A mineral systems approach to the development of structural targeting criteria for orogenic gold deposits in the Asankrangwa gold belt of the Kumasi Basin, South-west Ghana
- Authors: Gelber, Benjamin D J
- Date: 2018
- Subjects: Gold ores -- Geology -- Ghana -- Kumasi , Gold mines and mining -- Ghana -- Kumasi , Asankrangwa (Ghana) , Geodynamics -- Ghana -- Kumasi , Prospecting -- Geophysical methods , Orogenic belts -- Ghana -- Kumasi
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63143 , vital:28367
- Description: The Kumasi Basin in South-west Ghana lies at the centre of the best-endowed Paleoproterozoic gold province in the world. The Kumasi Basin and margins of the adjacent volcanic belts are host to six world class gold camps: (1) 62 Moz Obuasi camp, (2) 22 Moz Prestea-Bogoso camp, (3) 11 Moz Asanko Gold Mine camp, (4) 9 Moz Edikan camp, (5) 7 Moz Bibiani camp, (6) 5 Moz Chirano camp, as well as several additional minor gold camps and many more prospects. Cumulatively these camps account for>116 Moz of endowment and contribute to making south-west Ghana the greatest Paleoproterozoic gold province in the world. Gold deposits in the Kumasi Basin are shear zone hosted and mineralisation ranges from disseminated to massive sulphide refractory deposits, to free milling quartz vein style deposits. Structural relationships and age dating indicate that most deposits are genetically related and were formed during a single episode of gold mineralisation during the D4 NNW-SSE crustal shortening deformation event of the Eburnean Orogeny (2125 – 1980 Ma). The understanding of structural controls on mineralisation is critical for exploration success as it allows exploration to focus on areas where these structural controls exist. This study uses a mineral systems approach to understand the relationship between the geodynamic history and structural controls on gold mineralisation in the Kumasi Basin at various scales, and define targeting criteria which can be applied for the purpose of developing predictive exploration models for making new discoveries in the Asanko Gold Mine camp located in the Asankrangwa Belt. The study used a quantitative analysis to establish residual endowment potential in the Asankrangwa Belt, providing the basis for a business model and resulting exploration strategy. Once established, a Fry autocorrelation analysis was applied to identify trends in deposit and camp spatial distribution to which critical geological processes were ascribed. Observed trends were mapped from multi-scale geophysical data sets and through interpretation of existing geophysical structure models, and structural criteria for targeting orogenic gold deposits at the regional and camp scales were developed. Results show that different structural controls on mineralisation act at the regional and camp scale. At the regional scale the distribution of gold camps was found to be controlled by fundamental N-S and NW-SE basement structures with gold camps forming where they intersect NE-SW first and second order structural corridors. At the Asanko Gold Mine camp scale, deposit distribution was found to be related to the intersection between major second order D3 NE-SW shear zones, minor third order D4 NNE-SSW brittle faults, and cryptic NW-SE upward propagating basement structures. In addition to these structural criteria, deposits in the Asanko Gold Mine camp were found to be aligned along a NNE-SSW lineament caused by the interaction between the N-S basement structure and the NE-SW trending Asankrangwa Belt shear corridor.
