Development and application of the magnetotelluric method to study the crustal structure of central Finnish Lapland

In this thesis, the geophysical magnetotelluric method was applied to study the crustal structure in central Finnish Lapland and new data analysis methods were developed. The magnetotelluric method provides information about the electrical conductivity of the subsurface down to tens of kilometers and, thus, provides clues for the geological structure and evolution of the bedrock.

In 2014, magnetotelluric data from 79 sites were acquired from Lapland. Based on the data, a three-dimensional electrical conductivity model was derived, which contains multiple anomalous features. They can be interpreted as graphite bearing sedimentary rocks or shear zones located deep in the bedrock.

Part of the measurement data show a special kind of behavior rarely documented in geophysical literature. Such data behaviour has been clarified using mathematical analysis and numerical modelling.

The knowledge produced in the thesis about the bedrock is beneficial for mineral potential evaluation in Lapland. Moreover, the developments related to the magnetotelluric method are important since the method can be directly applied to mineral and geothermal exploration.