A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the Degree of Master of Science in Engineering (Metallurgy and Materials Engineering) July 2015 / The research report is premised on three aspects which are critical in the heavy mineral beneficiation. These aspects are classified as (i) understanding the densimetric profile of the available ore body, (ii) understanding the properties of the heavy medium utilised at the plant to beneficiate the ore, and (iii) the automation and modelling of the processing plant in order to maximise plant efficiency. Ore characterisation is mainly focused on understanding the densimetric profile of the ore body, in order to determine the probability of producing a saleable product as well as predicting the expected yields and quality. This is done to utilise the endowment entrusted upon the operating entity by the government and shareholders to treat the mineral resource to its full potential. Understanding of the beneficiation potential of the ore body will assist the mine planning and processing plant to optimise the product tons and quality. This will ensure the marketing plans are in accordance with the expected product as beneficiation will vary depending on the mining block reserves. The mining blocks have potential to produce varying product grades with different recoveries. Ore characterisation was conducted on the GR80 mining block, low-grade stockpiles (i.e. C-grade ore reserves & Jig discard and dense medium separation (DMS) run-of-mine (ROM) material. The GR80 material was characterised as having low proportion of near-density material and would be easy to beneficiate as well as produce high volumes of high grade product. Furthermore, it was revealed that the 2014 DMS ROM had an increased proportion of low-density material; however this material was also had low proportion of near-density material. The low-grade stockpiles was characterised by high proportion of near density material, which necessitate the beneficiation process to operate at high density in excess of 3.8 t/m3. Maintaining a higher operating density requires more dense medium which leads to viscosity problems and impact performance. The characterisation of the FeSi medium was imperative to understand its behaviour and potential influence on beneficiation of low-grade stockpiles and mining blocks with elevated proportion of near-density material. As the proportion of near-density waste material increases in the run-of-mine (ROM), it is necessary to beneficiate the material at elevated operating medium densities. However, when cyclones are operated at high densities, the negative influence of the medium viscosity becomes more apparent and thus influences the separation efficiency. Heavy medium, ferrosilicon (FeSi) characterisation looked at identifying the effects of viscosity on the FeSi stability and whether there would be a need for a viscosity modifier. Thus, the importance of controlling the stability, viscosity, and density of the medium cannot be under-estimated and can very often override the improvements attainable through better designs of cyclones. Furthermore, the slurry mixture of the heavy medium utilised for the purpose of dense medium separation should be non-detrimental to the effectiveness of separation in the DMS Fine cyclone plant. Medium characterisation showed that removal of ultra-fines leads to unstable media as indicated by faster settling rates. This would result in medium segregation in the beneficiation cyclone thereby leading to unacceptable high density differential which will negatively impact the cut-point shift and cause high yield losses to waste. The overall control of the metallurgical processes at Sishen’s Cyclone Plant is still done on manually and thus operation still varies from person-to-person and/or from shift-to-shift. This result in some of the process data and trends not being available online as well as being captured inaccurately. Furthermore, this negatively affects the traceability and reproducibility of the production metallurgical key performance indicators (KPI’s) as well as process stability and efficiency. It has been demonstrated that real-time online measurements are crucial to maintaining processing plant stability and efficiency thereby ensuring that the final product grade and its value is not eroded. Modelling and automation of the key metallurgical parameters for the cyclone plant circuit was achieved by installation of appropriate instrumentation and interlocking to the programmable logic control (PLC). This allowed for the control of the correct medium sump level, cyclone inlet pressure, medium-to-ore ratio as well as online monitoring of density differential as “proxy” for medium rheological characteristics. The benefit of modelling and simulation allows the virtual investigation and optimisation of the processing plant efficiency as well as analysis of the impact of varying ore characteristics, throughput variations and changing operating parameters. Therefore it is imperative that all cyclone operating modules are operated at the same efficiency which can be achieved by optimized process through proper automation and monitoring, thereby improving the total plant profitability. Keywords: dense medium separation; densimetric profile; dynamic modelling; FeSi rheology; iron-ore beneficiation; process automation; process control.

