Graphite: origin, deposits and economics : an exploration study of the Orom Graphite project
- Authors: Van den Berg, Jacobus Petrus
- Date: 2018
- Subjects: Graphite , Ore deposits , Geophysics , Graphite mines and mining Economic aspects Africa, East , Trenches , Project management
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63786 , vital:28489
- Description: Developing exploration projects successfully requires that the Reasonable Prospects for Eventual Economic Extraction (RPEEE) be confirmed and based on the global market perception and trend. The exploration methods applied in the attempt to establish this RPEEE must be based on a key management framework that assures the results, and eventually the conclusion, are obtained with best practical and technical approaches whilst managing the risks and capitalizing on each result. The Orom Graphite project is located within the East African Orogenic belt, a suture zone between the Congo craton and the SLAMIN shield, formed during the formation of Gondwana during the late Proterozoic to early-Phanerozoic era. The closing of the Mozambique ocean, and the eventual collision between the craton and shield, occurred along the paleo-earths equator and migrated towards lower latitudes. This, along with the period’s biodiversity boom, provided the perfect deposition environment for carbonaceous sediments which were later metamorphosed to amphibolite and granulites grade metamorphism, resulting in the carbonization and the eventual graphitization of these carbonaceous sediments. The project is located within a poorly developed part of Uganda with the closest port situated some 1 500 km to the east in Kenya. The poorly developed infrastructure along with probable high logistical cost assigns a low competitivity index if compared to the economic costs of peer projects. However, the potential resources of the Orom Graphite project suggest that the Life of Mine (LOM) can rival the largest resource currently reported within the market. The current market conditions suggest that a possible oversupply of graphite concentrate will dominate the market within the next 4 to 10 years. This suggests that new graphite projects such as the Orom Graphite project are likely to develop into the production phase once the global supply and demand stabilize. This requires the Orom Graphite project to develop from its current scoping study level to a project development study level associated with a definitive feasibility study. To date, the project developed through mapping, reconnaissance drilling, geophysical survey and trenching programs increasing the Net Present Value (NPV) considerably based upon a Cost-Based Valuation approach using Prospectivity Enhancement Multiplier (PEM). The metallurgical studies could however not produce a graphite concentrate product within industrial grade standards. The risk associated with developing the project further into the Mineral Resource Estimation (MRE) phase was quantified and risk was evaluated by implementing a point decision tree and calculating the Expected Monetary Value (EMV). Due to the unfavourable metallurgical results obtained to date, the risk associated with undertaking an additional metallurgical test is considerable with a slight chance of producing a negative project value estimated at 65%. JP van den Berg Rhodes University Overall, the Orom Graphite project contains favourable geological formations with a potential large resource. Market trends indicate that a considerable resource is currently being developed and can supply the global market for the next 4 to 10 years. The project’s location within a landlocked country decreases its economic competitiveness with peer project and the unfavourable, but not conclusive, metallurgical results obtained during the scoping phase do not instil confidence that the project will develop into a productive mine soon. Managing the project development with future graphite demand in mind is the key to determining whether the project still has future value.
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- Date Issued: 2018
Towards modelling the formation of ore bodies initial results dealing with the fluid mechanical aspects of magma chamber convection
- Authors: Botha, André Erasmus
- Date: 1999
- Subjects: Ore deposits , Fluid mechanics , Magmatism
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5492 , http://hdl.handle.net/10962/d1005278 , Ore deposits , Fluid mechanics , Magmatism
- Description: This thesis forms part of a larger effort which aims to establish the means of assessing the fluid mechanical behaviour of magma 1 as it cools inside a magma chamber surrounded by porous country rock. The reason for doing so is to advance the understanding of some types of mineral deposits; for example,the Platinum Group Elements (PGEs). The magma is modelled with the governing equations for a single-phase incompressible Newtonian fluid with variable viscosity and density. In this thesis, thermal conductivity and specific heat are approximated as constants and the country rock is treated as a conducting solid so as to save on computational time in the initial phases of the project. A basic review of the relevant literature is presented as background material and three basic models of magma chambers are discussed: crystal settling, compositional convection and double diffusive convection.The results presented in this thesis are from finite element calculations by a commercial computer code: ANSYS 5.4. This code has been employed in industry for over 26 years and has a long and successful benchmark history. In this context, finite element methods that are applicable to the code are discussed in chapter 5. In chapter 6, results that were obtained in the course of this research are presented. The thesis concludes with an indication of the possible geological significance of the results and various refinements that should be made to future models.
