A review of mineral exploration drilling with particular reference to Southern Africa
- Authors: Bertram, N G E
- Date: 1980
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4931 , http://hdl.handle.net/10962/d1004930
- Description: The field of mineral exploration drilling is reviewed with particular reference to examples, and techniques practised, in southern Africa. Drilling is the most· definitive process in exploration and the most cost intensive. It is, therefore, imperative to insure that the maximum geological information available is obtained from a borehole to warrant the cost of drilling it. Methods and techniques of obtaining this information, at little additional expense, are described and reviewed. Non-core percussion and rotary drilled boreholes cost significantly less than diamond drill holes and, as a result, many more holes can be drilled for the money available. While the logging of cuttings is notoriously neglected in most exploration programmes; a great deal of information is available to the conscientious evaluator. Down-the-hole logging and sampling techniques improve the reliability of the borehole samples and provide rapid and inexpensive analyses and lithological data. Cored, or diamond drill boreholes, are the most versatile of the drilling methods available and provide the most reliable lithological and grade information. The handling, logging, sampling and storage of core and core data is discussed. For little additional expense, comprehensive and accurate borehole surveys can be conducted and oriented cores obtained from the borehole. The natural tendency of a borehole to deviate can be used to advantage with controlled drilling techniques. Multiple ore intersections are possible through controlled deflections from a master hole. Mathematical, statistical and simulation models are available to optimise borehole siting, spacing and grid dimensions .
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- Date Issued: 1980
A review of unconformity-type uranium deposits
- Authors: Dabrowski, F A
- Date: 1980 , 2013-04-02
- Subjects: Uranium ores , Mineralogy , Geochemistry , Unconformities (Geology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4917 , http://hdl.handle.net/10962/d1003289 , Uranium ores , Mineralogy , Geochemistry , Unconformities (Geology)
- Description: Intense interest in uranium in the past decade has led to the discovery of new kinds of deposits of which the so-called unconformity-type are economically the most important. Presently known occurrences are restricted to Australia and Canada where they are characterized chiefly by their spatial relationship to Lower-Middle Proterozoic unconformities. Other common features include similar host-rock assemblages, structural controls, alteration, mineralogy, age relationships and fluid-inclusion data. Similar characteristics in other vein-type deposits, including those of the Beaverlodge district in Canada, deposits in France and Portugal, and the Schwartzwalder mine in the United States, suggest that they may also be of the unconformity-type. Various interpretations of the geological relationships of unconformity-type deposits have resulted in a number of genetic hypotheses, which require different exploration philosophies. Nearsurface supergene processes are considered to be most important although other mechanisms may have played contributing roles in the concentration of uranium. There is considerable potential for further discoveries of unconformity-type uranium deposits throughout the world. No such deposits are yet known in southern Africa although several favourable Precambrian unconformities are present.
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- Date Issued: 1980
Geochemical and mineralogical aspects of the Molteno Formation, South Africa
- Authors: Reynolds, Adrian J
- Date: 1980
- Subjects: Sediments (Geology) -- South Africa , Mineralogy -- South Africa , Petrology -- South Africa , Geochemistry -- South Africa , Molteno Formation (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4901 , http://hdl.handle.net/10962/d1001561
- Description: The Triassic Molteno Formation is a clastic sedimentary sequence consisting of a series of cycles, dominated lithologically by coarse grained sandstones. Aspects of the petrography have been examined using the conventional petrographic microscope as well as the scanning electron microscope. Both solution and overgrowth features are present not only on the quartz grains but also on certain of the heavy mineral species present. Intrastratal solution of garnet would appear to be a significant feature in the Molteno Formation. Mineralogical examination of the laterally persistent Indwe Sandstone Member indicates no significant variation in heavy mineral content. Evidence from a study of zircon elongation ratios shows the presence of two distinct zircon populations indicating two provenance areas. X-ray diffraction and electron microprobe analysis has identified mineral species characteristic of granites, pegmatitic granite and metamorphic rocks, especially amphibolites. Palaeocurrent data indicates that this source area lay to the south-east; to the south the source area consisted mainly of the Cape Supergroup sediments. Analysis for Nb, Zr, Y, Sr, Rb, Zn, Mn, Ba, Cu, Ni, Co, Cr, V and Ti for 22 samples from the Molteno Formation, indicates, as expected for a highly arenaceous sequence, a substantial depletion in these trace elements. No consistent variation of trace element concentration occurs with height in the sequence so trace element content may not be used for purposes of stratigraphic correlation. There are indications of trace element variation with geographical position, no doubt a reflection of the contribution of 2 source areas of different compositions. Factor analysis of the interelement correlations has identified 3 factors which influence the trace element content of the Molteno Formation these are a "heavy mineral" factor, a "pH-Eh" factor and a "clay mineral" factor. These trace factors are ultimately an expression of the source rock composition, the prevailing climate and a combination of the two. Comparison with the more argillaceous overlying Elliot Formation, indicates that factors influencing geochemical variation in this sequence were far more complex than for the Molteno Formation
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- Date Issued: 1980
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
Geological factors in the evaluation of vein deposits
- Authors: Neuhoff, Larry E.
