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Veress, E. C. (2023). Crustal architecture of the Kiruna mining district: Structural framework, geological modeling, and physical rock property distribution. (Licentiate dissertation). Luleå: Luleå University of Technology
Open this publication in new window or tab >>Crustal architecture of the Kiruna mining district: Structural framework, geological modeling, and physical rock property distribution
2023 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Rapid technological advancements and growing environmental consciousness created a shifting dynamic of metal demand within the context of contemporary global challenges. The metals play a pivotal role in this transformation and remarkable surge in demand is expected. Mining districts such as the Kiruna area in northern Sweden, provide access to raw materials, assuring supply chain security, sustainability, and an environmentally friendly future. The district is part of the northern Norrbotten ore province, Sweden and is known for hosting the Kiruna-type iron oxide-apatite (IOA) deposits with associated magnetite-hematite-REE ores such as the Per Geijer deposits, and a range of other deposits, including the Viscaria Cu-(Fe-Zn), Pahtohavare Cu-Au and the Rakkurijärvi iron oxide-copper-gold (IOCG) deposits. 

As the discoveries of significant near-surface deposits are declining, mining companies face a pivotal choice between pursuing resource extraction from lower-grade reserves or to focus on deeper exploration targets. The geological understanding of the subsurface decreases with increasing depth, and the reliance on geophysical techniques becomes more important in reducing the search space. Using geophysics to locate and understand elements of a mineral system requires a good understanding of the physical and chemical properties of the rocks that can be translated into geological implications. Mineral system knowledge and geological concepts can be translated into geological models that can be further used in geophysical inversions with the aim of improving targeting by iterative modeling. A geophysical inversion is in fact a realization of a physical property model, therefore the value added by the geophysical model is dependent of how well the relationship between the geology and its petrophysical signature is understood. The petrophysical characterization of geological environments offers the possibility to improve the understanding of geophysical responses, serving as a link in iterative geological-geophysical modeling. 

The approach presented in the current study includes the building of three-dimensional lithological and structural framework models, and investigating the petrophysical footprint in connection with lithology, alteration, and rock fabric from the Kiruna mining district. Geological modeling and petrophysical characterization are important components within the comprehensive mineral system modeling framework and enhance geophysical investigations aimed at detecting and assessing iron oxide mineral systems. A rule-based hybrid implicit-explicit geological modeling technique proved to be useful in the integration of surface and subsurface data of the Kiruna mining district, and a structural framework and geological model was produced that provides insights into the relationship between lithological units and structures. Drill core observations indicate a competency contrast between lithological units confirming previous surface-based observations. Deposit scale structural analysis in connection with the geological models indicated the proximity of NW-SE to SW-NE trending brittle conjugate fault networks with iron-oxide apatite ore lenses, revealing juxtaposition of individual ore lenses. Complementing structural analysis and geological modeling, petrophysical characterization in connection with lithogeochemical, mineralogical, and textural investigations revealed that density and p-wave seismic velocity can be used as a general lithological indicator, while magnetic susceptibility is influenced by secondary processes. Heterogeneous strain accommodation by lithological units indicates a strong influence on density, seismic properties, and the ferromagnetic properties of the samples. Metasomatic processes alter the intrinsic properties of the samples by increasing or decreasing the physical properties of the rocks from the Kiruna area, by controlling the feldspar, mica, magnetite, and ferromagnesian mineral content. Nevertheless, an extensive sample population must be investigated to understand the large-scale effects. The present work serves as a foundation for quantitatively integrated exploration models that use geological models and petrophysical characterization as calibration tools to model mineral systems. 

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2023
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
Kiruna mining district, geological modeling, structural framework, common earth modeling, petrophysical characterization, mineral exploration, iron oxide-apatite
National Category
Geology
Research subject
Ore Geology
Identifiers
urn:nbn:se:ltu:diva-101603 (URN)978-91-8048-395-7 (ISBN)978-91-8048-396-4 (ISBN)
Presentation
2023-12-13, F1031, Luleå University of Technology, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2023-10-09 Created: 2023-10-09 Last updated: 2023-12-12Bibliographically approved
Logan, L., Veress, E. C., Andersson, J. B. H., Martinsson, O. & Bauer, T. E. (2023). Structural framework and timing of the Pahtohavare Cu ± Au deposits, Kiruna mining district, Sweden. Solid Earth, 14(7), 763-784
Open this publication in new window or tab >>Structural framework and timing of the Pahtohavare Cu ± Au deposits, Kiruna mining district, Sweden
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2023 (English)In: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 14, no 7, p. 763-784Article in journal (Refereed) Published
Abstract [en]

