A Novel 3D Seismic Survey over the 2.5-2.4 Ga Koillismaa Layered Intrusion Complex, Finland

A novel ~22 km2 3D seismic survey was acquired in NE Finland to study the 2.5-2.4 Ga old Koillismaa Layered Igneous Complex (KLIC) using single Vibroseis source and single-receiver technology involving low-cost piezoelectric nimble nodes. Similar intrusions have been recognized worldwide for their potential for hosting Ni-Cu-Co-PGE and Cr-V-Ti-Fe mineralization.

To the authors knowledge this is one of the very few 3D seismic surveys imaging layered intrusions and their feeder system below 1 km depth. Good quality data were recorded with reflections visible in the raw gathers, enabling successful application of 5D interpolation and automatic velocity analysis. Processed volume reveals rich and strong reflectivity associated with the intrusion as calibrated by the Koillismaa deep drillhole, which reached ultramafic rocks (pyroxenite, peridotite) at 1.4 km depth. Significant along-strike changes are also observed with more pronounced reflectivity present west of the Koillismaa drillhole.