UNIVERSITY OF GOTHENBURG Department of Earth Sciences Geovetarcentrum/Earth Science Centre

Footwall porphyry nodules

of the Kiirunavaara and

Luossavaara apatite-iron ores:

Mineralogy and mineral

chemistry of magnetite,

amphibole and mica

Puck Palm

ISSN 1400-3821 B849 Bachelor of Science thesis Göteborg 2015

Mailing address Address Telephone Telefax Geovetarcentrum Geovetarcentrum Geovetarcentrum 031-786 19 56 031-786 19 86 Göteborg University S 405 30 Göteborg Guldhedsgatan 5A S-405 30 Göteborg SWEDEN Abstract

Kiirunavaara is one of the world’s largest known iron ore deposits and represents the type area of what has come to be called AIO (Apatite-Iron Ore) or Kiruna-type ore deposits. The footwall of the Kirunavaara and smaller Luossavaara ores consists mainly of porphyritic rocks of which the top-most part carries nodules – often rounded in shape, containing minerals of larger grain sizes than in the matrix and mostly holding several different types of minerals. The footwall porphyry is not only a potential low grade ore in itself as it is often rich in magnetite but may also be of importance for understanding of the genesis of the Kiruna ores. The footwall porphyry nodules thus comprise a relevant area of study within the ongoing debate on the origin of the Kiruna ores. In this study, the overall mineralogy, textures and microstructures of the nodules have been documented and the mineral chemistry of representative nodule magnetites, amphiboles and micas have been analysed. Magnetites were studied with regard to minor and trace element chemistry, amphiboles primarily with regard to the major elements and micas were analysed mainly for the purpose of classification. Finally, the mineral chemistry composition of the nodule magnetites, amphiboles and micas were compared to data from the Kiirunavaara ore body. This investigation has found that a descriptive classification of nodular porphyry based on colour may be useful as the “red”, “dark” and “white-pink” groups appear to represent slightly different mineral assemblages and microstructures in nodules. Mineral chemistry results from the nodules show a similarity to data from the Kiirunavaara and other AIO ore deposits and may indicate a cogenetic origin of the footwall porphyry nodules and the Kiruna ore bodies.

2

Index

Abstract ______2 1.0 INTRODUCTION ______4 2.0 BACKGROUND ______5 2.1 Regional geology ______6 2.2 Characteristics of the Kiirunavaara-Luossvaara ores and the nodular porphyry of their footwall ______7 2.3 The debate on the connection of the Porphyry Group to the Kiirunavaara-Luossavaara ore bodies and their genesis ______9 3.0 METHODS ______11 3.1 Selection of samples ______11 3.2 Microscopical description ______12 3.3 SEM-EDS ______12 3.4 LA-ICPMS ______13 3.5 Presentation of data ______13 4.0 RESULTS ______15 4.1 Macroscopic and microscopic description ______15 4.1.1 Red nodular porphyries ______17 4.1.2 Dark nodular porphyries ______21 4.1.3 White-pink nodular porphyries ______25 4.2 Mineral chemistry ______28 4.2.1 Magnetite ______28 4.2.3 Dark mica ______40 5.0 DISCUSSION ______42 5.1 Macroscopic and microscopic characteristics of the nodular porphyry ______42 5.2 Minor and trace element chemistry of nodule magnetite ______42 5.3 Mineral chemistry of nodule amphibole and mica ______44 6.0 CONCLUSIONS ______45 6.0 ACKNOWLEDGEMENTS ______46 7.0 REFERENCES ______47 APPENDIX I – SAMPLE IMAGES

3

1.0 INTRODUCTION

Northern Norrbotten is a region known for its wealth of iron and copper deposits. Comprising more than 2000 megatonnes of ore, Kiirunavaara is one of the world’s largest known iron ore deposits. The deposit represents the type area of what has come to be called AIO (Apatite-Iron Ore) or Kiruna-type ore deposits. These are apatite-iron ores with an iron content of 30-70 % and a phosphorous content of 0,05-5 %. There are about 40 smaller apatite-iron ore deposits in northern Norrbotten (Bergman et al., 2001). The Kiirunavaara outcrop was discovered in 1696 and mining operations commenced in 1900. This tabular ore body reaches a depth of at least 1890 metres from the former top of Kiirunavaara, is 50- 150 metres thick and 4-5 kilometres in length (LKAB, personal communication). The smaller Luossavaara ore body is situated in the same stratigraphic position to the north of Kiirunavaara. Today, the Luossavaara-Kiirunavaara (LK) ores and the apatite-iron ore deposits at Malmberget and Gruvberget are mined by LKAB, which contributes 90 percent of the iron ore production of Western Europe (LKAB). The apatite-iron ores usually occur within rocks of the so called Porphyry or Porphyrite Groups (Bergman et al., 2001). The footwall of the LK ores consists mainly of porphyritic rocks that were probably originally trachyandesitic lavas. The top-most part closest to the LK ore bodies carries nodules – often rounded in shape, containing minerals of larger grain sizes than in the matrix and mostly holding several different types of minerals (e.g. Geijer, 1910; Andersson, 2013). These nodule- carrying porphyry rocks are intimately associated with the ore bodies and often occur in direct contact with the ore itself or with a zone of magnetite dominated slivers and veins in between. The footwall porphyry is not only a potential low grade ore in itself as it is often rich in magnetite but may also be of importance for understanding of the genesis of the Kiruna ores. The origin of these nodules, as well as that of the ore bodies, is still incompletely understood. The dominant silicate in the ore is actinolite (Nordstrand, 2012; Nordstrand and Andersson, 2013). Actinolite is also a common mineral in the nodules of the footwall, as is magnetite. There may be a connection between the origin of the ore and that of these nodules (Lundberg and Smellie, 1979; Andersson, 2013), and the composition of the latter is thus a relevant area of study within the ongoing debate on the origin of the Kiruna ores. The nature of some aspects of these unusual footwall nodules is therefore the focus of this study. The general aim to examine the characteristics of the nodules is delimited in this study into an aim that is fourfold: 1. First, to document the overall mineralogy, textures and microstructures of the nodules and observe how these parameters vary between different types of nodular porphyry. 2. Secondly, to study the mineral chemistry of amphiboles in terms of primarily the major elements in representative nodules. Micas will also be analysed for the purpose of classification. 3. Thirdly, to study the minor and trace element chemistry of nodule magnetite grains. 4. Fourthly, the mineral chemistry composition of the nodule amphiboles, micas and magnetites will be compared to data from the ore body itself.

4

2.0 BACKGROUND

Figure 1. Geological map of the Kiruna area. Modified from Forsell and Parák (1972).

5

2.1 Regional geology

The rocks of the Kiruna area are part of the Fennoscandian Shield, which has a complex geological history comprising a variety of tectonic and metamorphic episodes that have created a diversity of rock types. The Archean basement rocks, consisting primarily of granitoids and found in outcrop north of Kiruna, are thought to have different magmatic origins related to oceanic and later more continental arc-settings (Bergman et al., 2001). These rocks range in age between 2.83 to 2.7 Ga. (Martinsson, 2004). They used to be part of the Archean craton which broke up around 2.45-2.1 Ga, resulting in an ocean and the formation of a passive margin (Storey et al., 2007). Overlying the Archean basement is a Paleoproterozoic series beginning at the bottom with a 2.5 to 2.0 Ga Karelian unit starting with the rift-related Kovo Group; a basal quartzite and conglomerate overlain by andesitic and basaltic volcanic rocks and volcaniclastic sediments. A second rifting event around 2.1 Ga produced the overlying Kiruna Greenstone Group comprising a few kilometres of basalts, tuffites and intercalations of evaporites, graphitic schist and carbonate rocks as well as MOR- type pillow lava (Martinsson, 2004). The Kurravaara conglomerate, also of MORB origin, marks the first Svecofennian unit1. Subduction of the oceanic crust subsequently commenced and a juvenile arc system was established around 1.94 Ga (Storey et al, 2007). Subduction magmatism produced the arc-related rocks and sediments of the Porphyrite Group (Martinsson, 2004). Overlying these rocks is the Kiirunavaara Group, most often called the Porphyry Group; a group of felsic to intermediate rocks that includes the here studied porphyries. This group is described further in the coming sections. Renewed subduction led to the accretion of the arc system to the Archaean craton throughout about 1.9-1.8 Ga in the Svecokarelian orogeny (Storey at al. 2007). The Svecofennian Porphyrite and Porphyry Groups host AIO ore bodies (Storey et al., 2007). Finally, at the top of the pile lies the youngest member of the Svecofennian unit, the Hauki Quartzite, produced during uplift and erosion (Martinsson, 2004). The rocks of northern Norrbotten are characterized by regional metasomatic alteration in the form of albitisation, indicating alkali metasomatism, and scapolitisation. These alterations occur in relation with the apatite-iron ores. The alterations originate from highly saline hydrothermal fluids that may have also been ore-forming. (Frietsch et al., 1997; Smith et al., 2009, 2013; Billström et al., 2010). This is discussed further in section 2.3.

1 Svecofennian here refers to the supracrustal rock sequence while Svecokarelian refers to the orogenic period in accordance with Storey et al. (2007). 6

2.2 Characteristics of the Kiirunavaara-Luossvaara ores and the nodular porphyry of their footwall

2.2.1 The Kiirunavaara-Luossvaara ores

The LK ore bodies consist dominantly of magnetite but other deposits also include more hematite (Martinsson, 2004). Characteristic of the AIO deposits is a low content of titanium (0.04-0.31 %) and a high content of vanadium (317-2310 ppm). Cobalt and nickel levels have been noted to be higher than for skarn-rich magnetite deposits. The apatite-iron ores are enriched in rare earth elements (REE) and in light rare earth elements (LREE) in particular (Bergman et al., 2001). Apatite-iron ore deposits are characterized by higher Ti and V than for example IOCG deposits as well as by relatively low Mn and Al (Dupuis and Beaudoin, 2011). The Kiirunavaara ore shows a bimodal phosphorous distribution with content either above 1.0 % (D- ore) or below 0.05 % (B-ore). The latter apatite-poor ore is closest to the footwall and contains up to 15 % actinolite along this border, but there is also some D-ore in this part (Bergman et al., 2001).

The apatite-iron ores are either of a breccia, a stratiform-stratabound, or a mixed variety. The LK deposit belongs to the group with mixed characteristics. The Kiruna deposits are stratabound with ore breccia along contacts with the wallrocks (Bergman et al., 2001).

2.2.2 The nodular porphyry of the footwall

The footwall porphyry closest to the ore is often characterized by its nodules. These nodules are in turn characterized by their often rounded shape and by the larger grain size of their minerals compared to the matrix (Geijer, 1910; Andersson, 2013). Each nodule often contains several minerals. The genetically neutral term ‘nodule’ is preferable to’ amygdule’ as the term ‘amygdule’ implies a genetic interpretation (bubbles in magma) and can therefore be considered to be inapproprate as the genesis of the nodules has not yet been determined. Also the term ‘glomerocryst’, defined as aggregates of phenocrysts, implies a genetic, magmatic, origin (Barker, 1998). Nodules are often oriented in a texture indicating flow or compaction and occuring in association with a network of extensive ore veins (Andersson, 2013). It has not been determined to what extent the different mineral phases in these nodules are primary or represent secondary alteration.

Figure 2. Magnetite- dominated nodules in Kiirunavaara footwall porphyry (Andersson, 2013).

The footwall belongs to the Porphyry Group, which has been called “syenite porphyry” or the Hopukka Formation (Geijer, 1910; Martinsson, 2004). It is comprised of intermediate volcanic rocks that were most likely emplaced as trachyandesite lava but have undergone extensive hydrothermal alteration. These lava flows now make up a sequence that is 300 to 1400 meters thick, consisting of layers in the range of 5-20 meters in thickness. In addition to the volcanic flow structure there are

7 also other volcanic structural features, including lava domes and beds of pyroclastic material in the bottom of the sequence (Martinsson, 2004). Veins of magnetite and titanite cut through the footwall. Both the footwall and hanging wall contain magnetite-actinolite breccia along their contacts with the ore (Bergman et al., 2001). The porphyry is supposed to have been exposed to lower amphibolite and upper greenschist, i.e. low to medium-grade, metamorphic conditions, accompanying the intrusion into the Kiirunavaara Group of the Haparanda, Perthite Monzonite and Lina suites between 1.9 to 1.79 Ga (Smith et al., 2009). However, Berglund and Andersson (2013; 2014) suggest that the ore body and its immediate surroundings have experienced no regional metamorphism, based on the presence of clay of the same age as the ore body. Geijer (1910) divides the Kiirunavaara footwall into three categories with the end members syenite and syenite-porphyries and with “fine-grained, porphyritic syenite” as an intermediate category. These categories grade into each other from medium-grained syenite in the western part of the mountain to syenite-porphyries towards the east. The latter are fine-grained and characterized by carrying nodules. The syenite-porphyries dominate to the west of the ore, i.e. its footwall.

The syenite-porphyries are further divided into two major types by Geijer (1910), namely a group with a grey matrix and one with a pink matrix. These groups are the “dark” and “red” colour groups in this study (see methods section), and varieties especially rich in magnetite and in apatite respectively, occurring as schlieren, are further discussed by Geijer.

