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Mineralogy and character of the Liikavaara Östra Cu-(W-Au) deposit, northern Sweden
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.ORCID iD: 0000-0003-3593-3786
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.ORCID iD: 0000-0003-4711-7671
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.ORCID iD: 0000-0002-0935-3430
Aitik, Boliden AB, Gällivare, Sweden.
2020 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 142, no 3, p. 169-189Article in journal (Refereed) Published
Abstract [en]

The Liikavaara Östra Cu-(W-Au) deposit is situated close to the operating Aitik Cu-Au mine in northern Sweden. It is scheduled for production in 2023. Modern geological descriptions of the deposit are lacking though knowledge of geological and mineralogical details prior to operation is beneficial to avoid surprises. In this study, petrological, mineralogical and geochemical investigations of the wall rocks, host rock and mineralisation, and zircon U-Pb analysis of a footwall granodioritic intrusion were carried out. The mineralisation is hosted by quartz±tourmaline-calcite veins, calcite veins and aplite dykes that cross-cut biotite-amphibole schists and gneisses. The wall rocks to the ore are metavolcaniclastic rocks of basaltic to andesitic composition. A granodiorite intrusion occurs in the footwall. The mineralisation is mainly chalcopyrite, pyrrhotite and pyrite with some sphalerite, galena, scheelite, molybdenite and magnetite. It shows slight enrichments in Au, Ag and Bi. Gold and Ag occur as electrum and Ag also in hessite and an Ag-sulphide. The Bi mineralogy includes native Bi, Bi-tellurides and Bi-sulphides. These minerals are found as inclusions, along the borders of and in cracks in chalcopyrite, pyrite, pyrrhotite, sphalerite, molybdenite and quartz. The footwall granodiorite intrusion was dated at 1.87 Ga. It is suggested here to be the source for ore genesis based on its spatial relation to the mineralisation, as well as on high-salinity fluids and metal composition of the ore. The aplite dykes may have acted as pathways for the magmatic hydrothermal fluids that carried the metals from the intrusion to the host rock.

Place, publisher, year, edition, pages
Taylor & Francis, 2020. Vol. 142, no 3, p. 169-189
Keywords [en]
Trace metals, critical raw materials, scheelite, gold, bismuth, mineralogy, U-Pb geochronology, Northern Norrbotten ore district
National Category
Geology
Research subject
Ore Geology
Identifiers
URN: urn:nbn:se:ltu:diva-79930DOI: 10.1080/11035897.2020.1753807ISI: 000545805000001Scopus ID: 2-s2.0-85087128230OAI: oai:DiVA.org:ltu-79930DiVA, id: diva2:1445779
Note

Validerad;2020;Nivå 2;2020-09-21 (johcin)

Available from: 2020-06-23 Created: 2020-06-23 Last updated: 2025-01-08Bibliographically approved
In thesis
1. Improving trace metal characterisation of ore deposits – a crucial step towards sustainable mining
Open this publication in new window or tab >>Improving trace metal characterisation of ore deposits – a crucial step towards sustainable mining
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Sustainable mining, including the utilisation of an ore body to its full potential, is becoming increasingly important for human society as the demand for metals increases. In order to maximise the recovery of useful metals, detailed characterisation of the ore prior to processing is vital. Characterisation should include major and minor ore minerals, gangue minerals, and also trace metals. Trace metals despite their low abundance are often particularly important, either due to their high economic value and criticality for society, or their negative impact on the quality of the main commodity recovered and/or the environment. To properly characterise trace metals in an ore deposit the use of micro-analytical techniques is necessary. Nowadays, a plethora of techniques exist, each with their own strengths and weaknesses. In the mining industry, automated scanning electron microscopy systems are widely used. These systems allow for rapid mineralogical characterisation and quantification of a sample and are commonly used to quantify the mineralogy of the ore feed and subsequent products. Operators of these systems benefit from prior knowledge of the mineralogy of a sample/deposit to fine-tune their processing software to deliver data of highest quality. In this study, a method to improve trace metal characterisation in ore deposits with automated scanning electron microscopy systems is presented. It is implemented as a case study on the Liikavaara Cu-(W-Au) deposit in northern Sweden. The deposit is enriched in several trace metals including Au, Ag, Bi and Sn, and is planned for production in 2023. The mine will produce Cu as the main product and Au and Ag as by-products, and the processing of the ore will be performed in the nearby Aitik plant. For this study, a detailed geological and mineralogical investigation of the deposit was performed prior to analysis with the automated scanning electron microscopy system. A good understanding of the mineralogy is necessary to be able to select a representative sample for the subsequent automated analysis and to guarantee optimal data quality produced by the automated system, and to judge the performance of the automated system, to improve the method of analysis.

Manuscript 1 deals with the geological description and genetic aspects of the Liikavaara ore deposit. Results indicate that Liikavaara is an intrusion-related vein-style deposit. Mineralisation is hosted by quartz-tourmaline and calcite veins in a metadiabase that is partly metamorphosed to biotite schist. A 1.87 Ga granodiorite intrudes the footwall. Aplite dikes, genetically related to the intrusion, crosscut the metadiabase host rock. Mineralised veins are concentrated in and around these dikes.

