Lic.-avh. Luleå : Luleå tekniska univ., 2008.

In recent years, a variably high amount of uranium (U) and radon (Rn) were found in the water and airof the Kiirunavaara mine in Kiruna, northern Sweden. The Swedish Agency for Marine and WaterManagement (Havs och vattenmyndigheten) has maximum limits for “special polluting substances” inwater that is released to natural recipients (HVMFS 2019:25), therefore, the mining company LKAB,owner and operator of the Kiirunavaara mine, decided to conduct a study to investigate the issueregarding these findings, triggering this master thesis.From LKAB’s geochemical database, 25 samples were selected, prepared and studied throughpetrographic microscopy. Fourteen samples went through more than 70h of EPMA and BSE imageanalysis and 5 of them went through MLA. All methods were performed either in Uppsala’s Universitylaboratories or in Kiruna, at LKAB´s research facility in Malmberget. The ultimate goal of this projectwas to determine the primary metal source of uranium that could cause future problems in the watertreatment processes and leakages to recipients.In order to aboard this study in Kiirunavaara, where no previous uranium related study was everconducted, the main objectives were divided into identifying the main mineral carrier(s) of uranium thatcould be the source for these U anomalies, the characterization of the rock types and mineralassemblages associated with U-bearing minerals, and last, to try to propose preliminary implications forU solubility and distribution in the rock mass and mine water. This study found uraninite, thorite and anunknown species bearing uranium in some of the samples, both hanging and foot wall, all related tohydrothermal alterations and anhydrite. The water circulation throughout the rock mass of the minecould have been the trigger and transporter of these elements that were causing the anomalies in the firstplace.

The Kiirunavaara mine hosts one of the world’s largest apatite-iron ore mineralisations. This ore body has been subject to large amounts of research as well as extensive mining. The ore body is situated between the syenitic foot wall and the rhyodacitic hanging wall, of which consists of differing mineralogy and characteristics. Both these rock masses contain intrusive porphyry dykes, with distinct characteristics of it own. The aim of this study was to analyse 31 samples, mainly in the form of thin sections, and determine the mineralogy and identify eventual microstructures. This was done through the use of optical mineralogy as well as EDS/WDS analysis at the National Microprobe Lab at Uppsala University. The foot wall consists of syenite-porphyry and is dominated by feldspar in both groundmass as well as phenocrysts. Characteristic for the syenite-porphyry is the rounded nodules containing actinolite, titanite, magnetite and chlorite. The hanging wall is defined as quartz-bearing porphyry. It is a rhyodacitic rock with large amounts of feldspar along with green silicates, quartz, titanite and calcite. The intrusive porphyry dyke-rocks share many similarities with the quartz-bearing porphyry, but contain a finer groundmass with larger amounts of clinopyroxene, as well as lower amounts of quartz, magnetite and titanite. Hydrothermal alteration is prevalent in all the types of rock. Alteration minerals such as actinolite, biotite and chlorite are very common within the Kiirunavaara-rocks. The quartz-bearing porphyry displays the most extensive exposure to hydrothermal fluids. The hydrothermal fluids have penetrated several samples, replacing minerals and leaving very few remnant, older minerals. The quartz-bearing porphyry contains the most prominent deformation structures, of varying extent and magnitude. Magmatic flow structures can be seen in the groundmass, as parallel alignment of feldspar and silicate grains. Evidence of solid-state deformation most commonly occurs as pressure shadows around feldspar phenocrysts. / Kiirunavaara-gruvan är belägen vid en av världens största mineraliseringar av apatit-järnmalm. Denna malmkropp har stått i fokus för både omfattande gruvdrift samt genomgripande forskning. Malmkroppen är belägen mellan den syenitiska liggväggen och den ryodacitiska hängväggen, som består av varierande mineralogi och karaktär. Båda av dessa bergmassor innehåller intrusiv gångporfyr med distinkt karaktär. Målet med denna studie var att analysera 31 prover, främst i form av tunnsliper, och bestämma dess mineralogi samt att identifiera eventuella mikrostrukturer. Detta genomfördes genom användning av optisk mineralogi och EDS/WDS-analys vid det nationella mikrosondslaboratioriet vid Uppsala Universitet. Liggväggen består av syenitporfyr och domineras av fältspat i både mellanmassa och som fenokrister. Karaktäristiskt för syenitporfyren är de rundade nodulerna, innehållandes aktinolit, titanit, magnetit och klorit. Hängväggen definieras som kvartsförande porfyr. Det är en ryodacitisk bergart med stora mängder fältspat, gröna silikater, kvarts, titanit och kalcit. Gångporfyren delar många likheter med den kvartsförande porfyren, men består av en finare mellanmassa med större mängd klinopyroxen, samt innehåller mindre mängder kvarts, magnetit och titanit. Hydrotermal omvandling är allmänt förekommande i alla bergarter i Kiirunavaara. Omvandlingsmineral så som aktinolit, biotit och klorit är väldigt vanliga hos Kiirunavaara-bergarterna. Den kvartsförande porfyren uppvisar den mest omfattande exponeringen av hydrotermala vätskor. De hydrotermala vätskorna har penetrerat ett antal prover och därigenom omvandlat mineral, med liten mängd äldre mineral kvar. Den kvartsförande porfyren innehåller de mest prominenta deformationsstrukturer, av olika omfattning och magnitud. Magmatiska flytstrukturer kan observeras i mellanmassan som parallell orientering av fältspat- och silikatkorn. Tecken av fastfasdeformation förekommer främst i form av tryckskuggor runt fältspatsfenokrister.

