A microstructural kinematic study of selected shear zones in the Hartbees River Thrust Belt, northeastern Namaqua Tectonic Province
- Authors: Jackson, Christopher
- Date: 1992
- Subjects: Metamorphic rocks -- South Africa -- Northern Cape , Mylonite -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4976 , http://hdl.handle.net/10962/d1005588 , Metamorphic rocks -- South Africa -- Northern Cape , Mylonite -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape
- Description: The Hartbees River Thrust Belt (HRTS) is a 40-60 km wide, southwest-vergent zone of complex structure, lithostratigraphy and high-grade metamorphism in the northeastern part of the mid-Proterozoic Namaqua Tectonic Province. The HRTS comprises the boundary zone separating the Bushmanland and Gordonia Subprovinces of the Namaqua Province. A knowledge of the movement histories of major ductile shear zones within the HRTS is fundamental to understanding the tectonic development of the belt, and Namaqua tectogenesis as a whole. In spite of this, no detailed microstructural kinematic studies have been attempted and the movement histories and age relationships of these shear zones have not been described in detail. This thesis represents a detailed microstructural kinematic study of a representative suite of orientated samples of mylonitic rocks, collected from five ductile shear zones within the HRTS. These shear zones include the Neusspruit Lineament, the Kakamas shear zone (KSZ), the Hugosput shear system (HSS), the Rozynenbosch-Ganzenmond shear zone (RGSZ) and the Graafwater shear system (GSS). Accepted modern methods of microstructural kinematic analysis were applied to samples of mylonite from these shear zones, in order to determine the precise orientation of the kinematic vectors, and the sense and relative ages of movements on each of the shear zones. Shear sense criteria, including composite SoC planar fabrics and shear band foliations, asymmetrical porphyroclast systems, mica-fish, oblique grain-shape and subgrain fabrics, asymmetrical microfolds, and the displacement of fractured rigid grains, together with a well-developed mylonite elongation lineation, conclusively indicate that SSW-directed thrusting occurred along the HSS, RGSZ, GSS and possibly along the Neusspruit Lineament, while normal, top-to-NE movements occurred on the Neusspruit Lineament, KSZ and HSS. Rare transposition criteria, and textural and paragenetic contrasts between syn-kinematic fabrics, strongly suggest that the phase of normal, top-to-NE movement seen in the northeastern HRTS shear zones is younger than the more widespread top-to-SW thrusting event. On the basis of mesoscopic structural criteria, SSW-directed thrusting is correlated with the D₂ deformation event in the HRTS. The mylonite zones have been refolded by ENE-SSW trending F₃ crossfolds, whose demonstrated coaxial relationship to the mylonite elongation lineation precluded reorientation of primary kinematic vectors. In the southwestern HRTS, primary thrust vectors have been reoriented by right-lateral, strike-slip shearing adjacent to the Pofadder Lineament during D₄. Simple shear dispersion of mylonite lineations related to normal movement, suggests that they too have been modified by D₄ shearing, and this constrains the timing of extensional movements to post-D₂ and pre- or syn-D₄. Syn-kinematic mineral assemblages, rheological criteria and the annealing states of the mylonites, provide insight into the thermotectonic evolution of the shear zones. A model is proposed in which the movement histories of shear zones within the HRTS are explained in terms of a typical orogenic cycle, involving crustal thickening by thrusting during a compressional orogenic phase, followed by collapse of the thickened crust during an extensional taphrogenic phase.
- Full Text:
- Date Issued: 1992
- Authors: Jackson, Christopher
- Date: 1992
- Subjects: Metamorphic rocks -- South Africa -- Northern Cape , Mylonite -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4976 , http://hdl.handle.net/10962/d1005588 , Metamorphic rocks -- South Africa -- Northern Cape , Mylonite -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape
- Description: The Hartbees River Thrust Belt (HRTS) is a 40-60 km wide, southwest-vergent zone of complex structure, lithostratigraphy and high-grade metamorphism in the northeastern part of the mid-Proterozoic Namaqua Tectonic Province. The HRTS comprises the boundary zone separating the Bushmanland and Gordonia Subprovinces of the Namaqua Province. A knowledge of the movement histories of major ductile shear zones within the HRTS is fundamental to understanding the tectonic development of the belt, and Namaqua tectogenesis as a whole. In spite of this, no detailed microstructural kinematic studies have been attempted and the movement histories and age relationships of these shear zones have not been described in detail. This thesis represents a detailed microstructural kinematic study of a representative suite of orientated samples of mylonitic rocks, collected from five ductile shear zones within the HRTS. These shear zones include the Neusspruit Lineament, the Kakamas shear zone (KSZ), the Hugosput shear system (HSS), the Rozynenbosch-Ganzenmond shear zone (RGSZ) and the Graafwater shear system (GSS). Accepted modern methods of microstructural kinematic analysis were applied to samples of mylonite from these shear zones, in order to determine the precise orientation of the kinematic vectors, and the sense and relative ages of movements on each of the shear zones. Shear sense criteria, including composite SoC planar fabrics and shear band foliations, asymmetrical porphyroclast systems, mica-fish, oblique grain-shape and subgrain fabrics, asymmetrical microfolds, and the displacement of fractured rigid grains, together with a well-developed mylonite elongation lineation, conclusively indicate that SSW-directed thrusting occurred along the HSS, RGSZ, GSS and possibly along the Neusspruit Lineament, while normal, top-to-NE movements occurred on the Neusspruit Lineament, KSZ and HSS. Rare transposition criteria, and textural and paragenetic contrasts between syn-kinematic fabrics, strongly suggest that the phase of normal, top-to-NE movement seen in the northeastern HRTS shear zones is younger than the more widespread top-to-SW thrusting event. On the basis of mesoscopic structural criteria, SSW-directed thrusting is correlated with the D₂ deformation event in the HRTS. The mylonite zones have been refolded by ENE-SSW trending F₃ crossfolds, whose demonstrated coaxial relationship to the mylonite elongation lineation precluded reorientation of primary kinematic vectors. In the southwestern HRTS, primary thrust vectors have been reoriented by right-lateral, strike-slip shearing adjacent to the Pofadder Lineament during D₄. Simple shear dispersion of mylonite lineations related to normal movement, suggests that they too have been modified by D₄ shearing, and this constrains the timing of extensional movements to post-D₂ and pre- or syn-D₄. Syn-kinematic mineral assemblages, rheological criteria and the annealing states of the mylonites, provide insight into the thermotectonic evolution of the shear zones. A model is proposed in which the movement histories of shear zones within the HRTS are explained in terms of a typical orogenic cycle, involving crustal thickening by thrusting during a compressional orogenic phase, followed by collapse of the thickened crust during an extensional taphrogenic phase.
- Full Text:
- Date Issued: 1992
Exploration for stratabound copper, lead and zinc deposits in the Damara-Katanga orogen, central-southern Africa
- Authors: Latorre, J J
- Date: 1992
- Subjects: Mining geology -- Research -- Africa , Copper ores -- Africa , Lead ores -- Africa , Zinc ores -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4946 , http://hdl.handle.net/10962/d1005558
- Description: The Damara-Katanga orogen in central-southern Africa represents an area of 1.73xl0⁶ sq. km. The region is considered one of the wealthiest metallogenic provinces in the world. Successful exploration for stratabound base-metal deposits has taken place at this particular area since the introduction of more organised methodology in the early 1920s. The genesis, location and distribution of the ore deposits are related to their tectonic settings. Geodynamic evolution of the orogen, which initially formed part of a complex Pan-African rift system, comprises the following stages rifting; downwarping, including spreading on the western portion; syn-orogeny and late-orogeny. Two major tectonic events in the history of the region have been identified: the Katangan (900-750 Ma) and the Damaran episodes (750-500 Ma). Timing of mineralisation of ore deposits has been related to the evolutionary stages of the orogen. Genetic models of the most productive deposits are briefly discussed in this dissertation. The sedimentological, geochemical, paleogeographic and structural features can be employed as geological guidelines for integrated exploration programmes. Discoveries of major deposits and prospects in the orogen are also summarised, focussing on the exploration methods employed. The cost-effective use of the exploration techniques includes the classical copper-lead-zinc soil sampling for residual soils such as those in the Copperbelt area. Airborne magnetics and electromagnetics and follow-up ground geophysics have proved successful in areas where the cover is transported in the search for shallow ore deposits such as the Matchless massive sulphides. Remote sensing, geochemical and geophysical techniques have been tried in covered areas of western Botswana. The lack of geological control makes this interpretation difficult. A detailed geological mapping and the use of geochemical and geophysical techniques has been used to delineate carbonate-hosted base-metal deposits at the Otavi Land. The more expensive traditional methods necessary for the delineation of orebodies, such as pitting, trenching and drilling, are also discussed. Using a sequential approach, a possible exploration strategy is suggested, outlining the cost-effective use of remote sensing, geochemical and geophysical techniques. Standardisation in basic geological information is required for future successful explorations in the Damara-Katanga orogen, as well as attractive mining policies. In the event of their implementation, exploration perspectives are promising, specifically in terms of ore potential.
