The Vihanti-Pyhäsalmi Area

Abstract

The Vihanti-Pyhasalmi district is located at the border zone between the Archaean craton in the northeast and the Palaeoproterozoic Svecofennian domain in central Finland. It is part of the Savo belt and contains one operating and four past mines and several uneconomic VHMS (Volcanic Hosted Massive Sulphide) deposits. Regional, semi-regional and mine scale 3D models of the Vihanti-Pyhasalmi area were built in order to understand the formation of the VHMS deposit and accordingly map the ore critical geological formations and structures. In addition to the 3D modelling of the present day geology, structural geological inference was used to build 3D geological models visualizing the main deformational stages in past. The used data and information consisted of geological maps and reports, drill core logs, lithogeochemistry, reflection seismic profiles, potential field measurements and electromagnetic surveys. The geophysical 2D and 3D inversion were used to assist the 3D geological modelling seeking for continuity of the surficial structures especially in areas with only few or no drill core data. As a result, regional and semi-regional 3D models of the Vihanti-Pyhasalmi area were obtained and new zones with VHMS exploration potential were identified in the vicinity of the Pyhasalmi mine.