No description available.

Sustainable mining, including the utilisation of an ore body to its full potential, is becoming increasingly important for human society as the demand for metals increases. In order to maximise the recovery of useful metals, detailed characterisation of the ore prior to processing is vital. Characterisation should include major and minor ore minerals, gangue minerals, and also trace metals. Trace metals despite their low abundance are often particularly important, either due to their high economic value and criticality for society, or their negative impact on the quality of the main commodity recovered and/or the environment. To properly characterise trace metals in an ore deposit the use of micro-analytical techniques is necessary. Nowadays, a plethora of techniques exist, each with their own strengths and weaknesses. In the mining industry, automated scanning electron microscopy systems are widely used. These systems allow for rapid mineralogical characterisation and quantification of a sample and are commonly used to quantify the mineralogy of the ore feed and subsequent products. Operators of these systems benefit from prior knowledge of the mineralogy of a sample/deposit to fine-tune their processing software to deliver data of highest quality. In this study, a method to improve trace metal characterisation in ore deposits with automated scanning electron microscopy systems is presented. It is implemented as a case study on the Liikavaara Cu-(W-Au) deposit in northern Sweden. The deposit is enriched in several trace metals including Au, Ag, Bi and Sn, and is planned for production in 2023. The mine will produce Cu as the main product and Au and Ag as by-products, and the processing of the ore will be performed in the nearby Aitik plant. For this study, a detailed geological and mineralogical investigation of the deposit was performed prior to analysis with the automated scanning electron microscopy system. A good understanding of the mineralogy is necessary to be able to select a representative sample for the subsequent automated analysis and to guarantee optimal data quality produced by the automated system, and to judge the performance of the automated system, to improve the method of analysis. Manuscript 1 deals with the geological description and genetic aspects of the Liikavaara ore deposit. Results indicate that Liikavaara is an intrusion-related vein-style deposit. Mineralisation is hosted by quartz-tourmaline and calcite veins in a metadiabase that is partly metamorphosed to biotite schist. A 1.87 Ga granodiorite intrudes the footwall. Aplite dikes, genetically related to the intrusion, crosscut the metadiabase host rock. Mineralised veins are concentrated in and around these dikes. Manuscript 2 deals with method development of automated mineralogical analysis. A sample from a mineralised quartz-tourmaline vein at Liikavaara was analysed in great detail with the QEMSCAN® system. Apart from ore minerals in major and minor abundance the sample also contains ore minerals in trace quantities, e.g. Au and Ag minerals. The sample was analysed using two different analytical settings, at two different laboratories, one typical of a production-focused industrial approach and one quality-focused scientific approach. A first analysis using the industrial approach was unable to detect any Au and Ag minerals in the sample. By modification of the QEMSCAN® mineral reference library, through iterative use of the data from both the industrial- and the scientific approach, detection and quantification of Au and Ag minerals was successful. This method can be implemented as an add-on for routine industrial analysis by automated scanning electron microscopy systems to gain information on trace metal occurrence and distribution. This information can then be used for targeted sample selection for further in-depth analysis of the trace metal content and occurrence in the deposit.