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- Date Issued: 1999
Overview and comparison of Besshi-type deposits ancient and recent
- Authors: Schoeman, Philo
- Date: 1996
- Subjects: Ore deposits -- Japan , Ore deposits -- Canada , Ore deposits -- Namibia , Ore deposits -- South Africa , Ore deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4983 , http://hdl.handle.net/10962/d1005595 , Ore deposits -- Japan , Ore deposits -- Canada , Ore deposits -- Namibia , Ore deposits -- South Africa , Ore deposits
- Description: Besshi-type deposits range in age from early Proterozoic to early Tertiary, of which the largest number are late Proterozoic, early Palaeozoic or Mesozoic in age. No Archaean examples of Besshi-type deposits are known, probably due to insufficient availability of sialic crust for erosion and clastic marine sedimentation before the start of the Proterozoic. All Besshi-type deposits are contained within sequences of clastic sedimentary rock and intercalated basalts in a marine environment. The basalts and amphibolites are principally tholeiitic in composition. Besshi-type deposits characteristically form stratiform 1enses and sheet-like accumulations of semi-massive to massive sulphide. The main ore assemblage consists dominantly of pyrite and/or pyrrhotite with variable amounts of chalcopyrite, sphalerite and trace galena, arsenopyrite, gold and e1ectrum, barite being absent in general. The median Besshi-type deposit (n=75) contains 1.3 million tonnes (Mt) of massive sulphide with a Cu grade running at 1.43%. It is suggested that Besshi-type deposits form by both exhalative and synsedimentary replacement processes when considering geological features and comparisons with modern analogues in the Guaymas Basin, Middle Valley and Escanaba Trough. The currently forming metalliferous sediments in the Red Sea provide for a brine pool model explaining the lack of footwall feeder zones below sheet-like deposits. Where thick sulphide lenses are contained in some Besshi-type deposits, combinations of exhalative precipitation and sub-sea-floor replacement of permeable sediments and/or volcanic rocks, take place in the upper parts of submarine hydrothermal systems.
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- Date Issued: 1996
A review of the sediment-hosted, disseminated precious metal deposits of Nevada : geological setting, classification, genesis and exploration
- Authors: Ash, Philip John
- Date: 1986
- Subjects: Ore deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4906 , http://hdl.handle.net/10962/d1001566
- Description: Carlin-type, fine-grained, "invisible" or Disseminated Replacement Type gold-silver deposits are all different names for a major new type of ore deposit that is currently being extensively developed in the Western United States. This type of deposit is now being found elsewhere. Thus a descriptive empirical model that emphasizes the geological and geochemical environment of formation is needed to assist the mining industry in the search for similar deposits. These deposits are typically formed in carbonaceous, silty dolomites and Iimestones or mineralization calcareous siltstones rocks and is exceedingly fine-grained is disseminated in the and claystones. host sedimentary Gold-silver , ore. Primary alteration usually less than one micron in size in unoxidized types include decalcification, argillitization, silicification resulting in the and pyritization. Silicification is commonly intense formation of jasperoid bodies which may be the host to higher grade ore. Supergene alteration is dominated by oxidation resulting in the formation of numerous oxides and sulphates and the release of gold from its association with sulphides and organic carbon. elements are As, Ba, Hg, Sb, and TI. Commonly associated trace Available geological, geochemical, fluid inclusion and stable-isotope studies lead to the conclusion that a circulating hydrothermal system is the important factor necessary for gold-silver concentration and deposition. A direct genetic or only casual relation between are deposition and discrete igneous formations remains unclear. However, it is considered that volcanism provided the source of heat necessary for the generation of a circulating hydrothermal system. High angle faults and fold structures facilitate transport and are of prime importance in directing are fluids to favourable host lithologies. The host rocks, overwhelmingly carbonate - rich, include those whose original and/or altered compositions and resulting permeability provide favourable sites for the precipitation of disseminated gold. The processes specialized. resulting Any th ick in the formation of these deposits are section of carbonate rocks has the potential not to produce Disseminated Replacement Type deposits wherever underlying igneous activity has developed a hydrothermal system