- Full Text:
- Date Issued: 1992
- Authors: Latorre, J J
- Date: 1992
- Subjects: Mining geology -- Research -- Africa , Copper ores -- Africa , Lead ores -- Africa , Zinc ores -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4946 , http://hdl.handle.net/10962/d1005558
- Description: The Damara-Katanga orogen in central-southern Africa represents an area of 1.73xl0⁶ sq. km. The region is considered one of the wealthiest metallogenic provinces in the world. Successful exploration for stratabound base-metal deposits has taken place at this particular area since the introduction of more organised methodology in the early 1920s. The genesis, location and distribution of the ore deposits are related to their tectonic settings. Geodynamic evolution of the orogen, which initially formed part of a complex Pan-African rift system, comprises the following stages rifting; downwarping, including spreading on the western portion; syn-orogeny and late-orogeny. Two major tectonic events in the history of the region have been identified: the Katangan (900-750 Ma) and the Damaran episodes (750-500 Ma). Timing of mineralisation of ore deposits has been related to the evolutionary stages of the orogen. Genetic models of the most productive deposits are briefly discussed in this dissertation. The sedimentological, geochemical, paleogeographic and structural features can be employed as geological guidelines for integrated exploration programmes. Discoveries of major deposits and prospects in the orogen are also summarised, focussing on the exploration methods employed. The cost-effective use of the exploration techniques includes the classical copper-lead-zinc soil sampling for residual soils such as those in the Copperbelt area. Airborne magnetics and electromagnetics and follow-up ground geophysics have proved successful in areas where the cover is transported in the search for shallow ore deposits such as the Matchless massive sulphides. Remote sensing, geochemical and geophysical techniques have been tried in covered areas of western Botswana. The lack of geological control makes this interpretation difficult. A detailed geological mapping and the use of geochemical and geophysical techniques has been used to delineate carbonate-hosted base-metal deposits at the Otavi Land. The more expensive traditional methods necessary for the delineation of orebodies, such as pitting, trenching and drilling, are also discussed. Using a sequential approach, a possible exploration strategy is suggested, outlining the cost-effective use of remote sensing, geochemical and geophysical techniques. Standardisation in basic geological information is required for future successful explorations in the Damara-Katanga orogen, as well as attractive mining policies. In the event of their implementation, exploration perspectives are promising, specifically in terms of ore potential.
- Full Text:
- Date Issued: 1992
Facies mapping of the Vaal Reef placer as an aid to remnant pillar extraction and stope width optimisation
- Authors: O'Donovan, Anthony Gareth
- Date: 1992
- Subjects: Facies (Geology) -- South Africa -- Vaal Reef placer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4947 , http://hdl.handle.net/10962/d1005559 , Facies (Geology) -- South Africa -- Vaal Reef placer
- Description: The Vaal Reef placer is situated on the unconformable junction of the Strathmore and Stilfontein formations of the Johannesburg Subgroup. Within the South Division of the Vaal Reefs Exploration and Mining company lease, the Vaal Reef Placer is shown to be composed of several different units. Each unit exhibits its own specific characteristics and trend direction which can be used to establish distinct "Reef packages". These packages can be mapped in such a way as to provide a preliminary lithofacies map for the Vaal Reef Placer. The delineation of such geologically homogenous zones, and the development of a suitable depositional model, can be utilised in several ways. The characteristics of a particular zone are shown to influence the control of stoping width, evaluation of remnant pillars and the geostatistical methodology of evaluating current and future ore reserve blocks.
- Full Text:
- Date Issued: 1992
- Authors: O'Donovan, Anthony Gareth
- Date: 1992
- Subjects: Facies (Geology) -- South Africa -- Vaal Reef placer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4947 , http://hdl.handle.net/10962/d1005559 , Facies (Geology) -- South Africa -- Vaal Reef placer
- Description: The Vaal Reef placer is situated on the unconformable junction of the Strathmore and Stilfontein formations of the Johannesburg Subgroup. Within the South Division of the Vaal Reefs Exploration and Mining company lease, the Vaal Reef Placer is shown to be composed of several different units. Each unit exhibits its own specific characteristics and trend direction which can be used to establish distinct "Reef packages". These packages can be mapped in such a way as to provide a preliminary lithofacies map for the Vaal Reef Placer. The delineation of such geologically homogenous zones, and the development of a suitable depositional model, can be utilised in several ways. The characteristics of a particular zone are shown to influence the control of stoping width, evaluation of remnant pillars and the geostatistical methodology of evaluating current and future ore reserve blocks.
- Full Text:
- Date Issued: 1992
Genetic models for epithermal gold deposits and applications to exploration
- Authors: Veselinović, Milica
- Date: 1992
- Subjects: Gold ores -- Geology , Hydrothermal deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4950 , http://hdl.handle.net/10962/d1005562 , Gold ores -- Geology , Hydrothermal deposits
- Description: Epithermal gold deposits are the product of large-scale hydrothermal systems in tectonically active regions. They form at shallow crustal levels where the physico-chemical conditions change abruptly. Two major groups of epithermal gold deposits can be distinguished based on their genetic connection with: A) Copper-molybdenum porphyry systems and B) Geothermal systems related to volcanic centres and calderas. Epithermal gold deposits connected with geothermal systems encompass three major types: adularia-sericite, acid-sulphate and disseminated replacement (the Carlin-type). Their essential ingredients are: high heat source which leads to convection of groundwater in the upper crust; source of hydrothermal fluid, metals and reduced sulphur; and high-permeability structures which allow fluid convection and metal deposition. Mixing of these ingredients leads to the formation of epithermal gold deposits throughout crustal history, without any restriction on age. The ores were deposited from near-neutral (adularia-sericite type and some of the Carlin-type) to acidic (acid-sulphate type and porphyry-related epithermal gold deposits), low-salinity, high C0₂ and high H₂S fluids, which were predominantly meteoritic in origin. The transport capability of deep fluids in epithermal hydrothermal systems may be shown to be dependent largely on their H₂S content and, through a series of fluid mineral equilibria, on temperature and on C0₂ content. The most common mechanisms of ore deposition are boiling (phase separation), mixing of fluids of different temperatures and salinities, reaction between them and wall rocks, dilution and cooling. An understanding of genetic models for epithermal gold deposits provides the basis for the selection of favourable areas for regional to prospect-scale exploration.
- Full Text:
- Date Issued: 1992
- Authors: Veselinović, Milica
- Date: 1992
- Subjects: Gold ores -- Geology , Hydrothermal deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4950 , http://hdl.handle.net/10962/d1005562 , Gold ores -- Geology , Hydrothermal deposits
- Description: Epithermal gold deposits are the product of large-scale hydrothermal systems in tectonically active regions. They form at shallow crustal levels where the physico-chemical conditions change abruptly. Two major groups of epithermal gold deposits can be distinguished based on their genetic connection with: A) Copper-molybdenum porphyry systems and B) Geothermal systems related to volcanic centres and calderas. Epithermal gold deposits connected with geothermal systems encompass three major types: adularia-sericite, acid-sulphate and disseminated replacement (the Carlin-type). Their essential ingredients are: high heat source which leads to convection of groundwater in the upper crust; source of hydrothermal fluid, metals and reduced sulphur; and high-permeability structures which allow fluid convection and metal deposition. Mixing of these ingredients leads to the formation of epithermal gold deposits throughout crustal history, without any restriction on age. The ores were deposited from near-neutral (adularia-sericite type and some of the Carlin-type) to acidic (acid-sulphate type and porphyry-related epithermal gold deposits), low-salinity, high C0₂ and high H₂S fluids, which were predominantly meteoritic in origin. The transport capability of deep fluids in epithermal hydrothermal systems may be shown to be dependent largely on their H₂S content and, through a series of fluid mineral equilibria, on temperature and on C0₂ content. The most common mechanisms of ore deposition are boiling (phase separation), mixing of fluids of different temperatures and salinities, reaction between them and wall rocks, dilution and cooling. An understanding of genetic models for epithermal gold deposits provides the basis for the selection of favourable areas for regional to prospect-scale exploration.
- Full Text:
- Date Issued: 1992
Geochemical and petrological trends in the UG2-Merensky unit interval of the upper critical zone in the Western Bushveld Complex
- Authors: Maier, Wolfgang Derek
- Date: 1992
- Subjects: Petrology -- South Africa -- North-western Transvaal Geochemistry -- South Africa -- North-western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4951 , http://hdl.handle.net/10962/d1005563
- Description: One of the most remarkable features of the layered sequence of the Bushveld Complex is its lateral consistency in lithology. This work has established a geochemical and lithological correlation along 170 km of strike of the interval between the UG2 chromitite and the Merensky Reef within the Upper Critical zone of the western limb of the Bushveld Complex. The correlation is based on geochemical investigations of 10 borehole intersections and lithological comparisons of more than 20 borehole intersections around the western lobe of the complex. The basic data presented include 123 whole-rock analyses for major and 12 trace elements, 97 analyses for ' 12 trace elements, and ca. 5500 microprobe analyses of all major phases. Patterns of cryptic variation are established. Some layers (the UG2 chromitite and pyroxenite) show considerable consistency with regard to geochemistry and lithology. Others can be traced along most of the investigated strike length, such as the Lone Chrome Seam, the Footwall Marker anorthosite and the immediate anorthosite footwall to the Merensky Unit. Most of the distinguishable members within the study section, however, show great variation along strike (i.e., the Lower and Upper Pseudoreef Markers, the central noritic sequence in the southern arm of the western limb and parts of the immediate Merensky Reef footwall succession). Several models have been evaluated to interpret the geochemical and lithological data. The author comes to the conclusion that the degree of lithological consistency depends on the variability of magmatic parameters within different parts of the chamber. The most important of these parameters are: (i) the size of fresh primitive influxes and consequently the heat flux, (ii) the composition of the residual liquid, and (iii) the frequency of the influxes. Fresh influxes of more or less similar composition thus spread out along the floor if the residual liquid was less dense than the fresh primitive liquid, but intruded the chamber as a plume where plagioclase had crystallized for some time and the residual liquid had become relatively dense. The size of the influx may be regarded as a measure of the amount of heat flux from the feeder into the chamber. A large influx created uniform physicochemical conditions in the chamber whereas a smaller influx created a strong lateral gradient of physicochemical parameters in the chamber, with subsequent differences in viscosity, density, convection currents, yield strength and thus different mixing behaviour of different liquids. Furthermore, a persistent heat flux from the feeder may have delayed crystallization of successive phases in those parts of the chamber proximal to the feeder . Therefore, new influxes would have been deposited on a footwall of varying thickness and lithology in response to different degrees of crystallization and accumulation along strike. The development of a normal cyclic unit (chromititeharzburgite-pyroxenite-norite (+anorthosite?)) may thus have been interrupted at various stages in different parts of the chamber. The ability to correlate anorthosites over great strike distances implies that their formation did not follow entirely random processes but was dependent on specific magmatic conditions which prevailed over laterally extensive portions of the chamber at certain stages during the evolution of the crystallizing liquid.
