The Per Geijer iron oxide-apatite deposits are important potential future resources for Luossavaara-Kiirunavaara Aktiebolag (LKAB), which has been continuously mining magnetite/hematite ores in northern Sweden for almost 130 years. The Per Geijer deposits reveal a high phosphorus content and vary from magnetite-dominated to hematite-dominated ores, respectively. The high phosphorus concentration of these ores results from highly elevated content of apatite as gangue mineral. Reliable, robust, and qualitative characterization of the mineralization is required as these ores inherit complex mineralogical and textural features. The precise mineralogical information obtained by optical microscopy, SEM-MLA and Raman improves the characterization of ore types and will benefit future processing strategies for this complex mineralization. The different approaches demonstrate advantages and disadvantages in classification, imaging, discrimination of iron oxides, and time consumption of measurement and processing. A comprehensive mineral-chemical dataset of magnetite, hematite and apatite obtained by electron microprobe analysis (EPMA) and LA-ICP-MS from representative drill core samples is presented. Magnetite, four different types of hematite and five types of apatite constitute the massive orebodies: Primary and pristine magnetite with moderate to high concentrations of Ti (∼61–2180 ppm), Ni (∼11–480 ppm), Co (∼5–300 ppm) and V (∼553–1831 ppm) indicate a magmatic origin for magnetite. The presence of fluorapatite and associated monazite inclusions and disseminated pyrite enclosed by magnetite with high Co:Ni ratios (> 10) in massive magnetite ores are consistent with a high temperature (∼ 800°C) genesis for the deposit. The different and abundant types of hematite, especially hematite type I, state subsequent hydrothermal events. Chromium, Ni, Co and V in both magnetite and hematite have low concentrations in terms of current product regulations and thus no effect on final products in the future. In terms of a possible future hematite product, titanium seems to be the most critical trace element due to very high concentrations in hematite types I and IV, of which type I is most abundant in zones dominated by hematite. Further interest on other products is generated due to the high variability of hematite and apatite in some of these ores. Information obtained from comminution test works in the laboratory scale can be utilized to characterize ore types and to predict the behavior of ore during comminution circuit in the industrial scale. Comminution tests with a laboratory rod and ball mill of 13 pre-defined ore types from the Per Geijer iron-oxide apatite deposits were conducted in this study. The highest P80 values were obtained by grinding in the rod mill for 10 minutes only (step A). Grinding steps B (25 min ball mill) and C (35 min ball mill) reveal very narrow P80 values. Ore types dominated by hematite have significantly higher P80 values after the primary grinding step (A), which indicates different hardness of the ore types. P80 values are generally lowest after the secondary grinding step C ranging between 26 µm (ore type M1a) and 80 µm (ore type H2a). Generally, Fe content increases in the finer particle size classes while CaO and P contents decrease. The influence of silica or phosphorus seems to be dependent on the dominant iron oxide. Magnetite-dominated ore types are more likely to be affected in their comminution behavior by the presence of the silicates. Contrary, hematite-dominant ore types are rather influenced by the presence of apatite. The difference in the degree of liberation of magnetite and hematite between ore types depends rather on size fractions than the amount of gangue in the ore. Davis tube data indicates that magnetite can be separated from gangue quite efficiently in the magnetite-dominated ore types. Contrary