@techreport{epos2108,
          number = {Q 23/2009/43},
           month = {February},
          author = {Ilmo Kukkonen and Pekka Heikkinen and Suvi Heinonen and Jukka Laitinen},
           title = {HIRE Seismic Reflection Survey in the Pyh{\"a}salmi Zn-Cu mining area, central Finland},
            type = {Technical Report},
       publisher = {GEOLOGICAL SURVEY OF FINLAND},
     institution = {GEOLOGICAL SURVEY OF FINLAND},
            year = {2010},
        keywords = {Seismic reflection surveys, massive sulphide deposits, Zn-Cu deposits, Pyh{\"a}salmi, Fennoscandian Shield},
             url = {https://episodesplatform.eu/eprints/2108/},
        abstract = {A seismic reflection survey comprising four vibroseis lines (total length of 25.1 km) and two explosion seismic lines (total
length 12.5 km) was carried out in the Pyh{\"a}salmi Zn-Cu mining area, in central Finland, in November, 2007. The survey is a
part of the project HIRE (High Resolution Reflection Seismics for Ore Exploration 2007-2010) of the Geological Survey of
Finland (GTK). The Pyh{\"a}salmi survey was done in co-operation with the Pyh{\"a}sami Mine Oy.
 The Pyh{\"a}salmi area is well known for its massive Zn-Cu sulphide deposits in altered metavolcanic rocks in the thoroughly
deformed and folded host rocks of the 1.88-1.93 Ga Savo Belt. The HIRE results show a detailed structure of the uppermost
5 km of crust. The most prominent feature is the bimodal general characteristics of the reflectivity. An E-NE dipping strongly
reflective layer was detected at depths exceeding 1-2.5 km. Above this layer the reflectivity is very weak and not simple to
correlate with surface geology. Drill hole data from the mine suggest that the strong reflectivity could be attributed to mafic
volcanic rocks with interlayers of felsic volcanics and pegmatite dykes at least in the uppermost part of the reflector.
 Using large-scale reflection seismic data of the FIRE-1 transect the strongly reflective system can be correlated to a 50 km
wide and 10 km deep synform structure of the Savo Belt. Surface geology suggests that the synform and the strongly
reflective layer represent mainly mafic volcanic rocks with felsic interlayers as well as metasediments. Considerable
shortening has taken place in E-W direction, and several deep, mostly east-dipping (thrust) faults can be identified between
Pyh{\"a}salmi and the Archaean-Proterozoic boundary. The Ruotanen and the Mullikkor{\"a}me Schist Belts are both located in the
immediate vicinity of interpreted deep faults and boundaries of up-thrown blocks.
 The Pyh{\"a}salmi deep ore deposit is located at the upper boundary of the strongly reflective layer where the reflectors
beneath the deposit seem to form an antiform-like structure. The reflection image of the pear-shaped deep ore body at the
depth of 1.1 - 1.5 km is characterized by strong reflectors beneath and on the eastern side of the massive ore. The observed
reflectivity is due to impedance contrast between, on one hand, the massive ore and its host rocks (mafic volcanic rocks and
interlayers of felsic rocks), and on the other hand, to internal reflection contrasts within the host rocks.
 The data is applied for indicating potential targets for further exploration and possible analogues of the Pyh{\"a}salmi
deposits.}
}