In light of the increased demand for raw materials to support the transition away from a fossil-fuel society, mineral exploration for future raw material sources is imperative, requiring a holistic mineral systems approach. This thesis focuses on the Pahtohavare area in the Kiruna mining district where three epigenetic Cu ± Au deposits of unknown age and structural setting occur within 0.5 km of a pre-orogenic stratiform Cu (Fe ± Zn) deposit, 2 km of the Rakkurijärvi iron oxide-copper-gold (IOCG) deposit, and 5 km of the giant Kiirunavaara iron oxide-apatite (IOA) deposit, which may have shared mineral system ingredients during ore formation. The aim of the thesis is to characterize the mineral system ingredients of the epigenetic Pahtohavare deposits utilizing an up-to-date regional tectonic framework and to assess parallels between other mineral systems in the district. The following ingredients were investigated in this study: 1) driving force, using U-Pb zircon geochronology of local igneous intrusions, 2) transport pathways and structural traps, utilizing structural analysis and field mapping, 3) metal sources, based on sulfide trace element and carbonate REE geochemistry, and 4) ligand and fluid sources, using S, Sr, and Nd-isotope analyses.

U-Pb zircon geochronology of intrusions in the district where Cu-mineralization is spatially proximal yields ages unanimously from the early phase of the Svecokarelian orogeny (ca. 1923-1867 Ma including age uncertainties). These ages suggest magmatism provided a thermal energy drive for the mineral systems developing during this time such as the Kiirunavaara IOA and Rakkurijärvi IOCG.

Structural analysis and petrographic investigation from the Pahtohavare area show that the host rocks for the Pahtohavare deposits are folded into a noncylindrical, SE-plunging anticline and that cleavage measurements mirror the fold geometry. Foliation trails, mylonitic fabrics, and porphyroclasts with pressure shadows characterize the S0/S1 fabric as tectonic and constrains the fold as F2, indicating the folding event occurred during the late phase of the Svecokarelian orogeny (ca. 1.81-1.78 Ga). The epigenetic Pahtohavare deposits sit in brittle-ductile second-order structures that cross cut earlier foliation and the F2 fold, indicating that the deposits formed ca. 80 m.y. after the IOA and IOCG deposits in a distinct tectonic regime.

Petrographic investigation of microstructures identifies remobilization textures linking the pre-orogenic stratiform Cu (Fe ± Zn) and late-orogenic Pahtohavare Cu ± Au deposits. Comparison of Co/Ni ratios between structurally constrained early and late sulfide generations (0.1-10 vs. 0.1-100) indicate the late-orogenic fluids were capable of efficiently transporting and concentrating Co, implying hot and saline conditions. However, a weak Co/Ni ratio mixing trend between the two generations suggest the late-orogenic fluids primarily sourced metals from the pre-existing host rocks and sulfides, rather than an external reservoir. This is supported by flat REE (chondrite normalized) patterns from ore-related carbonate, reflecting a source from the mafic host rocks.

Both the pre- and late-orogenic sulfide generations have overlapping δ34S values ranging between ca. -20‰ and ca. -5‰ to near-zero values. The sulfur source for both mineral systems likely originated from local graphite schist horizons (ca. -22‰ to -21‰) and the volcanic host rocks. 87Sr/86Sr values for ore-related carbonates from the epigenetic Pahtohavare deposits are radiogenic (ca. 0.7095-0.7154) and form a mixing trend with strongly radiogenic (ca. 0.7134-0.7740) non-ore-related syn-sedimentary carbonate in biotite-altered rocks. This suggests a metamorphic fluid derived from crustal and Rb-rich rocks was responsible for the formation of the ore-related carbonate. Therefore, the Pahtohavare epigenetic deposits are suggested to have formed from metamorphic fluids during prograde metamorphism modified by the pre-enriched and altered host rocks in the Pahtohavare area.

The results of this thesis suggest that late-orogenic tectonism played a key role in reactivating mineral system ingredients, highlighting the potential of second-order structures near pre-existing mineral deposits as a strategic exploration target for Cu-mineralization in the region.  

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.

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.

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.