- Full Text:
- Date Issued: 1992
- Authors: Maier, Wolfgang Derek
- Date: 1992
- Subjects: Petrology -- South Africa -- North-western Transvaal Geochemistry -- South Africa -- North-western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4951 , http://hdl.handle.net/10962/d1005563
- Description: One of the most remarkable features of the layered sequence of the Bushveld Complex is its lateral consistency in lithology. This work has established a geochemical and lithological correlation along 170 km of strike of the interval between the UG2 chromitite and the Merensky Reef within the Upper Critical zone of the western limb of the Bushveld Complex. The correlation is based on geochemical investigations of 10 borehole intersections and lithological comparisons of more than 20 borehole intersections around the western lobe of the complex. The basic data presented include 123 whole-rock analyses for major and 12 trace elements, 97 analyses for ' 12 trace elements, and ca. 5500 microprobe analyses of all major phases. Patterns of cryptic variation are established. Some layers (the UG2 chromitite and pyroxenite) show considerable consistency with regard to geochemistry and lithology. Others can be traced along most of the investigated strike length, such as the Lone Chrome Seam, the Footwall Marker anorthosite and the immediate anorthosite footwall to the Merensky Unit. Most of the distinguishable members within the study section, however, show great variation along strike (i.e., the Lower and Upper Pseudoreef Markers, the central noritic sequence in the southern arm of the western limb and parts of the immediate Merensky Reef footwall succession). Several models have been evaluated to interpret the geochemical and lithological data. The author comes to the conclusion that the degree of lithological consistency depends on the variability of magmatic parameters within different parts of the chamber. The most important of these parameters are: (i) the size of fresh primitive influxes and consequently the heat flux, (ii) the composition of the residual liquid, and (iii) the frequency of the influxes. Fresh influxes of more or less similar composition thus spread out along the floor if the residual liquid was less dense than the fresh primitive liquid, but intruded the chamber as a plume where plagioclase had crystallized for some time and the residual liquid had become relatively dense. The size of the influx may be regarded as a measure of the amount of heat flux from the feeder into the chamber. A large influx created uniform physicochemical conditions in the chamber whereas a smaller influx created a strong lateral gradient of physicochemical parameters in the chamber, with subsequent differences in viscosity, density, convection currents, yield strength and thus different mixing behaviour of different liquids. Furthermore, a persistent heat flux from the feeder may have delayed crystallization of successive phases in those parts of the chamber proximal to the feeder . Therefore, new influxes would have been deposited on a footwall of varying thickness and lithology in response to different degrees of crystallization and accumulation along strike. The development of a normal cyclic unit (chromititeharzburgite-pyroxenite-norite (+anorthosite?)) may thus have been interrupted at various stages in different parts of the chamber. The ability to correlate anorthosites over great strike distances implies that their formation did not follow entirely random processes but was dependent on specific magmatic conditions which prevailed over laterally extensive portions of the chamber at certain stages during the evolution of the crystallizing liquid.
- Full Text:
- Date Issued: 1992
Geological controls for coal exploration and mining
- Authors: Noppé , Mark Adrian
- Date: 1992
- Subjects: Coal -- Geology , Coal mines and mining
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4954 , http://hdl.handle.net/10962/d1005566 , Coal -- Geology , Coal mines and mining
- Description: The identification and interpretation of geological features is essential for the planning and ultimate success of any mining venture. Examples of geological features significant for mining are presented, and their identification during exploration discussed. In particular, the importance of coal qualities, seam thickness and seam elevation are emphasised in relation to longwall mining. Geostatistical analysis provides a powerful tool for improving the prediction and decision-making capabilities of both exploration and mine geologists. The availability of geostatistics, and the benefits resulting from its application, are demonstrated using actual data for calorific value, seam thickness and seam elevation. Contamination of run-of-mine coal is a common problem on highly-mechanised collieries. The problem generally arises from over-cutting of the designated mining horizon. A practical system for monitoring and controlling contamination on a mechanised bord-and-pillar and longwall colliery is presented. The results and benefits of applying such a system are cited for an actual longwall colliery. Numerical geological predictions are not always reported in terms of the reliability of such estimates. Many of these values can be reported in terms of confidence limits, particularly for routine grade control purposes. The methods and benefits of such reporting are described and illustrated by way of examples for calorific value and contamination levels.
- Full Text:
- Date Issued: 1992
- Authors: Noppé , Mark Adrian
- Date: 1992
- Subjects: Coal -- Geology , Coal mines and mining
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4954 , http://hdl.handle.net/10962/d1005566 , Coal -- Geology , Coal mines and mining
- Description: The identification and interpretation of geological features is essential for the planning and ultimate success of any mining venture. Examples of geological features significant for mining are presented, and their identification during exploration discussed. In particular, the importance of coal qualities, seam thickness and seam elevation are emphasised in relation to longwall mining. Geostatistical analysis provides a powerful tool for improving the prediction and decision-making capabilities of both exploration and mine geologists. The availability of geostatistics, and the benefits resulting from its application, are demonstrated using actual data for calorific value, seam thickness and seam elevation. Contamination of run-of-mine coal is a common problem on highly-mechanised collieries. The problem generally arises from over-cutting of the designated mining horizon. A practical system for monitoring and controlling contamination on a mechanised bord-and-pillar and longwall colliery is presented. The results and benefits of applying such a system are cited for an actual longwall colliery. Numerical geological predictions are not always reported in terms of the reliability of such estimates. Many of these values can be reported in terms of confidence limits, particularly for routine grade control purposes. The methods and benefits of such reporting are described and illustrated by way of examples for calorific value and contamination levels.
- Full Text:
- Date Issued: 1992
Guidelines to the evaluation of selectively mined, open pit gold deposits during the exploration stage of mine creation
- Pelly, Frederick Douglas Peter
- Authors: Pelly, Frederick Douglas Peter
- Date: 1992
- Subjects: Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4970 , http://hdl.handle.net/10962/d1005582 , Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Description: This dissertation studies the evaluation of selectively mined, open pit gold deposits during the exploration stage of the mine's life. Since 1970 a large number of selectively mined, open pit gold mines have come into operation. The most common deposits include epithermal vein, mesothermal lode and laterite gold deposits. In general the deposits are characterized by small tonnages (1-20 million tonnes), relatively high grades (2-10 grams per tonne gold), submicroscopic to coarse gold, inexpensive mining, and both free milling and refractory ores.The key components that require evaluating during the exploration period are the deposit's geology, ore reserves, pit design, ore metallurgy and environmental impact. Feasibility studies are the main vehicle by which to report and guide the exploration programme. During the exploration period a company may undertake an initial (geological feasibility), second (preliminary mine feasibility) and third (final feasibility) delineation programme in order to gather sufficient data to justify a mine development decision. The responsibility of evaluating the mineral prospect lies primarily with the exploration geologist and mining engineer. Broad experience, a professional attitude, a thorough understanding of mining economics, and a high level of geological, engineering and technical skills are traits required by the evaluators. In order for mining companies to make sound investment decisions the geographical, geological, mining, metallurgical, environmental, marketing, political and financial aspects affecting the economic potential of the venture must be integrated so that the likely costs, risks and returns of the investment alternative are quantified. Ultimately, it is the economic analysis of these three items that determine whether the mineral prospect is developed into a mine I delineated further I retained until economic circumstances improve, or abandoned. To assess the costs, risks and returns, extensive use of the risk analysis is advocated throughout the exploration period . When combined with intelligent judgement of the intangible risk elements, the probabilistic distribution of discounted cash flows are invaluable in making sound investment decisions. However, the economic analysis is only as good as the information on which it is founded. Accurate and representative field data is the most important prerequisite to successfully evaluating and developing a new mine.
