In this thesis, results of experimental investigations in the dry system PtS-PdS-NiS at 1200°C, 11 OO°C, 1 OOO°C, 900°C, 800°C, and 700°C are presented. Experimental results are compared with analyses of naturally occurring cooperite (ideally PtS), braggite ((Pt,Pd)S), and vysotskite (ideally PdS) of this study and with analyses reported in the literature. Synthetic cooperite is stable at temperatures above 1200°C, whereas synthetic braggite at temperatures below 1100°C, and synthetic vysotskite below 1000°C. Below 900°C in the system PtS-PdS-NiS, Ni-saturated synthetic cooperite, -braggite, and -vysotskite coexist with Ni1_xS, At 900°C only Ni-saturated, Pd-free synthetic cooperite coexists with Ni1_xS, and synthetic braggite and Pd-containing synthetic cooperite coexist with a Pd-Ni-Pt - sulphide melt. At temperatures > 1000°C all Ni-saturated synthetic cooperite and -braggite coexists with a Pd-Ni-Pt - sulphide melt. There is a clearly defined miscibility gap between cooperite and braggite, but no gap was observed between braggite and vysotskite. There are well defined, positive, relationships between the Pd-contents of synthetic cooperite, -braggite, and -vysotskite and the Pd-content of the coexisting melt or that of the coexisting Ni1_xS. The Ni-content of synthetic braggite and -vysotskite with varying PtlPd ratios in a Ni-saturated environment is a function of temperature; a higher Ni-content resulting from a lower equilibration temperature. In synthetic cooperite, a similar relationship between the Ni-content and the temperature of formation or equilibration is applicable between 1200° and 900°C. At 800°C, the Ni-content is higher than that at 700°C. The variation in the Ni-content in synthetic cooperite is more restricted than that for synthetic braggite and -vysotskite. Sulphur fugacity has an effect on the system Pt-Pd-Ni-S. If formed under higher S-pressure, synthetic braggite synthesized at 1000°C contains higher amounts of Ni than formed at lower S-pressure at given PtlPd ratios in the initial charge. At constant bulk PtlPd ratio, the PtlPd ratio of the synthetic braggite decreases with increasing sulphur fugacity. The inter-element relationships for synthetic braggite are not as pronounced for cooperite synthesized at 1000°C. Compositions of cooperite, braggite, and vysotskite have the potential to indicate at which stage of the development of an ore deposit these phases were exsolved or equilibrated. Comparison of the experimental results with analyses of natural cooperite, braggite, and vysotskite of this study and from the literature, indicate that: (i) Cooperite and braggite from the Merensky Reef have equilibrated below 900°C. (ii) Analyses of cooperite, braggite, and vysotskite from the UG-2, coexisting with pentlandite follow the trend similar to that experimentally established for temperatures < 700°C and where coexisting with millerite, the trend established for temperatures between 800°C and 700°C. (iii) Temperatures of formation or equilibration of cooperite, braggite, and vysotskite from the Sompujävi Reef of the Penikat Intrusion and of Placer Deposits, as well as cooperite from the Stillwater Complex cannot be estimated with certainty. (iv) Braggite and vysotskite from the Stillwater Complex may have formed at temperatures below 700°C. (v) Cooperite-, braggite-, and vysotskite analyses from Noril'sk indicate formation temperatures of < 700°C. / Thesis (PhD)--University of Pretoria, 2007. / Geology / Unrestricted

Large quantities of sulphide-bearing mining wastes produced from ore processing are deposited throughout the world. Sulphide oxidation in the wastes may release acidic water with high concentrations of metals to the environment. Remediation strategies are usually site specific, since the physical and chemical properties of the wastes vary. Therefore, sulphide oxidation, oxygen diffusion and metal mobility in unoxidised and oxidised, remediated and unremediated wastes have been studied in the present work. The efficiency of different cover systems on unoxidised tailings from Kristineberg, were studied in pilot-scale test cells (5*5*3 m3)under field conditions. Clayey till, sewage sludge, apatite and Trisoplast were used as sealing layers and unspecified till as a protective cover. In one cell tailings were left uncovered. Unoxidised tailings in the test-cells in the initial stage after deposition showed relatively low sulphur release (600- 800 mg/l)in leachate waters, which probably was an effect of high moisture content in the tailings prior to deposition. Near-neutral pH found in the leachates was an effect of neutralisation by carbonate minerals present and lime (Ca(OH)2) added prior to deposition. Similar sulphur concentrations were found also in the uncovered tailings. The sulphide oxidation rate increased with time in the uncovered