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- Date Issued: 1986
Economic geology of sulphide nickel deposits
- Authors: Harrison, P A
- Date: 1983
- Subjects: Nickel sulfide , Ore deposits , Geology, Economic , Silicate minerals , Geochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5022 , http://hdl.handle.net/10962/d1006349
- Description: From Chapter 1: It has been a long standing belief that many nickel sulphide ores are derivatives of magmatic processes in ultramafic and mafic rocks, and that they segregate from these magmas as immiscible sulphide droplets which are then concentrated into an orebody by gravitational settling either during intrusion or extrusion, or during the early stages of crystallization of the magma (Naldrett, 1981). Some geologists however, have suggested alternative mechanisms to explain the concentration of nickeliferous sulphides in the mafic and ultramafic hosts. These include hydrothermal replacement (Fleet, 1977), exhalative volcanic processes (Lusk, 1976), or major metamorphic upgrading of low grade, initially magmatic deposits (Barrett et al., 1977). It is not the purpose of this study to verify or disprove these hypotheses, but in so far as the initial concentration of sulphides in most deposits is concerned, these effects are relatively unimportant (Naldrett, 1981). The nickel sulphide ores associated with these mafic and ultramafic host rocks, invariably consist of nickeliferous pyrrhotite as the dominant phase, together with lesser, but variable, amounts of magnetite, pentlandite, chalcopyrite, cubanite, and platinum group elements (Reynolds, 1982).
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- Date Issued: 1983
The concept of grade in mineral deposits
- Authors: Esterhuizen, Anton G
- Date: 1983 , 2013-04-04
- Subjects: Mines and mineral resources , Ore deposits , Mineralogy , Geology, Economic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5020 , http://hdl.handle.net/10962/d1006331 , Mines and mineral resources , Ore deposits , Mineralogy , Geology, Economic
- Description: The grade of a mineral deposit is determined by the effectiveness of a geological ore forming process, which is the result of the interaction between an ore forming mechanism and the environment in which it operates. Properties of a mineral deposit controlled by ore forming processes include the distribution, density and nature of ore minerals and gangue, and the metal content and impurities of the ore minerals. More efficient ore forming processes tend to develop in the larger mineralizing systems giving rise to richer deposits. As the geological environment within which a mineral deposit evolves becomes more complex a greater number of variables interact to determine the grade of the deposit. This is reflected in the greater variability of the grade distribution, resulting in greater difficulties in obtaining reliable estimates of the recoverable grade, and increased difficulties in the processing of ores. In response to economic fluctuations the working grade of heterogeneous orebodies, that form in geologically complex environments, can often be altered to ensure the continued viability of a mining venture. In contrast the evenly mineralized orebodies that tend to develop in geologically simple environments do not have this flexibility. All the important decisions in the mining industry, such as feasibility studies, choice of ~ining and processing methods, selection and planning, are made on the basis of, or are related to, grade estimates. If the geological controls of grade are fully understood, then it is possible to optimize the selection of the various mining alternatives, leading to the efficient exploitation of ore deposits.