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The intrusion-related Cerro Negro Norte Fe-oxide (Cu-Au) deposit is hosted in andesites and diorites of the early to middle Cretaceous Coastal Cordilleran arc of northern Chile. Tabular and irregularly shaped magnetite orebodies are localized on splays and fractures of the regional NINE striking Atacama Fault Zone. Production from this district was [approximately]100 MT @ [approximately] 65 wt. % Fe. Early Na-Ca alteration assemblages associated with magnetite �� apatite �� pyrite �� chalcopyrite ore include actinolite, marialitic scapolite, oligoclase, titanite, and epidote. Na-Ca alteration is extensive (>4 km�� in area), locally pervasive in the district, and is locally associated with granodiorite dike emplacement. The alkali-rich alteration and sulfide poor mineralization at CNN is characterized by metasomatic exchange of major, minor, and trace elements (added Fe, Na, Ca, Cl, P, Rare Earth Elements) between andesitic and diorite host rocks and halite-saturated saline hydrothermal fluids preserved as inclusions. Intrusion-heated fluids converge along the Atacama Fault Zone, and dikes, and may have been derived either from seawater or evaporitic water trapped in sedimentary rocks of the protoarc. Younger, cross-cutting hydrothermal assemblages such as tourmaline-quartzsericite (�� breccias), associated with granodiorite dikes, and chiorite-calcite-tourmalinequartz assemblages are related to pyrite �� chalcopyrite �� hematite and Cu-Au mineralization. Supergene minerals include goethite, Cu-carbonates and Cu-oxide. Later carbonate (dolomite) alteration is also localized along northeast-striking faults. Inferred Cu-Au estimates are [approximately] 1 MT @ [approximately] 1 g/T Au and 0.25 wt. % Cu. Late alteration assemblages may contain a component of magmatic saline fluids generated by observed monzodiorite-granodiorite dikes and pluton emplacement. Massive magnetite ore and associated Na-Ca alteration assemblages were deposited at high temperatures ( 500 to 6000 C), with igneous intrusions providing heat but not necessarily fluids and metals. Later moderate to low temperature Cu-Au mineralization (sulfide + oxide) replaces magnetite, and records the transition to more brittle faulting, with NW �� re-activated NNE structural control, and a greater proportion of magmatic fluids, sulfur ([delta]�����S[subscriptpy] = -1 0/00), and metals. / Graduation date: 2002

The petrogenesis of magmatic Fe-Ti oxide ores associated with massif-type andesine anorthosites is investigated through detailed studies of the world-class Tellnes ilmenite deposit (SW Norway), the Grader layered intrusion (Quebec, Canada) and Fe-Ti ores from the Suwalki anorthosite (NE Poland). Extensive sampling in the field and in drill-cores reveals significant petrographical and compositional variations within a single ore body and between deposits from different anorthosite complexes. The composition of phases from bulk XRF analyses on mineral separates and from in situ LA-ICP-MS, Sr isotopic composition of plagioclase, bulk rocks major and trace element contents and the spatial variation of these data are used to understand controlling factors on ore composition. Phase diagrams and experimental data on ferrobasalts as well as comparisons with the well-documented Bjerkreim-Sokndal layered intrusion (SW Norway) are systematically used to further refine our understanding on the genesis of Fe-Ti ores. More than 100 samples from drill-cores in the Tellnes ilmenite deposit, part of the late-Proterozoic (930-920 Ma) Rogaland Anorthosite Province (SW Norway), reveal significant petrographical and compositional variations within the ore body. Four zones are defined, based on variations in modal proportions and cumulus mineral assemblages: the Lower and Upper Central Zones and the Lower and Upper Marginal Zones. Plagioclase and whole-rock compositions discriminate the zones and display patterns interpreted as a result of mixing of either plagioclase-ilmenite or plagioclase-ilmenite-orthopyroxene-olivine cumulates with a melt of ferrodioritic (jotunitic) composition. Its content decreases from 80 to 20 % from the margins to the central part of the ore body. Phase diagrams for a jotunitic parental magma reproduce the crystallization sequence at 5 kbar. Uniform Sr isotope ratios do not support magma mixing. The cryptic layering of the ore body precludes injection as a crystal mush but favours in situ crystallization from an evolving magma in a sill-like magma chamber. The present trough-shape and mineral orientations result from deformation during gravity-induced subsidence and by up-doming of the anorthosite. Major and trace element XRF and in situ LA-ICP-MS analyses of ilmenite in the Tellnes ilmenite deposit further constrain the two-stage fractional crystallization model of a ferrodioritic Fe-Ti-P rich melt. Stage 1 is characterized by ilmenite-plagioclase cumulates, and stage 2 by ilmenite-plagioclase-orthopyroxene-olivine cumulates. The concentration of V and Cr in ilmenite, corrected for the trapped liquid effect, (1) defines the cotectic proportion of ilmenite to be 17.5 wt.% during stage 1, and (2) implies an increase of during stage 2, most likely related to a shift in fO2. The proportion of 17.5 wt.