- Full Text:
- Date Issued: 1992
- Authors: Pelly, Frederick Douglas Peter
- Date: 1992
- Subjects: Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4970 , http://hdl.handle.net/10962/d1005582 , Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Description: This dissertation studies the evaluation of selectively mined, open pit gold deposits during the exploration stage of the mine's life. Since 1970 a large number of selectively mined, open pit gold mines have come into operation. The most common deposits include epithermal vein, mesothermal lode and laterite gold deposits. In general the deposits are characterized by small tonnages (1-20 million tonnes), relatively high grades (2-10 grams per tonne gold), submicroscopic to coarse gold, inexpensive mining, and both free milling and refractory ores.The key components that require evaluating during the exploration period are the deposit's geology, ore reserves, pit design, ore metallurgy and environmental impact. Feasibility studies are the main vehicle by which to report and guide the exploration programme. During the exploration period a company may undertake an initial (geological feasibility), second (preliminary mine feasibility) and third (final feasibility) delineation programme in order to gather sufficient data to justify a mine development decision. The responsibility of evaluating the mineral prospect lies primarily with the exploration geologist and mining engineer. Broad experience, a professional attitude, a thorough understanding of mining economics, and a high level of geological, engineering and technical skills are traits required by the evaluators. In order for mining companies to make sound investment decisions the geographical, geological, mining, metallurgical, environmental, marketing, political and financial aspects affecting the economic potential of the venture must be integrated so that the likely costs, risks and returns of the investment alternative are quantified. Ultimately, it is the economic analysis of these three items that determine whether the mineral prospect is developed into a mine I delineated further I retained until economic circumstances improve, or abandoned. To assess the costs, risks and returns, extensive use of the risk analysis is advocated throughout the exploration period . When combined with intelligent judgement of the intangible risk elements, the probabilistic distribution of discounted cash flows are invaluable in making sound investment decisions. However, the economic analysis is only as good as the information on which it is founded. Accurate and representative field data is the most important prerequisite to successfully evaluating and developing a new mine.
- Full Text:
- Date Issued: 1992
Nickel sulphide mineralization associated with Archean komatiites
- Authors: Lane, Monica Leonie
- Date: 1992
- Subjects: Nickel sulfide , Geology, Stratigraphic -- Archaean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4982 , http://hdl.handle.net/10962/d1005594 , Nickel sulfide , Geology, Stratigraphic -- Archaean
- Description: The distribution of Archean Nickel sulphide deposits reflects tectonic controls operating during the evolution of the granitoid greenstone terrains. Important deposits of komatiitic-affinity are concentrated within, and adjacent to, younger (∼2.7 Ga), rift-related greenstone belts (e.g. Canada, Western Australia and Zimababwe). Two important classes of Archean Nickel sulphide deposits exist, formerly known as "Dunitic" and "Peridotitic", these are now referred to as Group I and Group II deposits, based on their characteristic structure and composition. Mineralization varies from massive and matrix to disseminated, and is nearly always concentrated at the base of the host unit. Primary ores have a relatively simple mineralogy, dominated by pyrrhotite-pentlandite-pyrite, and to a lesser degree millerite. Metamorphic grades tend to range from prehnite-pumpellyite facies through to lower and upper amphibolite facies. Genesis of Group I and II deposits is explained by the eruption of komatiites into rift-phase greenstone belts, as channelized flows, which assimilated variable amounts of footwall rocks during emplacement. Sulphide saturation was dependent on the mode of emplacement and, the amount of sulphidic sediments that became assimilated prior to crystallization. This possibly accounts for variations in ore tenor. The Six Mile Deposit (SMD) in Western Australia, is an adcumulate body of the Group IIB-type, exhibiting disseminated mineralization. The ore has been "upgraded" due to hydration and serpentinization. A profound weathering sequence exists, which was subsequently utilized during initial exploration. Exploration techniques has been focused on Western Australia, as it is here that the most innovative ideas have emerged.
- Full Text:
- Date Issued: 1992
- Authors: Lane, Monica Leonie
- Date: 1992
- Subjects: Nickel sulfide , Geology, Stratigraphic -- Archaean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4982 , http://hdl.handle.net/10962/d1005594 , Nickel sulfide , Geology, Stratigraphic -- Archaean
- Description: The distribution of Archean Nickel sulphide deposits reflects tectonic controls operating during the evolution of the granitoid greenstone terrains. Important deposits of komatiitic-affinity are concentrated within, and adjacent to, younger (∼2.7 Ga), rift-related greenstone belts (e.g. Canada, Western Australia and Zimababwe). Two important classes of Archean Nickel sulphide deposits exist, formerly known as "Dunitic" and "Peridotitic", these are now referred to as Group I and Group II deposits, based on their characteristic structure and composition. Mineralization varies from massive and matrix to disseminated, and is nearly always concentrated at the base of the host unit. Primary ores have a relatively simple mineralogy, dominated by pyrrhotite-pentlandite-pyrite, and to a lesser degree millerite. Metamorphic grades tend to range from prehnite-pumpellyite facies through to lower and upper amphibolite facies. Genesis of Group I and II deposits is explained by the eruption of komatiites into rift-phase greenstone belts, as channelized flows, which assimilated variable amounts of footwall rocks during emplacement. Sulphide saturation was dependent on the mode of emplacement and, the amount of sulphidic sediments that became assimilated prior to crystallization. This possibly accounts for variations in ore tenor. The Six Mile Deposit (SMD) in Western Australia, is an adcumulate body of the Group IIB-type, exhibiting disseminated mineralization. The ore has been "upgraded" due to hydration and serpentinization. A profound weathering sequence exists, which was subsequently utilized during initial exploration. Exploration techniques has been focused on Western Australia, as it is here that the most innovative ideas have emerged.
- Full Text:
- Date Issued: 1992
Pegmatite-hosted mineral deposits of central and southern Africa : regional geological settings and preliminary exploration target considerations
- Senzani, Freeman Elther David
- Authors: Senzani, Freeman Elther David
- Date: 1992
- Subjects: Pegmatites -- Africa, Southern , Mineralogy -- Africa, Southern , Pegmatites -- Africa, Central , Mineralogy -- Africa, Central
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5011 , http://hdl.handle.net/10962/d1006087
- Description: Review of literature shows that rocks of all ages from the Archaean to the early Phanerozoic host pegmatite-based mineralisation in the central and southern region of the African continent. The greatest concentrations occur in the Archaean and late Proterozoic orogenic belts, while early to middle Proterozoic granites do not, in general, host mineralisation. Pan-African mineralisation is present, but is not widespread. Some deposits previously considered to be of Pan-African have been shown to be of Proterozoic age. In common with occurrences of other regions, the deposits are closely associated with small, late- to post-tectonic granites. Therefore, preliminary assessment of the potential of granites as sources of pegmatite mineralisation should utilise satellite data or aerial photographs. The granites also tend to be alkaline and peraluminous. Thus, in the next stage, chemical analysis for selected major and trace elements should be conducted directly on granites if they occur as small plutons. For large granitic batholiths or terranes, preliminary stream-sediment surveys may be necessary to reduce the size of the target area. Subsequently, pegmatite zonation around suitable granites should be assessed as it allows attention to be focussed on areas likely to host the specific type of mineralisation being explored for.
- Full Text:
- Date Issued: 1992
- Authors: Senzani, Freeman Elther David
- Date: 1992
- Subjects: Pegmatites -- Africa, Southern , Mineralogy -- Africa, Southern , Pegmatites -- Africa, Central , Mineralogy -- Africa, Central
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5011 , http://hdl.handle.net/10962/d1006087
- Description: Review of literature shows that rocks of all ages from the Archaean to the early Phanerozoic host pegmatite-based mineralisation in the central and southern region of the African continent. The greatest concentrations occur in the Archaean and late Proterozoic orogenic belts, while early to middle Proterozoic granites do not, in general, host mineralisation. Pan-African mineralisation is present, but is not widespread. Some deposits previously considered to be of Pan-African have been shown to be of Proterozoic age. In common with occurrences of other regions, the deposits are closely associated with small, late- to post-tectonic granites. Therefore, preliminary assessment of the potential of granites as sources of pegmatite mineralisation should utilise satellite data or aerial photographs. The granites also tend to be alkaline and peraluminous. Thus, in the next stage, chemical analysis for selected major and trace elements should be conducted directly on granites if they occur as small plutons. For large granitic batholiths or terranes, preliminary stream-sediment surveys may be necessary to reduce the size of the target area. Subsequently, pegmatite zonation around suitable granites should be assessed as it allows attention to be focussed on areas likely to host the specific type of mineralisation being explored for.