As part of the larger mineral systems approach to Cu-bearing mineralization in northern Norrbotten, this study utilizes structural geology to set the classic Pahtohavare Cu ± Au deposits into an up-to-date tectonic framework. The Pahtohavare Cu ± Au deposits, situated only 5 km southwest of the Kiirunavaara world-class iron oxide–apatite (IOA) deposit, have a dubious timing, and their link to IOA formation is not constrained. The study area contains both epigenic Cu ± Au (Pahtohavare) and iron oxide–copper–gold (IOCG; Rakkurijärvi) mineral occurrences which are hosted in bedrock that has been folded and bound by two shear zones trending northeast to southwest and northwest to southeast to the east and southwest, respectively. Structural mapping and petrographic investigation of the area reveal a noncylindrical, SE-plunging anticline. The cleavage measurements mirror the fold geometry, which characterizes the fold as F2 associated with the late phase of the Svecokarelian orogeny. Porphyroclasts with pressure shadows, mylonitic fabrics, and foliation trails in porphyroblasts indicate S0/S1  is a tectonic fabric. The epigenetic Pahtohavare Cu ± Au mineralization sits in brittle–ductile structures that cross-cut an earlier foliation and the F2 fold, indicating that the timing of the deposits occurred syn- to post-F2 folding, at least ca. 80 Myr after the Kiirunavaara IOA formation. A 3D model and cross-sections of the Pahtohavare–Rakkurijärvi area and a new structural framework of the district are presented and used to suggest that the shear zones bounding the area are likely reactivated early structures that have played a critical role in ore formation in the Kiruna mining district.

Place, publisher, year, edition, pages
Copernicus Publications, 2023
National Category
Geology
Research subject
Ore Geology
Identifiers
urn:nbn:se:ltu:diva-100661 (URN)10.5194/se-14-763-2023 (DOI)001031584400001 ()2-s2.0-85170210557 (Scopus ID)
Projects
New Exploration Technologies – NEXT
Funder
EU, Horizon 2020, 776804
Note

Validerad;2023;Nivå 2;2023-08-21 (hanlid)

Available from: 2023-08-21 Created: 2023-08-21 Last updated: 2023-10-11Bibliographically approved
Veress, E. C., Rydman, O., Warlo, M., Andersson, J., Annesley, I. R. & Bauer, T.Characterization of lithogeochemistry, mineralogy, and fabric, in connection with petrophysical properties: Implications on mineral exploration in the Kiruna mining district.
Open this publication in new window or tab >>Characterization of lithogeochemistry, mineralogy, and fabric, in connection with petrophysical properties: Implications on mineral exploration in the Kiruna mining district
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(English)Manuscript (preprint) (Other academic)
National Category
Geology Geophysics
Research subject
Ore Geology
Identifiers
urn:nbn:se:ltu:diva-101553 (URN)
Available from: 2023-10-03 Created: 2023-10-03 Last updated: 2023-10-09
Rydman, O., Veress, E. C., Smirnov, M., Bauer, T., Rasmussen, T. M. & Juhojuntti, N.Common Earth Modelling of the Northern Kiruna mining district using combined geophysical modelling and petrophysical unit characterization using machine learning..
Open this publication in new window or tab >>Common Earth Modelling of the Northern Kiruna mining district using combined geophysical modelling and petrophysical unit characterization using machine learning.
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(English)Manuscript (preprint) (Other academic)
National Category
Geophysics
Research subject
Applied Geophysics
Identifiers
urn:nbn:se:ltu:diva-104943 (URN)
Available from: 2024-04-02 Created: 2024-04-02 Last updated: 2024-04-02
Veress, E., Andersson, J., Popova, I., Annesley, I. R. & Bauer, T.Three-dimensional geological modeling of the Kiruna mining district, Sweden: Insights into the crustal architecture and structural controls on iron oxide-apatite mineralization.
Open this publication in new window or tab >>Three-dimensional geological modeling of the Kiruna mining district, Sweden: Insights into the crustal architecture and structural controls on iron oxide-apatite mineralization
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences Geology
Research subject
Ore Geology
Identifiers
urn:nbn:se:ltu:diva-101550 (URN)
Available from: 2023-10-03 Created: 2023-10-03 Last updated: 2023-10-09
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0009-0007-4495-7364

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