The upper crustal 3-D resistivity structure of the Kristineberg area, Skellefte district, northern Sweden revealed by magnetotelluric data

Juliane Huebert*, Maria de los Angeles Garcia Juanatey, Alireza Malehmir, Ari Tryggvason, Laust B. Pedersen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

A 3-D model of the crustal electrical resistivity was constructed from the inversion of magnetotelluric data in the Kristineberg area, Skellefte district, the location of one of Sweden's most successful mining activities. Forward modelling of vertical magnetic transfer data supports our model which was derived from the magnetotelluric impedance only. The dominant features in the 3-D model are the strong conductors at various depth levels and resistive bodies of variable thickness occurring in the shallower subsurface. The deepest conductor, previously associated with the Skellefte crustal conductivity anomaly, is imaged in the southern part of the area as a north-dipping feature starting at similar to 4 km depth. Several shallow conductors are attributed to graphite in the black shales defining the contact between the metasedimentary rocks and the underlying metavolcanic rocks. Furthermore, an elongated intermediate depth conductor is possibly associated with alteration zones in the metavolcanic rocks that host the ore occurrences. The most prominent crustal resistors occur in the southern and northern part of the area, where their lateral extent on the surface coincides with the late-orogenic Revsund type intrusions. To the east, a resistive feature can be correlated to the early-orogenic Viterliden intrusion. The 3-D model is compared with two previous 2-D inversion models along two perpendicular profiles. The main electrical features are confirmed with the new model and previous uncertainties regarding 3-D effects, caused by off-profile conductors, can be better assessed in 3-D, although the resolution is lower due to a coarser model discretization. The comparison with seismic sections along two north-south profiles reveals structural correspondence between electrical features, zones of different reflectivity and geological units.

Original languageEnglish
Pages (from-to)500-513
Number of pages14
JournalGeophysical Journal International
Volume192
Issue number2
DOIs
Publication statusPublished - Feb 2013

Keywords

  • Crustal structure
  • Electrical properties
  • Magnetotelluric
  • FENNOSCANDIAN SHIELD
  • WESTERN PART
  • ORE DISTRICT
  • MINING AREA
  • INVERSION
  • FIELD
  • CONSTRAINTS
  • RESOLUTION
  • EVOLUTION
  • DEPOSITS

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