- Full Text:
- Date Issued: 2018
- Authors: Gelber, Benjamin D J
- Date: 2018
- Subjects: Gold ores -- Geology -- Ghana -- Kumasi , Gold mines and mining -- Ghana -- Kumasi , Asankrangwa (Ghana) , Geodynamics -- Ghana -- Kumasi , Prospecting -- Geophysical methods , Orogenic belts -- Ghana -- Kumasi
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63143 , vital:28367
- Description: The Kumasi Basin in South-west Ghana lies at the centre of the best-endowed Paleoproterozoic gold province in the world. The Kumasi Basin and margins of the adjacent volcanic belts are host to six world class gold camps: (1) 62 Moz Obuasi camp, (2) 22 Moz Prestea-Bogoso camp, (3) 11 Moz Asanko Gold Mine camp, (4) 9 Moz Edikan camp, (5) 7 Moz Bibiani camp, (6) 5 Moz Chirano camp, as well as several additional minor gold camps and many more prospects. Cumulatively these camps account for>116 Moz of endowment and contribute to making south-west Ghana the greatest Paleoproterozoic gold province in the world. Gold deposits in the Kumasi Basin are shear zone hosted and mineralisation ranges from disseminated to massive sulphide refractory deposits, to free milling quartz vein style deposits. Structural relationships and age dating indicate that most deposits are genetically related and were formed during a single episode of gold mineralisation during the D4 NNW-SSE crustal shortening deformation event of the Eburnean Orogeny (2125 – 1980 Ma). The understanding of structural controls on mineralisation is critical for exploration success as it allows exploration to focus on areas where these structural controls exist. This study uses a mineral systems approach to understand the relationship between the geodynamic history and structural controls on gold mineralisation in the Kumasi Basin at various scales, and define targeting criteria which can be applied for the purpose of developing predictive exploration models for making new discoveries in the Asanko Gold Mine camp located in the Asankrangwa Belt. The study used a quantitative analysis to establish residual endowment potential in the Asankrangwa Belt, providing the basis for a business model and resulting exploration strategy. Once established, a Fry autocorrelation analysis was applied to identify trends in deposit and camp spatial distribution to which critical geological processes were ascribed. Observed trends were mapped from multi-scale geophysical data sets and through interpretation of existing geophysical structure models, and structural criteria for targeting orogenic gold deposits at the regional and camp scales were developed. Results show that different structural controls on mineralisation act at the regional and camp scale. At the regional scale the distribution of gold camps was found to be controlled by fundamental N-S and NW-SE basement structures with gold camps forming where they intersect NE-SW first and second order structural corridors. At the Asanko Gold Mine camp scale, deposit distribution was found to be related to the intersection between major second order D3 NE-SW shear zones, minor third order D4 NNE-SSW brittle faults, and cryptic NW-SE upward propagating basement structures. In addition to these structural criteria, deposits in the Asanko Gold Mine camp were found to be aligned along a NNE-SSW lineament caused by the interaction between the N-S basement structure and the NE-SW trending Asankrangwa Belt shear corridor.
- Full Text:
- Date Issued: 2018
A mineralogical study of phosphate mineralisation in the Nkombwa Hill Carbonatite
- Authors: Mapholi, Thendo
- Date: 2021-10-29
- Subjects: To be added
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/294797 , vital:57256
- Description: Thesis embargoed. Release date October 2023. , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mapholi, Thendo
- Date: 2021-10-29
- Subjects: To be added
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/294797 , vital:57256
- Description: Thesis embargoed. Release date October 2023. , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-10-29
A mineralogical, geochemical and metallogenic study of unusual Mn/Na/Ba assemblages at the footwall of conglomeratic iron-ore at farm Langverwacht, Northern Cape Province of South Africa
- Authors: Bursey, James Rodney
- Date: 2018
- Subjects: Iron ores -- Geology -- South Africa -- Northern Cape , Conglomerate -- South Africa -- Northern Cape , Petrology -- South Africa -- Northern Cape , Manganese -- South Africa -- Northern Cape , Sodium -- South Africa -- Northern Cape , Barium -- South Africa -- Northern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62516 , vital:28201
- Description: The Postmasburg Manganese Field (PMF), located in the Northern Cape province of South Africa, plays host to significant deposits of iron and manganese that have been utilized since their discovery in 1922 by Captain L.T. Shone. Further afield, lies the massive high-grade manganese deposit of the Kalahari Manganese Field (KMF), which drew attention away from the PMF after its discovery. These deposits are not limited to iron and manganese ore, but contain significant assemblages of alkali-rich rocks - which is the focus of this study. The existence of alkali-rich assemblages beneath conglomeratic iron-ore on farm Langwervacht, has come under investigation in this study, and in particular, the enrichment of these rocks in Ba, Na and Mn. Petrographic analysis of the clast-supported conglomerate unit (ore-zone), has uncovered the presence of vugs (up to 8mm across) which contain barite, K-feldspar and fluorapatite. In addition to this, the ore-zone of one of the three boreholes contains late carbonate veins (kutnohorite), which travel along Fe-clast boundaries, and exploit clast-fractures and areas of weakness. Further