The Kiruna mining district, located in the northern Norrbotten ore province, Sweden, is a geologically and economically important area, being the type-locality for Kiruna iron oxide-apatite (IOA) deposits and also host to a variety of other deposits including syngenetic stratiform exhalative Cu-(Fe-Zn) (Viscaria, Eastern Pahtohavare), epigenetic stratabound Cu ± Au (Pahtohavare), and iron oxide-copper-gold (IOCG, Rakkurijärvi) deposits. However, the timing of IOA versus IOCG within the tectonic evolution is in question based on structural investigations showing Cu- and Fe-sulfides occur in late-orogenic structures. Here we use an established tectonic framework to constrain mineral systems (tectonic/thermal drives, metal and ligand sources, fluid pathways, traps, remobilization mechanisms) related to the early and late phases of the Svecokarelian orogeny in the Kiruna mining district. U-Pb zircon geochronology of intrusions in the district indicates a thermal drive was present during the early phase of the Svecokarelian orogeny from ca. 1920-1865 Ma, however remains enigmatic for the late Svecokarelian orogeny. Zircon grains from a magnetite-ilmenite gabbro yielded an age of 1881 ± 8 Ma, coeval with the Kiirunavaara IOA deposit and suggested to represent an important generation of mafic magmatism related to the ore. Lithogeochemistry of early bimodal Svecokarelian intrusions in the district indicates a within-plate to active continental margin environment with a volcanic arc affinity, pointing to a back arc environment. Epsilon Ndi and 87Sr/86Sri values calculated from the U-Pb ages for the igneous intrusions were compared to samples of ore-related alteration from epigenetic Pahtohavare and Rakkurijärvi deposits, district greenstone, and Archean samples. Results show that each deposit sourced Sr and Nd from a variety of rocks suggesting broad fluid transport. Each deposit has a distinct Sr mixing trend suggesting they formed from different ore-forming fluids and pathways. This is supported by new structural data that constrain the folding event and the ore-related quartz-carbonate-sulfide veins in the Pahtohavare area to a late orogenic timing, compared to the early orogenic timing of Rakkurijärvi. Sulfide trace element and sulfur isotope data from structurally constrained ores within the tectonic framework also record distinct characteristics between early and late deposits. However, remobilization of early Pahtohavare sulfides associated to an increase in Co content and heavier sulfur isotope compositions is recorded. The results of this study illustrate that using a structural framework approach to constrain the ingredients of mineral systems is a powerful strategy for interpreting ore deposit processes in tectonically complex terrains where both IOA and IOCG deposits occur.

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.

The Kiruna mining district in northern Norrbotten, Sweden, is situated in a region that is broadly described as an iron oxide-copper-gold (IOCG) district. Kiruna is well known for the iron oxide-apatite (IOA) deposits (Kiruna-type), but also hosts several Cu-bearing prospects including the Viscaria and Eastern Pahtohavare stratabound-stratiform Cu-(Fe-Zn), the Rakkurijärvi IOCG, and the Pahtohavare epigenetic Cu ± Au prospects. However the genesis of the Cu mineralization in the district has not been studied from a structural perspective in relation to the tectonic evolution of the region. Utilizing recent structural characterization of the Svecokarelian orogenic cycle as a framework, Cu- and Fe-bearing sulfides have been identified from the pre-, early, and late orogenic phases and assessed for primary and overprinting signatures with in situ δ34S and trace element data. Results indicate that the youngest stage of epigenetic mineralization (late orogenic) in the Pahtohavare area precipitated vein-hosted pyrite from a strongly Co-enriched hydrothermal fluid with δ34S values between 2‰ and 6 ‰. The late mineralization event occurred syn- to post-folding of the host rocks together with remobilization of sulfides from the younger Eastern Pahtohavare deposit. This remobilization is characterized by a fractionation of sulfur isotopes towards heavier values and dispersion of Co and Ni data towards higher and lower concentrations, respectively, and indicates redistribution of metals occurred as a result of the late orogenic mineralization and deformation. This implies a distinct Cu-forming event occurred in the late Svecokarelian orogeny both that introduced new metals and redistributed (and possibly incorporated) metals from a preexisting source. Metamorphic and low temperature remobilization is also recorded in samples from the district characterized by increases in Co and Ni, respectively. 

The Kiruna mining district, Sweden, is well known for its many iron oxide-apatite (IOA) deposits (Kiruna-type), but also hosts several Cu-bearing ore bodies of different ages. This includes the Pahtohavare area which hosts both a pre-orogenic stratiform Cu (Fe ± Zn) ore body as well as three late-orogenic epigenetic Cu ± Au deposits. The region has undergone multiple phases of deformation, metasomatism, and mineralization during the Svecokarelian orogeny and the effect of each overprinting event on the sulfur and metal budget of later mineralization events remains unclear. Utilizing the structural framework of the Svecokarelian orogeny, Cu- and Fe-sulfides from the Pahtohavare area are classified based on microstructures into early and late generations, which are subsequently analyzed for in situ δ34S and trace element contents and assessed with Linear Mixed Effects (LME) modelling to test for statistical significance. Results indicate that δ34S values from both the early and late mineralization exhibit a wide range from ca. -26‰ to +6‰. Early sulfur fractionation occurred during biogenic sulfate reduction in a system with excess sulfate forming syn-depositional pyrrhotite with δ34S signatures from ca. -22‰ to -21‰. LME modelling indicates a slightly higher δ34S range (ca. -20‰ to +6‰) is associated with the epigenetic mineralization compared to the pre-orogenic mineralization (ca. -26‰ to -5‰) but overlapping signatures suggest mixing occurred between pre-existing sulfur reservoirs leading to inherited signatures for the late mineralizing event. Similarly, at the pre-orogenic deposit, Co/Ni ratios of pyrrhotite in remobilized textures show a strong overlap with pyrrhotite in syn-depositional textures, indicating a local metal source for remobilized sulfides. Pyrite Co/Ni ratios for the pre-orogenic mineralization are lower (c. 0.1-10) in comparison to the epigenetic mineralization (c. 0.1-100) but a mixing trend is interpreted between the deposits. The late mineralization event is therefore characterized by higher Co contents and δ34S values but mixing trends suggest metals and sulfur were also inherited from pre-existing sulfides.