to magnetite ore, hematite-dominated ore types cannot be processed by DT. It is favored to use strong magnetic separation in order to achieve a desirable hematite concentrate. The magnetic material recovered by DT is most efficiently separated at an intensity current of 0.2 A, whereas above 0.5 A the separation process is neglectable. Based on comminution and magnetic separation tests a consolidation to eight ore types is favored which supports possible future mining of the Per Geijer deposits.:Contents ABSTRACT ……………………………………………………………………… I CONTENTS ……………………………………………………………………… II LIST OF FIGURES AND TABLES ……………………………………………… IV LIST OF ABBREVIATIONS ……………………………………………… V 1 INTRODUCTION ……………………………………………………… 1 1.1 Background and motivation of study ……………………………… 2 1.2 Previous and current work on the Per Geijer deposits ……………… 3 1.3 The need for mineral processing and in-situ ore description ……………… 4 1.4 General and generic aspects on iron oxide apatite deposits ……………… 5 Chapter A 2 REGIONAL GEOLOGY ………………………………………………. 7 2.1 Local geology of the Kiruna area ……………………………………… 7 2.2 Geology of the Per Geijer deposits ……………………………………… 9 3 METHODOLOGY ……………………………………………………… 12 3.1 Core sampling and preparation ……………………………………… 12 3.2 SEM – MLA in-situ ore ……………………………………………… 14 3.3 Electron Probe Microanalyses (EPMA) ……………………………… 15 3.3.1 Iron oxide measurements ……………………………………… 15 3.3.2 Apatite measurements ……………………………………… 15 3.4 In-situ LA-ICP-MS ……………………………………………………… 16 3.5 Whole-rock geochemistry ……………………………………………… 18 3.5.1 Exploration drill core assays ……………………………… 18 3.5.2 Chemical assays of rock chips ……………………………… 18 4 RESULTS ……………………………………………………………… 19 4.1 Pre-definition of ore types ………………………………...……………. 19 4.2 Mineralogy of in situ ore ……………………………………………… 21 4.2.1 Ore Type M1a ……………………………………………… 21 4.2.2 Ore Type M1b ……………………………………………… 22 4.2.3 Ore Type M2a ……………………………………………… 23 4.2.4 Ore Type M2b ……………………………………………… 25 4.2.5 Ore Type HM1b ……………………………………………… 26 4.2.6 Ore Type HM2a ……………………………………………… 27 4.2.7 Ore Type HM2b ……………………………………………… 28 4.2.8 Ore Type H1a ……………………………………………… 29 4.2.9 Ore Type H1b ……………………………………………… 30 4.2.10 Ore Type H2a ……………………………………………… 31 4.2.11 Ore Type H2b ……………………………………………… 32 4.2.12 Comparison of ore types ……………………………………… 33 4.3 Geochemistry of in situ ore types ……………………………… 36 4.3.1 Whole-rock chemical assays of drill cores ……………………… 36 4.3.2 Whole-rock geochemistry of rock chips ……………………… 39 4.4 Mineral chemistry of iron oxides ……………………………………… 42 4.4.1 Iron oxides and associated minerals ……………………………… 42 4.4.2 Mineral chemistry of magnetite from Per Geijer ……………… 43 4.4.3 Mineral chemistry of hematite from Per Geijer ……………… 47 4.5 Mineral chemistry of apatite ……………………………………… 51 4.5.1 Apatite and associated minerals ……………………………… 51 4.5.2 Mineral chemistry of apatite from Per Geijer ……………… 53 Chapter B 5 COMMINUTION TESTS ……………………………………………… 58 5.1 Methodology of comminution tests ……………………………………… 59 5.1.1 Sampling for comminution tests ……………………………… 59 5.1.2 Comminution circuit ……………………………………………… 61 5.1.3 Energy consumption calculation ……………………………… 62 5.1.4 SEM – MLA ……………………………………………………… 64 6 MAGNETIC SEPARATION TESTS ……………………………… 65 6.1 Methodology of magnetic separation by Davis magnetic tube ……… 66 6.2 Davis magnetic tube tests for characterization of the Per Geijer ore types 66 6.3 Separation analysis based on the Henry-Reinhard charts .……………... 