3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Comparative analysis of linear and non-linear estimation techniques for the determination of recoverable resources in a sedimentary hosted cu-co type deposit(2021) Johnson, Russell DouglasMineral Resource estimation heavily impacts the technical and financial merits of mining feasibility studies, carried out prior to any material extraction. Since exploration requires significant investment, the feasibility of a project needs to be understood as soon as possible in the development of a mining lifecycle. To help define the feasibility of a mining project, resource geologists estimate the Mineral Resource and in-situ recoverable resources available for mining. Techno economic studies are then carried out to assess the economic viability of mining and metallurgical extraction of the recoverable resource. This is achieved by geostatistically estimating the tonnage and grade of mineralisation above a given cut-off grade and at a chosen mining unit or size, (Isaaks and Srivastava, 1989). The research presented is a comparative case study aimed at assessing the suitability of linear and non-linear estimation techniques in the determination of recoverable resources from exploration drilling data in a sedimentary hosted copper-cobalt type deposit. In an operating mine, recoverable resources are typically determined after a grade control drilling programme, drilled on a tight grid to identify subtle variations in grade within a deposit. By comparison, exploration data is inherently broadly spaced and occurs at a much earlier stage in the mining project life-cycle. The geostatistical techniques considered for the estimation of recoverable resources are ordinary kriging, uniform conditioning, and localised uniform conditioning. The localised estimate is contrasted against a grade control estimate, produced from ordinary kriging, to verify the success in determining the recoverable resources from exploration drilling data. The research study found that the dense drilling pattern of the grade control data provides an increased understanding of the distribution of average copper grades at Tshifufia than localised uniform conditioning from exploration data. The success of uniform conditioning on exploration data and the subsequent localisation is dependent on the size of the selective mining unit and grades that have been ranked and spatially referenced according to the average ordinary kriging block estimates. This direct proportionality means that where ordinary kriging estimates are high or low, the localised uniform conditioning estimate will be proportionally high and low as well. Despite the aim of determining the recoverable resources at selective mining unit-scale, localised uniform conditioning grades performed on exploration data provide no more resolution than the ordinary kriging mineral resource estimate, since the underlying data inherently determines the uniform conditioning and localised uniform conditioning. Any additional resolution on the distribution of average grades at selective mining unit level and determination of recoverable resources is subject to the amount and spatial representation of available information during estimation. Therefore, no suitable substitute was determined for grade control drilling and the resulting ordinary kriging grade control mineral resource estimate.Item Orebody characterisation and structural features that govern copper and cobalt mineralisation in the eastern limb of the Lufilian Arc, Democratic Republic of Congo(2015-02-06) Johnson, Russell DouglasThe Central African Copperbelt is located in the Lufilian Arc which straddles the border between Zambia and the Democratic Republic of Congo (DRC). Mineralisation of the cupriferous Arc is found in basal Neoproterozoic Katangan Supergroup sedimentary rocks, which in DRC are termed the Mines Series Subgroup. The Mines Series is divided into the dolomitic and carbonaceous GRAT, DStrat RSF, RSC, SD and CMN units. The composition of the units is homogeneous across the Lubumbashi district and potentially across the Katangan basin. This study focussed on the Kinsevere and Ruashi deposits in the Lubumbashi district, which are approximately 50 km apart. The study confirmed that relative eustatic sea level changes resulted in the non-deposition of the RSF and RSC stratigraphic units at Kinsevere. Sedimentation was followed by early pervasive potassic alteration and silicification at the diagenetic stage whilst a magnesian dolomitisation event resulted in alteration of potassic feldspars and recrystallisation of carbonates. Albitisation was veincontrolled and late-stage scapolitisation altered evaporitic nodules. Finally, haematisation by late iron-rich fluids circulating through the Roan Group strata resulted in oxidation of sulphides. The structural analysis of Kinsevere Central pit indicates E-W and N-S shortening whereas the Ruashi pit 1 deposit underwent NE-SW and N-S shortening. Initial shortening, associated with Kolwezian deformation (D1), resulted in the formation of NE-thrust folds and a primary set of joints. The Kolwezian deformation event (D2), reoriented the shortening direction from E-W to N-S, creating interference folds and possibly a second set of joints. The final phase in the structural evolution of the Kinsevere and Ruashi deposits was late-stage brittle deformation (faulting). Mineralisation was a multi-stage process. Disseminated chalcopyrite and carrollite were deposited from formation waters during diagenesis in a stable basin environment. Chalcopyrite, carrollite, chalcocite and bornite are predominantly located at the base of the DStrat, whereas chalcopyrite and pyrite dominate the stratigraphically higher portions of the deposits. Hypogene vein mineralisation began at the syn- to late- orogenic stage with carrollite and chalcopyrite in beddingparallel veins. Possible changes in the compression direction created the perpendicularly oriented veins that host chalcopyrite, carrollite, bornite, covellite, digenite and chalcocite. Finally a late stage of chalcopyrite and pyrite deposition occurred in and around the evaporites, indicating a strong correlation between mineralisation, evaporites and scapolitisation. iii Near-surface supergene alteration of hypogene sulphide ores, resulted in Cu-Co carbonates and oxides, such as malachite, azurite, cobaltiferous malachite, chrysocolla, kolwezite and sphaerocobaltite being deposited in vugs and pore spaces above the meteoric water line. Faulted and brecciated zones tend to have deeper supergene alteration. Between the sulphide facies at depth and the supergene oxide facies at surface is a transition zone which marks the depth to which oxidation has penetrated. Sulphur isotope analysis from the Kinsevere and Ruashi deposits suggests a sulphur contribution from a continental Red-Bed sedimentary source and from an evaporitic source.