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- Date Issued: 1983
The factors affecting the interpretation of geochemical surveys in mineral exploration
- Authors: Fletcher, B A
- Date: 1982
- Subjects: Geochemistry , Geochemistry -- Environmental aspects , Mining geology , Minerals , Ore deposits , Geochemical prospecting
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5014 , http://hdl.handle.net/10962/d1006142
- Description: [From introduction] Exploration geochemistry is an indirect method of detecting mineral deposits by measuring the abundance and distribution of ore elements and elements closely associated with ore in natural materials at or near the earth's surface. The method relies on the assumption that a mineral deposit is reflected by unusual element abundances or distribution patterns (geochemical halos), and that these indications of mineralization can be detected by geochemical surveys involving the collection and analysis of natural materials. The interpretation of geochemical surveys in mineral exploration involves: 1) The use of geological and statistical inference, based on a knowledge of the normal behaviour and distribution of indicator elements in the exploration area, to recognize apparent geochemical anomalies in field and analytical data and to predict the type of geochemical halo reflected by the anomalies. 11) The use of geological inference, based on a knowledge of the characteristics of geochemical halos and their relationship to mineral deposits, to predict the presence and probable location of an ore body. The interpretation process is, however, complicated by the absence of a simple universal formula that relates the abundance and distribution of elements in natural materials to the presence or absence of a mineral deposit. The interpretation of a geochemical survey must, thus, be based on an empirical approach which avaluates each survey as an individual problem. The objective of this dissertation is to illustrate the factors affecting the "nuts and bolts" approach to the interpretation of geochemical surveys in mineral exploration. The discussion is aimed at providing field geologists responsible -for the planning and execution of geochemical surveys with some basic guidelines for interpreting the surveys. I hope that the contents of this dissertation will help field geologists to "look in the last place first".
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- Date Issued: 1982
Geodynamics, rifting, stratiform and stratabound mineral deposits
- Authors: Dingemans, D.R.W.
- Date: 1981 , 2013-03-19
- Subjects: Ore deposits , Geodynamics , Mines and mineral resources , Rifts (Geology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5012 , http://hdl.handle.net/10962/d1006107 , Ore deposits , Geodynamics , Mines and mineral resources , Rifts (Geology)
- Description: Stratiform and stratabound ore deposits commonly show a direct relationship with rifts. This association is studied by developing a geodynamic model of mantle processes and crustal responses. The geodynamics of the earth can be modelled by the process of mantle advection, which involves the episodic generation and segregation of low density mantle diapirs and their rise and subsequent interaction with the crust. The theory of mantle advection explains the genetic association between rifting, magmatism, basin development and subsequent orogeny and metamorphism. Global evolution has passed through a number of major stages of non-uniformitarian development in which each cycle was characterized by fairly uniform behaviour terminated by intense geodynamic upheaval. The relationship between geological evolution and mantle advection is examined by reviewing the major characteristics of each of the cycles, which correspond to the Archean, Early Proterozoic, Mid Proterozoic, Late Proterozoic-Palaeo2oic, and Mesozoic - Cainozoic eras. Although mentle advection has controlled crustal processes throughout time, the decrease in the thermal energy of the earth has caused >the major evolutionary changes in response to thickening and a greater rigidity of the sialic crust. Rifts are penetrative taphrogenic faults in the earths crust which act as major conduits for the transfer of magmas, from the mantle and lower crustal levels, to the upper crust and the surface. Rifts are also permeable zones for the migration of metalliferous brines, generated by magmatic differentiation. These metalliferous brines would either be exhaled at surface to form stratiform volcanogenic and volcanosedimentary ore deposits , or would interact with preferential host horizons to form stratabound ore deposits . The associat ion between rifting and stratiform and stratabound ore deposits is illustrated by examining :he tectonic setting, and st ratigraphic relationships of typical ore deposit types .
