The current mining method in Zinkgruvan today is underhand stoping. With this method the ore is mined downwards in disks. When the ore is extracted the stope is backfilled with paste which contains tailings, cement and water. The paste will constitute the ceiling in lower levels and are therefore vital for the safety and the requirements of the strength. The goal of this thesis is to increase knowledge about the paste’s strength after the usual tests within 28 days. Test objects are taken from two different paste’s in Burkland and Nygruvan and compares with old data from the same sights. Besides the test objects that are taken from the mine there are also some studys on the literature with consideration on mine backfill in other mines using a similar mining method. By interviewing experts at Zinkgruvan increased knowledge is acquired about the production and the company. By the results an indication is given regarding the possibility of optimizing the paste containing eight percent cement to a lower amount in order to reduce costs. The results shows that the paste increases in strength after standard testing within 28 days.

Zinkgruvan is a stratiform Zn-Pb-Ag deposit located in the Bergslagen ore district in south central Sweden. Elevated concentrations of cobalt have been detected in zinc ore from the mine. Cobalt is one of EU’s critical raw materials, since cobalt is mainly mined in politically unstable countries like Congo and is an important metal needed in batteries for modern technology, e.g., electrical cars. However, elevated contents of cobalt can also cause problems during smelting of zinc ore and lower the value of zinc concentrates. Knowledge of the mineralogical deportment of cobalt is in this context critical, since accessory cobalt minerals could potentially be separated from zinc concentrates, whereas lattice-bound cobalt in sphalerite will follow the latter throughout the processing chain. In this study, the mineralogical distribution in zinc ore from three different main areas of Zinkgruvan (Knalla, Nygruvan and Westfield) has been investigated using optical microscopy, whole rock lithogeochemistry, Scanning Electron Microscope (SEM), Electron Microprobe Analysis (EMPA), Quantitative Target Mineralogy (QanTmin) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The different datasets have been integrated in order to provide quantitative data on cobalt deportment in the samples, and for defining geochemical proxies that can be used to predict the cobalt deportment using only whole rock assay data. For the majority of the samples of this study, the cobalt content in sphalerite is higher than what has been reported in earlier studies of Zinkgruvan and are among the highest globally. In addition, this study provides the first account of high levels of lattice-bound cobalt in pyrrhotite at Zinkgruvan, for some samples being even higher than in sphalerite. Thus, the pyrrhotite could also potentially be separated from the zinc concentrate in order to dispose of some of the cobalt in the samples.  However, for the samples on which cobalt deportment calculations have been made, the results of the calculations suggest that for 50% of the samples most of the whole rock cobalt is lattice-bound to sphalerite, which is by far the predominant mineral in the zinc ore. For the remaining 50% of the samples most of the whole rock cobalt is bound to the cobalt mineral safflorite, which locally forms an important accessory mineral. No sample has the majority of the whole rock cobalt in pyrrhotite, reflecting the generally minor contents of this mineral in the zinc ore. In general, there is more lattice-bound cobalt in pyrrhotite and sphalerite in samples from Westfield and more cobalt bound to cobalt minerals in samples from Knalla. Samples from Nygruvan have very low whole rock cobalt contents altogether and contain no cobalt minerals. These spatial variations support ore genetic zonation models presented by earlier studies, with increasing Zn/Pb ratios and decreasing cobalt content in zinc ore from proximal to distal, in relation to an old hydrothermal vent zone at Knalla. However, the high cobalt and cadmium contents found at Westfield could imply that the vent zone might be more widespread than assumed by earlier studies. / Zinkgruvan är en stratiform Zn-Pb-Ag-malmförekomst som ligger i malmdistriktet Bergslagen i södra Sverige. Förhöjda koncentrationer av kobolt har upptäckts i zinkmalmen från gruvan. Kobolt är en av EU:s kritiska råmaterial eftersom kobolt främst bryts i politiskt instabila länder som t.ex. Kongo och eftersom det är en viktig metall som behövs i batterier för modern teknik, exempelvis elbilar. Förhöjda halter av kobolt kan dock också orsaka extra kostnader och försämrat utbyte vid zinkframställning från zinkmalm, och kan därmed sänka en zinkmalms värde. Kunskap om den mineralogiska fördelningen av kobolt i zinkmalmen är i detta fall avgörande, eftersom accessoriska koboltmineral potentiellt skulle kunna avlägsnas innan smältprocessen, till skillnad från gitterbunden kobolt i zinkblände som följer med zinken i hela utvinningsprocessen. I denna studie har den mineralogiska distributionen i zinkmalm från tre olika huvudområden i Zinkgruvan (Knalla, Nygruvan och Västra fältet) undersökts genom användning av optisk mikroskopering, geokemisk analys av bulkprover, svepelektronmikroskopi (SEM), elektronmikrosondanalys (EMPA), kvantitativ mineralogi (QanTmin) och laserablation-induktivt kopplad plasma-masspektrometri (LA-ICP-MS). De olika dataseten har integrerats för att tillhandahålla kvantitativa data för koboltfördelning i proverna och för att kunna definiera geokemiska kriterier som kan användas för att förutsäga koboltfördelningen med hjälp av endast litogeokemisk analysdata. För majoriteten av proverna i denna studie är koboltinnehållet i zinkblände högre än vad som har rapporterats i tidigare studier av Zinkgruvan, och är bland de högsta globalt. Dessutom tillhandahåller denna studie den första redogörelsen för höga nivåer av gitterbunden kobolt i magnetkis. För vissa prover är det sistnämnda till och med högre än i zinkblände. Således skulle även magnetkisen potentiellt kunna separeras från zinkkoncentratet för att bli av med en del av kobolten i proverna. För de prover där beräkningar på koboltfördelningen har gjorts visar dock resultaten av beräkningarna att för 50% av proverna förekommer merparten av bulkinnehållet av kobolt i malmen som gitterbundet i zinkblände, vilket är det överlägset dominerande mineralet i zinkmalmen. För de resterande 50% av bulkproverna är det mesta av kobolten bundet till koboltmineralet safflorit, som lokalt är ett viktigt accessoriskt mineral. Inget bulkprov har merparten av koboltinnehållet i magnetkis, vilket reflekterar det generellt lägre innehållet av detta mineral i zinkmalmen. I allmänhet finns det mer gitterbunden kobolt i magnetkis och zinkblände i bulkprover från Västra fältet och mer kobolt bundet till koboltmineral i bulkprover från Knalla. Bulkproverna från Nygruvan har väldigt lågt koboltinnehåll överlag, och innehåller inga koboltmineral. Dessa spatiala variationer stödjer malmgenetiska zoneringsmodeller presenterade i tidigare studier, med ökande Zn/Pb kvoter och minskande koboltinnehåll i zinkmalmen från proximal till distal, i relation till en fossil hydrotermal tillförselkanal i Knalla.  Det höga kobolt- och kadmiuminnehållet som detekterats i Västra fältet kan dock antyda att den hydrotermala tillförselkanalen skulle kunna vara mer utbredd än vad som antagits av tidigare studier.

Zinkgruvan is a stratiform Zn-Pb-Ag and Cu sulphide deposit hosted by Paleoproterozoic strata in southern Bergslagen, Sweden. The deposit underwent medium-high grade regional metamorphism during the Svecokarelian orogeny, including partial melting of the host succession. Subordinate zones of semi-massive to massive magnetite and Fe-rich skarns occur in marble stratigraphically below the stratiform Zn-Pb-Ag ore but have so far not been described in detail in the scientific literature. This thesis presents results from detailed geological drill core logging, light optical microscopy (LOM) and scanning electron microscopy (SEM), which have been integrated with results from electron microprobe analysis (FE-EMPA) and whole-rock lithogeochemical analysis to provide a comprehensive description of the magnetite mineralization. Samples from the formerly mined magnetite deposits Västerby, Garpa and Åmme - distal to Zinkgruvan - have also been studied to allow for a comparison. The combined dataset has been used to 1) discuss the genesis of the magnetite mineralizations, including their relationship to base metal sulphide mineralization, and 2) evaluate potential vectors to Zn-Pb-Ag and Cu mineralization based on variations in the magnetite deposits. The semi-massive to massive magnetite, adjacent and associated Fe-rich skarn at Zinkgruvan are located in the stratigraphic upper part of the marble host. Three different varieties of magnetite mineralization can be defined: 1) semi-massive to massive magnetite mineralization in marble, 2) magnetite-bearing veins and 3) retrograde magnetite after olivine. Detailed optical microscopy has revealed a positive spatial correlation between aluminium spinel, apatite, magnetite and graphite. Semi-massive to massive magnetite mineralization at Zinkgruvan is enriched in P2O5, ΣREELa-Lu and Mn relative to a carbonate precursor. A positive correlation exists between P2O5 and ∑REELa-Lu, suggesting apatite and monazite are the primary REE-bearing minerals. The fact that the samples with highest P2O5 and ∑REELa-Lu are all Fe-rich rocks suggest the enrichment of the latter is related to the event which formed the Fe mineralization. Magnetite mineralization from the historic iron mines NW of Zinkgruvan share several key attributes with magnetite mineralization at Zinkgruvan. These include: 1) magnetite is the only iron oxide, 2) lithological and mineralogical similarities, including spatial association with marble, 3) equally high whole-rock Fe content, 4) equally high Mn (1-4 wt.