| 1. |
- Andersson, Joel B.H., et al.
(author)
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U-Pb zircon-titanite-apatite age constraints on basin development and basin inversion in the Kiruna mining district, Sweden
- 2022
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In: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 372
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Journal article (peer-reviewed)abstract
- To constrain the tectonothermal evolution of the type locality for iron oxide-apatite deposits, we have obtained U-Pb zircon, titanite, and apatite age data for the Kiruna mining district in northernmost Sweden. The results indicate that the host basin initiated in an overall extensional regime as indicated by the deposition of alluvial conglomerates and greywackes. A volcanic intercalation in a conglomerate unit northwest of the Luossavaara iron oxide-apatite deposit yields a U-Pb zircon age of 1887 ± 3 Ma representing the timing of the earliest Orosirian volcanism in the central Kiruna mining district coinciding with the onset of basin development. In-situ analysis of titanite on hydrothermally altered fracture planes within a cataclastic fault damage zone (c. 270 m from the fault core system associated to the Luossavaara iron oxide-apatite deposit) yields complex U-Pb data. Applying a strict discordance filter yields a 207Pb/206Pb age of 1889 ± 26 Ma. The age implies that the fault probably has a syn-volcanic origin and that syn-volcanic faults may have played an important role during iron ore emplacement. The mineralized basin was subsequently buried and metamorphosed under upper greenschist-facies conditions and later tectonically exhumed and cooled below the apatite closure temperature at 1805 ± 26 Ma indicated by apatite from the Nukutus iron oxide-apatite deposit. Basin inversion is temporally constrained by syn-tectonic titanite as part of sodic-calcic + Fe + Cl hydrothermal alteration along a brittle-ductile reverse shear zone to the east of the study area. Titanite grains that show sector and oscillatory zoning yield an age of 1812 ± 3 Ma, which we interpret as the onset of basin inversion. Homogeneous (relatively unzoned) titanite in the same sample yields an age of 1802 ± 8 Ma, tentatively indicating that the tectonothermal activity lasted up to c. 20 m.y.
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| 2. |
- Fahlvik, Anton, et al.
(author)
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Hydrothermal alteration, lithogeochemical marker units and vectors towards mineralisation at the Svärdsjö Zn-Pb-Cu deposit, Bergslagen, Sweden
- 2022
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In: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 144:3-4, s. 177-195
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Journal article (peer-reviewed)abstract
- The Svärdsjö Zn-Pb-Cu deposit is situated in the heavily mineralised Bergslagen lithotectonic unit of the Fennoscandian shield, south-central Sweden. Intense hydrothermal alteration followed by a strong overprint by deformation and metamorphism during the Svecokarelian orogeny complicate interpretation of the local geology. Integration of whole-rock lithogeochemical and petrographic methods has allowed the mainly dacitic volcanic host succession and effects of ore-related hydrothermal alteration to be characterised. Mineralisation is hosted by 2–15 m thick, commonly skarn-altered dolomitic marble interbeds. Zones of strong–intense hydrothermal chlorite-sericite alteration envelop the marble units, recording mass gains of Fe and Mg, as well as Na depletion. Minerals such as cordierite, anthophyllite and sillimanite formed in these rocks during regional metamorphism. Mineralisation via sub-seafloor replacement is suggested for the deposit based on alteration zoning and the irregular, stratabound, marble-hosted style of sulphide lenses. It is inferred that mineralisation formed via neutralisation of hot, acidic metalliferous fluids. Geochemically and lithologically distinct units adjacent to the mineralised zones can serve as marker units to aid further exploration in the area. Mass change calculations reveal that Fe and Mg enrichment, as well as Na depletion exhibit detectable changes extending up to 100 m from the mineralised lenses, providing exploration vectors.
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| 3. |
- Sanjuan-Delmás, David, et al.
(author)
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Environmental assessment of copper production in Europe: an LCA case study from Sweden conducted using two conventional software-database setups
- 2022
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In: The International Journal of Life Cycle Assessment. - : Springer. - 0948-3349 .- 1614-7502. ; 27:2, s. 255-266
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Journal article (peer-reviewed)abstract
- PurposeThis study focuses on the environmental assessment of European copper production. Life cycle assessment is applied to analyse copper cathode production in Sweden, including its mining (an open-pit mine) and refining (pyrometallurgy), and using two combinations of software and databases: SimaPro software with ecoinvent database and GaBi software with GaBi database. The results are compared with results from other case studies from literature.MethodsA cradle-to-gate LCA was conducted considering 1 tonne of copper as functional unit. The inventory for the foreground system was elaborated using primary data gathered by the staff from the mine, the concentrator and the smelter. For the background data, LCA databases are used considering datasets for the Swedish market whenever possible. As the smelter has multiple useful outputs, economic allocation was applied at the inventory level. The calculation method CML-IA baseline 3.5 was considered for both combinations of software and database, reporting all the impact categories of the method plus the Cumulative Energy Demand.Results and discussionThe inventory of the system and the main environmental hotspots were presented, such as the explosives for blasting (due to their supply chain) or the electricity used in the concentrator. The results obtained with the two combinations of LCA software and databases yield large differences for categories such as abiotic depletion (7.5 times higher for SimaPro and ecoinvent), possibly due to differences in the system boundaries of the databases and the characterisation factors of the method. Although the case study has a relatively high cumulative energy demand (140/168 kMJ/tonne Cu) compared to other mines, its performance in global warming (3.5/4.7 tonne CO2eq/tonne Cu) is much better due to the low greenhouse gas emissions from electricity, which shows that the electricity mix is a key aspect.ConclusionsThe environmental performance of mining depends partially on the specific conditions of the deposit, e.g., the ore grade and the mining type. LCA practitioners should consider the potential different results that can be obtained using different combinations of software and database and exert caution when comparing cases, especially for abiotic depletion, human toxicity and ecotoxicity categories. Finally, the use of renewable energies can be key to improve the environmental sustainability of copper production.
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