Geijer (1910) reports that, in the grey kind, “amygdule-like” nodules are common and contain amphibole, titanite, magnetite, apatite and biotite, in that order of abundances. These also occur in fissures. Further noted by Geijer are pink areas or rings of a minimum of 1 mm in thickness that generally surround the nodules and also fissures. These are however not present in all parts of the grey group, particularly not where nodules of titanite and biotite dominate. Geijer holds this sort of pink areas merged together as the reason for the colour of the other major group of syenite- porphyry, namely the pink group. This group is rarer than the grey type but has a larger amount of nodules, generally modally making out about a third of the volume. Amphibole, apatite and titanite are the dominant nodular minerals. The pink category occurs as schlieren and irregular areas within the grey category.

At Luossavaara, syenite-porphyry occurs with grey, dark grey (rich in magnetite), greyish green or reddish colour and with nodules containing magnetite, titanite and feldspars, and containing few dark silicates (Geijer, 1910). This group is called the “white-pink“ colour group in this study.

Differing from the footwall porphyry, the hanging wall of the LK ore is the so called “quartz porphyry”, also named the Luossavaara Formation. The hanging-wall rocks are of rhyodacitic composition and are primarily pyroclastic deposits with porphyritic tuff-lapilli tuff as their major constituent (Geijer, 1910; Martinsson, 2004). Dikes of rock similar to that of the hanging-wall porphyry occur in the footwall and in the ore, possibly representing feeder dikes for the hanging wall volcanism, thereby explaining the common presence of footwall rocks as well as ore in the hanging wall (Andersson, 2013). The hanging wall rocks do not carry nodules.

8

2.3 The debate on the connection of the Porphyry Group to the Kiirunavaara-Luossavaara ore bodies and their genesis

The tectonic environment in which the Kiirunavaara Group was emplaced has not yet been determined, as the chemical signatures are dubious. Its bimodal character, with basaltic lava flows intercalated throughout the sequence of intermediate to more felsic lavas, as well as the chemistry of the mafic and felsic parts respectively have prompted the suggestion that they are a sequence of flood-basalts (Martinsson, 2004). In such a scenario, the felsic rocks of the pile would then be the result of crustal melting. Another suggested origin is emplacement through alkaline and intermediate magmatism during basin inversion and uplift or during early arc-related extension, i.e. at a time preceeding the accretion of the Svecokarelian orogeny (Storey et al. 2007). A suggested minimum age for the Kiirunavaara Group is 1880 ± 3 Ma (Bergman et al., 2001; Martinsson, 2004; Romer et al., 1994). Storey et al., however, argue against an emplacement about 1.96-1.88 Ga (Storey et al., 2007; Smith et al., 2009. See e.g. Storey et al. 2007 for an overview of previous dating attempts). Rather, Storey at al. argue that the Kiirunavaara Group (i.e. Porphyry Group) is at least 2.1 Ga old, as suggested by dating of zoned titanite grain cores. This volcanism would then have occurred during the closing stages of the emplacement of the basic Greenstone Group. This has been contradicted by Westhues et al. (2014). Storey et al. (2007) argue in favour of a major resetting event at around 1.9-1.8 Ga, as represented by the rims of the zoned titanite grains. In this model, the resetting event would be due to metamorphism brought on by hydrothermal fluid flow and intrusion-related heat linked to the Svecokarelian orogeny. At this time, the apatite-iron deposits would also have formed and may then be related to this event. This metamorphic period further overlaps the intrusion into the Kiirunavaara Group of the Haparanda, Perthite Monzonite and Lina suites between 1.9 to 1.79 Ga (Smith et al., 2009), of which the Perthite Monzonite is comagmatic with the Kiirunavaara Group (Martinsson, 2004). Smith et al. (2009) suggest an ore age synchrous to that of the titanite rims of 1870 +/-24 Ma. The origin of apatite-iron oxide deposits is a subject of continuous debate. Magmatic, sedimentary and hydrothermal origins have been suggested (see for example Bergman et al., 2001, or Storey et al., 2007, for an overview of the debate). The massive structure of the Kiirunavaara ore body and textural features reminiscent of igneous flows, dikes and pyroclastic deposits are suggestive of an igneous origin by the intrusion of a magma unusually rich in Fe (e.g. Geijer, 1931; Frietsch 1978; Nyström, 1985). Others suggest a magmatic-hydrothermal origin by means of exhalative deposition by late-stage magmatic fluids. Sedimentary features such as graded and cross-bedding as well as the upward gradation into quartz-banded ore have been observed in the ore by Parák (1975), who suggested a marine volcanic exhalative-sedimentary origin. However, apatite-iron ores are characterised by a high V content relative to that of sedimentary iron ores (Müller et al., 2003). Finally, proponents of a strictly hydrothermal origin suggest metasomatic replacement or deposition by hydrothermal fluids (Smith et al, 2009, 2013; Storey et al., 2007). Likely, both magmatic and hydrothermal processes may have played various roles at different AIO deposits (Martinsson, 2004). In any case, there is consensus that highly saline hydrothermal fluids must have been present. It has been suggested that magnetite in the nodules of the footwall porphyry in fact represents droplets of a Fe,P-rich magma, separated with a silicate-rich magma from an original magma due to liquid immiscibility as it approached the Earth’s surface (Andersson, 2013). As shown experimentally by Lledo (2005) such a Fe,P-rich melt can remain liquid down a temperature of approximately 600o C. Actinolite is one of the most common minerals in Kiruna-type ore deposits. It is representative of the greenshist metamorphic facies. It generally occurs as metamorphic conversion of hornblende or pyroxene under greenschist-facies conditions at subsolidus (Deer et al., 1992). However, Lledo and

9

Jenkins (2008) argue that actinolite could have an igneous origin in Kiruna-type ore deposits. According to the experimental investigation of the thermal stability of Mg-rich actinolite with Fe- numbers in the range of 0-0.4 (i.e. most natural tremolites and actinolites) the high thermal stability of up to 750 and 900 oC overlaps the conditions of experimental Fe-P-rich melt formation as well as the range of water-saturated melting of most andesites and tonalites, thus indicating that such actinolites in Kiruna-type ore deposits may have an igneous origin. (Lledo and Jenkins., 2008). Nordstrand and Andersson (2013) have suggested an evolution from a magmatic system above 800oC o to a hydrothermal system, rich in Cl, S and CO2, below 600 C to explain the gangue mineral assemblage within the ore, which - just as the nodules - is dominated by calcic amphibole and include titanite, mica, chlorite, apatite, carbonates, talc and sulphates, and also allanite. In this development actinolite was part of the initial igneous stage together with magnetite, apatite and F-rich phlogopite, crystallising at below 900o C. The regional albitisation and scapolitisation occuring in relation with the ores in the Kiruna area and many other iron-oxide deposits (Barton and Johnston, 1996) originate from the circulation of highly saline hydrothermal solutions, which may or may not have been ore-forming. The Na and Cl of these fluids may have been reaped from the evaporites at the bottom of the Greenstone Group. In addition to the presence of such evaporites, the presence of major 1.9 to 1.8 Ga deformation zones that could have channelled fluids may also be related to the genesis of the apatite-iron ores in the region (Frietsch et al., 1997; Martinsson, 2004). S-poor brines from evaporite deposits would cause siderophile and lithophile element enrichment and hydrothermal sodic (albite + scapolite + hornblende) to alkaline alteration (Barton and Johnston, 1996). Barton and Johnston have noted that many iron-oxide rich deposits, in contrast to e.g. porphyry and skarn deposits, have evaporitic associations in common, while ages and tectonic environments as well as the types of igneous host rocks are highly variable, i.e. that it is nonmagmatic controls that matter. Chloride is necessary to enable metal transport and, together with Na, make fluids more oxidized and relatively more poor in sulfur (Barton and Johnston, 1996). Large volumes of Na would have been required to produce the vast volumes of albitization that Barton and Johnston claim to be present in the Kiruna area. Smith et al. suggest that these hydrothermal fluids were mobilized during the subduction and subsequent continental accretion of the Svecokarelian orogeny. As mentioned above, the suggested age for the iron-oxide apatite ore deposits of between 1.92 to 1.86 Ga overlaps the suggested, but not confirmed, period of regional sodic alteration and also is synchrous with ages for titanite rims in the porphyry. (Smith et al. 2009).

10

3.0 METHODS

3.1 Selection of samples

18 hand samples and 18 thin sections, 50 µm in thickness, were provided by LKAB. These samples have been taken from different parts of the footwall nodular porphyry as either pieces from blasting in the mines or as samples of drill cores (Table 1). The selection was made so that samples of different colours as observed by Geijer (1910) would be represented. Different colours appear in different parts of the rock mass. Geijer observed several different colours with the dominant ones being “grey” and “pink”. These will here be called “red nodular porphyry” and “dark nodular porphyry”. Additionally, “white-pink nodular porphyry” is included here, corresponding to the nodular porphyry from Luossavaara described by Geijer as dominated by feldspars and magnetite and containing few dark silicates. All samples were examined and described macroscopically and microscopically in terms of the overall mineralogy, texture and microstructures. The term “texture” is used here to refer to arrangements of grains which have a preferred orientation while “microstructure” is used for all other microscopic relationships between grains (Barker, 1998). Hand samples were photographed in dry condition to document their overall appearance. Five nodules from five different samples were then studied further in terms of amphibole and mica major element chemistry using a Scanning Electron Microscope with an Energy-Dispersive X-ray Spectrometer (SEM-EDS) and in terms of minor and trace elements of magnetite grains using a Laser Ablation - Inductively Coupled Plasma - Mass Spectrometer (LA-ICP-MS). It was decided that one representative nodule from each sample could be chosen as a systematic mineralogy in each sample was observed during initial microscopy. Nodules were chosen from two thin-sections of the “red nodular porphyry” and “dark nodular porphyry”, respectively, and from one thin-section of the “white-pink porphyry”. Nodules were selected on grounds of having the most distinct nodular shapes; comprehensively hosting the representative mineral phases of nodules in that sample, and, where possible, containing magnetite grains that looked euhedral to subhedral under the microscope. For the LA-ICP-MS analysis an additional sample was chosen from the white-pink category in order to analyse a magnetite vein for comparison with the nodules.

Table 1. Sample localities.

Sample localities Sample name Area Grid reference (LKAB Kirunavaara grid or SWEREF 99 TM) Red nodular porphyry: RMP1 Kirunavaara X6675,Y3995,Z1332 RMP2 Kirunavaara X6590,Y3850,Z1252 RMP3 Kirunavaara X6350,Y2605,Z1365 Kii2a Kirunavaara Open pit mine, N7531926 E718165 8053-Bh2 (223) Kirunavaara X6430,Y2220,Z1327 LUO5 Luossavaara Open pit mine, N7537750 E719300 KL8a Kirunavaara X6354,Y1570,Z1365 KL38 Kirunavaara X6355,Y4131,Z1074 Dark nodular porphyry: MMP1 Kirunavaara X6292,Y1580,Z1253 MMP2 Kirunavaara X6025,Y2005,Z1367 Kii1a Kirunavaara Top, N7538250 E715650 LUO4 Luossavaara Top, N7538250 E719500 6619 Kirunavaara X6223,Y1048,Z1113 6481 Kirunavaara X6393,Y2284,Z1154 KL8b Kirunavaara X6360,Y1570,Z1365 KL16 Kirunavaara X5687,Y1091,Z992 White-pink nodular porphyry: 6207 B Kirunavaara X6600,Y3937,Z1166 LUO 6 Luossavaara Open pit mine, N7537750 E719250 11

3.2 Microscopical description

Thin sections were examined using a petrographic microscope, primarily using transmitted light, although reflected light was used to photograph representative opaque phases. Thin sections were scanned with a resolution of 3200 or 4800 dpi. The overall nodule mineralogy, textures and microstructures were examined. As microscopic descriptions of nodules have been done meticulously by Geijer (1910), only the most relevant microscopical descriptions will be reported here.

3.3 SEM-EDS

Using a Scanning Electron Microscope with an Energy-Dispersive X-ray Spectrometer, the identity of the most generally occuring mineral phases were confirmed and amphiboles and micas were studied more in-depth in terms of primarily the major elements (Si, Al, Fe, Mg, Ca, Na, K) and also Mn and Ti. Livetime was set to 100 seconds for the amphiboles and to 40 seconds for the mica, as the latter analyses were conducted primarily for the purpose of classification. The selected thin sections were first carbon coated using a Bal-Tec carbon thread evaporator CED 030 to make them electrically conductive and grounded so that electrostatic charge would not accumulate at the insulating surface during SEM analysis. The selected nodules were then analysed using a Hitachi S-3400N SEM operated at a current of 20 eV and an Oxford Instruments X-MaxN EDS at Gothenburg university. The matrices of each sample were also examined superficially through testing of a single site for reference. EDS is used for qualitative and quantitative analysis of the abundance of specific elements by analysing the energy spectrum of X-rays emitted from the sample as it is hit by the primary electron beam of the SEM. This X-ray spectrometer can measure several elements simultaneously and the elemental energy peak height it produces has an approximately linear correlation with concentration so that mineral phases can be deducted. Results from SEM-EDS can be given in weight, atomic or compound percent. Backscattered electron (BSE) photographs were taken of grains of interest to document nodule characteristics. The BSE detector takes measurements as the high-energy electrons of the SEM electron beam are reflected, i.e. backscattered, in ways particular to the different chemical compositions in the sample. In BSE images, high atomic-density mineral phases appear brighter as elements with high atomic numbers backscatter electrons more strongly than those with low atomic numbers. Limitations of the EDS include the inability to detect elements with atomic numbers lower than C and a limited ability to detect elements with atomic numbers lower than Na. Moreover, there are overlaps between the energy peaks of certain elements. The SEM-EDS thus has several weaknesses when it comes to the analysis of the chemical composition of amphiboles and also micas (Locock, 2014; Rieder et al., 1998). First, it is unable to accurately distinguish the light elements that are included in amphibole classification, namely Li and H. Second, the SEM-EDS does not measure the oxidation state of iron or manganese. In order to classify amphiboles, their ferric and ferrous iron contents have instead been calculated by running the data from the SEM-EDS in the classification spreadsheet by Locock (2014).