67 7 RESULTS OF COMMINUTION OF ORE TYPES ……………………… 69 7.1 General characteristics of magnetite-dominated ore types ……………… 69 7.2 General characteristics of hematite-dominated ore types ……………… 72 7.3 General characteristics of magnetite/hematite-mixed ore types ……… 75 7.4 General characteristics of low-grade ore types ……………………… 77 7.5 Mineral liberation characteristics of magnetite-dominated ore types 79 7.6 Mineral liberation characteristics of hematite-dominated ore types 83 7.7 Mineral liberation characteristics of magnetite/hematite-mixed ore types 87 7.8 Mineral liberation characteristics of low-grade ore types ……………… 90 7.9 Total energy consumption of ore types from the Per Geijer deposits 94 8 RESULTS OF MAGNETIC SEPARATION OF ORE TYPES ……… 95 8.1 Magnetic separation of magnetite-dominated ore types ……………… 95 8.2 Magnetic separation of hematite-dominated ore types ……………… 96 8.3 Magnetic separation of magnetite/hematite-mixed ore types ……………… 97 8.4 Magnetic separation of low-grade ore types ……………………………… 98 8.5 Henry-Reinhard charts ……………………………………………… 99 9 DISCUSSION ……………………………………………………… 101 9.1 Mineralogy of the in-situ ore types from the Per Geijer deposits ……… 101 9.2 Geochemistry of the in-situ ore types from the Per Geijer deposits ……… 103 9.3 Mineral chemistry of iron oxides from the Per Geijer deposits ……… 105 9.4 Mineral chemistry of apatite from the Per Geijer deposits ……………… 114 9.5 Comminution of ore types from Per Geijer ……………………… 119 9.6 Magnetic separation of ore types from Per Geijer ……………………… 120 9.7 Issues with process mineralogy of in-situ and grinded ore types ……… 121 10 CONCLUSIONS ……………………………………………………… 128 11 IMPLICATIONS FOR FUTURE WORK ……………………………… 131 12 REFERENCES ……………………………………………………………… 134

The advent of unoccupied aerial systems (UAS) as disruptive technology has a lasting impact on remote sensing, geophysics and most geosciences. Small, lightweight, and low-cost UAS enable researchers and surveyors to acquire earth observation data in higher spatial and spectral resolution as compared to airborne and satellite data. UAS-based applications range from rapid topographic mapping using photogrammetric techniques to hyperspectral and geophysical measurements of surface and subsurface geology. UAS surveys contribute to identifying metal deposits, monitoring of mine sites and can reveal arising environmental issues associated with mining. Further, affordable UAS technology will boost exploration data availability and expertise in the global south. This thesis investigates the application of UAS-based multi-sensor data for mineral exploration, in particular the integration of hyperspectral imagers, magnetometers and digital cameras (covering the visible red, green, blue light spectrum). UAS-based research is maturing, however the aforementioned methods are not unified effectively. RGB-based photogrammetry is used to investigate topography and surface texture. Image spectrometers measure mineral-specific surface signatures. Magnetometers detect geomagnetic field changes caused by magnetic minerals at surface and depth. The integration of such UAS sensor-based methods in this thesis augments exploration potential with non-invasive, high-resolution, safe, rapid and practical survey methods. UAS-based surveying acquired, processed and integrated data from three distinct test sites. The sites are located in Finland (Fe-Ti-V at Otanmäki; apatite at Siilinjärvi) and Greenland (Ni-Cu-PGE at Qullissat, Disko Island) and were chosen as geologically diverse areas in subarctic to arctic environments. Restricted accessibility, unfavourable atmospheric conditions, dark rocks, debris and vegetation cover and low solar illumination were common features. While the topography in Finland was moderately flat, a steep landscape challenged the Greenland field work. These restraints meant that acquisitions varied from site to site and how data was integrated and interpreted is dependent on the commodity of interest. Iron-based spectral absorption and magnetic mineral response were detected using hyperspectral and magnetic surveying in Otanmäki. Multi-sensor-based image feature detection and classification combined with magnetic forward modelling enabled seamless geologic mapping in Siilinjärvi. Detailed magnetic inversion and multispectral photogrammetry led to the construction of a comprehensive 