Browsing by Subject "geologia"
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(2021)Aijala-Metsämonttu volcanogenic massive sulphide ore deposit belongs to Orijärvi regional volcanogenic massive sulphide mineralisation, localised within the schist zone southwestern Finland. Aijala-Orijärvi zone is an island-arc structure formed during the Paleoproterozoic (1895-1891 Ma). The mining operation in Aijala took place in 1949–1958 and Metsämonttu in 1952–1958 and 1964–1974. The Aijala and Metsämonttu deposits were 1 km apart. The main ore types were massive vein-like pyrite, sphalerite, pyrrhotite, chalcopyrite, and galena. The purpose of this thesis was to produce modern geological 3D models of the Aijala and Metsämonttu volcanogenic massive sulphide ore deposits and numerical grade models of the utilised minerals (copper, lead, zinc, silver, and gold) using historical material and to interpret the occurrences and emplacements of precious metals and base metals. In addition, compare the accuracy of the 3D models with digitised historical material. Geological 3D and numerical grade models were created using implicit modelling. Historical data used in this thesis consist of 266 drill holes from Aijala and 274 drill holes from Metsämonttu. Also, 61 mine tunnel maps and 47 cross-sections were used to create the geological models. The Aijala-Metsämonttu volcanogenic massive sulphide ore deposits are in the same stratigraphic zone between the footwall quartz-feldspar-porphyry and hanging wall amphibolite. Sulphide lenses of both deposits are vertically on the south side of the footwall and hanging wall contact. The main host rocks to sulphide ores are skarn and cordierite-gneiss. Several local faults intersect the deposits. The most significant faults displaced overlying blocks to the south in Aijala and to the north in Metsämonttu. The Aijala-Metsämonttu deposit belongs to the Zn-Pb-Cu group. The occurrence style and concentrations of metals vary between deposits. Copper ore is present in Aijala but absent in Metsämonttu, whilst zinc-lead ore is present in Metsämonttu but absent in Aijala. Precious metals occur in both deposits with a companion of base metals. The Metsämonttu deposit is rich in precious metals compared to the Aijala deposit, and the presence of high content of precious metals correlates with the incidence of lead ore. Precious metals concentrations increase from east to west and deeper in Metsämonttu.
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