| 1. |
- Sarlus, Zmar, 1984-, et al.
(författare)
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Timing and origin of the host rocks to the Malmberget iron oxide-apatite deposit, Sweden
- 2020
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Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 342
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Tidskriftsartikel (refereegranskat)abstract
- The northern Norrbotten region in Sweden hosts abundant iron-oxide apatite (IOA) deposits including Kiirunavaara, the type locality for Kiruna-type deposits, and Malmberget. Felsic and intermediate metavolcanic rocks hosting the Malmberget IOA deposit contain oscillatory zoned zircon which yield magmatic U-Pb SIMS ages of 1885±6 Ma and 1881±6 Ma, respectively. Metamorphic rims on zircon from these rocks yield 1797±7 Ma and 1775±6 Ma, respectively, and record the age of the latest Svecofennian regional metamorphic event in the Gällivare area, tentatively interpreted as regional contact metamorphism. Two granite dikes that cut the ore yield U-Pb zircon emplacement ages of 1790±6 Ma and 1791±7 Ma, respectively, overlapping with the metamorphic overgrowths, and set a lower age limit for ore formation in the Malmberget IOA deposit. Rocks hosting the Malmberget IOA deposit have an alkalic to alkali-calcic affinity with a geochemical signature that favors a continental-arc, transitional to extensional setting. These rocks are suggested to have been generated in a back-arc region, in response to subduction beneath the craton margin retreating to the SW or W. The obtained ages and geochemical signatures of these rocks coincide well with the regionally defined Kiirunavaara group rocks, hosting several other IOA deposits in northern Sweden.
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| 2. |
- Sarlus, Zmar, et al.
(författare)
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Timing of plutonism in the Gällivare area : mplications for Proterozoic crustal development in the northern Norrbotten ore district, Sweden
- 2018
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Ingår i: Geological Magazine. - : Cambridge University Press. - 0016-7568 .- 1469-5081. ; 155:6, s. 1351-1376
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Tidskriftsartikel (refereegranskat)abstract
- Zircon ion probe (secondary-ion mass spectrometry or SIMS) data from a set of intrusive rocks emplaced in the vicinity of major ore bodies, as well as from large igneous intrusions in the Gällivare area, gave the following results: (1) the Dundret ultramafic–mafic layered complex (1883±5 Ma), the Aitik granite (1883±5 Ma), the Nautanen diorite (1870±12 Ma), the Vassaravaara ultramafic–mafic layered complex (1798±4 Ma), the Aitik dolerite (1813±9 Ma), the Bergmästergruvan and Sikträsk syenites (1795±4 Ma and 1801±3 Ma, respectively) and the Naalojärvi granite (1782±5 Ma). These data broadly fall within the ranges 1.89–1.87 Ga (early Svecofennian) and 1.80–1.78 Ga (late Svecofennian), but geochronologically allow further subdivision into pulses at 1885–1880, 1875–1870, 1800 and 1780 Ma. During these events, large layered ultramafic–mafic and felsic plutonic rocks were generated with distinct overlap in time suggesting coeval felsic–mafic magmatism. Results also indicate the presence of inherited c. 1.87 Ga zircon crystals in the plutonic rocks at 1.78 Ga, supporting reworking of the previous crust. These data indicate the importance of mantle-derived mafic underplating in the process of crustal magma generation in the region. The c. 1.88 Ga event that generated ultramafic–mafic layered complexes is tentatively suggested to have played an important role in the formation of the Aitik Cu–Au porphyry system. The later event at c. 1.80 Ga, generating voluminous mafic–felsic units, is suggested to be coupled to the regional iron-oxide-copper-gold (IOCG) overprint.
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| 3. |
- Andersson, Joel B. H., et al.
(författare)
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Structural controls on sulphide (re)-distribution in Kiruna
- 2019
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Ingår i: Proceedings of the 15th SGA Biennial Meeting, 27-30 August. - : University of Glasgow Publicity Services. ; , s. 115-118
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Konferensbidrag (refereegranskat)abstract
- In this study, we investigate a potential structural control on sulphide distribution in phyllite from the Kiruna area, northern Norrbotten, Sweden. We use X-ray tomography and X-ray fluorescence analyzed in tandem on a 40 cm section of oriented drill core. Scanning Electron Microscopy and Energy Dispersive Spectrometry are used in combination with optical microscopy to analyze mineralogy and microstructures. The results show that sulphides are distributed along So bedding planes, re-distributed along S-2 axial planar cleavage planes, and trapped by F-2-hinge zones and shear bands visible as elevated sulphide concentrations. The results of this study underlines the strength of X-ray tomography to image 3D geological structures and their relation to mineral distributions.
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| 4. |
- Andersson, Joel B.H., et al.