tailings, and decreased in the covered. The lowest oxygen concentrations were observed below the cover system with sewage sludge, which was the most effective barriar against oxygen in a short-term perspective. The oxygen fluxes through the clayey till and apatite layers were within the same magnitude and varied between 0.5 and 4 mole/year,m2. The Trisoplast layer seemed to have failed as a barrier against oxygen. Tailings studied at field scale at Laver and Kristineberg had oxidised for more than 50 years. The tailings at Kristineberg have high pyrite content (c.25% and 50%) and those at Laver have low grade of pyrrhotite (2-3%). The Laver tailings are unremediated, while at Kristineberg the tailings were remediated in 1996. The transport of metals in the drainage water at Laver decreased during a study period of 8 years. The transport of dissolved sulphur indicated a declining trend of sulphide oxidation rate in the tailings, which was confirmed by oxygen measurements in the tailings and weathering rate estimations. The decline was considered to be natural as a result of the increased distance that oxygen has to travel to reach unoxidised sulphide grains. The major part of the amounts of metals released by sulphide oxidation were secondarily retained in the tailings, and to a small extent in layers cemented by jarosite and Fe-(oxy)hydroxides. Sequential extraction of these layers showed that metals such as Cu and Pb were mostly associated with crystalline Fe-(oxy)hydroxides. Most important retention mechanism was, however, sorption onto minerals surfaces below the oxidation front. The studied Impoundment 1 at Kristineberg was remediated by two different methods; on one part a dry cover consisting of a sealing layer and a protective cover were applied, and the groundwater table was raised and a single dry cover applied on the other part. When the groundwater table was raised in oxidised tailings, secondarily retained metals such as Fe, Mg, Mn, S and Zn were remobilised resulting in increased concentrations in the groundwater. The concentrations declined with time, due to dilution by inflowing uncontaminated water. Decreased concentrations of Fe, Mg, Mn, S and Zn were observed also in the groundwater below the dry cover as the amount of percolating water decreased. The concentrations of trace elements such as Cd, Co, Cr, Cu, Ni and Pb were almost depleted in the groundwater, since these metals were retained within the tailings by mechanisms such as co-precipitation, precipitation and sorption. Analysis of pyrite grains by LA-ICP-SMS showed that pyrite surfaces were important for retention of As and Cu, in particular, but also for Cd and Zn. This study shows that the physico-chemical conditions expressed by pH and redox potential have a large impact on element mobility’s. For example, As was mobilised as a result of remediation, while the concentrations of most metals decreased in the drainage waters. / Godkänd; 2006; 20061116 (pafi)

<p> The May Lake interpluton screen is a 4 km long, &sim;0.5 km wide swath of metamorphic rock cropping out between plutons of the &sim;103 Ma Yosemite Valley Intrusive Suite and the &sim;93-85 Ma Tuolumne Intrusive Suite in Yosemite National Park, California. Metasomatic alteration and recrystallization due to contact metamorphism and fluid infiltration resulted from the emplacement of the Cretaceous plutons. Mineral assemblages are consistent with metamorphism to hornblende-hornfels and amphibolite facies. The presence of sillimanite-bearing metapelite and more Mg-rich clinopyroxene in calc-silicate assemblages of the northeast section of the screen than the southwest suggest higher grade metamorphism was experienced to the northeast. Pseudosection diagrams created from whole rock chemical analyses of three metapelite rocks also indicate higher temperatures in the northeastern section of the screen with minimum temperatures estimated from &sim;540-617&deg;C. Based on petrographic analysis of andalusite- and sillimanite-bearing metapelite, it is likely that the screen experienced two stages of contact metamorphism: relatively lower temperature metamorphism during intrusion of the Yosemite Valley Intrusive Suite followed by relatively higher temperature contact metamorphism during intrusion of the more mafic Tuolumne Intrusive Suite. Stable isotope data suggest that rock permeability and preexisting structures were the strongest factors controlling fluid infiltration through the contact aureole.</p><p>

