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Character of gold within the Palaeoproterozoic Aitik porphyry Cu-Au-Ag-(Mo) deposit
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.ORCID iD: 0000-0003-4711-7671
Boliden AB.
Boliden AB.
2008 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

The Aitik Cu-Au-Ag-(Mo) deposit in northernmost Sweden is one of Europe's largest copper-gold mines with an on-going expansion bringing the annual production capacity up to 36 Mt of ore in 2010. Since the start of mining in 1968, approximately 465 Mt of ore has been mined. Proven and probable ore reserves at the beginning of 2008 were 610 Mt grading 0.28 % Cu, 0.2 ppm Au and 2 ppm Ag. Aitik is a Palaeoproterozoic porphyry Cu-Au-Ag-(Mo) deposit associated with the intrusion of a 1.89 Ga quartz monzodiorite, and modified by multistage metamorphic-tectonic and magmatic-hydrothermal events. Redistribution of metals and possible addition of copper and gold from a later (1.80 Ga) IOCG (iron oxide copper-gold) mineralizing event has led to a wide variety of mineralization styles and a complex mineralization pattern. The main copper-bearing mineral is chalcopyrite, which occurs disseminated, as veinlets, as patches and clots, and in several vein types together with quartz, amphibole, garnet, magnetite, zeolite, tourmaline, and barite.Aitik is by definition a gold-poor porphyry copper deposit (Cu/Au atomic ratio below 40,000). However, despite the low gold grade (0.2 ppm), gold is an important metal for the mine, which produces 1.5-2 tonnes of gold per year as a by-product. It is mainly the copper-associated gold, which constitutes about 50 % of the total amount, that is currently recovered in the flotation circuit. To guide R&D work in the attempts to increase the gold recovery, a better understanding of the sites, character and mineral associations of gold within the ore body has to be achieved. By performing petrographic, SEM, electron microprobe, and flotation and leaching laboratory test studies on gold, the diversity of its character and occurrence, and its response to different extraction techniques has been documented. Gold occurs as native gold, amalgam (Au-Ag-Hg) and electrum (Au-Ag), in close relationship to chalcopyrite, pyrite, magnetite and silicates. The gold varies considerably in grain size, ranging from coarse (∼ 400-20 m) to very fine (∼ <2-0.1 m) and it occurs mainly as inclusions, at grain boundaries and in cracks. A trend from dominantly sulphide-associated gold in the upper levels of the mine, to an increase in silicate-associated gold at deeper levels has been identified, highlighting the importance of understanding the gold variability for metallurgical processing. The character of gold within the Aitik ore body suggests that more than one generation of gold is likely to be present, and that the different mineralogical settings of gold correspond to different ore forming events.

Place, publisher, year, edition, pages
2008.
National Category
Geology
Research subject
Ore Geology
Identifiers
URN: urn:nbn:se:ltu:diva-31677Local ID: 5ee86e30-c82c-11dd-941d-000ea68e967bOAI: oai:DiVA.org:ltu-31677DiVA, id: diva2:1004911
Conference
International Geological Congress : 06/08/2008 - 14/08/2008
Note
Godkänd; 2008; 20081212 (chwa)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved

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http://www.cprm.gov.br/33IGC/1345216.html

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Wanhainen, Christina

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