(författare)
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Structural Evolution of the Central Kiruna Area, Northern Norrbotten, Sweden : Implications on the Geologic Setting Generating Iron Oxide-Apatite and Epigenetic Iron and Copper Sulfides
- 2021
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Ingår i: Economic geology and the bulletin of the Society of Economic Geologists. - : Society of Economic Geologists. - 0361-0128 .- 1554-0774. ; 116:8, s. 1981-2009
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Tidskriftsartikel (refereegranskat)abstract
- To guide future exploration, this predominantly field based study has investigated the structural evolution of the central Kiruna area, the type locality for iron oxide-apatite deposits that stands for a significant amount of the European iron ore production. Using a combination of geologic mapping focusing on structures and stratigraphy, petrography with focus on microstructures, X-ray computed tomography imaging of sulfide-structure relationships, and structural 2D-forward modeling, a structural framework is provided including spatial-temporal relationships between iron oxide-apatite emplacement, subeconomic Fe and Cu sulfide mineralization, and deformation. These relationships are important to constrain as a guidance for exploration in iron oxide-apatite and iron oxide copper-gold prospective terrains and may help to understand the genesis of these deposit types. Results suggest that the iron oxide-apatite deposits were emplaced in an intracontinental back-arc basin, and they formed precrustal shortening under shallow crustal conditions. Subsequent east-west crustal shortening under greenschist facies metamorphism inverted the basin along steep to moderately steep E-dipping structures, often subparallel with bedding and lithological contacts, with reverse, oblique to dip-slip, east-block-up sense of shears. Fe and Cu sulfides associated with Fe oxides are hosted by structures formed during the basin inversion and are spatially related to the iron oxide-apatite deposits but formed in fundamentally different structural settings and are separated in time. The inverted basin was gently refolded and later affected by hydraulic fracturing, which represent the last recorded deformation-hydrothermal events affecting the crustal architecture of central Kiruna.
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| 5. |
- Andersson, Joel B.H., et al.
(författare)
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The tectonic overprint on the Per Geijer apatite iron ores in Kiruna, northern Sweden
- 2017
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Ingår i: Mineral Resources to Discover. - : Society for Geology Applied to Mineral Deposits. - 9782981689801 ; , s. 903-906
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Konferensbidrag (refereegranskat)abstract
- This ongoing project focusses on the structural evolution of the Per Geijer apatite iron ores in Kiruna, northern Sweden. The Per Geijer iron ores are situated in a NNE-SSW trending shear zone. This study indicate that the shear zone was active during D2 E-W compression giving rise to dip-slip and oblique slip components. The ductile fabric is overprinted by brittle structures carrying Cu, possibly representing traces of a separate Iron Oxide Copper Gold event in northern Norrbotten.
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| 6. |
- Andersson, Joel B.H., et al.
(författare)
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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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Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 372
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Bauer, Tobias E., Associate professor, 1982-, et al.
(författare)
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Analysis of data from Unmanned Aerial Systems (UAS) in a Virtual Reality environment
- 2019
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Ingår i: Proceedings of the Visual3D conference 2019, 1–2 October 2019, Uppsala, Sweden: Visualization of 3D/4D models in geosciences, exploration and mining. - : Luleå University of Technology. ; , s. 19-19
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Konferensbidrag (refereegranskat)abstract
- The use of Unmanned Aerial Systems (UAS) is getting increasingly popular for many different types of applications. The field of geology is slowly catching up resulting in new and innovative UAS solutions for various kinds of airborne measurement techniques. These techniques comprise a wide range of geophysical and remote sensing methods used to investigate the sub-surface. At Luleå University of Technology two different types of UAS are used in combination with a Virtual Reality environment in order to analyze geological structures and related ore deposits and mineralizations. The two UAS comprise a) a custom made quadrocopter (HUGIN) with a pay load of approx. 3.5 kg and an operational time of 5 times (batteries) maximum 35 minutes depending on payload, ambient temperatures and wind speed; and b) a foldable DJI Mavic Pro with an operational time of 3 times 30 minutes. The HUGIN system can be operated with a high-resolution optical camera for photogrammetry surveys and a 3-axial fluxgate magnetometer for measuring magnetic anomalies within bedrock and ultimately delineating geological structures. The system is highly flexible and a thermal camera is currently added to the system in order detect water fluxes in relation to geological structures or exothermal mineral processes. The DJI system is equipped with an optical camera for photogrammetric surveying and is a highly valuable tool in remote areas due to its lightweight and compact construction.Data acquired from both UAS is subsequently analysed in a Virtual Reality lab utilizing a 6m wide screen with active stereo functions. Photogrammetry data is first processed using the Aigsoft software package following a Structure for Motion (SfM) workflow where dense point cloud models and subsequently meshed and textured 3D surface models are produced. These models are then converted and transferred to the GeoVisionary software package that allows visualization of models in stereo 3D view. This allows digitizing geological structures such as foliation, fractures, and faults among others in an immersive 3D environment and provides an efficient tool complimentary to traditional field mapping. In particular, this makes it possible to capture and analyse data from hardly accessible and dangerous areas such as rock faces in open pits. Another complimentary method of data analysis comprises SCAT analysis of the meshed surfaces using the MOVE software package.
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| 8. |
- Bauer, Tobias, Associate professor, 1982-, et al.
