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

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 Omega m) Paleozoic-Mesozoic sedimentary sequence, varying laterally in thickness (2-4 km), obstructed by a gently dipping Permian-Carboniferous succession ( > 1000 Omega m) 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 Omega m) 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/m(2)), 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.