Kukkonen, Ilmo and Heikkinen, Pekka and Heinonen, Suvi and Laitinen, Jukka (2010) HIRE Seismic Reflection Survey in the Pyhäsalmi Zn-Cu mining area, central Finland. Technical Report. GEOLOGICAL SURVEY OF FINLAND.
Full text not available from this repository.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 Pyhäsalmi 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 Pyhäsalmi survey was done in co-operation with the Pyhäsami Mine Oy. The Pyhäsalmi 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 Pyhäsalmi and the Archaean-Proterozoic boundary. The Ruotanen and the Mullikkoräme Schist Belts are both located in the immediate vicinity of interpreted deep faults and boundaries of up-thrown blocks. The Pyhäsalmi 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 Pyhäsalmi deposits.
| Item Type: | Reports (Technical Report) |
|---|---|
| Uncontrolled Keywords: | Seismic reflection surveys, massive sulphide deposits, Zn-Cu deposits, Pyhäsalmi, Fennoscandian Shield |
| Subjects: | Methodology > Other-additional study Region > Finland > Pyhäjärvi Inducing technology > Underground mining |
| Project: | EPOS-IP > PYHASALMI MINE: in situ underground laboratory |