- Full Text:
- Date Issued: 1992
Petrogenesis of the upper critical zone in the Western Bushveld Complex with emphasis on the UG1 Footwall and Bastard units
- Authors: De Klerk, William Johan
- Date: 1992
- Subjects: Petrogenesis -- South Africa Formations (Geology) -- South Africa Mineralogy -- South Africa Geochemistry -- South Africa Petrology -- Africa, Southern Rustenburg Platinum Mines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4986 , http://hdl.handle.net/10962/d1005598
- Description: This study is an account of the stratigraphic sequence, the petrography, mineralogy (microprobe investigations of orthopyroxene, clinopyroxene, olivine and plagioclase feldspar), and whole-rock major- and traceelement geochemistry of the silicate cumulates of the Upper Critical Zone in the western Bushveld Complex. Two parts of the study - an investigation of a 350m column incorporating the MG3 and UGI Footwall Units, and a comparison of two additional Upper Critical Zone profiles with a previously compiled profile between the UGI and Bastard Units - are focused on RPM Union Section in the northwestern sector of the Complex. The third part is a detailed vertical and lateral investigation of the Bastard Unit at the top of the Critical Zone, which draws on sampling and data compilation from seventeen profiles in the western limb of the Complex. The MG3 Unit (45m) is made up of a lower chromitite layer overlain by a norite-pyroxenite-anorthosite sequence while the UGlFW Unit (295m) is composed of a related series of lower chromitite layers (MG4) overlain by a pyroxenite-norite-anorthosite sequence capped by the UGI chromitite layer. These mafic cumulates display a distinctive pattern of oscillating cryptic variation in whole-rock Mg/(Mg+Fe), FeO/Ti0₂, Cr/Co and Ni/V ratios through the sequence. Sympathetic oscillations are recorded for compositions of orthopyroxene and plagioclase feldspar and eight subcycles are recognised through the UGlFW Unit. The entire sequence is characterised by the presence of small, spheroidal, embayed and irregularly shaped plagioclase grains which are poikilitically enclosed in cumulus orthopyroxene grains of both pyroxenites and norites. This texture is indicative of partial resorption of pre-existing feldspar primocrysts within the melt prior to their being incorporated into the host orthopyroxene grains. Textural, geochemical and isotopic data suggest that this sequence was built up by periodic additions of fresh, relatively primitive liquid into fractionated resident liquid, and subsequent mixing within the magma chamber. The Bastard Unit sequence, described in Chapter 4, is the last and most complete cyclic unit (c. 60m) of the Critical Zone, and its upper contact defines the boundary between the Critical and Main Zones of the Complex. This Unit can conveniently be sub-divided into a lower part, where orthopyroxene occurs as a cumulus phase, and the upper part which is composed entirely of anorthosite (Giant Mottled Anorthosite). The basal part of the Unit (≤ 18m) comprises a thin chromitite layer < O.5cm) overlain by a pyroxenite-melanorite-norite-leuconorite sequence. The basal pyroxenite is orthocumulate in character and rapidly gives way to norites and leuconorites. A distinct threefold subdivision emerges within the Giant Mottled Anorthosite which is predominantly an adcumulate which becomes orthocumulate in character at its top. Apart from minor deviations in thicknesses these lithologies are recorded over the entire strike-length covered in this study. Profiles of cryptic variation are compiled for orthopyroxene, plagioclase and whole-rock data and show that the Bastard Unit displays a characteristic pattern which is maintained throughout the western Bushveld Complex. A minor yet distinctive reversal in cryptic variation is revealed at a level which is stratigraphically variable within the lower Giant Mottled Anorthosite, and results in a double cuspate pattern. A remarkable feature of the basal Bastard pyroxenites is that although the modal proportion of mafic to felsic constituents varies systematically away from the northwestern sector, the Mg/(Mg+Fe) ratio of orthopyroxenes remains constant at 0.804 over a lateral strike distance of 171km. Within the upper part of the Unit the orthopyroxene is markedly Fe-rich and it is here that inverted primary pigeonite appears for the first time as a cumulus phase. In addition, K-feldspar, oscillatory zoned plagioclase grains and high levels of incompatible trace elements are noted at this level. On the basis of the data presented it is concluded that the Bastard Unit represents the crystallisation of a final, relatively large influx of hotter primitive liquid, with upper Critical Zone affinities, and subsequent mixing with a column of cooler (less dense) supernatant liquid which had in part hybridized with the overlying Main Zone magma. It is hypothesised that this new liquid was emplaced as a basal flow beneath supernatant liquid and that it initiated the deposition of mafic cumulates at its base. The supernatant liquid is interpreted as representing the fractionated residuum produced by crystallisation of earlier cyclic units, with plagioclase on the liquidus, and that it contained an abundance of small plagioclase primocrysts in suspension. Development of the Unit can be viewed as a two-stage process. In the lower half of the unit, chemical and physical parameters typical of the new magma dominated the crystallisation process, and resulted in cumulates very similar to other relatively complete Upper Critical Zone units. In the upper, leucocratic sequence, above a minor reversal, crystallisation was from a liquid which was the product of mixing of a minor pulse of primitive liquid with the reservoir of hybridized supernatant liquid. Although the Bastard Unit is not continuous around the entire Western limb of the Complex, it is concluded that it developed in a single, or connected, magma chamber and that its irruptive feeder zone was located in the proximal northwestern facies of the Complex.
- Full Text:
- Date Issued: 1992
- Authors: De Klerk, William Johan
- Date: 1992
- Subjects: Petrogenesis -- South Africa Formations (Geology) -- South Africa Mineralogy -- South Africa Geochemistry -- South Africa Petrology -- Africa, Southern Rustenburg Platinum Mines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4986 , http://hdl.handle.net/10962/d1005598
- Description: This study is an account of the stratigraphic sequence, the petrography, mineralogy (microprobe investigations of orthopyroxene, clinopyroxene, olivine and plagioclase feldspar), and whole-rock major- and traceelement geochemistry of the silicate cumulates of the Upper Critical Zone in the western Bushveld Complex. Two parts of the study - an investigation of a 350m column incorporating the MG3 and UGI Footwall Units, and a comparison of two additional Upper Critical Zone profiles with a previously compiled profile between the UGI and Bastard Units - are focused on RPM Union Section in the northwestern sector of the Complex. The third part is a detailed vertical and lateral investigation of the Bastard Unit at the top of the Critical Zone, which draws on sampling and data compilation from seventeen profiles in the western limb of the Complex. The MG3 Unit (45m) is made up of a lower chromitite layer overlain by a norite-pyroxenite-anorthosite sequence while the UGlFW Unit (295m) is composed of a related series of lower chromitite layers (MG4) overlain by a pyroxenite-norite-anorthosite sequence capped by the UGI chromitite layer. These mafic cumulates display a distinctive pattern of oscillating cryptic variation in whole-rock Mg/(Mg+Fe), FeO/Ti0₂, Cr/Co and Ni/V ratios through the sequence. Sympathetic oscillations are recorded for compositions of orthopyroxene and plagioclase feldspar and eight subcycles are recognised through the UGlFW Unit. The entire sequence is characterised by the presence of small, spheroidal, embayed and irregularly shaped plagioclase grains which are poikilitically enclosed in cumulus orthopyroxene grains of both pyroxenites and norites. This texture is indicative of partial resorption of pre-existing feldspar primocrysts within the melt prior to their being incorporated into the host orthopyroxene grains. Textural, geochemical and isotopic data suggest that this sequence was built up by periodic additions of fresh, relatively primitive liquid into fractionated resident liquid, and subsequent mixing within the magma chamber. The Bastard Unit sequence, described in Chapter 4, is the last and most complete cyclic unit (c. 60m) of the Critical Zone, and its upper contact defines the boundary between the Critical and Main Zones of the Complex. This Unit can conveniently be sub-divided into a lower part, where orthopyroxene occurs as a cumulus phase, and the upper part which is composed entirely of anorthosite (Giant Mottled Anorthosite). The basal part of the Unit (≤ 18m) comprises a thin chromitite layer < O.5cm) overlain by a pyroxenite-melanorite-norite-leuconorite sequence. The basal pyroxenite is orthocumulate in character and rapidly gives way to norites and leuconorites. A distinct threefold subdivision emerges within the Giant Mottled Anorthosite which is predominantly an adcumulate which becomes orthocumulate in character at its top. Apart from minor deviations in thicknesses these lithologies are recorded over the entire strike-length covered in this study. Profiles of cryptic variation are compiled for orthopyroxene, plagioclase and whole-rock data and show that the Bastard Unit displays a characteristic pattern which is maintained throughout the western Bushveld Complex. A minor yet distinctive reversal in cryptic variation is revealed at a level which is stratigraphically variable within the lower Giant Mottled Anorthosite, and results in a double cuspate pattern. A remarkable feature of the basal Bastard pyroxenites is that although the modal proportion of mafic to felsic constituents varies systematically away from the northwestern sector, the Mg/(Mg+Fe) ratio of orthopyroxenes remains constant at 0.804 over a lateral strike distance of 171km. Within the upper part of the Unit the orthopyroxene is markedly Fe-rich and it is here that inverted primary pigeonite appears for the first time as a cumulus phase. In addition, K-feldspar, oscillatory zoned plagioclase grains and high levels of incompatible trace elements are noted at this level. On the basis of the data presented it is concluded that the Bastard Unit represents the crystallisation of a final, relatively large influx of hotter primitive liquid, with upper Critical Zone affinities, and subsequent mixing with a column of cooler (less dense) supernatant liquid which had in part hybridized with the overlying Main Zone magma. It is hypothesised that this new liquid was emplaced as a basal flow beneath supernatant liquid and that it initiated the deposition of mafic cumulates at its base. The supernatant liquid is interpreted as representing the fractionated residuum produced by crystallisation of earlier cyclic units, with plagioclase on the liquidus, and that it contained an abundance of small plagioclase primocrysts in suspension. Development of the Unit can be viewed as a two-stage process. In the lower half of the unit, chemical and physical parameters typical of the new magma dominated the crystallisation process, and resulted in cumulates very similar to other relatively complete Upper Critical Zone units. In the upper, leucocratic sequence, above a minor reversal, crystallisation was from a liquid which was the product of mixing of a minor pulse of primitive liquid with the reservoir of hybridized supernatant liquid. Although the Bastard Unit is not continuous around the entire Western limb of the Complex, it is concluded that it developed in a single, or connected, magma chamber and that its irruptive feeder zone was located in the proximal northwestern facies of the Complex.