Manuscript 2 deals with method development of automated mineralogical analysis. A sample from a mineralised quartz-tourmaline vein at Liikavaara was analysed in great detail with the QEMSCAN® system. Apart from ore minerals in major and minor abundance the sample also contains ore minerals in trace quantities, e.g. Au and Ag minerals. The sample was analysed using two different analytical settings, at two different laboratories, one typical of a production-focused industrial approach and one quality-focused scientific approach. A first analysis using the industrial approach was unable to detect any Au and Ag minerals in the sample. By modification of the QEMSCAN® mineral reference library, through iterative use of the data from both the industrial- and the scientific approach, detection and quantification of Au and Ag minerals was successful. This method can be implemented as an add-on for routine industrial analysis by automated scanning electron microscopy systems to gain information on trace metal occurrence and distribution. This information can then be used for targeted sample selection for further in-depth analysis of the trace metal content and occurrence in the deposit.

Place, publisher, year, edition, pages
Luleå University of Technology, 2019
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Geology
Research subject
Ore Geology
Identifiers
urn:nbn:se:ltu:diva-73865 (URN)978-91-7790-386-4 (ISBN)978-91-7790-387-1 (ISBN)
Presentation
2019-06-19, F531, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2025-01-08Bibliographically approved
2. Improving trace metal characterisation of ore deposits through multi-modal, multi-scale, and multi-dimensional micro-analysis
Open this publication in new window or tab >>Improving trace metal characterisation of ore deposits through multi-modal, multi-scale, and multi-dimensional micro-analysis
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The variety and amount of metals consumed by human society is ever increasing. Meeting the demand requires exploration for new ore deposits, efficient production of active mines, and improved efficiency in metal recycling. A key element in mining-related enterprises is the improvement of ore characterisation. The study of the geology and mineralogy of ore deposits allows us to infer the processes behind ore genesis. This knowledge guides important exploration and processing decisions. Over the last few decades, technological advancements have enabled ore characterisation at increasing levels of detail. This has brought the trace metal mineralogy of ore deposits into focus. In many cases, trace metals occur as extremely fine-grained minerals or as lattice-bound impurities in the more common minerals in ore deposits. Hence, their study requires the use of micro-analytical techniques. Trace metals and their minerals can carry crucial information on the conditions of ore formation. They can be of economic value, harmful to the environment, or of strategic economic and geopolitical interest (e.g. Critical Raw Materials). Trace metal characterisation is therefore highly relevant to research, industry, and society.  In this project, micro-analysis was performed on the Liikavaara Östra Cu-(W-Au) deposit in northern Sweden to research the trace metal mineralogy of Au, Ag, Bi, Mo, Re, and W. The main goal of the project was the development, optimisation, and integration of various micro-analytical techniques for ore characterisation. The project was subdivided into four studies (scientific contributions): (1) Drill core logging, whole-rock geochemistry, and light microscopy were applied to identify lithology, alteration, and mineralisation of the deposit. An intrusion in the footwall, potentially related to ore genesis, was dated with LA-ICP-MS. Scanning electron microscopy with energy dispersive spectrometry was used to gain insight into the trace metal mineralogy of the deposit. This study provided an overview of the geology and mineralogy of the deposit and served as a basis for sample selection and data interpretation of subsequent studies. (2) A polished thin section of the ore containing trace metal minerals was scanned by automated mineralogy (QEMSCAN) at Boliden AB to assess the potential of trace metal mineral quantification in a production-focused environment. To delineate instrument limitations from operator input the same sample was also scanned at Camborne School of Mines, UK. Detection of trace metal minerals was generally difficult due to their fine-grained nature. Yet, quantification could be improved by optimisation of the mineral classification library. (3) Four polished epoxy-mounted drill core pieces of ore were analysed by automated mineralogy (Mineralogic) and x-ray computed tomography (XCT). In two samples, a smaller region of interest was drilled and re-analysed at higher resolution. Results from automated mineralogy were used to segment and interpret the XCT data. Vice versa, XCT data provided 3D spatial context for the 2D scans. (4) Three polished thin section pieces with grains of molybdenite, pyrite, and native Bi, all with Au-inclusions, were analysed by synchrotron radiation x-ray fluorescence mapping at the NanoMAX beamline of the MAX IV synchrotron facility in Lund, Sweden. Element fluorescence maps down to 50 nm pixel size revealed the distribution of micro- and nano-inclusions and lattice-bound impurities in the mineral grains. The studies demonstrated benefits and challenges of the various micro-analytical techniques, and how and what they may contribute to ore characterisation. Results allowed linking and integrating the techniques into a smart analytical flow to optimise the characterisation of trace metal minerals in ore deposits. This is useful for both ore geology research and the mining industry. 

Place, publisher, year, edition, pages
Luleå University of Technology, 2021
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Geosciences, Multidisciplinary
Research subject
Ore Geology
Identifiers
urn:nbn:se:ltu:diva-85848 (URN)978-91-7790-897-5 (ISBN)978-91-7790-898-2 (ISBN)
Public defence
2021-10-22, F1031, Luleå University of Technology, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2021-06-22 Created: 2021-06-22 Last updated: 2025-01-08Bibliographically approved

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Warlo, MathisWanhainen, ChristinaMartinsson, Olof

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