The distribution of the stable isotopes of Cu and Fe in nature is susceptible to isotope fractionation processes during the biogeochemical cycle. Since Cu and Fe are redox sensitive metals, differences in their oxidation states can lead to variations in the stable isotope composition of the aquatic species or compounds that they form. Stable isotopes of Cu and Fe have recently been used to trace metal redox cycles, nutrient pathways, metal contaminant sources and to develop isotopic biosignatures. The objective of this project was to study the geochemical processes governing the isotopic fractionation of Cu and Fe in mine impacted sites, including processes related to mineral processing. One of the key questions was to explain the role of bacteria in the variations of the isotopic composition of Cu and Fe. First, bioleaching and electroleaching of a chalcopyrite concentrate were performed. During the chalcopyrite leaching in both experiments the first release of Cu to the leachate is enriched in the heavier Cu isotope as a product of oxidative dissolution. At the later stages of leaching, the δ65Cu values for the leachate are similar to the initial material, confirming an equilibrium fractionation in a closed system. In the case of Fe isotope fractionation the dissolution of pyrite at redox potentials higher than 600mV leads to an enrichment of the heavier Fe isotope in the leachate in the bioleaching experiment, mainly regulated by the formation of secondary minerals such as jarosite. Soil bacteria were studied in three different experimental scales using pot, lysimeters and field experiments, amended with autochthonous plant growth promoting bacteria. Roots and plants from pots showed no variation in their Fe and Cu isotope composition compared to non-amended samples. However, plants growing in the amended substrates regardless of their experimental scale, showed variations in the Fe and Cu isotope composition of their roots with an increase in the heavier Cu isotope. Siderophores released either by bacteria or the plant can complexate available Cu and Fe in the soil, causing a change in the isotope fractionation of those metals. The second question is related to the biogeochemical cycle of Cu and Fe. In mine tailings the sulphide oxidation resulted in an enrichment of the lighter Cu isotope in secondary phases in the oxidized zone of the tailings compared to the original isotope composition in the unoxidised mineral. Precipitation of covellite at the oxidation front of the tailings profile resulted in a significant enrichment of the lighter Cu isotope in the bulk soil with a δ65Cu value as low as -4.35 ±0.02 ‰. Fe isotope fractionation in the Kristineberg test cell varied due to processes such as Fe(II)-Fe(III) equilibrium and precipitation of Fe-(oxy)hydroxides at the oxidation front, where δ56Fe values were higher than in the initial material. As a way to link the obtained results from this thesis, a self-restored mine site was studied. A variation towards higher δ65Cu values was seen from rocks, to water and biofilms. Cu absorption mainly by extrapolymeric substances and secondary mineral precipitation regulates the isotopic composition of the biofilm. Oxidative weathering of sulphide minerals and further precipitation of Fe-(oxy)hydroxides are considered to be the main causes for Fe isotope fractionation in this area. Summing up, this thesis provides several field studies to corroborate the data observed in the lab regarding processes that are important for the biogeochemical cycling of metals and could be further applied to the extraction of metals or for remediation purposes. / Godkänd; 2013; 20131028 (natper); Dissertation to be held in public in room E632 on Tuesday 17th of December at 10:00 am. External examiner: Dr. Dominik Weiss, Department for Earth Sciences and Engineering, Imperial College London. Chairman: Professor Björn Öhlander, Division of Geosciences and Environmental Engineering, Luleå University of Technology. --- Tillkännagivande disputation 2013-11-22 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Nathalie Pérez Rodríguez Ämne: Tillämpad geologi/Applied Geology Avhandling: Biotic and Abiotic Isotope Fractionation of Copper and Iron. From the Lab to the Field Scale Opponent: Dr Dominik Weiss, Reader, Department of Earth Science & Engineering, Imperial College of London, UK Ordförande: Professor Björn Öhlander, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Tisdag den 17 december 2013, kl 10.00 Plats: E632, Luleå tekniska universitet

