2D and 3D MT in the central Skellefte Ore District, northern Sweden

• Published in: Tectonophysics 2019-08, Vol.764, p.124-138
• Main Authors: García Juanatey, María A., Hübert, Juliane, Tryggvason, Ari, Juhlin, Christopher, Pedersen, Laust B., Bauer, Tobias E., Dehghannejad, Mahdieh
• Format: Article
• Language: English
• Subjects: 3D inversion; Algorithms; Broadband; Brownfield; Conductors; Data; Data acquisition; Deep exploration; Error analysis; Fossils; Geofysik med inriktning mot fasta jordens fysik; Geological faults; Geophysical studies; Geophysics; Geophysics with specialization in Solid Earth Physics; Inversion; Magnetotellurics; Magnetotellurics 3D inversion; Malmgeologi; Mineral systems; Modelling; Ore Geology; Profiles; Shear zone; Shear zones; Tensors; Three dimensional models; Two dimensional models
• ISSN: 0040-1951; 1879-3266; 1879-3266
• DOI: 10.1016/j.tecto.2019.04.003

New broadband magnetotelluric (MT) data have been acquired along two parallel profiles in the central part of the metallogenic Skellefte district in northern Sweden. The data were recorded as part of the Swedish 4D modelling of mineral belts project and cover an area with several economical and sub-economical deposits. The dimensionality and quality of the data were carefully analyzed and new error floors were systematically determined prior to inverse modelling in 2D and 3D. The algorithms used were EMILIA and WSINV3DMT. For the 2D inversion, only the determinant of the impedance tensor was used, while for the 3D inversion all elements were considered. The obtained models fit the inverted data, and image the main regional features. A detailed comparison reveals the superiority of the 3D model, both in model structures and data fit. After assessing the main features in the model, an interpretation is proposed and refined with the support of previous geophysical studies. The most interesting features are large and medium-sized conductors associated with crustal-scale shear zones and faults within the Skellefte Group rocks. These may be depicting a network of fossil pathways for hydrothermal fluid transport and as such, provide new insight into past processes in the area. •New broadband magnetotelluric data from a Palaeoproterozoic mining district.•The data were modelled through 2D and 3D inversion, with 3D fitting the data best.•Thorough model assessment confirms the presence of several resistivity anomalies.•Several mid-crustal conductors related to faults and shear zones are revealed.•The conductors might constitute fossil pathways for hydrothermal fluid transport.