12

3.4 LA-ICPMS

Minor and trace element analysis using Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry was undertaken on magnetite grains within the selected nodules, targeting euhedral to subhedral grains where possible. Analyses were conducted using the recently installed Agilent Technologies 8800 ICP-MS Triple Quad fitted to a NWR 213 ESI Laser Ablation instrument after having cleaned samples in an ultrasonic bath. Analyses were conducted at single ablation spots of 50 µm (5 Hz and an energy density (fluence) of 4.4 J/cm2. SRM NBS 610 was used as the primary standard (values from Jochem et al., 2011). For this study, Fe was used as an internal standard for magnetites (Fe at 730 000 ppm). LA-ICP-MS is a combination of instruments – the Laser Ablation instrument; the Inductively Coupled Plasma source and the Mass Spectrometer - for the analysis of trace elements with very high precision. The limit of detection is < 1 ppm for most elements. In an ICP-MS, argon gas is put under the influence of an oscillating electromagnetic field at the ICP torch, which ionizes the argon atoms. These then collide with other atoms and form a plasma. The sample to be analysed is ablated by Laser Ablation, creating an aerosol that is first transported by helium gas and then mixed with the argon into the ICP-MS. Once inside, it is converted by the ICP torch into gaseous atoms that are ionized by the plasma. The Mass Spectrometer then separates and detects the ions present from their mass-to-charge ratio, amounting to a count. In this study the count was converted to ppm using the Glitter software. Benefits of laser ablation include a minimum of sample preparation as solid samples can be analysed directly with high spatial resolution. However, the analysis destroys the sampled spots. Weaknesses of the LA-ICP-MS include the inability to identify the gas used within the instrument (usually argon) as well as less reliability for anions (such as Cl and I among others) than for cations. The LA-ICP-MS cannot analyse elements that are poorly ionized in the plasma, namely H, C, N, O, S, F and the noble gases.

3.5 Presentation of data

Diagrams were produced to characterise the magnetite. These include deposit type discrimination diagrams for magnetite trace elements after Dupuis and Beaudoin (2011. See section 4.2.1 for explanation) and Ti versus V diagrams with added delimitor values from chemistry data from the Kiirunavaara ore body itself. Diagrams for individual trace elements were produced. Finally, data was normalised to bulk continental crust (Dare et al., 2012) and compared to data from the Blötberget IOA deposit (Hogmalm et al., personal communication, 2014) as well as the Kiirunavaara ore body (Saravanen, personal communication, 2014) in spider diagrams inspired by Dare et al. (2012). The ore body data of these two deposits has been measured in the same lab under the same conditions as the data of this study. Ore body data for comparison has also been taken from Dupuis and Beaudoin (2011). Amphiboles were classified in accordance with the nomenclature recommended by the International Mineralogical Association (Hawthorne et al., 2012; Locock, 2014). This classification establishes an amphibole supergroup with the general formula AB2C5T8O22W2, where A=□, Na, K, Ca, Pb, Li; B=Na, Ca, Mn2+, Fe2+, Mg, Li; C=Mg, Fe2+, Mn2+, Zn, Ni2+, Co2+, Fe3+, Mn3+, Cr3+, V3+, Sc, Al, Ti, Zr, Li; T=Si, Al, Ti4+, Be; and W=(OH), F, Cl, O2−. The supergroup is divided into one group where OH, F and Cl anions dominate at W and one group where O anions dominate at W. The former group is further divided into eight subgroups based on the cations at B. Finally, species names are determined using specified ranges of cation compositions at A and C.

13

The amphiboles were subsequently plotted in a Mg/(Mg/Fe2+) vs Si plot, in accordance with the older classification of Leake (1997).

The mineral chemistry data of the porphyry nodule amphiboles was also compared to data from the Kiirunavaara ore. The ore body mineral chemistry data for amphiboles used for comparison was taken from Nordstrand (2012), who has studied the mineral chemistry of gangue minerals using an electron microprobe. Mineral chemistry data of nodule mica was classed in a similar manner to the data from gangue micas in Nordstrand (2012), in order to allow comparison with the latter data. The classification of Nordstrand is inspired by Deer et al. (1992). A possible source of error in this study is exsolution lamellae affecting SEM-EDS and LA-ICP-MS results for mineral chemistry. An additional source of error includes a possible calibration offset of the SEM-EDS due to possible minor current fluctuations during calibration related to an old filament, of ~1% for the data for the sample LUO5 and of ~-3% for MMP1. This potential offset has however been deemed too small to significantly affect the results.

14

4.0 RESULTS

4.1 Macroscopic and microscopic description

The red nodular porphyry sampled generally has a red aphanitic matrix, although a more white-pink, fine-grained example (8053-Bh2 (223)) occurs. Also, Kii2a has a more grey-red colour. Nodules are dominated by actinolite, usually followed by titanite, in most samples. However, one sample instead has nodules dominated by magnetite (LUO5). Magnetite occurs in nodules in all samples in varying amounts but is very sparse in some. Other minor phases include quartz, gypsym/anhydrite, feldspar, calcite, biotite and possibly apatite. Minor chalcopyrite was observed in one hand sample. Apart from in one sample (38) matrices are more “clean” from tiny magnetite grains than those of the dark nodular porphyry. See also Lindgren (2013).

The dark nodular porphyry generally has a dark-grey aphanitic to fine-grained matrix but it can also be red-grey (MMP2), red-green (LUO4) and grey-red (6619). Nodules are generally dominated by either magnetite; actinolite-tremolite; biotite, most likely phlogopite; or a combination thereof. Titanite follows in abundance after the dominant minerals in most samples and there are also minor amounts of apatite, albite, biotite, quartz, chlorite and calcite. Minor pyrite was observed in one hand sample and allanite in one thin section. Matrices are strongly dominated by albite. LUO4 – a sample that is dominated by magnetite nodules lacks the sprinkling of tiny opaque grains common in the others.

In the white-pink nodular porphyry, matrix is white-pink and aphanitic to fine-grained. Microstructures in the two samples are more chaotic than in the other colour group samples, with veins, cracks and what appears to be a compound of nodules occuring in thin sections. Magnetite, biotite or areas of small calcite and quartz grains dominate nodules and titanite follows in abundance. Actinolite-tremolite fills cracks in the rock and where nodules have broken apart in LUO6, but is lacking in the 6207B thin section. Veins of magnetite penetrate both hand samples.

Nodules vary greatly in size between samples and mostly also within samples regardless of group. Dominant features throughout all samples are the presence of pseudomorphs in the matrix and martitisation of magnetite grains. The pseudomorphs are often elongate and rectangular, most likely representing former feldspar phenocrysts. The original crystal has been replaced by small grains of similar composition as the matrix, i.e. primarily by albite and K-feldspar. Feldspars in earlier stages of alteration or none at all are also common. A textural orientation of elongate nodules is also very common, but not pervasive, throughout the samples. Finally, matrices of all samples are strongly albite-dominated.

15

Figure 3. Sample RMP1. Plane light. A feldspar pseudomorph in the matrix. Scale bar is 500 µm.

As appearing clearly in BSE, Kii2a, LUO5 and LUO4 have significantly martitised magnetite grains while MMP1 and 6207B have almost no martitisation. That is to say, both samples from the red nodular porphyry are significantly martitised, as are both samples from Luossavaara, including the only SEM-studied sample from the white-pink colour group. One sample from the dark nodular porphyry is significantly martitised while one is sparingly so.

Figures 4 and 5. Luo 5 (left) and Luo 4 (right). Backscattered electron images. Examples of martitisation. Brighter phase is unaltered magnetite; dark grey is secondary hematite.

16

4.1.1 Red nodular porphyries

RMP1

HAND SAMPLE: Green nodules sit densely in a red, aphanitic matrix. Nodules contain predominantly amphibole but titanite is also visible. Sizes are for the main part relatively small in the range of ~1 to 7 mm, but larger ones of up 26 mm occur. Nodules are often rounded and no clear orientation of more elongated nodules is visible in hand sample.

Figure 6. Hand sample. RMP1. Length of individual staples is 12 mm.

THIN SECTION: Nodule sizes vary between ~1.5 to 14 mm. Round and irregular nodules occur and there is an systematic textural orientation of elongate nodules. Nodules are dominated by actinolite- tremolite with titanite as the second most common mineral. Magnetite generally occurs sparingly in nodules and are then often relegated only to a small area. Nodules also contain minor amounts of gypsum/anhydrite and quartz, often around their edges. Here small holes are also found. These may have been occupied by softer minerals that were ablated during thin section preperation. Magnetites also occur freely in the matrix, as does actinolite-tremolite, and are then more irregular and broken apart. Larger elongate and smaller pseudomorphic feldspar grains are visible throughout the matrix. K-feldspar and albite dominate the matrix in equal amounts.

RMP2

HAND SAMPLE: Small to medium sized, up to 7 mm, rounded nodules sit in an aphanitic red matrix. One, 35 mm long, nodule also occurs in the sample. Nodules are dominated by amphibole and have minor magnetite. Larger K-feldspar crystals occur in the matrix.

THIN SECTION: Nodules are small relative to the other samples and occur relatively densely. Sizes vary from <0.1 to 0.6 cm in length and shapes are often rounded or sub-rounded. Elongated nodules do not appear to be oriented. Actinolite-tremolite dominate nodules, but there is also some titanite and what may be quartz. Magnetite occurs sparingly in nodules but more often together with titanite in pseudomorphic or altered feldspar grains, appearing in the matrix. They lack systematic orientation. The magnetites are generally anhedral and irregular. When occurring in nodules, magnetite grains are mostly small and placed along or the near edges. The matrix is fine-grained with a relatively sparse sprinkling of small magnetite grains. Some holes are present in areas outside of nodules.

17

RMP3

HAND SAMPLE: Small, up to 4 mm, often rounded nodules sit densely in a red aphanitic matrix. Nodules are dominated by amphibole. Feldspar mega-crystals, often elongate, are visible throughout the matrix.

THIN SECTION: Nodules, varying in length from <0.1 to 0.7 cm, sit in a matrix free from small magnetite grains. Nodules, rounded to elongate, without a systematic textural orientation. Actinolite-tremolite dominate the nodules. The second most common mineral is magnetite which occurs throughout nodules and sometimes has subhedral shapes. Some titanite also occurs in the nodules as well as calcite. Feldspar grains, intact to altered to pseudomorphic, occur throughout the matrix separately or as glomerocrysts.

Kii2a

HAND SAMPLE: Nodules sit in an aphanitic, grey-red matrix. They are small to large-sized, ranging up to 44 mm in length. The nodules are dominated by amphibole, followed by titanite. Shapes are round to elongate with a systematic orientation.

Figure 7. Hand sample. Kii2a. Length of individual staples is 12 mm.

THIN SECTION: Nodules, ~0.1 to 1 cm in length, are irregular to oval-shaped and show a common orientation along their axis of elongation. The dominant mineral in the nodules is actinolite- tremolite. There is also a smaller amount of zoned titanite and even smaller amounts of K-feldspar and quartz. Magnetite is sparse in the matrix and appear primarily within nodules, where they often appear to have euhedral shapes. The magnetites have hematite as small specks either along edges or throughout the crystal, most likely representing martitisation. The matrix consists of albite and K- feldspar and somewhat elongate pseudomorphs remain after previous feldspar mega-crystals.

18

Figure 8. Kii2a. Backscattered electron image. Magnetite (white) sitting in titanite (grey). Black areas are silicates in the surrounding nodule.

8053-Bh2 (223)

HAND SAMPLE: Small to large nodules sit in a white-pink, fine-grained matrix. Nodules are dominated by amphibole followed by titanite and are rounded to oval-shaped, possibly with a common orientation. Minor chalcopyrite was observed in the matrix. Figure 9. Hand sample. 8053-Bh2 (223). Length of individual staples is 12 mm.

THIN SECTION: Nodules are round to oval, <0.1 to 0.6 cm in length, with a possible common textural orientation. They are dominated by actinolite-tremolite but some consist almost exclusively of zoned titanite. There is also some calcite and quartz grains, primarily along the edges of the nodules. Magnetite grains in the nodules, if any, are very small and few. The matrix is very bright with a sparse sprinkling of small opaque grains, probably magnetite. Pseudomorphic as well as highly altered feldspar megacrysts are visible in the matrix. Any orientation of feldspar grains occuring in the matrix is hard to determine as elongate grains are few in the thin section.

19

LUO 5 HAND SAMPLE: Dark, elongated nodules with a clear common orientiation sit in a red, aphanitic matrix. Nodules are dominated by magnetite, followed by bright-green amphibole.