The mantle constitutes ~80% of Earths volume, however, due to its location deep beneath Earth’s surface the mantle is inaccessible to study in situ. Despite this, we still have information about its composition thanks to seismic studies which haven proven the mantle to be in generally homogenous and dominated by a rock called peridotite. However, mantle rocks such as peridotites sometimes, due to seismic activities, end up at Earth’s surface, for example as orogenic peridotite.The studied lithologies representing pyroxenitic and amphibolitic veins that were sampled near Härbergsdalen, located in northern Jämtland and within the Seve Nappe Complex (SNC). The SNC is interpreted as the outermost western margin of the paleocontinent of Baltica and part of the Middle Allochthon, one of four allochthons that together forms the Scandinavian Caledonides, an allochthon is a large sheet of rock that’s been displaced from its original position. During the Caledonian orogeny the western parts of Baltica was subducted under the paleo continent of Laurentia. Today ultramafic bodies are commonly occurring along the Seve Nappe, represented by peridotites, sometimes intruded by variety of veins. Such veining may shed light on P-T conditions and tectonic setting of the Earth’s mantle fragments and helps to understand the geological history of the Scandinavian Caledonides.Through applications of petrographic microscope (textural observations) and an electron microprobe (chemical analysis of minerals composition), collected samples from two different veins within orogenic peridotite outcrop on the western slopes of Aretstjakke mountain in Härbergsdalen were studied. The veins could easy be distinguished from each other as one almost black vein centered by red core and a second zonated, coarser sample. Results show that the veins don’t share a common history, one of the veins has a Garnet-bearing clinopyroxenitic core surrounded by zonated amphiboles. These amphiboles have an actinolite core and a rim of magnesio-hornblende, but also fully altered magnesio-hornblende grains. This shift in composition from relatively low P-T conditions in the actinolite core to more moderate P-T conditions in the magnesio-hornblende rim indicates progression into an environment deeper down into the Earths lithosphere. The other studied vein had amphiboles with pargasitic core surrounded by tremolite rim. Indicating retrogression through a drop in P-T conditions. In this second vein, there was also no signs of garnets, instead spinel’s where a common feature.These results indicate the veins were formed during different events, however further studies have to be made to correlate and understand all the processes recorded within the Aretstjakke peridotite outcrop. Further on, this outcrop is the third ever within the Seve Nappe Complex where garnet-bearing clinopyroxenite has been found, an interesting find worth more studies to put in context. / Manteln utgör ~80% av jordens volym, men trotts dess enorma volym så är manteln omöjlig att studera in-situ på grund av tjockleken på ovanliggande jordskorpa. Tack vare seismiska studier har vi ändå information om mantelns samansättning som visat sig vara homogen och dominerad av en bergart kallad peridotit. Mantelbergarter som peridotit kan trotts allt, tack vare seismisk aktivitet hamna på jordens yta, till exempel som orogena peridotiter.Härbergsdalen i norra Jämtland är en del av Seveskoll-komplexet och representerar paleokontinenten Baltikas yttersta västra gräns. Seve är i sin tur en del av den mellersta Skollberggrunden, en av fyra större skollor som tillsammans formar den skandinaviska bergskedjan, en skolla är en del av berggrunden som av tektoniska event förflyttas från sin ursprungliga position. Under den Kaledoniska orogenesen då de båda paleokontineterna Baltika och Laurentia kolliderade pressades Baltiska plattans västra delar ner djupt under Laurentia. Ultramafiska fragment i form av peridotiter, ibland genomskurna av olika typer av gångbergarter kan idag hittas på ett flertal platser längs med Seveskollan. Dessa bergarter formas under högt tryck inne i jordens mantel och fungerar som bra tryck och temperatur indikatorer när man studerar den skandinaviska bergskedjans historia.Med hjälp av ett petrografiskt mikroskop (för att identifiera mineral texturer) och en elektronmikrosond (för kemiska analyser av stuffer) undersöktes pyroxenitiska och amfibolitiska stuffer insamlade från ådror som tränger genom hällar av orogena-peridotiter på fjället Aretstjakke i Härbergsdalen. Resultaten visade på ett komplext samband mellan ådrorna där olika typer av bergarter tydde på olika bildningsmiljö. En av ådrorna visade sig ha en kärna av granatbärande klinopyroxenit omgiven av zonerade amfiboler. Amfibolerna som har blivit altererade uppvisar en aktinolitisk kärna och kanter bestående av magnesio-hornblende. Detta tyder på en förändring i miljö från relativt låga tryck och temperaturförhållanden till ett facies som kännetecknas av mer moderata tryck och temperaturer. Den andra venen som undersöktes visade på motsatta förhållanden där en pargasitisk kärna var omgiven av tremolit. Pargasit är stabilt under högre tryck och temperatur än pargasit, vilket visar att det skett ett dropp till lägre tryck och temperaturförhållande. Här hittades spineller i stället för granater vilket indikerar en bildningsmiljö med lägre tryck än i den granatbärande klinopyroxeniten.Resultaten visar att de båda ådrorna som proverna var tagna ur hade bildats under två skilda händelser. För att förstå de olika processer som skapat dessa gångar i Aretstjakke peridotiten och sätta händelserna i relation till varandra skulle ytterligare och mer omfattande studier behöva utföras. Vidare är det värt att notera att fyndet av granatbärande klinopyroxenit är det tredje någonsin inom Seve Skollkomplexet, vilket gör platsen intressant för ytterligare studier. / Polish National Science Centre no. 2019/35/N/ST10/00519 for Daniel Buczko

Some parts of the mineralogy and the petrology of the Enåsen gold-deposit, northern Hälsingland, Sweden are described. The gold in Enåsen is extracted from a sillimanite-rich quartzite. The rocks in the stratigraphic foot-wall of the ore are described as a part of a stratigraphic column. It is suggested that the sillimanite-quartzite is a part of an overturned stratigraphic sequence. The temperature and the pressure during the main metamorphose is determined to 620-670º C and 5-6.5 kbar by use of the mineral paragenesis and the graphite geothermometer. It is shown that the ores are of epigenetic origin and it is suggested that the different ores were formed by one continous ore-forming process. The earlier stages of the ore-formation were caracterized by a relatively homogeneous infiltration of the ore-bearing fluids. During the late stage of the ore formation, the ore-bearing fluids were restricted to localized veins. These veins are now recognized as grey sillimanite-rich veins surrounded by sulphides and as calcite-altered veins with sulphides. It is also suggested that the presence of graphite in the undermost stratigraphic level of the foot-wall reduced the water-molefraction which directly caused the deposition of the sulphides and the gold.