- Full Text:
- Date Issued: 1992
Small-scale gold mining in southern Africa
- Authors: Joubert, Barend Daniel
- Date: 1992
- Subjects: Gold mines and mining -- South Africa , Abandoned mines , Abandoned mines -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5002 , http://hdl.handle.net/10962/d1005615 , Gold mines and mining -- South Africa , Abandoned mines , Abandoned mines -- South Africa
- Description: The general characteristics of gold deposits are reviewed, and a classification of gold deposits based on mineability is proposed. Evaluation, mlnlng and beneficiation methods are briefly discussed. It is concluded that the most viable targets for small-scale companies comprise deposits that require the least pre-production time and expense. Great potential exists for the small-scale reclamation of gold from tailings dumps and abandoned mines in Southern Africa. There is also potential for developing new smallscale gold mines in the Archaean greenstone terranes of the Zimbabwean and Kaapvaal cratons.
- Full Text:
- Date Issued: 1992
- Authors: Joubert, Barend Daniel
- Date: 1992
- Subjects: Gold mines and mining -- South Africa , Abandoned mines , Abandoned mines -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5002 , http://hdl.handle.net/10962/d1005615 , Gold mines and mining -- South Africa , Abandoned mines , Abandoned mines -- South Africa
- Description: The general characteristics of gold deposits are reviewed, and a classification of gold deposits based on mineability is proposed. Evaluation, mlnlng and beneficiation methods are briefly discussed. It is concluded that the most viable targets for small-scale companies comprise deposits that require the least pre-production time and expense. Great potential exists for the small-scale reclamation of gold from tailings dumps and abandoned mines in Southern Africa. There is also potential for developing new smallscale gold mines in the Archaean greenstone terranes of the Zimbabwean and Kaapvaal cratons.
- Full Text:
- Date Issued: 1992
The development and distribution of heavy mineral concentrations in alluvial systems
- Authors: Lynn, Michael David
- Date: 1992
- Subjects: Heavy minerals -- Research , Alluvial plains -- Research , Geomorphology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4937 , http://hdl.handle.net/10962/d1005549 , Heavy minerals -- Research , Alluvial plains -- Research , Geomorphology -- South Africa
- Description: The objective of this review is to summarise the characteristics, significance and evolution of heavy minerals and their accumulations, and to identify the key controls on the development and distribution of heavy mineral concentrations in alluvial systems. These controls can be broadly classified as tectonic setting, geomorphic setting and grain-scale concentrating processes, each of which is discussed. Based on this review, exploration models are developed which are designed to indicate favourable localities for the accumulation of heavy minerals, and trends likely to be exhibited within these accumulations. The models are structured from the broadest scale of target selection, down to the local scale of sample site selection. The major conclusion of this work is that an understanding of process geomorphology is required to develop genetic models of placer development, including a detailed evaluation of climatic fluctuations throughout the Caenozoic. Palaeoplacers such as the Witwatersrand goldfield, are inferred to have formed under similar circumstances of tectonic setting as genetically comparable Caenozoic placers such as those of Otago, New Zealand. The means of preservation of such major basins is however poorly understood.
- Full Text:
- Date Issued: 1992
- Authors: Lynn, Michael David
- Date: 1992
- Subjects: Heavy minerals -- Research , Alluvial plains -- Research , Geomorphology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4937 , http://hdl.handle.net/10962/d1005549 , Heavy minerals -- Research , Alluvial plains -- Research , Geomorphology -- South Africa
- Description: The objective of this review is to summarise the characteristics, significance and evolution of heavy minerals and their accumulations, and to identify the key controls on the development and distribution of heavy mineral concentrations in alluvial systems. These controls can be broadly classified as tectonic setting, geomorphic setting and grain-scale concentrating processes, each of which is discussed. Based on this review, exploration models are developed which are designed to indicate favourable localities for the accumulation of heavy minerals, and trends likely to be exhibited within these accumulations. The models are structured from the broadest scale of target selection, down to the local scale of sample site selection. The major conclusion of this work is that an understanding of process geomorphology is required to develop genetic models of placer development, including a detailed evaluation of climatic fluctuations throughout the Caenozoic. Palaeoplacers such as the Witwatersrand goldfield, are inferred to have formed under similar circumstances of tectonic setting as genetically comparable Caenozoic placers such as those of Otago, New Zealand. The means of preservation of such major basins is however poorly understood.
- Full Text:
- Date Issued: 1992
The exploration for and possible genesis of, some Archaean granite/gneiss-hosted gold deposits in the Pietersburg granite-greenstone terrane
- Linklater, Michael Anthony Leonard Flanders
- Authors: Linklater, Michael Anthony Leonard Flanders
- Date: 1992
- Subjects: Gold ores -- Geology -- South Africa , Gneiss , Granite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4945 , http://hdl.handle.net/10962/d1005557 , Gold ores -- Geology -- South Africa , Gneiss , Granite
- Description: Abstract The gold mineralization event within Archaean granite-greenstone terranes occurred during the late Archaean, and followed the intrusion of syn- to late-tectonic granitic plutons into previously deformed greenstone belts. An Archaean granite/gneiss-hosted gold deposit, in terms of this project, is classified as having a gold-assay cutoff of 1g/metric ton over widths of at least several metres, or higher grades over narrower widths and/or verbal descriptions that indicate such values. Fluid inclusion studies and isotopic data identify two possible origins for the auriferous fluids; namely magmatic and metamorphic. The exploration target according to the magmatic model, is a late-Archaean, hydrothermally altered, mineralized and fractured granitic intrusion preferably with a granodioritic or quartz-dioritic composition. The exploration target according to the metamorphic replacement model is a granitic stock that has intruded a zone of crustal weakness such as a shear zone, active during the late Archaean. Alternatively, the granitic intrusion should be affected by regionally extensive late-Archaean shearing. It should be hydrothermally altered, deformed and mineralized. Five areas within the Pietersburg granite-greenstone terrane were selected for the 'Regional Area Selection' phase of exploration for Archaean granite/gneiss-hosted gold deposits; namely Roodepoort, Waterval, Ramagoep, Moletsie and Matlala. Roodepoort contains a known granodiorite-hosted gold deposit; the Knight's Pluton, and served as an orientation survey for this project. The use and interpretation of LANDSAT images formed an integral part of exploration techniques; to assess their usefulness in the exploration of Archaean granite/gneiss-hosted gold deposits. Area selection criteria for granite/gneiss-hosted gold mineralization at Roodepoort are the major ENE-trending shear zone, the NNW-trending lineament and hydrothermal alteration, shearing, quartz-stockworks and sulphide mineralization within the Knight's Pluton. The origin of the gold within the Knight's Pluton is uncertain; both magmatic and metamorphic models are possibilities. Ongoing exploration is in progress at Roodepoort. The only area selection criterion for granite/gneiss-hosted gold mineralization at Waterval is the sericitized, subcropping granites located within trenches. Gold mineralization is insignificant. No area selection criteria for Archaean granite/gneiss-hosted gold mineralization were located at Ramagoep, Matlala and Moletsie. No further exploration is recommended for all these areas. The MES image interpretations were successful in identifying lineaments, granitic outcrops, greenstones, vegetation and soil cover. The Clay-iron images adequately differentiated betweeen iron-rich and clay-bearing areas. However, not all clay-bearing areas were associated with hydrothermal alteratian; field checks were necessary to discriminate between weathered granites and hydrothermally altered granites. The Wallis images served to locally enhance the contrasts of the MES and Clay-iron images.
- Full Text:
- Date Issued: 1992
- Authors: Linklater, Michael Anthony Leonard Flanders
- Date: 1992
- Subjects: Gold ores -- Geology -- South Africa , Gneiss , Granite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4945 , http://hdl.handle.net/10962/d1005557 , Gold ores -- Geology -- South Africa , Gneiss , Granite
- Description: Abstract The gold mineralization event within Archaean granite-greenstone terranes occurred during the late Archaean, and followed the intrusion of syn- to late-tectonic granitic plutons into previously deformed greenstone belts. An Archaean granite/gneiss-hosted gold deposit, in terms of this project, is classified as having a gold-assay cutoff of 1g/metric ton over widths of at least several metres, or higher grades over narrower widths and/or verbal descriptions that indicate such values. Fluid inclusion studies and isotopic data identify two possible origins for the auriferous fluids; namely magmatic and metamorphic. The exploration target according to the magmatic model, is a late-Archaean, hydrothermally altered, mineralized and fractured granitic intrusion preferably with a granodioritic or quartz-dioritic composition. The exploration target according to the metamorphic replacement model is a granitic stock that has intruded a zone of crustal weakness such as a shear zone, active during the late Archaean. Alternatively, the granitic intrusion should be affected by regionally extensive late-Archaean shearing. It should be hydrothermally altered, deformed and mineralized. Five areas within the Pietersburg granite-greenstone terrane were selected for the 'Regional Area Selection' phase of exploration for Archaean granite/gneiss-hosted gold deposits; namely Roodepoort, Waterval, Ramagoep, Moletsie and Matlala. Roodepoort contains a known granodiorite-hosted gold deposit; the Knight's Pluton, and served as an orientation survey for this project. The use and interpretation of LANDSAT images formed an integral part of exploration techniques; to assess their usefulness in the exploration of Archaean granite/gneiss-hosted gold deposits. Area selection criteria for granite/gneiss-hosted gold mineralization at Roodepoort are the major ENE-trending shear zone, the NNW-trending lineament and hydrothermal alteration, shearing, quartz-stockworks and sulphide mineralization within the Knight's Pluton. The origin of the gold within the Knight's Pluton is uncertain; both magmatic and metamorphic models are possibilities. Ongoing exploration is in progress at Roodepoort. The only area selection criterion for granite/gneiss-hosted gold mineralization at Waterval is the sericitized, subcropping granites located within trenches. Gold mineralization is insignificant. No area selection criteria for Archaean granite/gneiss-hosted gold mineralization were located at Ramagoep, Matlala and Moletsie. No further exploration is recommended for all these areas. The MES image interpretations were successful in identifying lineaments, granitic outcrops, greenstones, vegetation and soil cover. The Clay-iron images adequately differentiated betweeen iron-rich and clay-bearing areas. However, not all clay-bearing areas were associated with hydrothermal alteratian; field checks were necessary to discriminate between weathered granites and hydrothermally altered granites. The Wallis images served to locally enhance the contrasts of the MES and Clay-iron images.