THIN SECTION: This sample is densely populated by smaller nodules, <0.1 to ~0.7 cm in length. Nodules are dominated by magnetite and only have other minerals as inclusions or in cracks in the nodules. Generally, nodules are oval in shape but round and irregular shapes also occur. There is a clear textural orientation of the nodules. Magnetites also occur outside of nodules and are then more irregular and less elongate in shape. Hematite specks are found throughout the magnetites, indicating martitisation. Titanite also occur within the magnetite, as do chlorite and biotite; the latter especially in cracks. In one magnetite, a rectangular area of matrix is visible. Actinolite-tremolite occurs as irregular-shaped grains roughly the same size as nodules and situated between them and also freely in the matrix. Holes are common throughout the thin section in areas outside of nodules and are often surrounded by K-feldspar, in one place growing inwards the hole, and quartz. One hole is hexagonal and may have contained an apatite that has been ablated. A hexagonal titanite sitting in a magnetite may be a pseudomorphic apatite crystal. Titanite occurs outside of nodules and is generally anhedral. Matrix consists of albite and K-feldspar. Pseudomorphic grain shapes and highly altered feldspar mega-crystals occur throughout. KL8a

HAND SAMPLE: Small, up to ~5 mm, rounded to elongate nodules sit in an aphanitic red matrix. There appears to be a common orientation of the nodules. Up to 9 mm elongate feldspar megacrysts occur throughout, possibly similarly oriented as the nodules.

THIN SECTION: Irregular, rounded to elongate nodules, <0.1 to ~0.7 cm in length, sit in a matrix which is mostly clean from visible small magnetite grains. Some elongate nodules appear to be oriented but it is not clear that there is a general orientation. Actinolite-tremolite dominates the nodules but there are also titanite and possibly biotite grains within them as well as minor quartz, calcite, and some allanite. Anhedral magnetite grains appear throughout nodules. Intact, altered to pseudomorphic feldspar grains are mostly tabular and sit separately or as glomerocrysts in the matrix. They lack apparent orientation. Holes occur in conjunction with nodules.

KL38

HAND SAMPLE: Small to medium sized nodules, up to 16 mm sit in a red aphanitic matrix. Nodules are dominated by amphibole. Nodules are round to elongate with no clear orientation.

THIN SECTION: Round to oval or elongate and irregular nodules of between < 0.1 to 0.9 cm in length are dominated by actinolite-tremolite, some with smaller magnetite grains along the rims. Small titanite and small amounts of quartz and some calcite are also found in the nodules. Pseudomorphic or highly altered feldspar megacrysts sit in the matrix, as well as occasional apatite. A hole with an empty seam running from it is found in the thin section. Nodules have a systematic orientation but the pseudomorphic feldspar megacrysts in the matrix do not. The matrix is sprinkled with small- grained magnetite.

20

4.1.2 Dark nodular porphyries MMP1 HAND SAMPLE: Nodules sit relatively sparsely in a dark-grey, aphanitic matrix. Nodules range in size from <1 to 20 mm. They are round to elongate and dominated by magnetite, although some nodules are dominated by amphibole. There is also some biotite. Feldspar mega-crystals occur throughout the sample.

Figure 10. Hand sample. MMP1. Length of individual staples is 12 mm.

THIN SECTION: Primarily oval, systematically oriented, nodules sit in a dark matrix but are surrounded by brighter rings. Nodule sizes vary from less than 1 mm to ~1.8 cm in length. Nodules are generally dominated by either biotite, magnetite, or actinolite-tremolite. In places, the magnetite appears to be zoned. Magnetites include a small amount of small hematite specks, primarily in the proximity of edges, that probably represent martitisation. There is also a varying but smaller amount of titanite in some. Within nodules there are also albite, K-feldspar and biotite. A very altered elongate pseudomorphic grain appears within an otherwise rather well-preserved nodule, with smaller grains of titanite, K-feldspar, albite and biotite within it, or in its direct vicinity. A pale hexagonal grain which may be secondary titanite as a pseudomorph replacing apatite sits in one nodule. Smaller holes appear in nodules. The matrix is dominated by albite and K-feldspar, as well as an abundance of small opaque grains which are probably magnetite. Unidentified anhedral, yellow grains occur outside nodules together with amphibole. Feldspar pseudomorphs occur throughout the matrix.

Figures 11 and 12. MMP1. Plane light. Magnetite (black) and actinolite- tremolite (green) in the nodules. Far left: Nodule is 4 mm in maximum length. Far right: Nodule is 5 mm long.

21

MMP2 HAND SAMPLE: Small rounded nodules sit relatively densely in a red-grey, fine-grained matrix. Nodules range in size from <1 to 6 mm. Nodules are dominated by amphibole. Feldspar crystals are seen throughout the matrix and minor quartz occurs.

Figure 13. Hand sample. MMP2. Finger is about 15 mm in width.

THIN SECTION: Nodules sit relatively densely and vary in size from <0.1 to ~1.4 cm in length. They have irregular and often elongate shapes and lack common orientation. The nodules consist primarily of actinolite and there are also smaller amounts of titanite. There is also some quartz. Anhedral to subhedral magnetite grains occur throughout nodules. Most have anhedral to subhedral shape. The matrix is sprinkled with small opaque grains, most likely magnetite. Highly altered and pseudomorphic feldspar megacrysts are present in the matrix.

Kii1a

HAND SAMPLE: Small round nodules sit in a dark grey fine-grained matrix. Sizes range from <1 to 12 mm. The matrix has somewhat larger feldspar grains occuring throughout. Nodules are dominated by biotite. Rounded to hexagonal apatite grains occur in the matrix and anhedral apatite may also occur in some nodules.

Figures 14 and 15. Kii1a. Left view: Macroscopic view. Right: Plane light. A rounded nodule, possibly holding allanite. Scale bar is 500 µm.

THIN SECTION: This sample contains smaller nodules ranging in size from 1-6 mm in width. Nodules are rounded or slightly oval with a common orientation. They contain primarily biotite. Minor titanite also occurs. Small opaque grains, probably mostly magnetite, occur throughout the matrix, which also holds highly altered to pseudomorphic feldspar grains, some elongate and some with sector

22 zoning. Holes sit at the edges of nodules. Nodules contain few and tiny opaque grains that may be magnetite or hematite. Rounded to hexagonal grains that may be apatite or pseudomorps after apatite, now holding titanite, occur separately in the matrix.

LUO 4

HAND SAMPLE: Thin, elongate and oriented nodules, varying in size up to ~11 mm in length, stretch out in a red-green aphanitic matrix. Spidery magnetite veins of varying thickness run through the sample. Nodules are dominated by magnetite. Titanite is also visible in nodules. Feldspar crystals occur throughout, also occuring sparsely in nodules.

THIN SECTION: <0.1 to 1.5 cm nodules are dominated by magnetite. They are round to elongate with an common textural orientiation. Some nodules are more irregular and some look as if they have been “smeared out”. Magnetite grains occur separately, as well as in clusters. Magnetites are significantly martitised. Zoned actinolite-tremolite, albite, biotite, quartz, chlorite and zoned titanite sit in cracks or otherwise within the magnetite. Epidote crystals occur on edges of magnetite nodules (Figure 14). What appears to be inclusions of matrix were observed in one magnetite grain.

The matrix contains albite and K-feldspar and is divided into sections, indicating relict grain boundaries, most likely of feldspar megacrysts. Amphibole sometimes grow along the borders of these pseudomorphic feldspars. The pseudomorphic grains often exhibit sector zoning under crossed polars.

Figure 16. Luo4. Epidote sitting on edge of magnetite-dominated nodule.

6619

HAND SAMPLE: Small and large nodules of an almost bimodal distribution sit in a grey-red, aphanitic matrix. Small nodules are rounded and of up to just a couple of mm in size. Larger nodules are elongate and range up to 34 mm in length. Nodules are dominated by amphibole, followed by biotite. Magnetite veins up to 10 mm in width run through the hand sample. Textural orientation is visible in parts of the drill core.

Figure 17. Hand sample. 6619. Large crystals of mica, amphibole and magnetite can be seen in the large nodules. Length of individual staples is 12 mm.

THIN SECTION: Nodules vary in size from <0.1 to ~1.9 cm in length. They generally have a round, irregular shape and thus any textural orientation cannot be observed. The nodules are dominated by

23 actinolite-tremolite and mica. There are plenty of smaller grains of calcite and quartz along the edges. There are also small amounts of titanite. The matrix is sputtered with small opaque grains, most likely magnetite. Pseudomorphs after feldspar grains are seen in the matrix and lack any obvious orientation.

6481

HAND SAMPLE: Round to oval nodules of varying sizes sit in a dark grey, fine-grained matrix. Nodule sizes range from <1 to 26 mm. Magnetite dominates the nodules but also amphibole, mica, and titanite occur. ~1 mm wide veinlets run through the hand sample, more or less in the direction of nodule elongation. Feldspar grains of various kinds are visible in the matrix and minor pyrite occurs.

THIN SECTION: Nodules vary in size from ~1 to ~20 mm in length and are dominated by actinolite- tremolite and/or titanite and biotite. They are generally elongate, often oval, and have a common textural orientation. The matrix is sprinkled with small magnetite grains. There is also quartz and calcite along grain boundaries or as larger crystals. Magnetite grains often have subhedral shapes. Highly altered or pseudomorphs after feldspar grains occur in the matrix.

KL8b

HAND SAMPLE: Small to medium sized nodules of up to 8 mm sit in a dark-grey aphanitic matrix. Nodules are dominated by magnetite and amphibole, also having some feldspar and biotite. They are oval and possibly oriented. Feldspar crystals are visible in the matrix.

THIN SECTION: This sample contains round to elongate nodules, oval or more irregular, that have a common orientation. Nodules are <1 to 11 mm in length and are dominated by magnetite, although biotite dominates in one nodule. Holes and inclusions of calcite and quartz sit in the magnetite. Pseudomorphic or highly altered grains of feldspar crystals that lack apparent orientation are found throughout the matrix. The matrix has fine-grained magnetite throughout. A seam of calcite and quartz run alongside a broken up magnetite nodule.

KL16

HAND SAMPLE: Rounded to oval nodules sit in a dark-grey, fine-grained matrix. The hand sample is relatively sparsely populated by nodules, which are dominated by amphibole. Larger, yet fine-grained K-feldspar occurs throughout the matrix.

THIN SECTION: Nodules range in size from less than 0.1 to larger than 0.5 cm. Smaller rounded but irregular nodules dominate, while larger nodules are oval and oriented. Actinolite dominates most nodules but titanite dominates in some. Matrix is quite densely sprinkled with small magnetite grains. Pseudomorps after, as well as altered and unaltered feldspar grains sit in the matrix, sometimes attached to smaller nodules. The more unaltered feldspar grains sometimes sit together as glomerocrysts. These are not elongate so orientation cannot be determined. Magnetite grains in nodules are small, have subhedral shapes, and sit at the centres of nodules.

24

4.1.3 White-pink nodular porphyries

Figures 18 and 19. Hand samples. Left: 6207B. Right: LUO6. crossed by magnetite veins. Length of individual staples is 12 mm. Thumb is 22 mm wide at mid-nail.

6207B

HAND SAMPLE: Black round to oval nodules with a common orientation sit sparsely in a white-pink aphanitic matrix. Small, medium (~6-~8 mm) and large (~25 mm) nodules occur. Magnetite dominate nodules but there is also generous amounts of calcite and quartz as well as mica, titanite, and possibly apatite in some nodules.

THIN SECTION: In the sample thin section, a larger nodule (~2.5 cm in diameter), or perhaps compound of nodules (Figure 20), incorporates a more distinct oval smaller nodule (~1.7x1.1 cm). This smaller nodule contains primarily large, green mica grains. These have been confirmed using SEM-EDS to be magnesium-rich and thus closer to the phlogopite end member of the biotite solid solution series. Crystallographically oriented grains of titanite, and maybe other minerals, are seen in at least one of the biotite grains (Figure 21). There is also a large grain of zoned titanite, as well as a small amount of calcite and quartz. In the outer compound/larger nodule there is also large grains of green biotite and grains of zoned titanite. A large area consists of grains of calcite, biotite and quartz and extends as a seam out into the matrix at one place. Small to large holes appear within the compound/larger nodule and may represent softer minerals that have been ablated during thin section preparation.

Magnetites sit throughout the compound/larger nodule as euhedral square to hexagonal grains, both within the oval smaller nodule as well as in the outer compound/larger nodule. Biotite can be seen to penetrate a magnetite grain (Figure 22). Hematite, if any, is rare.

Grains of irregular magnetites sit separately in the matrix. Actinolite-tremolite is included within their grain boundaries, as well as titanite. Part of the matrix is also incorporated within a rounded magnetite. The matrix itself is bright, consisting of albite and K-feldspar sprinkled with fine-grained magnetite. In the matrix, elongate relict shapes of highly altered feldspar crystals are still visible.

25

Figure 20. 6207B. Plane light. Larger nodule or compound of nodules. Length from top to bottom is about 25 mm.

Figure 21. 6207B. BSE image. Figure 22. 6207B. Plane Lamellaes or inclusions of light. Biotite penetrating titanite, and maybe other magnetite margin. Scale bar minerals, in biotite. is 200 µm.

LUO 6

HAND SAMPLE: Nodules sit densely in a white-pink matrix that appears to be fine-grained with pseudomorps after feldspar crystals still visible with pink or white colour hue. 6 mm and ~22 mm wide magnetite veins penetrate the sample. Nodules are round to elongate with a common textural orientation. They range from small up to ~9 mm in length. The minerology in the nodules is dominated by magnetite, followed by white minerals that may be calcite and quartz.

