The first magnetotelluric image of the lithospheric-scale geological architecture in central Svalbard, Arctic Norway

Beka, Thomas Ibsa; Smirnov, Maxim; Bergh, Steffen G.; Birkelund, Yngve

doi:10.3402/polar.v34.26766

Cited by 15 publications

(8 citation statements)

References 41 publications

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“…Previously reported results from 2D (Beka et al 2015) and 3D (Beka et al 2016) MT data interpretations of the broadband range (0.003-1000 s), acquired in the socalled Central Tertiary Basin of Spitsbergen (Dallmann 1999) east of Longyearbyen (Fig. 1a), display good agreement with geological models for the region (Bergh et al 1997;Baelum & Braathen 2012;Blinova et al 2012).…”

Section: Introductionsupporting

confidence: 73%

“…1a), display good agreement with geological models for the region (Bergh et al 1997;Baelum & Braathen 2012;Blinova et al 2012). From the 2D resistivity model Beka et al (2015) inferred the geological architecture of the area and used it to construct the main crustal-scale features as well as estimated a thinned lithosphere ca. 55-100 km in thickness, which made sense with respect to the region's known anomalous heat-flow (Khutorskoi et al 2009;Slagstad et al 2009) related to recent Cenozoic uplift and volcanism (Vågnes & Amundsen 1993;Harland 1997).…”

Section: Introductionmentioning

confidence: 61%

“…Magnetotelluric surveys have been carried out in Svalbard since 2013, motivated by reconnaissance geothermal exploration, focusing particularly on areas around the permanently settled regions of central and north-western Spitsbergen (Beka et al 2015;Beka et al 2016;Beka et al 2017). This series of surveys was the first to apply the magnetotellurics method in a region whose geological structures were previously inferred mainly from surface fieldwork, seismic and gravity studies (Haremo et al 1990;Eiken 1994;Bergh et al 1997;Harland 1997;Bergh & Grogan 2003), and with scarce data to deduce the framework of the deep crustal structure.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we extend the extent of the area on Svalbard covered by EM data (Beka et al 2015;Beka et al 2016) by interpreting the new MT data from Brøggerhalvøya using 3D inversion and by including the region's bathymetry (Jakobsson et al 2012) to account for coastal effects. As the amount of the available MT data is limited and the sites are measured along a single curved profile, we constrained the 3D model using a 2D model obtained from the impedance tensor determinant inversion.…”

Section: Introductionmentioning

confidence: 99%

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Magnetotelluric signatures of the complex tertiary fold–thrust belt and extensional fault architecture beneath Brøggerhalvøya, Svalbard

et al. 2017

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Magnetotelluric (MT) data were recently collected on Brøggerhalvøya, Svalbard, in a 0.003-1000 s period range along a curved WNW-ESE profile. The collected data manifested strong three-dimensional (3D) effects. We modelled the full impedance tensor with tipper and bathymetry included in 3D, and benchmarked the result with determinant data two-dimensional (2D) inversion. The final inversion results indicated striking similarity with known surface bedrock geology and well reflected the tectonic history of the region. The most convincing contribution of the MT data is perhaps the elegantly imaged interplay between repeated basement-involved fold-thrust belt structures and successive down-dropped strata along steeply dipping oblique-normal faults (e.g., the Scheteligfjellet Fault) that created a horst/ridge and graben/depression system. Peculiarly, the MT result suggests that the Paleocene-Eocene fold-thrust belt structures dominate the shallow crustal level, while later normal faults in the area can be traced deeper into the pre-Devonian basement formations strongly affecting fluid and heat migration towards the surface. Near the sub-vertical Scheteligfjellet Fault, the MT model indicates aquifers within the upraised horsts of the pre-Devonian system at 2-5 km depth, sandwiched between the down-faulted resistive (ca. 500-3000 Ωm) Carboniferous and Permian successions. The section west of the Ny-Ålesund settlement has signatures of lateral and subvertical cap-rock sealings, surrounding a steep and deep-seated major fault and aquifer systems. This section of the peninsula therefore requires closer investigation to evaluate the deep geothermal resource prospect.