3D model of magmatic exploration targets in Greenland. Ground truth at different intensity was employed to verify UAS-based data interpretations during all case studies. Laboratory analysis was applied when deemed necessary to acquire geologic-mineralogic validation (e.g., X-ray diffraction and optical microscopy for mineral identification to establish lithologic domains, magnetic susceptibility measurements for subsurface modelling), for example for trace amounts of magnetite in carbonatite (Siilinjärvi) and native iron occurrence in basalt (Qullissat). Technical achievements were the integration of a multicopter-based prototype fluxgate-magnetometer data from different survey altitudes with ground truth, and a feasibility study with a high-speed multispectral image system for fixed-wing UAS. The employed case studies transfer the experiences made towards general recommendations for UAS application-based multi-sensor integration. This thesis highlights the feasibility of UAS-based surveying at target scale (1–50 km2) and solidifies versatile survey approaches for multi-sensor integration. / Ziel dieser Arbeit war es, das Potenzial einer Drohnen-basierten Mineralexploration mit Multisensor-Datenintegration unter Verwendung optisch-spektroskopischer und magnetischer Methoden zu untersuchen, um u. a. übertragbare Arbeitsabläufe zu erstellen. Die untersuchte Literatur legt nahe, dass Drohnen-basierte Bildspektroskopie und magnetische Sensoren ein ausgereiftes technologisches Niveau erreichen und erhebliches Potenzial für die Anwendungsentwicklung bieten, aber es noch keine ausreichende Synergie von hyperspektralen und magnetischen Methoden gibt. Diese Arbeit umfasste drei Fallstudien, bei denen die Drohnengestützte Vermessung von geologischen Zielen in subarktischen bis arktischen Regionen angewendet wurde. Eine Kombination von Drohnen-Technologie mit RGB, Multi- und Hyperspektralkameras und Magnetometern ist vorteilhaft und schuf die Grundlage für eine integrierte Modellierung in den Fallstudien. Die Untersuchungen wurden in einem Gelände mit flacher und zerklüfteter Topografie, verdeckten Zielen und unter oft schlechten Lichtverhältnissen durchgeführt. Unter diesen Bedingungen war es das Ziel, die Anwendbarkeit von Drohnen-basierten Multisensordaten in verschiedenen Explorationsumgebungen zu bewerten. Hochauflösende Oberflächenbilder und Untergrundinformationen aus der Magnetik wurden fusioniert und gemeinsam interpretiert, dabei war eine selektive Gesteinsprobennahme und Analyse ein wesentlicher Bestandteil dieser Arbeit und für die Validierung notwendig. Für eine Eisenerzlagerstätte wurde eine einfache Ressourcenschätzung durchgeführt, indem Magnetik, bildspektroskopisch-basierte Indizes und 2D-Strukturinterpretation integriert wurden. Fotogrammetrische 3D-Modellierung, magnetisches forward-modelling und hyperspektrale Klassifizierungen wurden für eine Karbonatit-Intrusion angewendet, um einen kompletten Explorationsabschnitt zu erfassen. Eine Vektorinversion von magnetischen Daten von Disko Island, Grönland, wurden genutzt, um großräumige 3D-Modelle von undifferenzierten Erdrutschblöcken zu erstellen, sowie diese zu identifizieren und zu vermessen. Die integrierte spektrale und magnetische Kartierung in komplexen Gebieten verbesserte die Erkennungsrate und räumliche Auflösung von Erkundungszielen und reduzierte Zeit, Aufwand und benötigtes Probenmaterial für eine komplexe Interpretation. Der Prototyp einer Multispektralkamera, gebaut für eine Starrflügler-Drohne für die schnelle Vermessung, wurde entwickelt, erfolgreich getestet und zum Teil ausgewertet. Die vorgelegte Arbeit zeigt die Vorteile und Potenziale von Multisensor-Drohnen als praktisches, leichtes, sicheres, schnelles und komfortabel einsetzbares geowissenschaftliches Werkzeug, um digitale Modelle für präzise Rohstofferkundung und geologische Kartierung zu erstellen.