Open AccessMagnetotelluric Constraints on the Temperature, Composition, Partial Melt Content, and Viscosity of the Upper Mantle Beneath Svalbard
Author(s) -
Selway Kate,
Smirnov Maxim Yu,
Beka Thomas,
O'Donnell J. P.,
Minakov Alexander,
Senger Kim,
Faleide Jan Inge,
Kalscheuer Thomas
Publication year - 2020
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2020gc008985
Subject(s) - asthenosphere , geology , mantle (geology) , geophysics , magnetotellurics , post glacial rebound , transition zone , lithosphere , petrology , glacial period , electrical resistivity and conductivity , geomorphology , seismology , electrical engineering , tectonics , engineering
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.