Suvi Heinonen

2D reflection seismic investigations at the Kevitsa Ni-Cu-PGE deposit, northern Finland

In 2007, a 2D reflection seismic survey was conducted at the Kevitsa Ni-Cu-PGE (platinum group elements) deposit in northern Finland. The aims of the survey were to delineate the overall extent of ...

The Vihanti-Pyhäsalmi Area

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.

Using seismic reflection profiles to model 3D geology of VMS districts in the Raahe-Ladoga belt, Finland

Volcanogenic massive sulphide (VMS) deposits of Pyhasalmi, Vihanti and Outokumpu in Finland belong to the same mineralized belt but are different in terms of age and detailed deformation history. Results of sonic and density logging show that in these mining camps rock formations hosting the known ore deposits are reflective which encourages the use of seismic reflection method for mapping the subsurface geological structures. A network of seismic reflection profiles was acquired in each study site and these data are utilized in the geological 3D-modeling and deep mineral exploration.