Integrated analyses and interpretations of regional scale magnetotelluric and potential field data from the Precambrian crust of northern Sweden

• Main Author: Vadoodi, Roshanak
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Luleå tekniska universitet, Geovetenskap och miljöteknik 2022
• Subjects: Geophysics; Geofysik; Geophysical Engineering; Geofysisk teknik; Fennoscandian; Northern Sweden; Norrbotten
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-93143

The Norrbotten region in northern Sweden, as a part of the Fennoscandian (Baltic) Shield, is one of the most active mining areas in Europe. It is acknowledged that geological structures such as faults, shear zones, and associated fracture systems play a key role in providing a physical pathway connecting metal sources and the sites of mineral precipitation. In particular, several magnetotelluric (MT) surveys around the world have revealed a spatial relationship and correlation between mineral occurrences and regional scale conductive structures. Previous lithospheric studies in the Fennoscandian Shield have indicated enhanced conductivities in the Norrbotten region, and they served as a basis for the proposal to test the hypothesis of this genetic connection. Therefore, the current project was initiated with the aim of obtaining more detailed information on crustal and upper mantle structures in the Paleoproterozoic Norrbotten ore province by utilising a combination of regional geophysical data including, MT and potential field data. Potential field data (airborne magnetic, and ground gravity) are extensively used as the first choice in geophysical/geological mapping due to good areal coverage, whereas MT surveys are typically designed to answer more specific geological and geophysical questions. In order to improve utilisation of the geophysical methods, quantitative analyses and integration approaches have been developed and applied to the geophysical data. This thesis covers four topics: (i) a regional-scale study of Norrbotten County using 3D inversion of newly measured MT data to reveal crustal geoelectric structures, (ii) integration of the resistivity model with regional-scale magnetic susceptibility and density models using an unsupervised classification approach to extract and analyse the possible correlation between modelled petrophysical properties and provide a geophysical domain classification as input to geological interpretations, (iii) identification of a regional-scale tectonic feature in ...