% is lower than the modal proportion of ilmenite (ca. 50 wt.%) in the ore body, implying accumulation of ilmenite and flotation of plagioclase. The fraction of residual liquid left after crystallization of Tellnes cumulates is estimated at 0.6 and the flotation of plagioclase at 26 wt.% of the initial melt mass. The MgO content of ilmenite (1.4-4.4 wt.%) is much lower than the expected cumulus composition. It shows extensive postcumulus re-equilibration with trapped liquid and ferromagnesian silicates, correlated with distance to the host anorthosite. The Zr content of ilmenite, provided by in situ analyses, is low and uncorrelated with stratigraphy or Cr content. The data demonstrate that zircon coronas observed around ilmenite formed by subsolidus exsolution of ZrO2 from ilmenite. The U-Pb zircon age of 920 ± 3 Ma probably records this exsolution process. The Grader layered intrusion belongs to the Havre-Saint-Pierre anorthosite in the Grenville Province (Quebec, Canada). This intrusion has a basin-like morphology and contains significant resources of Fe-Ti-P in ilmenite and apatite. Outcropping lithologies are massive oxide alternating with anorthosite layers, banded ilmenite-apatite-plagioclase rocks and layered oxide apatite (gabbro-) norites. Several drill cores provide evidence for stratigraphic variations of mineral and bulk cumulate compositions controlled by fractional crystallization and importantly the successive appearance of liquidus phases: plagioclase and ilmenite followed by apatite, then orthopyroxene together with magnetite, and finally clinopyroxene. This atypical sequence of crystallization results in the formation of plagioclase-ilmenite-apatite cumulates or nelsonites in plagioclase-free layers. Fine-grained ferrodiorites which cross-cut the coarse cumulates are shown to be in equilibrium with the noritic rocks. The high TiO2 and P2O5 contents of these liquids explain the early saturation of ilmenite and apatite before Fe-Mg silicates, which implies that nelsonites actually represent cumulates rather than Fe-Ti-P-rich immiscible melts. The location of the most evolved mineral and bulk cumulates compositions at several tens of meters below the top of the intrusion, forming a sandwich horizon, suggests crystallization both from the base and top of the intrusion. The concentrations of V and Cr in ilmenite display a single fractionation path for the different cumulus assemblages and define the cotectic proportion of ilmenite to 21 wt.%. This corresponds to bulk cotectic cumulates with ca. 8 wt.% TiO2, which is significantly lower than what is commonly observed in the explored portion of the Grader intrusion. The proposed mechanism of ilmenite-enrichment is lateral removal of plagioclase due to its buoyancy in the dense ferrodiorite. This plagioclase has probably accumulated in other portions of the intrusion or has not been distinguished from the host anorthosite. Fe-Ti deposits in the Proterozoic Suwalki massif-type anorthosite (NE Poland), recognized through geophysical exploration, have been sampled in deep cores reaching 2800 m depth. Bulk cumulate analyses and liquidus phases composition of 70 Fe-Ti ores support their cumulate origin. The sequence of crystallization is: plagioclase, orthopyroxene, Ti-magnetite and ilmenite (64:36 on average), apatite and clinopyroxene. Fe-Ti-rich cumulates are commonly layered and display continuous relation with the host anorthosite. They do not represent well-defined intrusions such as the major Fe-Ti Tellnes and Lac Tio deposits. Fe-Ti oxides microtextures show conspicuous subsolidus re-equilibration, particularly external granule exsolution of pleonaste from Ti-magnetite. The composition of associated fine-grained ferrodiorites reveals relatively low Ti content and similar Mg# compared to jotunitic rocks associated with hemo-ilmenite ores in the Rogaland Anorthosite Province. Geochemical characteristics of these plausible parental magmas can account for the high Ti-magnetite/ilmenite ratio in cumulates. The diapiric emplacement of anorthositic plutons clearly influences the crystallization of Fe-Ti ores and is responsible for crystal sorting controlled by the density contrast of liquidus phases. Polybaric crystallization is evidenced by the high and variable Al2O3 content of orthopyroxene and by the occurrence of olivine corona around orthopyroxene interpreted from phases diagram to result from adiabatic decompression. The comparatively low V content in Ti-magnetite results from highly oxidized crystallization conditions. It thus emerges that principal controlling factors on the formation of Fe-Ti ore and on their characteristics are parental magma composition, sequence of crystallization, crystal sorting, crystallization of trapped liquid, oxygen fugacity and postcumulus re-equilibration. Indeed, fine-grained rocks of Fe-Ti-P-rich ferrodioritic (jotunitic) composition, interpreted as parental melt composition, are responsible for atypical sequence of crystallization with ilmenite as an early liquidus mineral and apatite saturation for high fraction of residual liquid. The trace element content of ilmenite, particularly V and Cr, has been used to calculate cotectic proportion of ilmenite during fractional crystallization of ferrodiorites. These proportions are usually lower than those observed in Fe-Ti