The geotechnical parameters of the different lithologies are of great importance regarding mining, infrastructures development and safety. The main aims of this thesis project are the evaluation of the previously acquired point load tests (PLT) data and the acquisition of a larger set for the various lithologies and alterations. In addition, the correlation to the Leeb Hardness test (LHT) method, and the determination of correlation factors (K) for estimating the uniaxial compressive strength (UCS) index from PLT data for various lithologies were evaluated. In total, 5236 previously PL tested samples, 1113 newly PL tested samples and 569 LHT measurements were obtained. The results showed that the highest values come from the footwall lithologies (Sp) ranging between 11-19 MPa, while the hanging wall lithologies (Qp) fall in range 10-14 MPa and the different ore types between 6-11 MPa. The correlation between PLT and LHT was poor, with the results completely overlapping for all country rock lithologies in the range 800-900 LHD, while the ore types fall in the range 600-700, and anhydrite at 500 LHD. On the other hand, the correlation factors K for the lithologies tested vary between 13-20 for the weaker and more altered rock types and 25-30 for the stronger ones, correlating well when compared to the actual UCS values found in the literature. In conclusion, it is evident that the LHT is not able to substitute the PLT as it captures different properties of the rock. The conversion from PLT to UCS gave rather accurate results, with slightly different correlation factors K for the tested lithologies.

Gruvavfall, i form av gråberg, från Kiirunavaara-gruvan i Kiruna, norra Sverige undersöktes för att se om surt lakvatten kan bildas från gråberget och om detta kan ha en påverkan på hur mycket kväve som kan lakas ut från gråberget. För detta ändamål gjordes dels en mineralogisk undersökning av gråberget, med siktning, röntgendiffraktion (XRD) och grundämnesanalys och dels laborativa skakförsök. Från skakförsöken, där olika kornstorlekar (8-16 mm, 2-4 mm och mindre än 1 mm) blandades med avjoniserat vatten med L/S-kvoten 10, kunde förändringar i pH, alkalinitet och lösta joner undersökas över en 10-veckors period.                       De främsta mineralen i gråberget i Kiirunavaara visades vara plagioklas, kvarts och biotit. I gråberget finns även 18 g pyrit/kg gråberg. Skakförsöken indikerar att lakvattnet från gråberget i Kiirunavaara är alkaliskt med ett pH över 9. Vittring av sulfidmineral sker, men neutraliseras av buffrande mineral som kalcit och ingen potential till produktion av surt lakvatten finns. Kväveutlakningen sker främst under de första dygnen, men mer än hälften av de kväveföreningar som antas finnas i gråberget lakas inte ut. Både nitrat och ammonium visade signifikanta korrelationer med pH, där högre pH-värden tydde på högre nitratkoncentrationer och lägre pH-värden på högre ammoniumkoncentrationer. Detta indikerar att även om inget samband kunde ses mellan produktion av surt lakvatten och kväveutlakning, så är mängden av olika kväveföreningar som lakas ut beroende av lakvattnets pH-värde. / Mining waste rock from the Kiirunavaara-mine in northern Sweden was studied to determine if there is a potential for production of acid mine drainage (AMD), if there is a leaching of nitrogen compounds from the waste rock and if a correlation between the two processes can be seen. A mineralogical characterization of the waste rock was done through dry sieving, X-Ray Diffraction (XRD) and elemental analysis. Through shake flask experiments, where waste rock of three different grain sizes (8-16 mm, 2-4 mm and less than 1 mm) were mixed with deionized water (L:S-ratio of 10), the change in pH, alkalinity and dissolved ions during a 10-week period was determined.                       The waste rock in Kiirunavaara was found to consist mainly of plagioclase, quartz and biotite, but the waste rock also contains 18 g pyrite per kg waste rock. The shake flask experiments indicate that the mine drainage from the waste rock in Kiirunavaara is alkaline, with a pH above 9. Weathering of sulphide minerals occur, but are neutralised by buffering minerals such as calcite and thus no potential for AMD-production exists. The leaking of nitrogen compounds occurs mainly during the first few days. Both ammonium and nitrate showed significant correlations with pH, where lower pH-values typically exhibited higher ammonium concentrations, while higher pH-values correlated with higher nitrate concentrations.