The notion of mine site reclamation is very recent compared to the history of mining. In thepast, mine sites were left as is following termination of the operations, but modern regulationsrequire anticipation of long-term contamination of the surrounding environment and return ofthe land to a sustainable use. A primary concern for mines used to extract sulphide-rich ores isthe generation of acid mine drainage (AMD), a low-pH and metal-rich solution formed whensulphidic mining wastes and mining surfaces come into contact with oxygen and water. AMDmay be responsible for the contamination of watercourses and other receiving environments fardownstream of the site. Thus, reclamation at such sites will usually involve measures intendedto prevent or mitigate its generation. Despite their relatively recent introduction, the increasingtime that has passed since the first prevention and mitigation programmes were applied at minesites, some two to three decades ago, provides an invaluable opportunity to assess their long-termeffects on the abatement of AMD.Reclamation at the Kimheden copper mine in Västerbotten, northern Sweden, involved theprogressive backfilling of two small open pits with waste rock and application of a dry cover in1996, in order to reduce the influx of atmospheric oxygen into the waste. The objective of thestudies this thesis is based upon, performed in 2009 – 2014, was to evaluate the effects of thesereclamation measures on the abatement of Cu and Zn-rich AMD and to identify potential inadequaciesin them, using geochemical, geophysical and hydrogeological methods.The results show that despite large reductions in Cu and Zn concentrations in the receivingstream following reclamation, its water quality has remained in a steady state for about a decadeand is still not considered satisfactory for discharge into the natural environment. Steady-statemoderately high concentrations in the stream, together with a relatively short turnover time forwater in contact with the waste rock, indicate that sulphide oxidation is continuing in the backfilldespite the cover. Hydrogeochemical modelling suggests that the rate of oxygen consumption bysulphide oxidation in the waste rock is higher than the expected rate of diffusion through the drycover. Substantial ingress of oxygen into the waste was also corroborated by stable isotope measurements and direct measurements of dissolved oxygen concentrations in the groundwater of the backfill. According to sulphate isotope distributions in the mine drainage, oxidation of pyrite by Fe(III) constantly rejuvenated by oxidation of Fe(II) with oxygen is suspected to be an importantprocess in the covered backfill. Potential sources of oxygen transport into the waste have been explored. Mapping of the groundwater table in one of the backfilled open pits showed that up to 40 % of the waste rock is unsaturated during baseflow, providing pathways for oxygen to enter through unsaturated fractures in the pit walls. Two sources of deterioration of the dry cover were identified during geophysical surveys: seepage of drainage water from the backfilled waste upwards into the dry cover and insufficient thickness of the cover in some areas. Geophysical and hydrogeochemical studies showed that the collection ditch constructed to divert the contaminated water to a liming treatment station fails to retain a large fraction of the drainage.Based on the results obtained, the sustainability of current approaches for AMD prevention andmitigation is discussed, and possible strategies for improving backfilling and sealing measures atsimilar sites are proposed.Keywords Acid mine drainage or acid and metalliferous drainage (AMD) or acid rock drainage(ARD); mine site reclamation; open pit; sulphidic waste rock; backfilling; dry cover; performance;unsaturated. / Godkänd; 2014; 20141016 (lucvyl); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Lucile Villain Ämne: Tillämpad geologi/Applied Geology Avhandling: Reclamation of Acid-Generating Waste Rock by In-Pit Backfilling and Sealing - An Evaulation of the Kimheden Mine Site, Northern Sweden Opponent: Professor Bernhard Dold, University of Chile, Santiago, Chile Ordförande: Professor Lena Alakangas, Avd för geovetenskap och miljöteknik, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Fredag den 12 december 2014, kl 10.00 Plats: E632, Luleå tekniska universitet

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Dissolved noble gas concentrations in Canadian Shield groundwaters from various depths of the Miramar Con Mine, Yellowknife, were examined for paleotemperature information and isotopic ratios. A high-vacuum stainless steel line with reactive gas gettering, isotope spike dilution and quadrupole mass spectrometer was constructed, tested and calibrated prior to sample analysis. In addition to noble gases, groundwater flow rates and formational pressures, as well as the major ions, stable isotopes and tritium values, were also measured. Data collected on flow rates and formational pressures was compared to that published by Intera Consultants Ltd. (1997). Trends indicate an almost universal decline in both parameters over the four year period, reflective of changing mine conditions. The major ions in solution are represented primarily by Ca, Na, Cl, SO 4, and HCO3, at shallow depths. In the deep subsurface, Ca, Na, and Cl become the dominant species, forming a Ca-Na/CI brine characteristic of the Canadian Shield that reaches a TDS of 304 g/L. (Abstract shortened by UMI.)