No description available.

No description available.

The Taimyr Peninsula is a key element in the circum-Arctic region and represents the northern margin of the Siberian Craton. The Taimyr Peninsula preserves late Paleozoic through Mesozoic clasitic sedimentary successions in its Mesozoic fold belt, providing an ideal location to investigate the Mesozoic tectonic evolution associated with the opening of Amerasia Basin within a circum-Arctic framework. This thesis aims to establish the tectonic setting in which the late Paleozoic through Mesozoic sediments of Taimyr were deposited, in order to correlate Taimyr with other Arctic terranes utilizing provenance investigations. Multiple methods are adopted, including petrography, heavy mineral analysis and detrital zircon U-Pb geochronology.  The preliminary results of this work indicate that the late Paleozoic sediments of southern Taimyr were deposited in a foreland basin of the Uralian orogen during Uralian orogeny. The final collision between Baltica and Siberia in the last stage of Uralian orogenesis occurred between Early and Late Permian. Early Cretaceous sediments in northern Taimyr were mainly derived from Siberian Trap-related magmatism in Taimyr. Cretaceous sediment deposition is unrelated to Jurassic to Cretaceous rifting associated with the Verkhoyansk fold belt and instead relates to a rifting or post-rifting passive margin setting.

Technological and societal developments in the past century have greatly increased our society’s demand for metals, many which occur in polymetallic ores mined in the Skellefte district, northern Sweden. Near-surface deposits are becoming depleted and as such targeting of deep deposits is needed, which places special demand on effective management, processing and interpretation of geological data obtained from exploration drill holes. New exploration tools and software solutions utilizing machine learning to assist data analysis are becoming increasingly important. However, to get the most of these new tools, a solid geological understanding of prospective areas must first be established. This thesis uses the Rävliden North Zn-Pb-Ag-Cu volcanic massive sulphide (VMS) deposit as a study location to understand its lithostratigraphy and enveloping alteration. The Skellefte district VMS deposits are mainly located at the lithostratigraphic contact between the metavolcanic 1.89 – 1.88 Ga Skellefte group (SG) and the stratigraphically overlying metasiliciclastic 1.89 – 1.87 Ga Vargfors group (VG) rocks. The VMS deposits are commonly enveloped by a zoned alteration with variable alteration intensity and mineral assemblages of quartz, sericite, chlorite and talc at different distance to mineralisation.  Sixteen lithofacies and eight precursors can be defined in the Rävliden North host succession, where the SG dominantly contains coherent and volcaniclastic facies of rhyolite, dacite and andesite. The VG contains graphitic phyllite interbedded with polymict breccia-conglomerates, andesitic turbidites and mafic mass-flow deposits. Immobile element lithogeochemistry reveals four rhyolitic (Rhy I – IV), two dacitic (Dac I and II), an andesitic (And I), and a basaltic (Bas I) precursors. The VMS deposits are hosted by graphitic phyllite Tr-rich calc-silicate rock, and a Chl>Ser±Tlc±Qz-altered rock in the contact between the SG and VG.  Four alteration types are recognised and spatially associated to mass changes of mobile elements. The Tr-rich calc-silicate and calcitic rocks are related to gains in CaO and occur proximal to mineralisation. Chlorite>Ser±Tlc±Qz alteration is related to gains in MgO and FeO and also occur proximal to mineralisation. The choice of least-altered volcanic rocks, needed for modelling fractionation, is found to have effect on the resulting mass-balance calculation; however, qualitative recognition of mass changes related to the ore-hosting alteration types is still possible. The uncertainty ranges of mass changes are determined to be ±0.5 wt.% for MgO, FeO and CaO. This thesis demonstrates that geological understanding and quantification of error and uncertainty in mass balance calculations are necessary prerequisites to advanced exploration techniques.