ores, which implies ilmenite sorting. This occurs by plagioclase flotation due to its buoyancy in the dense ferrodiorite. This plagioclase may have accumulated in other portions of the intrusion or has not been distinguished from the host anorthosite. Extensive postcumulus re-equilibration with trapped liquid and ferromagnesian silicates strongly modifies the primary liquidus composition of Fe-Ti oxides. The data also demonstrate that zircon coronas commonly observed around ilmenite in Fe-Ti ores formed by subsolidus exsolution of ZrO2 from ilmenite. The basin-like morphology of most Fe-Ti ores hosting intrusions results from the deformation during gravity-induced subsidence and by up-doming of the anorthosite. As immiscibility of a Fe-Ti-P-rich melt and magma mixing have not been evidenced in the studied Fe-Ti ores, early ilmenite saturation accompanied by ilmenite sorting due to plagioclase buoyancy are thus the only mechanisms responsible for the formation of Fe-Ti deposits in Proterozoic massif-type anorthosites.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1887. / The entire thesis text is included in file. Holograph [Handwritten and illustrated in entirety by author]. Title from title screen of thesis/dissertation PDF file (viewed December 28, 2009)

The Cenex uranium deposit occurs in gneisses and schists of the Tazin Group which represent supracrustal rocks folded and metamorphosed to amphibolite rank during the Hudsonian orogeny. During the late stages of the orogenic uplift, cataclastic deformation caused partial retrogression of the rocks to greenschist facies assemblages and their transformation into mylonites, ultramylonites, and mylonite schist. Continued uplift of these rocks led to their brittle fracture, and, contemporaneous erosion on surface resulted in the formation of successor basins in the area. The orebody occurs at the intersection of northwest and northeast-trending fault zones and the ore is localized in breccia zones, along faults, and in veins and the adjacent wallrocks. The host rocks are quartzo-feldspathic mylonites and ultramylonites and chlorite, sericite, quartz, graphite, feldspar mylonite schist. The uranium-bearing minerals are pitchblende and a uraniferous titanate, which commonly occur finely disseminated in the host rocks. Cross-cutting relationships between mineralized structures indicate five stages of uranium mineralization separated by fracturing events· The earliest episode of mineralization is associated with late-stage retrograde metamorphic processes in the mylonite schist, whereas later stages of mineralization are dominated by the intense hematization, carbonatization, and chloritization of the quartzo-feldspathic mylonites and ultramylonites. Traditional genetic models, which metamorphic-hydrothermal sources propose magmatic for the uranium and ore-bearing fluid, have been evaluated and found to be ·inconsistent with the geological history of the rocks and the relative time of emplacement of uranium mineralization. In the Cenex mine area there appears to have been contemporaneity of late uplift, erosion, and deposition of continental clastics on the one hand, and· brittle fracture and uranium mineralization in the basement, on the other. This suggests that the hydrologic system, during and after sedimentation, may have played an important role as a source for ore-bearing fluids- This source would be most important in areas of the basement which were faulted, fractured, and occurred close to the continental clastics - hence the close spatial relationship of the uranium deposits in the Beaverlodge area with the basal unconformity of the Martin Group.

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In this study the unique Magotteaux Mill® system was used to control the grinding chemical conditions, which may be adjusted by varying grinding media, purging gas and pH, during grinding. An electrochemical apparatus was used to investigate oxidation-reduction behaviour of grinding media and sulphide mineral electrodes, as well as their galvanic interaction in-situ of the Magotteaux Mill®. Galvanic interaction between the grinding media (mild steel, 15% chromium, 21% chromium and 30% chromium media) and the sulphide minerals (bornite, arsenopyrite and pyrite) was initially quantified in-situ of the mill by electrochemical techniques under different grinding atmospheres (nitrogen, air and oxygen). An innovative mathematical theoretical model was developed to describe the effect of galvanic interaction on oxidation rates of the grinding media during grinding, which was verified by the experimental data. Galvanic interaction enhanced the oxidation of the grinding media and produced more oxidized iron species in the mill discharge. It was observed that oxidized iron species (EDTA extractable iron) was linear with galvanic current between the grinding media and the sulphide minerals, in agreement with the prediction of the theoretical model. The effect of grinding conditions on pulp chemistry, surface properties and floatability was investigated by the measurement of dissolved oxygen (DO), pH, pulp potential (Eh), ethylene diamine-tetra acetic acid (EDTA) extraction, X-ray photoelectron spectroscopy (XPS) and floatation recovery. / Thesis (PhDAppliedScience)--University of South Australia, 2005.