| Summary: | The Aitik Cu-Au-Ag mine in the Gällivare area in northern Sweden is the biggest open pit operation in northern Europe and one of Europe’s largest metal producers. The open pit is almost 3 km long, 930 m wide and 345 m deep. Approximately 424 million tonnes of ore averaging 0.4% Cu, 0.2 g/t Au and 4 g/t Ag has been produced, and the metal production in year 2004 was 64,805 tons of copper, 2,035 kg of gold, and 45,110 kg of silver. Although multiply deformed, metamorphosed and hydrothermally altered, characteristic features of two major mineralization styles, porphyry copper and iron oxide-copper-gold (IOCG), have been identified by using field and microscopic observations in combination with techniques such as fluid inclusion microthermometry, sulphur isotopic analyses, U-Pb and Re-Os geochronology, and major and trace element geochemistry. Results from this study indicate that the Aitik deposit is of mixed origin, with a major part of the copper ore originating from an early porphyry copper system, and a second, minor part, originating from an overprinting IOCG-system. The Aitik porphyry Cu-Au-Ag deposit and its host rocks, situated approximately 200 km north of the Archaean-Proterozoic palaeoboundary in the Fennoscandian shield, are considered to have formed in a volcanic arc environment related to subduction of oceanic crust beneath the Archaean craton at ca. 1.9 Ga. An intrusion related to the formation of porphyry copper mineralization is situated in the footwall of the deposit. This source intrusion and related volcaniclastic rocks are mafic-intermediate in composition and belong to the regionally widespread Haparanda suite and Porphyrite group, respectively. The quartz monzodiorite intrusion is porphyritic and comprises younger, but comagmatic, phases of micro-quartz monzodiorite and diorite, and is suggested to represent a cupola protruding from a larger pluton at depth. High salinity fluids (30-38 eq. wt% NaCl + CaCl2) responsible for chalcopyrite-pyrite mineralization was released contemporaneously with ...
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