THIN SECTION: Nodules are generally oval but also circular and are ~0.2 to ~0.6 cm in length. They appear to have a common textural orientation. Some are almost completely dominated by magnetite, with small amounts of calcite and quartz. Others are dominated by calcite and quartz with some magnetite and actinolite-tremolite. In the calcite/quartz-dominated nodules, magnetite occurs primarily near or along the edges and is anhedral to subhedral in shape. A ring free from small magnetite grains is visible in the matrix surrounding a calcite/quartz-dominated nodule. A vein, 0.7 cm wide crosscuts the thin section. Another smaller vein, 0.1 cm across, is seen to taper out. The

26 veins are dominated by magnetite with predominantly quartz sitting in cracks perpendicular to the strike of the veins, and inclusions of titanite also are present.

The matrix is heterogenous with some areas being more densely sputtered with small opaque grains that are probably magnetite. Relatively larger grains, or fragments, of nodules appear throughout the matrix as do pseudomorphic and altered feldspar grains. Cracks approximately perpendicular to the veins and filled with actinolite-tremolite cross the border into the matrix at several places and go through what may formerly have been nodules in places.

27

4.2 Mineral chemistry

4.2.1 Magnetite Kiruna-type deposits are characterized by low Ti and high V concentrations (Frietsch, 1970; Parák, 1975; Müller et al., 2003). Ti contents in the nodule magnetites as measured here span from 0,001 to 0,353 wt % (from Ti-47) (Table 2). Dupuis and Beaudoin (2011) have suggested the minimum and maximum values for Kiruna-type deposits as 0.009 and 0.491 wt % and for V 0.062 to 0.479 wt %. These range limits are plotted as dotted lines in figures 23 and 24. As can be seen in figure 24, most samples plot within the range of V for Kiruna deposits according to the data of Dupuis and Beaudoin (2011) but most samples plot below the limit for Ti. Magnetite chemistry data (Saravanen, personal communication, 2014) from the ore body itself, sampled at various locations within the ore, plotted well below the Dupuis mean in terms of both Ti and V, but did plot within the data range of AIO as presented by Dupuis and Beaudoin (2011). One sampled spot from a white-pink Luossavaara sample and one from a dark Luossavaara sample did however plot within the AIO range, as did one sample from a vein within the white-pink porphyry and one sampled spot from the red porphyry. It is notable from the diagrams that the measured magnetites from the red nodular porphyry from Kirunavaara have markedly lower V levels than the other porphyries, and that it has V concentrations only slightly lower than the ore sample data. All sampled spots plot well below the V concentration of the mean AIO data of Dupuis and Beaudoin (2011).

28

0.013

0.019

0.059

0.329

0.008

0.039

0.073

0.164

0.145

0.037

0.282

0.502

0.027

0.010

0.025

0.037

0.332

1.048

0.234

0.170

0.141

0.545

0.182

0.103

0.087

0.152

0.059

0.384

0.052

0.090

0.128

0.164

0.638

0.137

0.490

0.127

U238

0.0111

0.0564

0.0168

0.2070

0.0416

0.0644

0.0041

0.0198

0.0811

0.0050

0.2170

0.2350

0.0102

0.0619

0.0117

0.1620

0.1191

0.2650

0.0845

0.1760

0.0039

0.1377

0.0126

0.0096

0.0433

0.0514

0.2540

0.0205

0.0503

0.0304

0.0818

0.0655

0.0626

0.2960

0.0781

0.0254

Th232

0.715

0.136

0.212

0.039

0.193

0.039

1.081

0.253

0.053

0.087

0.353

0.182

0.617

0.841

0.042

0.436

0.072

5.920

0.051

1.920

1.802

0.794

0.388

0.981

0.053

0.020

0.179

0.073

0.031

0.098

1.689

0.029

3.170

1.766

0.033

<0.0123

Pb208

0.0435

0.0174

0.0414

0.0159

0.0031

0.0023

0.0211

0.0068

0.3980

0.0096

0.0440

0.0079

0.2360

0.0624

0.1040

0.1040

0.0774

0.4750

0.6820

0.0956

0.0723

0.1280

0.0206

0.0451

0.0070

0.0019

0.0172

0.0697

0.8510

0.0496

0.0443

0.1420

0.1040

<0.0045

<0.00

<0.0038

W182

0.0005

0.0372

0.0005

0.0515

0.0146

0.0005

0.0016

0.0810

0.1012

0.2400

0.0385

0.2860

0.0009

0.1670

0.7680

0.3510

0.2850

0.1360

0.0027

0.1980

0.0007

0.0125

0.0019

0.2200

0.1199

0.0016

0.0247

0.0042

0.2750

0.3580

0.1265

0.0021

<0.00

<0.00131

<0.00

<0.00

Ta181

0.0286

0.0063

0.1180

0.0493

0.0024

0.1100

0.1950

0.0588

0.0395

0.4370

0.0346

0.1150

0.1080

0.3080

0.1010

0.0665

0.2310

0.1410

0.3380

0.1860

0.2140

0.1017

0.1190

0.0472

0.0304

0.0023

0.0508

0.0940

0.0045

0.1380

0.3390

0.1990

0.0883

0.1010

<0.0034

<0.043

Yb172

0.0542

0.0701

0.0882

0.2130

0.0968

0.0088

0.1060

0.0665

0.3830

0.1292

0.1109

0.1110

0.6330

0.1121

0.4660

1.2610

0.3040

0.6430

0.3570

0.4940

0.3700

0.4510

0.3410

0.2640

0.1890

0.0677

0.0094

0.2200

0.8140

0.1820

0.3680

0.5440

0.3960

0.6660

0.3940

0.3500

Ce140

0.039

0.044

0.019

4.480

0.039

0.199

0.197

0.029

1.084

0.067

0.382

0.025

0.022

0.193

0.165

0.033

0.634

0.067

0.049

<0.0217

<0.0241

<0.023

<0.0241

<0.025

<0.023

<0.0205

<0.022

<0.024

<0.025

<0.032

<0.026

<0.0240

<0.0173

<0.023

<0.0198

<0.029

Sb121

0.57

0.67

0.74

0.92

0.48

0.41

0.63

0.47

0.67

0.50

0.68

0.63

0.43

0.63

0.48

0.45

0.56

0.43

0.90

2.07

0.61

0.39

0.53

0.68

0.72

0.54

0.62

0.84

8.78

0.65

0.80

0.51

0.66

0.70

0.77

1.40

Sn118

0.775

0.014

0.009

0.105

0.009

0.130

0.049

0.270

0.019

0.013

0.671

0.071

0.327

0.262

0.437

0.059

0.498

0.097

1.153

0.061

0.077

0.122

0.008

0.009

0.011

0.085

0.199

0.067

0.142

0.089

1.370

0.357

0.180

<0.0082

<0.0062

<0.0062

In115

0.12

0.091

0.053

0.056

0.117

0.082

0.478

0.075

0.093

0.546

0.216

0.084

0.225

0.188

0.422

0.075

0.354

<0.053

<0.065

<0.048

<0.048

<0.063

<0.057

<0.066

<0.051

<0.057

<0.074

<0.052

<0.052

<0.047

<0.049

<0.060

<0.054

<0.052

<0.063

<0.060

Cd111

1.750

0.080

0.082

0.127

0.024

0.754

0.112

0.093

0.045

0.113

0.443

0.117

0.333

0.061

0.134

0.042

0.176

0.352

0.316

0.139

0.078

1.240

0.385

0.171

0.123

0.059

0.043

0.330

0.101

0.076

0.091

1.055

0.548

0.331

0.366

0.154

Mo95

0.0071

0.2280

0.0059

0.3510

0.1262

0.0012

0.0284

0.0349

0.1330

0.0995

0.2370

0.0211

0.0809

0.0051

0.1570

0.0194

0.8220

0.0750

0.1299

0.1010

0.1239

0.0727

0.3260

0.0348

0.0061

0.0011

0.0210

0.1368

0.0247

0.0755

0.3490

0.5200

0.2210

0.0313

0.7160

<0.00100

Nb93

0.1120

0.0339

0.2140

0.3230

0.0265

0.0986

0.0398

0.0291

0.0872

0.0312

0.3720

0.0590

0.0216

0.0429

0.0677

0.1770

0.0473

1.3390

0.0975

0.2710

0.0561

0.0124

0.0089

0.0058

0.0070

0.0227

0.0501

0.0730

0.0473

0.0931

0.2410

0.0307

0.1370

0.1102

59.2100

<0.0026

Zr90

0.0983

0.0048

0.2320

0.0327

0.0336

0.0031

0.0494

0.0597

0.0814

0.0039

2.0800

0.0131

0.2570

0.0036

0.0178

0.1950

0.3020

0.0231

0.0115

0.2280

0.0411

0.0021

0.7420

0.0943

0.0024

0.1840

0.1780

0.0483

0.0217

0.0046

0.3550

0.1374

0.0920

0.3720

<0.0025

<0.00141

Y89

4.1

4.2

4.2

4.8

4.1

5.1

4.0

4.5

4.2

4.3

5.1

4.6

3.3

4.4

4.8

4.3

4.4

4.0

4.0

4.2

3.8

4.1

4.1

3.6

4.2

4.0

3.7

3.8

3.8

3.8

4.6

5.4

5.0

4.0

4.8

4.0

Ge72

7

7

7

8

10

13

10

10

10

10

10

11

16

18

20

20

17

15

13

14

14

14

13

12

12

13

12

13

13

24

27

28

26

27

28

21

Ga69

13

13

18

20

16

14

23

19

15

15

19

20

20

21

26

27

21

42

45

43

41

44

40

23

24

26

24

27

25

42

51

50

49

60

50

26

Zn66

0.42

0.21

3.54

1.50

0.15

1.15

0.34

0.19

1.20

0.78

1.91

0.24

0.91

0.99

1.21

1.37

2.22

0.63

1.18

3.03

0.08

9.19

7.11

1.50

0.50

0.77

0.31

3.88

0.44

1.01

0.67

0.54

12.29

<0.058

<0.044

<0.043

Cu65

0.42

0.09

3.32

0.17

1.37

0.47

0.39

1.11

0.74

9.64

0.12

2.04

1.00

1.02

1.52

2.03

0.33

1.95

0.10

0.91

0.04

9.60

6.48

1.30

0.61

4.99

0.09

0.12

0.98

0.50

0.39

0.95

0.18

0.46

18.40

<0.20

Cu63

65

64

61

62

60

66

96

99

179

178

178

181

190

180

157

164

166

164

163

127

120

128

120

118

118

192

191

196

193

195

197

101

103

102

103

166

Ni60

65

65

65

66

66

65

37

37

39

39

38

39

90

93

94

91

91

76

72

73

74

74

72

94

94

97

96

97

98

91

96

97

97

98

98

94

Co59

376

380

408

421

398

390

673

740

631

641

651

689

786

784

755

781

810

811

793

781

778

806

769

846

834

891

834

904

915

668

797

810

769

731

782

836

Mn55

8

2

3

3

1

3

3

1

3

5

5

9

8

3

11

11

84

94

98

96

88

98

87

26

48

24

55

19

20

21

20

107

338

367

147

255

Cr53

915

891

912

900

913

964

1275

1244

1271

1262

1324

1287

1410

1365

1200

1253

1292

1356

1219

1264

1240

1266

1266

1295

1219

1288

1229

1230

1202

1301

1309

1330

1331

1332

1353

1246

V51

63

42

20

16

68

52

21

28

88

15

14

97

22

27

38

21

28

19

37

11

11

30

14

18

28

20

25

17

21

42

96

110

405

413

1175

3487

Ti49

66

42

20

17

69

51

20

28

87

14

13

20

18

22

21

30

23

26

11

11

28

13

23

29

20

28

21

23

31

95

112

394

107

402

1165

3529

of trace elements of nodule magnetites in in magnetites nodule of elements trace of

Ti47

0.26

0.17

0.17

0.74

0.50

0.22

0.86

0.61

0.25

0.29

0.68

0.83

0.10

0.17

0.28

0.17

0.21

0.17

0.12

0.18

0.15

0.06

0.13

0.07

0.20

0.12

0.09

0.08

0.06

0.22

0.22

0.16

0.24

0.29

0.33

<0.044

Sc45

69

88

77

116

149

124

137

161

440

207

177

117

143

134

104

319

154

475

203

249

285

122

113

203

<75.86

<65.55

<99.25

<76.22

<66.60

<72.34

<84.23

<66.41

<64.53

<62.47

<62.27

<65.51

Ca43

46

80

18

31

28

23

28

11

30

20

30

30

43

25

16

13

39

12

18

29

23

22

87

43

<10.86

<9.24

<11.44

<9.61

<10.29

<8.95

<11.45

<11.41

<11.22

<11.57

<12.29

<9.08

P31

MS results MS

-

455

513

488

514

665

745

577

278

845

310

190

482

943

958

384

499

400

2249

1311

1577

1136

1126

1356

1090

1673

<148.66

<127.43

<156.75

<133.53

<143.20

<127.76

<151.91

<162.68

<165.67

<174.72

<153.75

Si29

ICP

-

89

74

63

27

68

71

58

55

85

62

92

94

74

49

38

25

70

34

43

50

70

130

191

213

136

136

263

158

173

102

183

187

171

188

195

202

LA

Al27

.