The Älgträsk Au-deposit is situated in the Jörn Granitoid Complex (JGC) immediately north of the Skellefte VMS district, northern Sweden. The Skellefte VMS district comprise a complex volcanosedimentary sequence, which has been interpreted as the remnant of a Palaeoproterozoic island arc or continental margin arc situated behind a northward dipping subduction zone. The volcanosedimentary succession was intruded by the early orogenic-synvolcanic JGC, constituting I-type, calc-alkaline granitoids at c. 1.89-1.87 Ma. The outer zone of the JGC represents the oldest part and is the most compositionally heterogeneous, ranging from gabbro to granodiorite, while younger units are of a more felsic character ranging from granodiorite to granite in composition.The Älgträsk intrusive hosted Au-deposit is situated in the southern part of the oldest JGC intrusion, mainly hosted within a coarse grained, often quartz porphyritic, granodiorite. Mineralisation occurs as veins and disseminations of mainly pyrite with locally abundant arsenopyrite, chalcopyrite, sphalerite and minor electrum within a proximal silicic to phyllic hydrothermal alteration and distal propylitic hydrothermal alteration in close vicinity to deformation zones. Geochemical data suggest that hydrothermal alteration associated with mineralisation in the granodiorite caused addition of Si, Fe and K together with a significant increase in Au, Te, Cu, Zn, As and loss of Ca and Na. Gold alloys and telluride minerals such as petzite, tellurobismuthinite, krennerite, volynskite and hessite occur intergrown within fractures, along grain boundaries or as inclusions in pyrite and/or arsenopyrite and less common by together with quartz and phengite. Besides propylitic, phyllic and silicic alteration associated with mineralisation, sodic-calcic and quartz destructive alteration characterize the deposit, although with an unclear relationship to mineralisation. The tonalite hosted Tallberg porphyry Cu-deposit, situated only 3 km west of Älgträsk, is associated with quartz brecciation and quartz feldspar porphyritic dykes. These dykes are suggested to be genetically related to similar porphyry dykes overprinted by mineralisation in Älgträsk and the tonalitic host rock in Tallberg. However, the granodiorite hosting the Älgträsk Au-deposit does not appear to be genetically related to the tonalite in Tallberg or the porphyry dykes in neither Älgträsk nor Tallberg. Both styles of mineralisation are cut by mafic dykes, tentatively correlated with 1.87 Ga magmatism, hence representing the last magmatic event in the area. The mineralising fluids at Älgträsk are suggested to have been channelled by structurally weak zones in the upper crust where deposition of sulphide minerals was followed by precious metals. Structural interpretations suggest that the Au-deposit in Älgträsk is hosted by D2 and D3 structures and thus is younger than the porphyry Cu-deposit in Tallberg. Together with the style of mineralisation and associated alteration at the Älgträsk deposit, it resembles either intrusion related Au-systems or shallow level epithermal systems often developed above younger Phanerozoic porphyry Cu-deposits. Alternatively, ductile deformation took place during subsequent tectonic events, likely causing remobilization of sulphide minerals and precious metals, e.g. from a deeper lying porphyry style mineralisation, forming an orogenic style mineralisation.