- Full Text:
- Date Issued: 1992
The geochemical evolution of three alkaline complexes in the Kuboos-Bremen igneous province, southern Namibia
- Authors: Smithies, Robert Hugh
- Date: 1992
- Subjects: Alkalic igneous rocks -- Namibia Geochemistry -- Namibia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4952 , http://hdl.handle.net/10962/d1005564
- Description: The Kuboos-Bremen Igneous Province comprises a linear zone of alkaline complexes that intrude Proterozoic and Pan-African rocks and trends in a northeast direction from the northwest of the Cape Province in South Africa into southern Namibia. Of the three most southerly complexes in Namibia. two comprise silicate rocks ranging from nepheline syenite to alkali-granite and are called the Grootpenseiland and Marinkas Kwela Complexes (GPC and MKC). The Marinkas Kwela Carbonatite Complex is the third and most northerly of the complexes. Isotopic age determinations on a number of rock types from both the silicate complexes yield ages around 520Ma and are consistent with published Pan-African ages for the Province. Each silicate complex shows a migrating locus of intrusion from Siundersaturated rocks in the southwest to Si-oversaturated rocks in the northeast. The complexes overlap in outcrop. The rocks are moderately to highly felsiC and none reflects primary magma compositions. The Si-undersaturated rocks from both complexes include side-wall cumulates formed from magmas that fractionated alkali-feldspar, clinopyroxene and amphibole. Foyaites also occur in the MKC and have a compositional range reflecting alkali-feldspar fractionation and, probably, some interaction with dolomite country rocks. Major and trace element data suggest that critically saturated alkali syenites occurring in both complexes evolved via protracted feldspar fractionation, and that critically saturated alkali-feldspar syenite occurring only in the GPC is a cumulate. The two rock types cannot be related genetically. Of the SI-oversaturated rocks in both complexes, those in the compositional range monzonite to granite were intruded before alkali-granites. Compositional diversity amongst the former reflects fractionation of feldspar and of mafic phases, but that process cannot genetically link the rocks to the alkali-granites. Isotopic compositions of Sr and Nd indicate that the silicate magmas were derived from an upper mantle source region characterised by low time-integrated Rb/Sr ratios and high time-Integrated Sm/Nd ratios, However, the evidence of Sr and 0 isotopic data is that the Si-oversaturated melts possibly interacted with a crustal component. presumably the Proterowlc rocks of the Namaqua Metamorphic Province. This interaction may explain the occurrence of apparently co-genetic rock series that evolved on opposite sides of the feldspar join in Petrogeny's Residua System. The Marinkas Kwela Carbonatite Complex was emplaced before the final intrusive phases of the MKC and exhibits unusually pronounced late-stage enrichment in manganese. The earliest intrusive rocks in the complex were nepheline syenites which were fenitised by later intrusions of sôvites. Although the commonly occurring magmatic sequence of sôvite-beforsite-ferrocarbonatite is observed at Marinkas Kwela, sôvites do not appear to have been parental to beforsites. Removal of apatite and early crystallisation of magnetite distinguish magnetite-rich beforsite from co-genetic apatite-rich beforsite. Two further magmatic sequences. the first from apatite-rich beforsite through ferrocarbonatite to Mn-rich ferrocarbonatite (high Fe/Mn) and the second from magnetite-rich beforsite to Mn-rich ferrocarbonatite (low Fe/Mn). reflect fractionation of dolomite and of dolomite+magnetite respectively.
- Full Text:
- Date Issued: 1992
- Authors: Smithies, Robert Hugh
- Date: 1992
- Subjects: Alkalic igneous rocks -- Namibia Geochemistry -- Namibia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4952 , http://hdl.handle.net/10962/d1005564
- Description: The Kuboos-Bremen Igneous Province comprises a linear zone of alkaline complexes that intrude Proterozoic and Pan-African rocks and trends in a northeast direction from the northwest of the Cape Province in South Africa into southern Namibia. Of the three most southerly complexes in Namibia. two comprise silicate rocks ranging from nepheline syenite to alkali-granite and are called the Grootpenseiland and Marinkas Kwela Complexes (GPC and MKC). The Marinkas Kwela Carbonatite Complex is the third and most northerly of the complexes. Isotopic age determinations on a number of rock types from both the silicate complexes yield ages around 520Ma and are consistent with published Pan-African ages for the Province. Each silicate complex shows a migrating locus of intrusion from Siundersaturated rocks in the southwest to Si-oversaturated rocks in the northeast. The complexes overlap in outcrop. The rocks are moderately to highly felsiC and none reflects primary magma compositions. The Si-undersaturated rocks from both complexes include side-wall cumulates formed from magmas that fractionated alkali-feldspar, clinopyroxene and amphibole. Foyaites also occur in the MKC and have a compositional range reflecting alkali-feldspar fractionation and, probably, some interaction with dolomite country rocks. Major and trace element data suggest that critically saturated alkali syenites occurring in both complexes evolved via protracted feldspar fractionation, and that critically saturated alkali-feldspar syenite occurring only in the GPC is a cumulate. The two rock types cannot be related genetically. Of the SI-oversaturated rocks in both complexes, those in the compositional range monzonite to granite were intruded before alkali-granites. Compositional diversity amongst the former reflects fractionation of feldspar and of mafic phases, but that process cannot genetically link the rocks to the alkali-granites. Isotopic compositions of Sr and Nd indicate that the silicate magmas were derived from an upper mantle source region characterised by low time-integrated Rb/Sr ratios and high time-Integrated Sm/Nd ratios, However, the evidence of Sr and 0 isotopic data is that the Si-oversaturated melts possibly interacted with a crustal component. presumably the Proterowlc rocks of the Namaqua Metamorphic Province. This interaction may explain the occurrence of apparently co-genetic rock series that evolved on opposite sides of the feldspar join in Petrogeny's Residua System. The Marinkas Kwela Carbonatite Complex was emplaced before the final intrusive phases of the MKC and exhibits unusually pronounced late-stage enrichment in manganese. The earliest intrusive rocks in the complex were nepheline syenites which were fenitised by later intrusions of sôvites. Although the commonly occurring magmatic sequence of sôvite-beforsite-ferrocarbonatite is observed at Marinkas Kwela, sôvites do not appear to have been parental to beforsites. Removal of apatite and early crystallisation of magnetite distinguish magnetite-rich beforsite from co-genetic apatite-rich beforsite. Two further magmatic sequences. the first from apatite-rich beforsite through ferrocarbonatite to Mn-rich ferrocarbonatite (high Fe/Mn) and the second from magnetite-rich beforsite to Mn-rich ferrocarbonatite (low Fe/Mn). reflect fractionation of dolomite and of dolomite+magnetite respectively.
- Full Text:
- Date Issued: 1992
The geology and evaluation of the "A"-reef at No.3 shaft, Western Holdings Mine, Welkom goldfield
- Blamey, Nigel John Frederick
- Authors: Blamey, Nigel John Frederick
- Date: 1992
- Subjects: Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4957 , http://hdl.handle.net/10962/d1005569 , Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Description: The "A" -Reef occurs within the Aandenk Formation of the Central Rand Group, Witwatersrand Supergroup, in the Welkom Goldfield. It comprises the Witpan and Uitsig Reefs which are both oligomictic conglomerates, and are exploited for their gold content by Anglo American Corporation. The main Witpan channel complex is orientated in a NW-SE direction and occurs close to No.3 Shaft of Western Holdings Mine where it is currently being mined. The Witpan Reef varies in thickness from 7-220cm, with lateral facies changes controlling the thickness. Within the reef, gold is associated with degradation surfaces, carbonaceous material, increase in pebble sphericity, and channel edges. Two channel edges have yielded the best gold values on No.3 Shaft although the potential for further payable gold lies in the recognition of sieve conditions. The potential also exists for extensions of the "carbon"-bearing Uitsig channel currently being mined on President Steyn Mine. The palaeo-environment proposed for formation of the Witpan Reef is a braidplain that was partly reworked by a brief transgression. Ore evaluation using geostatistics was considered a valid technique as the dataset is sufficiently well structured. Semi-variograms in the channel and across-channel directions differ markedly. It was found that variograms of gold in cmg/t lacked sufficient structure for modelling, however, log semi-variogram modelling followed by simple log-kriging and back-transformation, proved to be the most successful method. Owing to the morphology and distribution of gold within the reef, a geologically based geostatistical valuation method is proposed. The potential for further exploration of "A" -Reef depends on a substantially higher gold price. In this event, exploration of Uitsig Reef to the southwest of the current mining area is recommended as well as a new exploration strategy for Witpan Reef.