% MnO), 5) equally high Eu anomalies (Eu/Eu* = 1.1- 2.8, avg. 1.75), and 6) local presence of sphalerite mineralization. Bending of the tectonic foliation from c. E-W to NW in the western part of Zinkgruvan suggest these magnetite mineralizations may be located along the same trend as those at Zinkgruvan. The normal calc-silicate mineralogy in Zinkgruvan marble (e.g. diopside, forsterite, phlogopite) can be explained by prograde regional metamorphic reactions between silicates and dolomite or calcite in impure carbonate rocks with a variable content of detrital siliciclastic and volcaniclastic material. However, the stratabound magnetite mineralization and associated Fe-rich skarns cannot be fully accounted for by this model. It is plausible that the Fe-rich skarns can be explained by similar reactions but involving more Fe-rich carbonates (ferrodolomite, ankerite, siderite). In the absence of quartz, siderite is known to thermally decompose into magnetite and graphite at temperatures above 465° C, whereby siderite-rich rocks may have been precursor to the semi-massive to massive magnetite mineralization. A recent genetic model suggests that the ore-forming fluids which formed Zinkgruvan where similar to those which formed McArthur-type SEDEX deposits. The presented results are consistent with this model, since e.g. siderite is a common alteration mineral in alteration envelopes to such deposits. Hence, magnetite mineralization, Zn-Pb-Ag and Cu-ore may all be related to the same pre-metamorphic hydrothermal system. The current genetic model places the magnetite mineralization at Zinkgruvan proximal to a fossil hydrothermal vent zone (the Burkland discontinuity). It is plausible that the magnetite mineralization mined at surface lay along the northern continuation of the Burkland discontinuity. Based on the assumption that the Burkland Cu-mineralization is most proximal and the old iron mines at Åmme are most distal along this structure, variations in whole-rock lithogeochemistry, mineral chemistry and mineralogy have been used to define nine vectors to economic Zn-Pb-Ag and Cu ore as is mined at Zinkgruvan.

<p>The potential of variations of <i>b-</i>values in the G-R relation, log<i>N=a-bM</i> as earthquake precursors for small events (rockbursts) in Zinkgruvan mine, Sweden and for tectonic (large) earthquakes in the Andaman-Sumatra region were investigated. </p><p>The temporal frequency-magnitude distribution, <i>b(t)</i>, of rockbursts in Zinkgruvan mine was examined using high quality data recorded during the period November 1996 to April 2004 with magnitude ranges from <i>M</i><i>w</i>= -2.4 to 2.6. A sliding time-window was applied to compute <i>b</i>-values. The windows contain 50 events and were shifted with steps of 5 events. The results indicated that <i>b</i>-values significantly drop preceding rockbursts of magnitude <i>M</i><i>w</i>≥1.6.</p><p>Temporal and spatial variations of <i>b</i>-values were also examined for tectonic earthquakes, magnitude <i>M</i><i>w</i>≥4.1, in the Andaman-Sumatra region. Earthquake data from the ISC, IDC, NEIC and HVRD earthquake catalogs for a period from 01/01/1995 to 12/26/2004 were used for analysis. Spatial variations of <i>b</i> were calculated from circular areas containing 50 events, with nodes on a 0.5° x 0.5° grid. The analysis shows that <i>b(t)</i> estimates using data from different catalogs<i> </i>are comparable and that large earthquakes are preceded by a drop in <i>b(t)</i> of about 0.3~1. The distribution of stress deduced from <i>b</i>-value mapping shows that large earthquakes occurred in the high stress, i.e. low <i>b</i>-value, areas.</p><p>Aftershock sequences of the <i>M</i><i>w</i>=9, December 26, 2004 and the <i>M</i><i>w</i>=8.7, March 28, 2005 shocks were investigated by using the same methods. Results from aftershock sequences show similar behaviour as for the large and presumed independent main events.</p><p>The observed variations of <i>b</i>-values with time and in space support the hypothesis that <i>b</i>-values have a precursory potential. The method can be used for a wide range of earthquake magnitude, from microearthquakes (<i>M</i><i>w</i><3) to giant tectonic shocks (<i>M</i><i>w</i>~9) and for both of independent shocks and aftershocks.</p>

The potential of variations of b-values in the G-R relation, logN=a-bM as earthquake precursors for small events (rockbursts) in Zinkgruvan mine, Sweden and for tectonic (large) earthquakes in the Andaman-Sumatra region were investigated. The temporal frequency-magnitude distribution, b(t), of rockbursts in Zinkgruvan mine was examined using high quality data recorded during the period November 1996 to April 2004 with magnitude ranges from Mw= -2.4 to 2.6. A sliding time-window was applied to compute b-values. The windows contain 50 events and were shifted with steps of 5 events. The results indicated that b-values significantly drop preceding rockbursts of magnitude Mw≥1.6. Temporal and spatial variations of b-values were also examined for tectonic earthquakes, magnitude Mw≥4.1, in the Andaman-Sumatra region. Earthquake data from the ISC, IDC, NEIC and HVRD earthquake catalogs for a period from 01/01/1995 to 12/26/2004 were used for analysis. Spatial variations of b were calculated from circular areas containing 50 events, with nodes on a 0.5° x 0.5° grid. The analysis shows that b(t) estimates using data from different catalogs are comparable and that large earthquakes are preceded by a drop in b(t) of about 0.3~1. The distribution of stress deduced from b-value mapping shows that large earthquakes occurred in the high stress, i.e. low b-value, areas. Aftershock sequences of the Mw=9, December 26, 2004 and the Mw=8.7, March 28, 2005 shocks were investigated by using the same methods. Results from aftershock sequences show similar behaviour as for the large and presumed independent main events. The observed variations of b-values with time and in space support the hypothesis that b-values have a precursory potential. The method can be used for a wide range of earthquake magnitude, from microearthquakes (Mw&lt;3) to giant tectonic shocks (Mw~9) and for both of independent shocks and aftershocks.