53

43

52

53

58

40

40

31

14

16

74

98

35

32

40

69

37

32

32

39

33

35

27

39

45

49

23

42

32

32

59

54

48

44

72

61

2

Mg24

KII2A

KII2A

KII2A

KII2A

KII2A

KII2A

LUO4

LUO4

LUO4

LUO4

LUO4

LUO5

LUO5

LUO5

LUO5

LUO5

LUO5

LUO4

6207B

6207B

6207B

6207B

6207B

6207B

MMP1

MMP1

MMP1

MMP1

MMP1

MMP1

LUO6

LUO6

LUO6

LUO6

LUO6

LUO6

Sample

43

42

41

40

25

24

39

38

37

36

23

22

49

19

18

17

15

35

34

33

32

21

20

47

46

45

44

27

26

48

14

13

12

11

10

16

measured isotope. measured Table respective from recalculated contents, element total show Values ppm.

White-pink nodular porphyry nodular White-pink

Dark nodular porphyry nodular Dark Red nodular porphyry nodular Red Spot 29

Figure 23. Comparison between Ti (from Ti-47) and V in nodule magnetites, ore body (Saravanen, personal communication, 2014) and a Kiruna-type deposit mean (Dupuis & Beaudoin (2011). Dotted lines show the minimum and maximum Ti and V concentration limits for Kiruna type deposits (Dupuis & Beaudoin, 2011).

Figure 24. Comparison between Ti (from Ti-47) and V in nodule magnetites, ore body (Saravanen, personal communication, 2014) and a Kiruna-type deposit mean (Dupuis & Beaudoin, 2011). Dotted line show the minimum Ti concentration limits for Kiruna type deposits (Dupuis & Beaudoin, 2011). Two anomalous values are outside the range of this scale, namely LUO-Spot 16 and LUO6-Spot 40. These may represent exsolution lamellae or primary magnetite of a composition closer to that of the ore body. See text for discussion. For figure caption see Figure 23. 30

Magnetite is common not only in iron ore deposits but also as minor and trace mineral in other types of ore deposits. In magnetite divalent, trivalent and tetravalent cations can substitute and it may thus show significant compositional diversity. Dupuis and Beaudoin (2011) have constructed petrogenetic discrimination diagrams for magnetite in various ore deposits, based on a large selection of minor and trace element microprobe data from a variety of deposit types. The premise is that iron oxide composition results from the physical and chemical environment during formation, which is thought to have been different for different deposit types. Thus, magnetite minor and trace compositional differences in terms of elements, element ratios and/or element combinations are used in discrimination diagrams to infer deposit type. Kiruna-type apatite-magnetite deposits can in this way be recognized from IOCG, porphyry Cu, BIF, skarn, Fe-Ti, and V deposits using Ni/(Cr+Mn) vs. Ti+V or Ca+Al+Mn vs. Ti+V diagrams. V and Ti vary strongly between different types of deposits. In the Ni/(Cr+Mn) discrimination plots, relevant for Kiruna type, i.e. AIO deposits, the nodular porphyry magnetites all plot outside the area for AIO (Figure 25). One sampled spot from a dark Luossavaara porphyry nodule and one from the white-pink Luossavaara vein instead plot as magnetites from a porphyry type deposit. Meanwhile, all other sampled spots except for the vein plot as skarn, while all but one of the sampled vein spots plot as IOCG. Interestingly, the unpublished data from the Kiruna ore body itself plot closely together with the nodular porphyries, and thus also ends up in the diagram field for skarn deposits.

Figure 25. Ore deposit type discrimination diagram after Dupuis and Beaudoin (2011). For figure caption see Figure 23.

In the Ca+Al+Mn vs Ti+V discrimination diagram, many of the porphyry nodule magnetites do plot within the AIO field (Figure 26). However, the vein instead plots clearly in a nondescript field, while the red nodular porphyry plots clearly in the IOCG field. Again, the unpublished ore data does not plot in the AIO field, but in the IOCG field. Generally, the nodules plot relatively closely together both amongst themselves and with the ore body data (unpublished) but far from from the Kiruna type deposit mean.

31

Figure 26. Ore deposit type discrimination diagram after Dupuis and Beaudoin (2011). For figure caption see Figure 23.

The Mn content of the nodule magnetite is in line with the ore body concentrations (unpublished data) as well as the maximum values for Kiruna-type deposits given by Dupuis and Beaudoin (2011). The vein in the white-pink porphyry was however markedly lower, more in the range of the mean value for Kiruna-type deposits.

Figure 27. Comparison between Mn content of ore body (Saravanen, personal communication, 2014) Kiruna-type deposit mean, min and max (Dupuis & Beaudoin, 2011) and nodule porphyry magnetites.

32

Cr concentration appears to be a distinguishing factor between samples but not between groups. The sampled white-pink nodule was markedly enriched in Cr. The ore data (Saravanen, personal communication, 2014) has very low levels of Cr.

Figure 28. Comparison between Cr content of ore body (Saravanen, personal communication, 2014); Kiruna-type deposit mean, min and max (Dupuis & Beaudoin, 2011) and nodule porphyry magnetites. Logarithmic scale.

Co differs systematically between samples but also between groups. Red nodular porphyry shows higher Co concentrations, both in the Luossavaara and Kirunavaara samples. The white pink nodular porphyry magnetite has the lowest Co amongst the porphyries and is most in line with ore body concentrations.

Figure 29. Comparison between Co content of ore body (Saravanen, personal communication, 2014) and nodule porphyry magnetites.

33

Ga concentrations were rather similar for the ore body and the Kiirunavaara red nodular porphyry. The white-pink porphyry nodule magnetites – including the vein – had the lowest Ga concentrations.

Figure 30. Comparison between Ga content of ore body (Saravanen, personal communication, 2014) and nodule porphyry magnetites.

Results for P concentrations were quite unsystematic in terms of rock types, as well as within samples.

Figure 31. Comparison between P content of ore body (Saravanen, personal communication, 2014) and nodule porphyry magnetites.

34

Sc concentration were somewhat similar for the ore body and the Kiirunavaara red nodular porphyry nodules and also the dark porphyry from Luossavaara. The white-pink variety including the vein show sporadic enrichment in Sc relative to the other data.

Figure 32. Comparison between Sc content of ore body (Saravanen, personal communication, 2014) and nodule porphyry magnetites.

When normalised to bulk continental crust (Dare et al., 2012) and plotted in a spider diagram inspired by Dare et al. (2012), the magnetite mineral chemistry of the nodules closely follows the curves for the IOA deposit in Blötberget (Hogmalm et al., 2014); as well as data from the Kirunavaara ore body (Figure 33). Deviating trends can be observed for Zn, where the peak for the Kiirunavaara and Blötberget ores is missing in the porphyry nodules. The white-pink nodule also deviates in terms of Cr.

Figure 33. Diagram after Dare et al. (2012) and Hogmalm et al. (2014) comparing data from the Kiirunavaara ore (Saravanen, personal communication, 2014), the Blötberget AIO deposit (Hogmalm et al., 2014) and the nodular porphyry magnetites, including the magnetite vein. Data has been normalised to bulk continental crust.

35

4.2.2 Amphiboles

Table 3. Mineral chemistry composition of sampled nodule amphiboles.

wt % Red nodular porphyry Dark Sample Kii2a LUO5 MMP1 LUO4 Site 8 9 10 12 15 26 2 6 Colour based darker darker brighter darker brighter brighter darker darkest darker brighter darker on BSE grey scale SiO2 54.77 56.71 54.91 55.22 54.64 55.69 55.54 53.14 53.93 55.4 53.96 55.56 54.26 TiO2 0.3 0.06 0.16 0.05 0.37 0.31 0.33 0.33 0.34 0 0.33 0.11 0.39 Al2O3 1.37 0.79 1.03 0.95 1.35 1.15 1.4 1.91 1.95 0.45 1.83 0.77 1.76 MnO 0.12 0.28 0.2 0.38 0.17 0.12 0.38 0.23 0.14 0.24 0.09 0.35 0.08 FeO 7.62 7.55 9.38 8.07 7.7 7.08 9.45 9.51 7.28 6.96 6.27 9.12 6.58 MgO 19.46 19.61 18.18 18.42 19.24 20.14 18.72 17.59 19.35 19.25 20.12 18.5 20.07 CaO 10.56 13.23 11.25 12.71 10.36 10.81 10.82 11.2 11.23 12.29 10.9 11.47 10.67 Na2O 2.47 0.32 1.25 0.42 1.63 1.54 1.39 1.57 1.79 0.68 2.25 0.83 2.13 K2O 0.52 0.06 0.5 0.09 0.58 0.51 0.48 0.44 0.45 0.11 0.57 0.23 0.58 Totals 97.19 98.61 96.86 96.31 96.04 97.35 98.51 95.92 96.46 95.38 96.32 96.94 96.52

Amphiboles were found in the nodules chosen for SEM-EDS only within the red and dark nodular porphyry groups, while the nodules in the white-pink varieties were instead dominated by biotite. The amphiboles have been classified based on the nomenclature of the International Mineralogical Association (Hawthorne et al., 2012; Locock, 2012). The sampled amphiboles classify as actinolites in the Group OH,F,Cl and Sub-Group Ca. See section 2.6 for a brief overview of the classification methods.

Using instead the earlier classification scheme of Leake (1997), the amphiboles also classify as actinolites (Figure 34). This classification classifies amphiboles with more than 1.5 Ca per formula unit in the B-site as calcic amphiboles. Calcic amphiboles with <0.5 Ti per formula unit and <0.5 Na+K per formula unit within the A-site can be further classed based on the Mg/(Mg+Fe2+) ratio and Si per formula unit.

Na and K vary notably within the actinolites, regardless of rock type. Levels range from 0.06-0.58 %

K2O and 0.32-2.47 % for Na2O. There appears to be no clear connection between levels of Na to those of K. Al2O3 levels also vary notably, ranging from 0.45 to 1.95 %. In the red porphyry the range is 0.79-1.37 % and in the dark porphyry it is 0.45-1.95 %; thus there is no clear difference between the groups. Finally, FeO also varies notably within the sampled actinolites, within the range of 6.27- 9.51 %. For the red porphyry, values are in between 7.08-9.45 %. In the dark group, the range is 6.27- 9.51 %. That is to say, there is no clear distinction between red and dark nodular pophyry.

In gangue amphiboles within the ore (Nordstrand, 2012), similar variations are also observed in Al, K, Na, Mg/(Mg+Fe2+) and Si.

The nodule actinolites display variations in both Mg/Mg+Fe2+ and Si (a.p.f.u.). Variations have no clear connection to porphyry group.

36

Figure 34. Nomenclature diagram for calcic amphiboles after Leake (1997). All samples of this study.

When compared to the classification of gangue amphiboles within the ore body (Nordstrand, 2012; Nordstrand and Andersson, 2013), the nodule amphiboles show overlapping composition with the gangue amphiboles (Figure 35).

Figure 35. Comparison with mineral chemical data for gangue amphiboles within the ore body Nordstrand (2012). Presented in a nomenclature diagram for calcic amphiboles after Leake et al. (1997).

The studied nodule actinolites generally exhibit a clear chemical zoning, also displayed as a variation in colour hue. Relative to the brighter BSE-areas, the darker areas have higher Mg. The chemical

37 zonation of the actinolites results in a higher Mg/(Mg+Fe2+) ratio for the darker, more Mg-rich, areas than for brighter parts (Figure 36). The Si (a.p.f.u.) content is variable without apparent connection to zonation.

Figure 36. Nomenclature diagram for calcic amphiboles after Leake (1997). Chemical zonation is visible in the amphiboles as higher-Mg areas are darker than lower-Mg, brighter, areas.

The gangue amphiboles (Nordstrand, 2012) display a similar chemical zoning, shown in differences in Mg/(Mg+Fe2+) between the different chemical/colour zones (Figure 37). Nordstrand has made the distinction of “core” and “rim” for the darker, higher Mg/(Mg+Fe2+) ratio, and brighter, lower Mg/(Mg+Fe2+) ratio, zones respectively.

Figure 37. Mineral chemical data of Nordstrand (2012) for gangue amphiboles within the ore body. The diagram shows the rims and cores of zoned grains together with reference samples from Sierra La Bandera, Chile (Lledo, 2005).

38

Calculations in the Locock (2014) spreadsheet indicated that Fe3+ was present in all the sampled nodule actinolites, in varying but small amounts (Table 4). The presence of Fe3+ was observed also in the gangue amphiboles (Nordstrand, 2012).

Table 4. Fe3+ and Fe2+ contents of actinolites calculated using the Locock spreadsheet (2014).

Atoms per formula unit (based on 23 oxygen) Red nodular porphyry Dark nodular porphyry Kii2a LUO5 MMP1 LUO4 Site 8 9 10 12 15 26 2 6 darker darker brighter darker brighter brighter darker darkest darker brighter darker Fe3+ 0.17 0.03 0.17 0.01 0.30 0.28 0.31 0.17 0.18 0.02 0.12 0.16 0.24 2+ Fe 0.73 0.85 0.95 0.96 0.62 0.55 0.80 0.98 0.68 0.81 0.63 0.92 0.54

39

4.2.3 Dark mica

Table 5. Mineral chemistry composition of sampled nodule micas.