(författare)
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Regional structural setting of late-orogenic IOCG mineralization along the northern Nautanen deformation zone, Norrbotten, Sweden
- 2023
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Ingår i: Ore Geology Reviews. - : Elsevier. - 0169-1368 .- 1872-7360. ; 163
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Tidskriftsartikel (refereegranskat)abstract
- The northern Norrbotten ore province in Sweden is one of the most mineralized areas in Europe. Iron, gold and/or copper deposits occur as iron oxide-apatite-style mineralization (IOA, Kiruna-type) as well as iron oxide-copper–gold (IOCG) style. Regardless of mineralization style, most deposits appear to be spatially controlled by a set of crustal-scale Palaeoproterozoic shear zones which share similar structural characteristics and deformation histories.Reappraisal of regional geological and geophysical data, coupled with structural mapping, suggests crustal-scale shear zones form continuous c. N-S-trending zones extending from the Skellefte district in the south into the northern Norrbotten ore province. One example from Norrbotten is a zone that extends SSW from Karesuando in the north towards Svappavaara. While this structure has traditionally been inferred to continue SW towards Arjeplog (i.e. the Karesuando – Arjeplog Deformation Zone; KADZ), we favour its deflection SSE into the Nautanen-Aitik trend, making it a continuous, IOCG-bearing, crustal-scale deformation zone. Similar shear zone geometries can be observed in analogous zones to the west. Most of these crustal scale structures record at least two time-separated deformation events of regional significance. IOA and IOCG deposits form in different tectonic environments, separated in time and overprinting each other.
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| 9. |
- Logan, Leslie, 1992-, et al.
(författare)
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A mineral systems-scale investigation into the Kiruna mining district and implications for the timing of ore forming processes within a regional tectonic framework
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The formation of iron oxide apatite (IOA) and iron oxide-copper-gold (IOCG) deposits and their relation to each other is currently strongly debated. Recent characterization of the polyphase Svecokarelian orogeny in the northern Norrbotten ore province provides a tectonic framework that can be used to assess the timing of IOA and IOCG genetic processes from a broader mineral systems perspective. This study combined whole rock lithogeochemistry, whole rock Sr and Nd isotopes, U-Pb zircon geochronology, and structural data to gain insight into the Kiruna mining district mineral system. Results show that the igneous intrusions range from mafic to felsic in composition and developed in an active continental margin with both volcanic arc and within-plate affinities. The intrusions have ages ranging from 1891 ± 6 Ma to 1876 ± 11 Ma. One magnetite-ilmenite gabbro gives a concordia age of 1881 ± 8 Ma. These ages indicate a thermal drive for the mineral system can be recognized occurring during an early-orogenic deformation phase (D0-D1) but remains enigmatic for a late-orogenic phase (D2). 87Sr/86Sri and εNdi data from ore-related alteration (Na-alteration and late K-Fe overprint) at Pahtohavare Cu ± Au and Rakkurijärvi IOCG deposits as well as district igneous, greenstone, and Archean rocks indicate that the deposits have distinct Sr-mixing trends and that both sourced Sr and Nd from a wide variety of protoliths. Alteration results show a prominent Na-metasomatism with certain areas showing a K-overprint. New structural analysis of the Pahtohavare area indicates the main ore-related generation of quartz-carbonate-sulfide veins cross cut foliation and were introduced during F2 folding in the late Svecokarelian (D2), suggesting that a late Cu-Au mineralization/remobilization occurred in the Kiruna mining district ca. 80 m.y. after the emplacement of the Kiirunavaara IOA deposit. In brief, our data show that IOA and IOCG systems can be of different ages and sources within the same district.
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| 10. |
- Logan, Leslie, 1992-, et al.
(författare)
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Energy Drive for the Kiruna Mining District Mineral System(s): Insights from U-Pb Zircon Geochronology
- 2022
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Ingår i: Minerals. - : MDPI. - 2075-163X. ; 12:7
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Tidskriftsartikel (refereegranskat)abstract
- The Kiruna mining district, Sweden, known for the type locality of Kiruna-type iron oxide-apatite (IOA) deposits, also hosts several Cu-mineralized deposits including iron oxide-copper-gold (IOCG), exhalative stratiform Cu-(Fe-Zn), and structurally controlled to stratabound Cu +/- Au. However the relationship between the IOA and Cu-systems has not been contextualized within the regional tectonic evolution. A broader mineral systems approach is taken to assess the timing of energy drive(s) within a regional tectonic framework by conducting U-Pb zircon geochronology on intrusions from areas where Cu-mineralization is spatially proximal. Results unanimously yield U-Pb ages from the early Svecokarelian orogeny (ca. 1923-1867 Ma including age uncertainties), except one sample from the Archean basement (2698 +/- 3 Ma), indicating that a distinct thermal drive from magmatic activity was prominent for the early orogenic phase. A weighted average Pb-207/Pb-206 age of 1877 +/- 10 Ma of an iron-oxide-enriched gabbroic pluton overlaps in age with the Kiirunavaara IOA deposit and is suggested as a candidate for contributing mafic signatures to the IOA ore. The results leave the role of a late energy drive (and subsequent late Cu-mineralization and/or remobilization) ambiguous, despite evidence showing a late regional magmatic-style hydrothermal alteration is present in the district.
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