This thesis combine two different but closely connected disciplines in a mining process to each other, ore geology and process mineralogy by studying mineralogical-textural features of the ore and the ore concentrate in an apatite iron ore deposit in Malmberget, Sweden. Apatite iron ore deposits (Kiruna type) exist in a few places around the world and the two most important deposits are mined by LKAB at Kiruna and Malmberget. Their contribution to the global iron ore market is minor but on a local scale these high grade deposits have a large economical importance. Three different ore bodies from the Malmberget deposit are included in the study; Hens, ViRi and Fabian. Each of these three ore bodies has characteristic mineralogy, chemical and textural properties. The first paper (Paper І) describes the metamorphic influence on the ore, particular the chemical and textural effects on the ore minerals. The ore bodies Fabian and ViRi have a similar mineralogy by the occurrence of Ti-minerals, pyrite and chalcopyrite as common minor components. Hematite is only present in Hens ore body. Magnetite from the different ore bodies and ore types show a chemical variation of the minor elements V2O3, TiO2, Al2O3, and MgO. Our data support a model with the massive ore formed from an iron oxide melt while the ore breccia is part of the same ore forming system but of hydrothermal origin. The second and third paper is about process mineralogy. Paper two (Paper ІІ) characterise the mineralogical properties of an apatite iron ore body in a quantitative manner by using an automated SEM based system QEMSCAN®. Two major ore types were used; massive ore and ore breccia. Each ore type was crushed and split in the fractions 150 µm, 75 µm and 38 µm. The results show a rather distinct difference between these two ore types, both in the mineralogy but particularly in their textural properties. The particle liberation of magnetite is high for massive ore, being much lower for ore breccia and has a decreasing liberation in finer fractions in each ore type. This has to do with grain size, mineralogy and textures of the magnetite and the gangue minerals. The mineral associations of ore breccia are more diverse than of massive ore by the presence of more binary and complex magnetite bearing particles. Ore breccia is an ore type where some of the magnetite bearing associations will cause an increasing amount of silica in the concentrate or iron content to the tailings. Paper three (Paper ІІІ) shows that is possible to find traceability in a concentration process by identifying significant mineralogical signatures in the ore and in the concentrate. Two possibly useful mineralogical signatures were found. The first is a rather simple association between magnetite and apatite existing as mixed grain and the second is a complex texture with smaller magnetite grains as inclusions in feldspars grains. These signatures can probably be used as a fingerprint for different ore types, particle fractions and grinding circuit which can create traceability in the process. The results from these two instruments show some differences, QEMSCAN® compared to PTA generate analysis which being more accurate and precise due to the amount of data in each sample. / I den här avhandlingen förenas två olika, men i en gruvprocess närliggande discipliner, malmgeologi och processmineralogi. Det sker genom att studera de mineralogiska-texturella egenskaperna om hur malmen ser ut i fast klyft och hur malmkoncentratet beter sig i en anrikningsprocess. Fyndigheten som studerats är LKAB:s apatitjärnmalm i Malmberget. Apatitjärnmalmer (av Kirunatyp) finns på ett fåtal platser runt om i världen och de två mest betydande fyndigheterna bryts idag av LKAB i Kiruna och Malmberget. Sett till den globala järnmalm marknaden är produktionen liten men i en lokal skala är dessa höghaltiga järnmalmer av största ekonomiska vikt. Tre olika malmkroppar ingår i denna studie Hens, ViRi och Fabian. Dessa är karaktäriserade i avseende på mineralogi, kemi och texturella egenskaper. Det första manuskriptet (Paper І) beskriver malmmineralen kemiskt och texturellt med tyngdpunkten på inverkan av den metamorfa överpräglingen. Mineralogiskt är ViRi och Fabian liknande, med avseende på förekomsten av Ti-mineral, pyrit och kopparkis. Hens skiljer sig från dessa två malmkroppar genom förekomsten av hematit. Magnetit från olika malmkroppar och malmtyper visar en kemisk variation mellan elementen TiO2, V2O3, Al2O3 och MgO. Magnetit från den massiva delen av Fabian malmkropp har kemiska likheter med andra apatitjärnmalmer och kan ursprungligen ha bildats genom kristallisation från en järnoxidmagma eller genom hydrotermala processer under höga temperaturer. Magnetit från malmbreccia har bildats under lägre temperatur och andra hydrotermala förhållanden. Det andra och tredje manuskriptet handlar om processmineralogi. I manuskript två (Paper ІІ) görs en kvantitativ mineralogisk karaktärisering av malmkroppen Fabian mineralogiskt genom att använda ett automatiserat SEM baserat system kallat QEMSCAN®. Två olika malmtyper massiv malm och malmbreccia har nedkrossats och siktats i tre fraktioner 150µm, 75µm och 38µm. Det är stor skillnad mellan malmtyperna både i avseende på mineralogin men även deras texturella egenskaper. Den modala mineralogin visar att malm breccia innehåller högre andel gångartsmineral. Magnetit från malm har en hög frikrossningsgrad medan den är lägre för malmbreccia. Båda malmtyperna visar en minskande frikrossningsgrad i finare fraktioner. Detta är ett resultat av kornstorlek, mineralogi och textur av både magnetit och gångartsmineral. Mineralassociationerna i malmbreccia är fler och mer komplexa än i malm och oavsett om mineralassociationer med magnetit hamnar i koncentratet eller avfallet så ökar kiselhalten i koncentratet eller så ökar järnhalten i avfallet. Manuskript tre (Paper ІІІ) beskriver en metod att hitta spårbarhet i anrikningsprocessen i Malmberget genom att påvisa och identifiera signifikanta mineralogiska signaturer både i malmen (fast klyft) och i anrikningskoncentratet. Två möjliga mineralogiska signaturer påvisades. Det är dels en enkel association med halvkorn bestående av magnetit och apatit och dels en mer komplicerad textur där små magnetitkorn sitter som inneslutningar inne i fältspatskorn. Dessa identifierade signaturer kan förmodligen fungera som "fingeravtryck" för olika malmtyper, partikel fraktioner och malningskretsar och kan därigenom användas till spårbarhet genom processen.