Zinkgruvan is a Pb-Zn-Ag deposit located in south-central Sweden, owned and operated by Lundin Mining. The ore is beneficiated by a collective-selective flotation circuit, recovering both galena and sphalerite in a bulk rougher-scavenger flotation stage and later on separating them into two final products. Opportunities for increase in zinc recovery in the bulk rougher scavenger flotation stage have been identified as the plant is relying on natural Pb-activation to process the ore. Process mineralogical tools were used to characterize four different orebodies from Zinkgruvan (Burkland, Borta Bakom, Nygruvan and Sävsjön) and evaluate the metallurgical performance for flotation and magnetic separation, following a geometallurgical approach to better understand and predict the behavior of such ore types in processing plant. The first hypothesis in this thesis is that by addition of copper sulfate and increased collector dosage, Zn recovery will be improved without being detrimental to galena flotation. Results demonstrated that there is a significant increase in Zn recovery by further increasing collector dosage and copper-activating the flotation pulp in the scavenger stage. For instance, an increase in zinc recovery up to 16% has been achieved after addition of copper sulfate. Galena is readily floatable while sphalerite takes longer to be recovered. In addition, iron sulfides take longer to be recovered and, after addition of copper sulfate, there was an increase in iron sulfide recovery. The amount of iron sulfides reporting to the concentrate should still not be a problem to the plant. Most of the Fe in the concentrate is still coming from the sphalerite lattice. However, it might be that some orebodies coming into production in the near future have higher amounts of pyrrhotite, which might be a problem. Therefore, magnetic separation methods have been tested to remove pyrrhotite from the bulk ore. The second hypothesis is that the high Fe content in the concentrate might be due to the presence of iron sulfides, in which case they could be selectively removed by magnetic separation. XRD analyses demonstrated that Sävsjön is a highly variable orebody, and that its high Fe content varies with the location inside the orebody, being caused by either iron sulfide or iron oxide minerals. Both monoclinic and hexagonal pyrrhotite have been observed. Davis Tube could remove monoclinic pyrrhotite but it was very inefficient when dealing with hexagonal pyrrhotite. WHIMS, on the other hand, performed well for both types of pyrrhotite. When applying Davis Tube on Sävsjön OLD feed, a concentrate with up to 52.3% pyrrhotite is achieved, at a recovery of 35.32%. However, sphalerite is also reporting to the magnetic concentrate, which would generate Zn losses for the overall process. Zinc losses were up to 15.3% when the highest field strength was applied. Therefore, the applicability of magnetic separation for Zinkgruvan ore must be further evaluated.

Lithological core logging is a subjective and time consuming endeavour which could possibly be automated, the question is if and to what extent this automation would affect the resulting core logs. This study presents a case from the Zinkgruvan Zn-Pb-Ag mine, Bergslagen, Sweden; in which Classification and Regression Trees and K-means Clustering on the Self Organising Map were applied to X-Ray Flourescence lithogeochemistry data derived from automated core scan technology. These two methods are assessed through comparison to manual core logging. It is found that the X-Ray Fluorescence data are not sufficiently accurate or precise for the purpose of automated full lithological classification since not all elements are successfully quantified. Furthermore, not all lithologies are possible to distinquish with lithogeochemsitry alone furter hindering the success of automated lithological classification. This study concludes that; 1) K-means on the Self Organising Map is the most successful approach, however; this may be influenced by the method of domain validation, 2) the choice of ground truth for learning is important for both supervised learning and the assessment of machine learning accuracy and 3) geology, data resolution and choice of elements are important parameters for machine learning. Both the supervised method of Classification and Regression Trees and the unsupervised method of K-means clustering applied to Self Organising Maps show potential to assist core logging procedures.