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- Date Issued: 1981
Sampling in the evaluation of ore deposits
- Authors: Grant, D E C S
- Date: 1981 , 2013-03-19
- Subjects: Ore deposits , Mine valuation , Ores -- Sampling and estimation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5008 , http://hdl.handle.net/10962/d1005912 , Ore deposits , Mine valuation , Ores -- Sampling and estimation
- Description: Sampling is an error generating process and these errors should be reduced to a minimum if an accurate ore reserve estimation is to be made from the sample values. Error in sampling can arise from the sampling procedure as well as where and how each sample is taken from the deposit . Sampling procedure involves sample collection, sample reduction and analysis, and the error from each of these three stages has an equal influence on the total error of the process. Error due to sampling procedure should be identified and eliminated at an early stage in the evaluation programme. An ore deposit should be subdivided into sampling strata along geological boundaries, and once these boundaries have been established they should be adhered to for the evaluation programme. The sampling of each stratum depends on the small-scale structures in which the grade is distributed, and this distribution in relation to sample size controls sample variance, sample bias and the volume of influence of each sample. Cluster sampling can be used where an impractically large sample is necessary to reduce sample variance or increase the volume of influence of samples. Sample bias can be reduced by composing a large number of small samples . Sampling patterns should be designed with reference to the volumes of influence of samples, and in favourable geology, geostatistical or statistical techniques can be used to predict the precision of an ore reserve estimation 1n terms of the number of samples taken. Different are deposits have different sampling characteristics and problems which can be directly related to the geology of the mineralization. If geology is disregarded when sampling an are deposit, an evaluation programme cannot claim to give an accurate estimate of the ore reserves .
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- Date Issued: 1981
Geological and economic factors affecting ore reserve estimation and grade control in porphyry type deposits
- Authors: Reichhard-Barends, E O
- Date: 1980
- Subjects: Porphyry , Geology, Economic , Ore deposits , Copper mines and mining
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4921 , http://hdl.handle.net/10962/d1004466
- Description: From introduction: The mining of porphyry type deposits accounts for about 50% of the world's present copper (Figs.I,2) and molybdenum production and resources. Mining organizations therefore invest substantial amounts of time, money and skills in the location and delineation of these types of deposit. The optimization of this investment effort is based on complex inter-relationships between geological, economic and political factors. The object of this dissertation is to review the geological and some of the economic aspects involved in the exploration and evaluation of porphyry deposits . These may hopefully provide some practical guidelines for decision making during the exploration and evaluation of such deposits. For the purpose of this dissertation, the exploration-evaluation of porphyry deposits, has been divided into three main stages:- Stage 1 : Geological mapping, interpretation of exploration drilling results and other geological factors which may help in understanding the shape and nature of the deposit. A knowledge of existing geological models for porphyry deposits will be essential in understanding the geological factors affecting tonnage and grade of these deposits Stage 2 Stage 3 (see Part I). Determination of grade-tonnage relationships. This is important in order to establish the different tonnage-grade alternatives for the deposit. Based on this, reserve estimations are calculated for different possible scales of mining. Drilling and sampling techniques, as well as statistical and preliminary economic evaluation methods are applied during this stage (see Part 2). Mine development and feasibility studies involve factors that influence type and scale of mining, and factors affecting mineral processing and extraction in relation to tonnage- grade alternatives. These factors are reviewed in Part 3.
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- Date Issued: 1980
The behaviour of the elements Ni, Co, Cu, Pb, Zn, Au, Ag, Mo, Sn, W and U in the magmatic, hydrothermal, sedimentary and weathering environments
- Authors: Anderson, J R
- Date: 1979
- Subjects: Elements , Environment , Ore deposits , Classification , Geochemistry , Crystal chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4896 , http://hdl.handle.net/10962/d1001555
- Description: In the last two decades much has been published on the behaviour of certain elements in the magmatic , hydrothermal, sedimentary and weathering environments , but the information is scattered throughout the literature . This situation prompted the present study on the elements Ni, Co, Cu, Pb , Zn , Au, Ag , Mo , Sn, W and U. The behaviour of the elements Ni, Cu, Pb , ZN, Au, Sn , W and U has been studied experimentally in some depth. Ag has been moderately studied, but there is very little information about Co and Mo. Studies on the complexes formed by the elements within the hydrothermal and aqueous environment are often inconclusive and controversial , but conclusions are drawn as to the more likely complexes formed . A genetic classification of ore deposits is used as a framework for the discussion . The source of the elements is regarded as being the mantle, and therefore discussion on other possible sources is beyond the scope of this dissertation. The crystal chemistry and geochemistry of the elements are presented and the essay concludes with a discussion on the elements within their depositional environments
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- Date Issued: 1979