Atoms per formula unit (based on 22 O) wt % Red nodular porphyry Dark nodular porphyry White-pink nodular porphyry Sample LUO5 MMP1 LUO4 6207B OUTER COMPOUND Site 4 Site 12 Site 13 Site 25 Site 27 Site 28 Site 30 Site 32 Site 5 Site 10 Site 11 Site 6 Site 7 Site 10 Site 11 Site 12 Site 13 Site 8 Site 9 Site 16 Spectrum 1 2 1 2 1 2 1 1 2 3 1 1 3 2 1 1 1 2 1 1 2 1 1 2 Al total 2,40 2,40 2,18 2,20 1,90 1,86 1,98 2,04 2,14 2,06 2,44 2,46 2,46 2,54 1,90 1,94 1,98 2,20 2,10 2,04 2,12 2,06 2,00 2,18 Fe total 1,48 1,54 1,48 1,36 1,38 1,38 1,42 1,38 1,44 1,34 1,54 1,48 1,48 1,58 1,32 1,54 1,54 1,74 1,68 1,76 1,62 1,62 1,56 1,70 Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Site T Si 5,82 5,88 6,00 6,04 6,12 6,18 6,12 6,04 5,96 6,04 5,82 5,90 5,84 5,78 6,14 6,28 6,22 5,98 6,08 6,00 6,04 6,08 6,16 5,98 Al T 2,18 2,12 2,00 1,96 1,88 1,82 1,88 1,96 2,04 1,96 2,18 2,10 2,16 2,22 1,86 1,72 1,78 2,02 1,92 2,00 1,96 1,92 1,84 2,02 Number of ions T 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8,00 8 8,00 8,00 8,00 Fe3+ 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0 0,00 0,00 0,00 Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Site M Al M 0,22 0,28 0,18 0,24 0,02 0,04 0,10 0,08 0,10 0,10 0,26 0,36 0,30 0,32 0,04 0,22 0,20 0,18 0,18 0,04 0,16 0,14 0,16 0,16 Ti 0,14 0,12 0,12 0,12 0,18 0,18 0,12 0,04 0,04 0,04 0,10 0,10 0,10 0,10 0,18 0,08 0,08 0,10 0,10 0,20 0,08 0,10 0,08 0,10 Fe M 1,48 1,54 1,48 1,36 1,38 1,38 1,42 1,38 1,44 1,34 1,54 1,48 1,48 1,58 1,32 1,54 1,54 1,74 1,68 1,76 1,62 1,62 1,56 1,70 Mn 0,04 0,04 0,04 0,04 0,02 0,02 0,02 0,02 0,04 0,04 0,02 0,04 0,04 0,04 0,02 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 Mg 3,98 3,98 4,00 4,10 4,22 4,20 4,20 4,38 4,32 4,38 3,90 3,92 3,92 3,84 4,30 3,94 3,96 3,78 3,84 3,72 3,92 3,94 3,98 3,86

Ca 0,04 0,02 0,02 0,02 0,02 0,00 0,00 0,00 0,00 0,00 0,00 0,02 0,02 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,02 0,00 0,00 0,02 K 1,84 1,58 1,74 1,62 1,80 1,70 1,76 1,92 1,92 1,90 1,86 1,70 1,86 1,82 1,66 1,62 1,66 1,78 1,74 1,88 1,78 1,84 1,74 1,80

OH Not analysed. F Cl Mg/(Mg+Fe) 0,73 0,72 0,73 0,75 0,75 0,75 0,75 0,76 0,75 0,77 0,72 0,73 0,73 0,71 0,77 0,72 0,72 0,68 0,70 0,68 0,71 0,71 0,72 0,69

No mica was found in the red nodular porphyry sample Kii2a.

Dark mica was found in the nodules chosen for SEM-EDS within nodules of all samples, except for the red nodular porphyry sample Kii2a. All the measured mica classify as phlogopite in a nomenclature diagram after Deer et. al (2004) (Figure 38). Calculations showed that there is no substitution of Fe3+ for Al in the M site of the mica (Appendix II). When compared to the classification of gangue mica within the ore body, the nodule micas show overlapping composition with the group 1 micas, which are also phlogopites (Figure 39) (Nordstrand, 2012; Nordstrand and Andersson, 2013).

40

Figure 38. Nomenclature diagram for mica after Deer et al. (1992). The number of oxygen has been set to 22 a.p.f.u. in order to benefit comparison with Nordstrand (2012). All the nodule biotites sampled plot as phlogopite. Ellipses marked 1 to 3 represent ranges for gangue mica within the ore body (Nordstrand, 2012).

41

5.0 DISCUSSION

5.1 Macroscopic and microscopic characteristics of the nodular porphyry

The red nodular porphyry sampled generally has a red aphanitic matrix and nodules are mostly dominated by actinolite-tremolite or, in one sample, by magnetite. The dark nodular porphyry mostly has a dark-grey aphanitic to fine-grained matrix. Nodules are generally dominated by either magnetite, actinolite-tremolite, phlogopite, or a combination thereof. In the white-pink nodular porphyry, matrix is white-pink and appears to be aphanitic to fine-grained. Microstructures appear to be the most chaotic among the rock types. Magnetite, phlogopite, or areas of small calcite and quartz grains dominate nodules. Geijer (1910) observed a presence of apatite in the porphyries that was not noted in this study. It can not be ruled out that small grains of apatite have been overlooked during microscopy, potentially through confusion with quartz.

Nodules vary greatly in size between samples and mostly also within samples regardless of porphyry type. Titanite is generally present in the nodules of all groups in varying amounts. Four dominant features throughout the samples were the presence of pseudomorphs, probably representing former feldspar varieties, in the matrix; the martitisation of magnetite grains; a common orientation of elongate nodules in most samples; and, a strong presence of albite in matrices.

The nodular porphyry groups chosen for this study and inspired by Geijer (1910) thus show many overarching similarities. However, a division based on colour may still be viable as the three groups appear to represent slightly different mineral abundances in nodules; with ample actinolite-tremolite and a lack of biotite being most characteristic of the red group; abundant phlogopite and less areas of quartz and calcite relative the white-pink group characterising the dark group; and, more chaotic microstructures, more abundant quartz and calcite aggregates and a small presence of amphibole characterising the white-pink group. All three porphyry types appear to have higher abundances of magnetite in samples from Luossavaara but a much larger number of samples would be needed to confirm this.

5.2 Minor and trace element chemistry of nodule magnetite

Kiruna-type (AIO) deposits are characterized by low Ti and high V concentrations (e.g. Dupuis and Beaudoin, 2011). Ti contents in the nodule magnetites span from 0,001 to 0,353 wt % (10 to 3530 ppm). Bergman et al. (2001) presents the range of titanium and vanadium concentrations characteristic of Kiruna-type deposits as 0.04-0.31 wt % and 0.0317- 0.231 wt %, respectively, while Dupuis and Beaudoin (2011) have presented the Ti minimum and maximum values for Kiruna-type deposits as 0.009 and 0.491 wt % and the V range to 0.062 to 0.479 wt %. Thus, most of the nodule magnetites are below the Ti limit of the Dupuis and Beaudoin (2011), as well as that of Bergman et al.. However, some are within the Kiruna-type Ti range (only two spots are however within the range for the Bergman et al. (2001) range. Moreover, the ore data (Saravanen, personal communication, 2014) plot very close to the lower limit. V in the nodules is in the range of 0.08 to 0.14, which is in the AIO deposit type range of both Dupuis and Beaudoin (2011) and Bergman et al. (2001). In terms of V as well as Ti, a common origin of the nodules and the ore can thus not be ruled out.

42

The similarity in chemical composition between nodule groups, as visualised in the Dupuis and Beaudoin (2011) discrimination diagrams, may indicate that nodules from different parts of the footwall indeed share a common origin. That nodule magnetites plot closely to the ore body data in the Dupuis and Beaudoin (2011) discrimination diagrams, albeit far from the Kiruna-type (AIO) deposit mean from the same authors may indicate a wide range in chemical composition within the ore body, as well as point to the possibility of a common origin for the ore body and the porphyry nodules. Additional processes could possibly have later depleted the porphyry nodules in Ti relative to the ore body. However, as the Kirunavaara ore data (Saravanen, personal communication, 2014) used for reference does not plot in the Kiruna-type deposit field of the discrimination diagrams of Dupuis and Beaudoin (2011), the diagrams cannot be said to adequately indicate whether the nodular porphyry magnetites are related to Kiruna-type deposits or not. If the ore data is representative of Kiruna-type deposits the utility of the Dupuis and Beaudoin (2011) discrimination diagrams is put in doubt. The nodule magnetites are often, but sometimes not at all, heavily martitised, which is a common phenomenon in apatite iron ore deposits as well as in most IOCG and porphyry Cu deposits (Dupuis and Beaudoin, 2011). The red nodular porphyry magnetites from Kirunavaara plot particularly close to magnetite from the ore body (Saravanen, personal communication, 2014) in terms of both Ti and V content, and also in the Ni/(Cr+Mn) vs Ti+V discrimination diagram (Dupuis and Beaudoin, 2011) as well as the Ca+ Al+ Mn vs. Ti+V diagram. In terms of Mn and Sc concentration, the red nodular porphyry from Kiirunavaara is also similar to that of the ore. It may thus be that the ore body samples and this red nodular porphyry are somehow closer related, either by interaction with similar fluids, or in the way that magnetites in the red nodular porphyry from Kiirunavaara in fact originate in the ore body, or, in the way that the nodular porphyry served as a supplier of ore magma. The red nodular porphyry from Luossavaara did, however, not plot as closely, in part due to a higher V content, so any relation between the sampled ore and the Kiirunavaara red nodular porphyry cannot be generalized to all porphyries of that colour. Also, in terms of Co, Ga and Cr content, the Kiirunavaara red nodular porphyry has higher concentrations than the ore. The composition of the magnetite vein in the white-pink porphyry diverges from the other porphyries in both discrimination diagrams of Dupuis and Beaudoin (2011) and also ranges to higher Ti values than the other porphyries. It plots in different, but not coherent, deposit-type fields – none of which are for Kiruna-type deposits - than the porphyry nodules in both diagrams. Moreover, the vein consistently plots the farthest from the ore data in these diagrams as well as far from the Kiruna-type deposit mean of Dupuis and Beaudoin (2011). However, as the discrimination diagrams can be regarded as less suitable in terms of identifying Kiruna-type deposit magnetites (see discussion above) it can still not be ruled out that the vein is related to the ore. To adequately discuss the origin of similar veins, more samples would be needed. Among the trace elements, Co concentrations appears to be the only element that give the impression of varying in accordance with the colour grouping of the nodular porphyries. Looking instead at the other elements, there is no clear distinction between colour groups, but rather between samples. The descriptive classification of nodular porphyries based on colour and inspired by Geijer (1910), can thus not be said to represent chemical affinities amongst magnetites of the same rock type. Mn was at relatively similar levels in the magnetites, irrespective of porphyry type, and at similar levels to the ore body. The vein however had lower manganese levels. The white-pink porphyry nodules and the vein within this same colour group showed similar results in terms of Sc and Ga concentrations, not particularly similar results in terms of Mn and Co and not at all in terms of Cr. Cr concentration appears to be a distinguishing factor between samples but not between groups.

43

When normalised to bulk continental crust (Dare et al., 2012) and plotted in a spider diagram after Dare et al. (2012), the nodule magnetites plot remarkably close to the curves for data from the IOA deposit in Blötberget (Hogmalm et al., 2014); as well as data from the Kirunavaara ore body. This may indicate a cogenetic origin of the porphyry nodule magnetites and the Kiruna ore bodies. A future trace element study of amphiboles might confirm such a relationship and could then be used as en indicator as to whether the nodules represent ore-related entities or not. Zn is the element in the nodules that clearly deviates from the trends of the Blötberget and Kirunavaara ore bodies. The white-pink nodule also deviates in terms of Cr.

5.3 Mineral chemistry of nodule amphibole and mica

Based on their mineral chemistry, the nodule amphiboles classify as actinolites according to the 2012 nomenclature of the International Mineralogical Association (Hawthorne et al., 2012). This is consistent with earlier classification of gangue amphiboles (Nordstrand, 2012; Nordstrand and Andersson, 2013) within the ore body. It can thus not be ruled out based on this study that the nodule and gangue amphiboles are in fact related in terms of origin. Similarities also include widespread chemical zonation with a BSE-darker, more Mg-rich phase, and a BSE-brighter phase with lower Mg levels. Similarities were also observed in the range of major element concentrations between the nodule amphiboles and gangue amphiboles as similar variations occur in Al, K, Na, Mg/(Mg+Fe2+) and Si. These variations can be explained with the following substitutional mechanisms (Nordstrand 2012; Nordstrand and Andersson, 2013): [M] [M] 2+ Mg = Fe [M1,2,3](Mg,Fe,Mn)2+ + [T]Si4+= [M1,2,3]Al3++ [T]Al3+ (the Tschermak substitution) [T]Si4+ =[M4,A](Na,K)+ + [T]Al3+ [M4]Ca2+ = [M4](Na)+ +[A](Na,K)+ [M4]Ca2+ = [M4](Mg,Fe,Mn)2+. No clear connection between major element concentrations and nodular porphyry group was observed, indicating that this is a descriptive classification unrelated to the mineral chemistry of nodular amphiboles. Mg-rich actinolite has been shown experimentally by Lledo and Jenkins (Lledo, 2005; Lledo and Jenkins 2008) to be able to endure P-T conditions such that it could have an igneous origin in Kiruna- type deposits. Mg-rich actinolite is one of the most common minerals in Kiruna-type ore deposits, and is often proximal to the footwall nodular porphyry. This study has shown a similar composition of amphiboles in the nodules of the footwall, which may indicate a common origin for these amphiboles. The mica found in nodules of all porphyry types that was analysed using SEM-EDS are phlogopites. All but one sample (Kii2a), belonging to the red nodular porphyry group, were found to contain mica. In terms of classification, micas thus belong to the same class of micas as gangue mica within the ore body (Nordstrand, 2012; Nordstrand and Andersson, 2013), thereby indicating that nodule micas of the footwall porphyry may share a similar origin with gangue micas within the ore body.