- Full Text:
- Date Issued: 1992
- Authors: Blamey, Nigel John Frederick
- Date: 1992
- Subjects: Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4957 , http://hdl.handle.net/10962/d1005569 , Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
- Description: The "A" -Reef occurs within the Aandenk Formation of the Central Rand Group, Witwatersrand Supergroup, in the Welkom Goldfield. It comprises the Witpan and Uitsig Reefs which are both oligomictic conglomerates, and are exploited for their gold content by Anglo American Corporation. The main Witpan channel complex is orientated in a NW-SE direction and occurs close to No.3 Shaft of Western Holdings Mine where it is currently being mined. The Witpan Reef varies in thickness from 7-220cm, with lateral facies changes controlling the thickness. Within the reef, gold is associated with degradation surfaces, carbonaceous material, increase in pebble sphericity, and channel edges. Two channel edges have yielded the best gold values on No.3 Shaft although the potential for further payable gold lies in the recognition of sieve conditions. The potential also exists for extensions of the "carbon"-bearing Uitsig channel currently being mined on President Steyn Mine. The palaeo-environment proposed for formation of the Witpan Reef is a braidplain that was partly reworked by a brief transgression. Ore evaluation using geostatistics was considered a valid technique as the dataset is sufficiently well structured. Semi-variograms in the channel and across-channel directions differ markedly. It was found that variograms of gold in cmg/t lacked sufficient structure for modelling, however, log semi-variogram modelling followed by simple log-kriging and back-transformation, proved to be the most successful method. Owing to the morphology and distribution of gold within the reef, a geologically based geostatistical valuation method is proposed. The potential for further exploration of "A" -Reef depends on a substantially higher gold price. In this event, exploration of Uitsig Reef to the southwest of the current mining area is recommended as well as a new exploration strategy for Witpan Reef.
- Full Text:
- Date Issued: 1992
The geology and geochemistry of the north-western portion of the Usushwana Complex, South-Eastern Transvaal
- Authors: Riganti, Angela
- Date: 1992
- Subjects: Geology -- South Africa -- Transvaal , Geochemistry -- South Africa -- Transvaal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4958 , http://hdl.handle.net/10962/d1005570 , Geology -- South Africa -- Transvaal , Geochemistry -- South Africa -- Transvaal
- Description: The 2.9 Ga old Usushwana Complex in the Piet Retief-Amsterdam area (south-eastern Transvaal) represents an exposed segment of a layered intrusion. It has the form of a dyke-like body elongated in a northwesterly direction, and extends to an estimated depth of 3000 -5500 m. Lithologically, the Complex consists of a cumulate succession of mafic rocks capped by granitoids and has intruded along the contact between the basement and the supracrustal sequences of the Kaapvaal Craton. Differentiation of an already contaminated gabbroic magma resulted in an ordered stratigraphic sequence comprising progressively more evolved lithotypes, with at least two imperfect cyclic units developed over a stratigraphic thickness of about 700 metres (Hlelo River Section). Meso- to orthocumulate textured gabbros and quartz gabbros grade upwards into magnetite- and apatite-bearing quartz gabbros, interlayered with discontinuous magnetitite horizons. The gabbros in turn grade into hornblende-rich, granophyric granodiorites. The differentiation process is regarded as having been considerably enhanced by the assimilation of acidic material, derived by partial melting of the felsic country rocks at the roof of the magma chamber. Recrystallisation of these rocks gave rise to the microgranites that locally overlie the granodiorites. Mineralogical, textural and geochemical features indicate a relatively advanced fractionation stage, suggesting that the exposed sequence of the Usushwana Complex in the study area represents the upper portion of the intrusion. No significant mineralised occurrences were identified. However, on the basis of similarities between the Usushwana Complex and other mafic layered intrusions which host significant ore deposits, it is suggested that economic concentrations of base metal(Cu-Ni) sulphides, PGE and chromitites are likely to be developed at lower stratigraphic levels.
- Full Text:
- Date Issued: 1992
- Authors: Riganti, Angela
- Date: 1992
- Subjects: Geology -- South Africa -- Transvaal , Geochemistry -- South Africa -- Transvaal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4958 , http://hdl.handle.net/10962/d1005570 , Geology -- South Africa -- Transvaal , Geochemistry -- South Africa -- Transvaal
- Description: The 2.9 Ga old Usushwana Complex in the Piet Retief-Amsterdam area (south-eastern Transvaal) represents an exposed segment of a layered intrusion. It has the form of a dyke-like body elongated in a northwesterly direction, and extends to an estimated depth of 3000 -5500 m. Lithologically, the Complex consists of a cumulate succession of mafic rocks capped by granitoids and has intruded along the contact between the basement and the supracrustal sequences of the Kaapvaal Craton. Differentiation of an already contaminated gabbroic magma resulted in an ordered stratigraphic sequence comprising progressively more evolved lithotypes, with at least two imperfect cyclic units developed over a stratigraphic thickness of about 700 metres (Hlelo River Section). Meso- to orthocumulate textured gabbros and quartz gabbros grade upwards into magnetite- and apatite-bearing quartz gabbros, interlayered with discontinuous magnetitite horizons. The gabbros in turn grade into hornblende-rich, granophyric granodiorites. The differentiation process is regarded as having been considerably enhanced by the assimilation of acidic material, derived by partial melting of the felsic country rocks at the roof of the magma chamber. Recrystallisation of these rocks gave rise to the microgranites that locally overlie the granodiorites. Mineralogical, textural and geochemical features indicate a relatively advanced fractionation stage, suggesting that the exposed sequence of the Usushwana Complex in the study area represents the upper portion of the intrusion. No significant mineralised occurrences were identified. However, on the basis of similarities between the Usushwana Complex and other mafic layered intrusions which host significant ore deposits, it is suggested that economic concentrations of base metal(Cu-Ni) sulphides, PGE and chromitites are likely to be developed at lower stratigraphic levels.
- Full Text:
- Date Issued: 1992
The surface geology of the Lavino Chrome Mine of the farm Grootboom 336KT, eastern Transvaal
- Authors: Tinney, Christopher Bruce
- Date: 1992
- Subjects: Chromium ores -- Geology -- South Africa -- Mpumalanga
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5067 , http://hdl.handle.net/10962/d1013404
- Description: A mapping project of the surface geology of the Lavino chrome mine and its surroundings was initiated in order to establish the surface geological relationships in the area. In so doing the chromitite layer presently being mined has been identified and potential exploration targets in the area have been outlined. The Lavino Chrome mine field area is situated within the eastern lobe of the Bushveld Igneous Complex. The area is bounded by in the north by the Steelpoort Lineament, in the west by the Dwars River fault and in the east by the contact with the Transvaal Sequence floor rocks. Layered igneous rocks (pyroxenites, norites and anorthosites) of the Rustenburg Layered Suite dominate the geological landscape at the Lavino mine. The fact that outcropping igneous rocks of the Critical Zone abut directly against the quartzite floor rocks on the mine property makes this area unique in the Bushveld Complex. The hills in the field area are capped by mafic/ultramafic iron-rich sheet - like bodies. Extensive strike-slip faulting is seen in outcrop in the area to the north/northwest of present mining operations. On the basis of field relationships, the main chromitite layer presently being mined at Lavino is identified as the Middle Group chromitite layer MG 1. Three other prominent chromitite layers stratigraphically associated with MG 1 are identified as the Middle Group chromitites MG 2, MG 3 and MG 4. Several other less prominent outcropping chromitite layers are tentatively identified as those belonging to the Lower and Upper group of chromitites. The disconformable nature of the contact between the layered igneous rocks and the Transvaal Sequence floor rocks has resulted in the development of a wedge of undifferentiated pyroxenites in the north of the field area. The economically important LG 6 chromitite layer may be developed in subcrop within this wedge.
- Full Text:
- Date Issued: 1992
- Authors: Tinney, Christopher Bruce
- Date: 1992
- Subjects: Chromium ores -- Geology -- South Africa -- Mpumalanga
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5067 , http://hdl.handle.net/10962/d1013404
- Description: A mapping project of the surface geology of the Lavino chrome mine and its surroundings was initiated in order to establish the surface geological relationships in the area. In so doing the chromitite layer presently being mined has been identified and potential exploration targets in the area have been outlined. The Lavino Chrome mine field area is situated within the eastern lobe of the Bushveld Igneous Complex. The area is bounded by in the north by the Steelpoort Lineament, in the west by the Dwars River fault and in the east by the contact with the Transvaal Sequence floor rocks. Layered igneous rocks (pyroxenites, norites and anorthosites) of the Rustenburg Layered Suite dominate the geological landscape at the Lavino mine. The fact that outcropping igneous rocks of the Critical Zone abut directly against the quartzite floor rocks on the mine property makes this area unique in the Bushveld Complex. The hills in the field area are capped by mafic/ultramafic iron-rich sheet - like bodies. Extensive strike-slip faulting is seen in outcrop in the area to the north/northwest of present mining operations. On the basis of field relationships, the main chromitite layer presently being mined at Lavino is identified as the Middle Group chromitite layer MG 1. Three other prominent chromitite layers stratigraphically associated with MG 1 are identified as the Middle Group chromitites MG 2, MG 3 and MG 4. Several other less prominent outcropping chromitite layers are tentatively identified as those belonging to the Lower and Upper group of chromitites. The disconformable nature of the contact between the layered igneous rocks and the Transvaal Sequence floor rocks has resulted in the development of a wedge of undifferentiated pyroxenites in the north of the field area. The economically important LG 6 chromitite layer may be developed in subcrop within this wedge.
- Full Text:
- Date Issued: 1992
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