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

  • Thomas I. Beka Department of Physics and Technology, Faculty of Science and Technology, UiT-The Arctic University of Norway, N-9037 Tromsø, Norway
  • Maxim Smirnov Oulu Mining School, Geophysics, University of Oulu, POB 3000, FI-90014 Oulu, Finland
  • Steffen G. Bergh Department of Geology, Faculty of Science and Technology, UiT-The Arctic University of Norway, N-9037 Tromsø, Norway
  • Yngve Birkelund Department of Engineering and Safety, Faculty of Science and Technology, UiT-The Arctic University of Norway, N-9037 Tromsø, Norway
Keywords: Magnetotellurics, 2D modelling, lithosphere architecture, geothermal, Svalbard

Abstract

Magnetotelluric data, collected from 30 stations on Spitsbergen as part of a reconnaissance geothermal resource assessment along a profile with 0.5–3-km spacing in 0.003–1000-s period range, were used to develop a lithospheric-scale two-dimensional (2D) resistivity model, heretofore unavailable for the region. Inverting the determinant of the impedance tensor in 2D, we found the smoothest model fitting the data within a specified tolerance level. We justified the model by perturbing it, performing sensitivity analysis and re-running the inversion with a different algorithm and starting models. From our final model, we constructed a crustal-scale stratigraphic framework, using it to estimate the depth of major geological features and to locate structural deformations. The 2D resistivity model indicates a shallow low resistive (<100 Ωm) Paleozoic–Mesozoic sedimentary sequence, varying laterally in thickness (2–4 km), obstructed by a gently dipping Permian–Carboniferous succession (>1000 Ωm) east of the Billefjorden Fault Zone. Underneath, a (possibly Devonian) basin is imaged as a thick conductive anomaly stretching >15 km downwards. Beneath a deformed Paleozoic–Mesozoic successions, an uplifted pre-Devonian shallow basement (>3000 Ωm) is revealed. We estimated a thin lithosphere, in the range of ca. 55–100 km thick, that could explain the area’s elevated surface heat flow (ca. 60–90 mW/m2), consistent with the calculated depth of thermal lithosphere heat-base boundaries for a partially melting mantle. The model indicates a possible replenishment pathway of upward heat transport from the shallow convective mantle to the composite crustal conductive units. This is encouraging for low-enthalpy geothermal development.

Keywords: Magnetotellurics; 2D modelling; lithosphere architecture; geothermal; Svalbard.

(Published: 17 December 2015)

Citation: Polar Research 2015, 34, 26766, http://dx.doi.org/10.3402/polar.v34.26766

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Author Biographies

Thomas I. Beka, Department of Physics and Technology, Faculty of Science and Technology, UiT-The Arctic University of Norway, N-9037 Tromsø, Norway
Phd. student
Maxim Smirnov, Oulu Mining School, Geophysics, University of Oulu, POB 3000, FI-90014 Oulu, Finland
Associate Professor
Steffen G. Bergh, Department of Geology, Faculty of Science and Technology, UiT-The Arctic University of Norway, N-9037 Tromsø, Norway
Professor
Yngve Birkelund, Department of Engineering and Safety, Faculty of Science and Technology, UiT-The Arctic University of Norway, N-9037 Tromsø, Norway
Head of Department, Associate Professor
Published
2015-12-17
How to Cite
Beka, T., Smirnov, M., Bergh, S., & Birkelund, Y. (2015). The first magnetotelluric image of the lithospheric-scale geological architecture in central Svalbard, Arctic Norway. Polar Research, 34. https://doi.org/10.3402/polar.v34.26766
Section
Research/review articles