonly interpreted to be 3-D (e.g. out of OOQ phase and large phase tensor skew) are shown to be interpretable with this 2-D anisotropic model.

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

Cited by 27 publications

References 100 publications

Heterogeneity and anisotropy in the lithospheric mantle

Heterogeneity and anisotropy in the lithospheric mantle

Electrically Anisotropic Crust From Three‐Dimensional Magnetotelluric Modeling in the Western Junggar, NW China

Magnetotelluric imaging of anisotropic crust near Fort McMurray, Alberta: implications for engineered geothermal system development

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