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Section: Introductionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetotelluric signatures of the complex tertiary fold–thrust belt and extensional fault architecture beneath Brøggerhalvøya, Svalbard

et al. 2017

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“…(b) Simplified geological map of the survey area. Gray circles are locations of broadband MT stations described in Beka et al (2015Beka et al ( , 2016, and white circles are location of long-period MT deployments. The stations included in the analysis and modeling are marked with red stars.…”

Section: Tectonic Settingmentioning

confidence: 99%

Magnetotelluric Constraints on the Temperature, Composition, Partial Melt Content, and Viscosity of the Upper Mantle Beneath Svalbard

Selway

Smirnov

Beka

et al. 2020

Geochem Geophys Geosyst

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Long-period magnetotelluric (MT) data can be used to interpret upper mantle temperature, hydrogen content, and the presence of partial melt, all of which strongly influence mantle viscosity. We have collected the first long-period MT data in Svalbard and have combined them with preexisting broadband MT data to produce a model of the electrical resistivity of Svalbard's upper mantle. Asthenospheric resistivities are low compared to stable continental settings but more comparable to young oceanic asthenosphere, suggesting that the physical state of Svalbard's upper mantle is controlled by its proximity to the Mid-Atlantic Ridge. Interpretation of the MT model using a petrologically constrained genetic algorithm approach shows that partial melt is present in the uppermost asthenosphere beneath Svalbard. This is the first direct evidence of partial melt in Svalbard's asthenosphere from deep geophysical soundings. Viscosities calculated from the geophysical data show a low viscosity layer (~10 18 Pa s) coincident with the partial melt layer, underlain by a higher viscosity layer (~10 20 Pa s) extending to the transition zone. Viscosities calculated from glacial isostatic adjustment (GIA) data in Svalbard show a considerable range due mainly to uncertainties in past ice sheet models. Improved constraints on Svalbard's mantle viscosity from geophysical data may help to improve these GIA models.

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On the Use of Electromagnetics for Earth Imaging of the Polar Regions

Hill

2019

Surv Geophys

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The polar regions are host to fundamental unresolved challenges in Earth studies. The nature of these regions necessitates the use of geophysics to address these issues, with electromagnetic and, in particular, magnetotelluric studies finding favour and being applied over a number of different scales. The unique geography and climatic conditions of the polar regions means collecting magnetotelluric data at high latitudes, which presents challenges not typically encountered and may result in significant measurement errors. (1) The very high contact resistance between electrodes and the surficial snow and ice cover (commonly MΩ) can interfere with the electric field measurement. This is overcome by using custom-designed amplifiers placed at the active electrodes to buffer their high impedance contacts.(2) The proximity to the geomagnetic poles requires verification of the fundamental assumption in magnetotellurics that the magnetic source field is a vertically propagating, horizontally polarised plane wave. Behaviour of the polar electro-jet must be assessed to identify increased activity (high energy periods) that create strong current systems and may generate non-planar contributions. (3) The generation of 'blizstatic', localised random electric fields caused by the spin drift of moving charged snow and ice particles that produce significant noise in the electric fields during periods of strong winds. At wind speeds above ~ 10 m s −1 , the effect of the distortion created by the moving snow is broad-band. Station occupation times need to be of sufficient length to ensure data are collected when wind speed is low. (4) Working on glaciated terrain introduces additional safety challenges, e.g., weather, crevasse hazards, etc. Inclusion of a mountaineer in the team, both during the site location planning and onsite operations, allows these hazards to be properly managed. Examples spanning studies covering development and application of novel electromagnetic approaches for the polar regions as well as results from studies addressing a variety of differing geologic questions are presented. Electromagnetic studies focusing on near-surface hydrologic systems, glacial and ice sheet dynamics, as well as large-scale volcanic and tectonic problems are discussed providing an overview of the use of electromagnetic methods to investigate fundamental questions in solid earth studies that have both been completed and are currently ongoing in polar regions.

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The first magnetotelluric image of the lithospheric-scale geological architecture in central Svalbard, Arctic Norway

Cited by 15 publications

References 41 publications

Magnetotelluric signatures of the complex tertiary fold–thrust belt and extensional fault architecture beneath Brøggerhalvøya, Svalbard

Magnetotelluric signatures of the complex tertiary fold–thrust belt and extensional fault architecture beneath Brøggerhalvøya, Svalbard

Magnetotelluric Constraints on the Temperature, Composition, Partial Melt Content, and Viscosity of the Upper Mantle Beneath Svalbard

On the Use of Electromagnetics for Earth Imaging of the Polar Regions

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