The Lac des Iles Pd mine is hosted by 2.69 Ga. gabbroic rocks of the Lac des Iles Intrusive Complex in the southern Wabigoon subprovince, Superior province of Canada. Economic mineralization, &sim; 159 Mt at 1.55 g/t Pd before major mining in 2001, occurs in the Roby zone of the Mine Block Intrusion. The southern Roby and Twilight zones contain gabbroic/gabbronoritic intrusions with complicated textures, such as brecciation and magma mingling. Ore has low concentrations of sulphide (&sim; 1-3 vol. %) and high Pd/Pt of &sim;8-10. Detailed mapping and geochemical analysis of the southern Roby and Twilight Zones indicate that early leucocratic rocks are barren and that the bulk of the platinum group elements (PGE) were introduced by late melanocratic magmas. Sulphur correlates positively with base and precious metals. In addition to exsolution of pentlandite and chalcopyrite from pyrrhotite, the data suggests a magmatic origin of the PGE where immiscible sulphide melt concentrated PGE. Fractionation of olivine, chromite, and high temperature platinum group minerals likely resulted in high concentrations of Pt-group PGE/Ir-group PGE in the parental magmas. Extreme enrichment of Pd and high Pd/Pt ratios in the late melanocratic magmas is interpreted to be due to incorporation of earlier formed sulphide melt. The High Grade Zone, on the eastern margin of the Roby Zone, contains only &sim;7 vol. % of the Roby Zone but hosts &sim; 35% of the Pd at the mine. The zone is intensely altered and contains two mineral assemblages: (a) millerite + siegenite +/- chalcopyrite +/- pyrite co-existing with hornblende + plagioclase +/- quartz +/- carbonate, and (b) pyrite +/- chalcopyrite with chlorite + actinolite +/- albite +/-quartz +/- carbonate. The ore is high in Pd and Pd/Pt (mean of 16.5; max. 25) compared to the southern Roby and Twilight zones. Although plots of S versus Se and base and precious metals show scatters, positive correlations are observed for Se versus Te and less mobile elements, such as Pt, Ni and Co. The data suggest that magmatic mineralization was followed by hydrothermal transport of mobile elements. Hydrothermal activity enriched the zone by up to 40 ppm Pd. The lack of fluid pathways and the distribution of the zone adjacent to mineralized breccia are consistent with magmatic-hydrothermal activity by aqueous fluids exsolved from the parental magmas of the Roby zone. Geochemical and Pb, Sr, and Nd isotope compositions from the Mine Block Intrusion suggest that the parental magmas were derived through high degrees of partial melting of a previously metasomatized depleted mantle source. The Lac des Iles Intrusion, as well as the surrounding mafic/ultramafic and sanukitoid suite of intrusions, display subduction influenced geochemical signatures, such as negative HFSE and enriched LILE. (Abstract shortened by UMI.)