- Date: 1980 , 2013-04-02
- Subjects: Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5029 , http://hdl.handle.net/10962/d1006911 , Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
- Description: From introduction: Vein-type mineralization, particularly gold, copper, tin and tungsten has provided a source of metal to man for over 2000 years. These deposits are usually small but in some cases are of very high grade. Prior to 1940 veins were extremely important sources of metals because of their relatively high-grades. However, with improved mining, smelting and concentrating methods, much lower grade material became economic, hence these smaller deposits could no longer hold their dominance. Recently the energy crisis and escalating costs of capital for large projects has made smaller deposits attractive once more (Temblay and Descarreaux, 1978) . At the present time gold, tin and tungsten command high prices on world markets. It is for these reasons that a study of the evaluation techniques pertaining to these deposits has been undertaken. In this review the geological factors which influence the evaluation are stressed. In particular, emphasis is placed on the emplacement of vein deposits, and the subsequent chemical and structural modifications of these deposits. The latter part of the review concentrates on the limitations of the sampling and ore reserve techniques that can be applied to the evaluation of mineralized veins. In the conclusion those techniques that are most applicable are stressed, and an evaluation model is outlined.
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- Date Issued: 1980
Interpretation of mineralogical, chemical and morphological features of duricrusts and its application to mineral exploration
- Authors: Friggens, Peter John
- Date: 1980 , 2013-04-02
- Subjects: Duricrusts , Mineralogy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5021 , http://hdl.handle.net/10962/d1006345 , Duricrusts , Mineralogy
- Description: Introduction: The object of mineral exploration is to locate economic deposits with minimum expenditure in time and money . In order to achieve this goal it is essential to select the most favourable environment and to design the search procedures for the environment in question. Duricrusts are a striking feature of tropical and subtropical landscapes where they occur as extensive, resistant horizons which form a surface or near-surface caprock and are best seen in incised landscapes. Since they cover many potentially rich mineral , provinces of the world, it is important to question what effect they have on mineral exploration. Duricrusts are defined as specific soil types formed by near-surface processes associated with weathering . In spite of the sheer aerial extent of soils over the landsurfaces of the earth, Levinson (1974) expressed surprise at how little exploration geologists know about this surficial environment . Weathering and pedogenetic processes therefore, require discussion in this text. However, in order to adhere to the scope of this dissertation only a brief description of the factors and characteristics of soil formation are given in the first chapter. In the second part, duricrusts are differentiated on the basis of composition into laterite, silcrete and calcrete. Beginning with a concise description of both natural and experimental investigations concerned with mineral decomposition and neomineralisation during weathering, the morphological, physical and chemical characters of each type are described. Environmental factors are then discussed in an attempt to identify specific duricrust types in terms of climate, geographic location, age and formation process . Once duricrust structure and texture are related to topography, specific types may be used to assess the significance of suspected markers in the landscape and permit identification of individual weathering surfaces on which mineralisation may give rise to gossans of widely different physical and chemical characteristics. The interpretation of photogeological, geochemical and geophysical data acquired during mineral exploration in duricrust terrains is problematical and some of the limitations to these search procedures are discussed in the final .chapter
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- Date Issued: 1980
The extrusive and intrusive basaltic rocks of the Molteno-Jamestown area
- Authors: Mitchell, Andrew Alexander
- Date: 1980
- Subjects: Basalt -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4900 , http://hdl.handle.net/10962/d1001559
- Description: The Karoo basalt outliers between Molteno and Jamestown in the north-eastern Cape Province are associated with two central volcanic vent complexes, referred to in the text as the Brosterlea and the Modderfontein complexes. The basalts, particularly those associated with the Brosterlea complex, show geochemical variations throughout the sequence, a factor which has facilitated the subdivision of the Brosterlea basalts into a series of discrete units, each having its own chemical characteristics. Most of the basalt units at Brosterlea can be correlated with units identified in the Barkly East basalt suite. As is the case around Barkly East, the Brosterlea basalt units cannot be related to one another by any simple crystal fractionation or partial melting process, and the most feasible alternative explanation lies in the existence of inhomogeneities in the upper mantle at the time of generation of the magmas. New electron microprobe data are presented for the silicate phases in the Karoo basalts. Analyses of augites from a limited number of slides indicate that pyroxenes from different basalt units define different trends on the Ca - Mg - Fe triangular diagram. The plagioclases in the Brosterlea basalts are fairly Ca-rich (average 70% An), and the K-content of the plagioclases is shown to vary with the K-content of the parent basalt. A comparison of the Karoo Central Province with the younger Columbia River and Deccan Trap Provinces shows many similarities in the evolutionary history of the three provinces. The Karoo Province, however, is distinct from the other two provinces in some aspects of the geochemistry. Broadly speaking, the Karoo basalts are depleted in the incompatible elements relative to the Columbia River and Deccan basalts, and often enriched in the transition metals, most specifically Cr
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- Date Issued: 1980