Exploring Kiruna iron ore fields with large-scale, semi-airborne, controlled-source electromagnetics

Abstract

Abstract The Kiruna mine is the largest underground iron ore mine in the world and provides a large portion of the iron ore produced within the EU. To facilitate the mineral exploration for such deep deposits, a novel semi-airborne controlled-source electromagnetic (CSEM) system was developed in the DESMEX project. In this approach, the transmitter is positioned on the ground, while the magnetic field is measured airborne with the support of additional ground observations of five components of the EM field. Such a set-up takes advantage of both ground and airborne techniques. High-moment transmitters are installed on the Earth’s surface, enabling injection of strong primary EM fields in the subsurface. The airborne receivers in turn ensure efficient, fast and spatially dense surveying. The semi-airborne EM system was validated in several field experiments in Germany. However, none of the tests were done at an active mineral exploration site. Here, we present the first results of the semi-airborne EM survey conducted at the Per Geijer iron ore deposit near Kiruna to explore the spatial and depth distribution of the ore body. The sophisticated 3D conductivity model matches the well-known surface geology and other geophysical information yet brings new insights into the general model of the ore body.