Re-processing and Interpretation of 2D Seismic Line in the Kristineberg Mining Area, Northern Sweden

Abstract: The Skellefte district, 1.90 to 1.80 Ga, is one of the most important base metal mining districts of Sweden with over 85 volcanic-hosted massive sulfide (VHMS) deposits. The study area focuses on the western part of the Skellefte district which contains volcanic, metasedimentary and intrusive rocks. In 2003, seismic data acquisition was carried out in the western part of the Skellefte district in the vicinity of the Kristineberg mine. Two parallel seismic lines were acquired about 8 km apart from each other. Profile 1 is about 22 km long and selected for the re-processing and interpretation in this thesis. The acquisition geometry, low fold coverage, the complex tectonic history and fewer outcrops in the area make the data processing and interpretation quite challenging and required a careful processing design to obtain interpretable seismic image. The re-processed Profile 1 is correlated with two other newly acquired seismic lines in the area for the purpose of possible 3D visualization and interpretation. The re-processing work includes a careful velocity analysis along with a series of iterations in residual statics, poststack and prestack migrations and cross dip analysis. The re-processed seismic section clearly shows a north dipping reflector which truncates against the Revsund Granites at depth. The possible interpretation for this reflector is a structural basement to the Skellefte Group constituting Bothnian Basin or a fault zone within the Viterliden intrusion. The Kristineberg mine is situated on the northern limb of a synform structure with prominent southwards dipping reflections. The major lithological contacts between different rock units are series of latest thrust faults. The prominent reflectivity within and at the contact with the Viterliden intrusion may suggest deep seated mineralized horizons. The cross dip analysis helps finding the eastward dipping component for the shallow horizons. The re-processed image is also compared with the previous processed seismic section and improvements in reflectors are evident.