44

6.0 CONCLUSIONS

A descriptive classification of nodular porphyry based on colour and inspired by Geijer (1910) may indeed be useful as the “red”, “dark” and “white-pink” groups appear to represent slightly different mineral assemblages in nodules; with ample actinolite-tremolite and a lack of biotite being most characteristic of the red group; abundant phlogopite and less amounts of quartz and calcite relative the white-pink group characterising the dark group; and, more chaotic microstructures, more abundant quartz and calcite aggregates and little to no amphibole characterising the white-pink group. However, more samples are needed to confirm such a relationship. Samples from Luossavaara appear to have higher abundances of magnetite in all three porphyry types, but the samples in this study have been too few to substantiate this observation. Apart from possibly Co, there is no clear distinction between porphyry groups in terms of minor and trace element concentration in nodule magnetites, but concentrations are rather characteristic for individual samples. The colour classification of nodular porphyry can thus not be said to represent chemical affinities amongst magnetites in nodules from the same colour group. The Ti levels of the magnetite in the nodular porphyry are low even for apatite-iron ore deposits but a few spots still plot within the range for Kiruna-type deposits. The V concentrations are within the range of data for AIO deposits. Nodule magnetites plot closely together in discrimination diagrams after Dupuis and Beaudoin (2011), which indicates that nodules share a similar origin. They also share similar Mn levels. In these same diagrams, nodular porphyry magnetites plot tightly with ore body data. This could thus mean that the nodules and ore body are in fact related, but that additional processes have depleted magnetites in the porphyry nodules in Ti relative to those in the ore body. The Dupuis and Beaudoin (2011) discrimination diagrams for identification of deposit types based on trace element chemistry do not adequately identify apatite-iron ore deposits and have thus not contributed to the solution of the origin of nodular porphyry magnetites. The red nodular porphyry magnetites from Kirunavaara plot particularly close to magnetite from the ore body in terms of both Ti and V content; Ni/(Cr+Mn) vs Ti+V; Ca+ Al+ Mn vs. Ti+V; as well as in terms of Mn and Sc concentration. It may thus be that the ore body samples are more closely related to this red nodular porphyry than to the other nodular porphyries. This relationsship can not be generalised to that entire porphyry group. However, in terms of Co, Ga and Cr content, the Kirunavaara red nodular porphyry has higher concentrations than the ore. When normalised to bulk continental crust the footwall nodule magnetites show a similar overall trend to data from other AIO deposits, including Blötberget, as well as to the Kiirunavaara ore body itself. This could speak in favour of a cogenetic origin of the porphyry nodule magnetites and the Kiruna ore bodies. The nodule amphiboles classify as actinolites according to the 2012 nomenclature of the International Mineralogical Association. They show a similar mineral chemistry to that of gangue amphiboles within the Kiruna ore in terms both of a clear chemical zonation and in terms of similar variations in Al, K, Na, Mg/(Mg+Fe2+) and Si. Also nodule micas show similarities with gangue micas as both groups belong to the phlogopite mica variety. A common origin can thus not be rejected.

45

6.0 ACKNOWLEDGEMENTS

I would like to thank LKAB and my supervisor at LKAB, Ulf B. Andersson. At Gothenburg University, I would like to thank my supervisor Johan Hogmalm and examinator Thomas Zack, as well as David Cornell, Mikael Tillberg, Axel Sjöqvist and Andreas Karlsson for additional assistance.

46

7.0 REFERENCES

Andersson, Ulf B. (2013). “Coeval iron oxide and silicate magmas; structural evidence for immiscibility and mingling at Kiirunavaara and Luossavaara, Sweden”. 12th SGA Biennial Metting, Proceedings, Uppsala, Sweden 12-15/8. Geological Survey of Sweden, 1635-1638 Barker, A. J. (1998). Introduction to metamorphic textures and microstructures. London: Stanley Thornes

Barton, M. D., and Johnson, D. A. (1996). Evaporitic-source model for igneous-related fe oxide-(REE- cu-au-U) mineralization. Geology, 24(3), 259-262 Berglund, J. and Andersson, U.B. (2013): Kinematic analysis of geological structures in Block 34, Kiirunavaara. LKAB Utredning 13-746, 48 pp. + 2 Appendices, 29 pp Berglund, J. and Andersson, U.B. (2014): Elements of the structural evolution at Kiirunavaara, northernmost Sweden. 31st Nordic Geological Wintermeeting, Lund, 7-10/1 2014. Abstracts Vol. pp. 104-105 Bergman, S., Kübler, L. and Martinsson, O. (2001). Description of regional geological and geophysical maps of northern Norrbotten county (east of the Caledonian orogen). Geological Survey of Sweden, Ba56, 110 pp. Billström, K., Eilu, P., Martinsson, O., Niiranen, T., Broman, C., Weihed, P., Wanhainen, C. and Ojala, J. (2010): IOCG and related mineral deposits of the northern Fennoscandian Shield. In Porter, T.M. (ed.): Hydrothermal iron oxide copper-gold and related deposits: a global perspective. PGC Publishing, Adelaide, pp. 381-414

Dare, Sarah A.S.; Barnes, Sarah-Jane; Beaudoin, Georges (2012). “Variation in trace element content of magnetite crystallized from a fractionating sulfide liquid, Sudbury, Canada: Implications for provenance discrimination”. Geochimica et Cosmochimica Acta, v 88, p 27-50

Deer, W. A., Howie, R. A., and Zussman, J. (1992). An introduction to the rock-forming minerals. Harlow: Longman

Dupuis, Céline. Beaudoin, Georges (2011). “Discriminant diagrams for iron oxide trace element fingerprinting of mineral deposit types”. Mineralium Deposita, v 46, n 4, p 319-335 Forsell, P. and Parák, T. (1972). The stratigraphy of the Precambrian Rocks of the Kiruna District, Northern Sweden. SGU Serie C 812 Frietsch, R. (1970). Trace elements in magnetite and hematite mainly from Northern Sweden. Geological Survey of Sweden, C 646, 136 pp. Frietsch, R. (1978). On the magmatic origin of iron ores of the kiruna type. Economic Geology, 73(4), 478-485 Frietsch, R. (1997). The Iron Ore Inventory Programme 1963-1972 in Norrbotten County. Geological Survey of Sweden. Rapporter och Meddelanden nr. 92, 74 pp. Frietsch, R.; Tuisku, P.; Martinsson, O.; Perdahl, J-A (1997) - Early Proterozoic Cu-(Au) and Fe ore deposits associated with regional Na-Cl metasomatism in northern Fennoscandia. Ore Geology Reviews 12, 1-34 Geijer, P. (1910). Igneous rocks and iron ores of Kiirunavaara, Luossavaara and Tuolluvaara. Scientific and practical researches in Lapland arranged by the Luossavaara-Kiirunavaara Aktiebolag, Geology of the Kiruna district 2, Stockholm, 278 pp

47

Geijer, P. (1931): The iron ores of the Kiruna type. Geological Survey of Sweden C 367, 39 pp.

Hawthorne, Frank C. et al (2012). IMA report. Nomenclature of the amphibole supergroup. American Mineralogist, v 97, p 2031–2048

Jochum, K. P., Weis, U., Stoll, B., Kuzmin, D., Yang, Q., Raczek, I., Jacob, D. E., Stracke, A., Birbaum, K., Frick, D. A., Günther, D. and Enzweiler, J. (2011). Determination of Reference Values for NIST SRM 610–617 Glasses Following ISO Guidelines. Geostandards and Geoanalytical Research, 35: 397–429

Leake, B.E. (1997); Woolley, A.R.; Arps, C.E.S.; Birch, W.D.; Gilbert, M.C.; Grice, J.D.; Hawthorne, F.C.; Kato, A.; Kisch, H.J.; Krivovichev, V.G.; Linthout, K.; Laird, J.; Mandarino, J.A.; Maresch, W.V.; Nickel, E.H.; Rock, N.M.S.; Schumacher, J.C.; Smith, D.C.; Stephenson, C.N.. “Nomenclature of amphiboles: report of the Subcommittee on Amphiboles of the International Mineralogical Association, Commission on New Minerals and Mineral Names “. Canadian Mineralogist, v 35, n 1, p 219-246

Lindgren, K. (2013): Punktlasttestning av olika bergartstyper i Kiirunavaaras liggvägg. Batchelor´s thesis, Luleå University of Technology, 102 pp LKAB homepage, https://www.lkab.com/en/About-us/Overview/Customers/ (2014-05-18) Lledo, H. L. (2005). Experimental studies on the origin of iron deposits; and mineralization of Sierra la Bandera, Chile. ProQuest Dissertations and Theses Lledo, H. L., and Jenkins, D. M. (2008). Experimental investigation of the upper thermal stability of mg-rich actinolite; implications for kiruna-type iron deposits. Journal of Petrology, 49(2), 225-238 Locock, Andrew J. (2014). “An Excel spreadsheet to classify chemical analyses of amphiboles following the IMA 2012 recommendations”. Computers and Geosciences, v 62, p 1-11 Lundberg B. and Smellie J.A.T. (1979). Painorova and Mertainen Iron Ores: Two deposits of the Kiruna Iron Ore Type in Northern Sweden. Economic Geology, v 74, p 1131-1152 Martinsson, Olof (2004). Geology and Metallogeny of the Northern Norrbotten Fe-Cu-Au Province. Society of Economic Geologists Guidebook, Series Number 33, p 131-148 Müller, Barbara; Axelsson, Mikael D.; Ohlander, Björn (2003). ” Trace elements in magnetite from Kiruna, northern Sweden, as determined by LA-ICP-MS”. GFF, v 125, n 1, p 1-5 Nyström, Jan Olov (1985). Apatite iron ores of the Kiruna Field, northern Sweden: Magmatic textures and carbonatitic affinity. GFF, v. 107, p. 133-141 Nordstrand, J. (2012). Mineral chemistry of gangue minerals in the Kiirunavaara iron ore. Master’s thesis. Luleå University of Technology, 53 pp. Nordstrand, J.; Andersson, U.B. (2013). Mineral chemistry of gangue of the Kiirunavaara iron ore, evidence for a transition from magmatic to hydrothermal conditions. 12th SGA Biennial Metting, Proceedings, Uppsala, Sweden 12-15/8. Geological Survey of Sweden, 1663-1666 Parák, Tibor (1975). The Origin of the Kiruna Iron Ores. Geological Survey of Sweden, C 709, 209 pp. Rieder, Milan; Cavazzini, Giancarlo; D'Yakonov, Yuriis; Frank-Kamenetskii, Viktor A.; Gottardi, Glauco; Guggenheim, Stephen; Koval, Pavel V.; Müller, Georg; Neiva, Anam R.; Radoslovich, Edward W.; Robert, Jean-Louis; Sassi, Francesco P.; Takeda, Hiroshi; Weiss, Zdenek; Wones, David R. (1998) Nomenclature of the Micas. Canadian Mineralogist, v 36, n 3, p 905-912 Romer, R. L.; Martinsson, O.; Perdahl, J. A. (1994). Geochronology of the Kiruna iron ores and hydrothermal alterations. Economic Geology and the Bulletin of the Society of Economic Geologists, 89, 6, 1249-1261

48

SERC (Science Education Research Center at Carleton College) website. http://serc.carleton.edu/research_education/geochemsheets/eds.html (2014-04-16)Smith, M.P.; Gleeson, S.A.; Yardley, B.W.D. (2013). Hydrothermal fluid evolution and metal transport in the Kiruna District, Sweden: Contrasting metal behaviour in aqueous and aqueous–carbonic brines. Geochimica et Cosmochimica Acta, v 102, p 89-112 Smith, M. P., Storey, C. D., Jeffries, T. E., and Ryan, C. (2009). In situ U-pb and trace element analysis of accessory minerals in the Kiruna district, Norrbotten, Sweden: New constraints on the timing and origin of mineralization. Journal of Petrology, 50(11), 2063-2094 Smith, M.P.; Gleeson, S.A.; Yardley, B.W.D (2013). Hydrothermal fluid evolution and metal transport in the Kiruna District, Sweden: Contrasting metal behaviour in aqueous and aqueous-carbonic brines. Geochimica et Cosmochimica Acta, v 102, p 89-112 Storey, C. D., Smith, M. P., and Jeffries, T. E. (2007). In situ LA-ICP-MS U–Pb dating of metavolcanics of norrbotten, sweden: Records of extended geological histories in complex titanite grains. Chemical Geology, 240(1), 163-181 Westhues A, Hanchar JM and Whitehouse MJ (2014). The Kiruna apatite iron oxide deposits, Sweden – new ages and isotopic constraints. Goldschmidt Abstracts, 2691

49

APPENDIX I – SAMPLE IMAGES Microscope images are scans of 28*48 mm sized thin sections. Length of individual staples is 12 mm. Thumb is 22 mm in width at mid-nail. RED NODULAR PORPHYRY RMP1

RMP2

1

RMP3

8053-Bh2 (223)

2

Kii2a

LUO5

3

8a

38

4

DARK NODULAR PORPHYRY MMP1

MMP2

5

Kii1a

6619

6

6481

LUO 4

7

8 b

16

8

WHITE-PINK NODULAR PORPHYRY 6207 B

LUO 6

9