down, within the ‘enriched-zone’ of alkalis, the mineralogy is more diverse - containing elevated concentrations of Ba, Na and Mn. Seventeen distinct minerals containing these three key elements have been identified - along with one solid-solution series in the form of hollandite-coronadite. The existence of minerals such as natrolite, aegirine, albite, banalsite, barite, serandite, celsian and hollandite-coronadite are indicative of hydrothermal activity having influenced these rocks. Bulk-geochemistry was used to compare the major and trace elements of each borehole and the associated units. Both the trace elements and the REE’s from the ore-zone are enriched by an average of 5-10x relative to the BIF standard used - which immediately suggests an influx of elements. Compared to PAAS (Post Archaean Australian Shales), the ore-zone REE’s are slightly depleted, but more importantly the profiles are very similar to that of the Mapedi shales achieved in previous studies. This result points towards a strong shale influence in the ore-zone protolith. Expectedly, many of the enriched-zone trace elements and REE’s show far greater enrichment than what is observed in the ore-zone. Trace and Rare Earth Element profiles between the ore-zone and the enriched-zone are, however, generally correlative, with profiles reflecting similar enrichments and depletions for a given element - even within different rock units. This suggests that the hydrothermal fluid has moved in a general upward direction, reacting with host-rock units, and relinquishing elements carried in solution - wherever conditions have been favourable for the accommodation of these elements. This study has shed light on the relationship between the ore-zone and the enriched-zone, and results suggest that the process of alkali enrichment is not directly related to the process of upgrading of the iron ores. This is due to the extent of the alkali-enrichment below the ore-zone, as well as enrichment factors in some trace elements being superior to that of Fe2O3 in the ore- zone. Hence, both of these zones have both been affected by a later hydrothermal fluid. The source of the fluid is likely a mature basinal brine, of oxidized, alkaline nature - which leached elements (Ba, K, Na, Pb, Ca) from older rocks, and carried them in solution. On a local-scale, this fluid has exploited areas of weakness in the form of fractures, less consolidated conglomeratic material and crosscutting veins. Manganese and iron has been remobilized on a local scale - producing secondary textures and partitioning into phases such as Mn-rich calcite and serandite. Comparisons to other studies in the PMF and KMF have revealed very similar alkali-rich assemblages, bearing many of the same minerals observed in this study - even within more manganiferous deposits. These findings have led to suggestions of a possible regional-scale hydrothermal overprint, which may have imparted a similar geochemical signal over the entire region - with the assistance of faults and unconformities. Of course, proving this is no mean feat, but current work on the source of barium in barite, using Sr isotopes from samples across the region may shed light on the source of at least one key element of these deposits.
- Full Text:
- Date Issued: 2018
- Authors: Bursey, James Rodney
- Date: 2018
- Subjects: Iron ores -- Geology -- South Africa -- Northern Cape , Conglomerate -- South Africa -- Northern Cape , Petrology -- South Africa -- Northern Cape , Manganese -- South Africa -- Northern Cape , Sodium -- South Africa -- Northern Cape , Barium -- South Africa -- Northern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62516 , vital:28201
- Description: The Postmasburg Manganese Field (PMF), located in the Northern Cape province of South Africa, plays host to significant deposits of iron and manganese that have been utilized since their discovery in 1922 by Captain L.T. Shone. Further afield, lies the massive high-grade manganese deposit of the Kalahari Manganese Field (KMF), which drew attention away from the PMF after its discovery. These deposits are not limited to iron and manganese ore, but contain significant assemblages of alkali-rich rocks - which is the focus of this study. The existence of alkali-rich assemblages beneath conglomeratic iron-ore on farm Langwervacht, has come under investigation in this study, and in particular, the enrichment of these rocks in Ba, Na and Mn. Petrographic analysis of the clast-supported conglomerate unit (ore-zone), has uncovered the presence of vugs (up to 8mm across) which contain barite, K-feldspar and fluorapatite. In addition to this, the ore-zone of one of the three boreholes contains late carbonate veins (kutnohorite), which travel along Fe-clast boundaries, and exploit clast-fractures and areas of weakness. Further down, within the ‘enriched-zone’ of alkalis, the mineralogy is more diverse - containing elevated concentrations of Ba, Na and Mn. Seventeen distinct minerals containing these three key elements have been identified - along with one solid-solution series in the form of hollandite-coronadite. The existence of minerals such as natrolite, aegirine, albite, banalsite, barite, serandite, celsian and hollandite-coronadite are indicative of hydrothermal activity having influenced these rocks. Bulk-geochemistry was used to compare the major and trace elements of each borehole and the associated units. Both the trace elements and the REE’s from the ore-zone are enriched by an average of 5-10x relative to the BIF standard used - which immediately suggests an influx of elements. Compared to PAAS (Post Archaean Australian Shales), the ore-zone REE’s are slightly depleted, but more importantly the profiles are very similar to that of the Mapedi shales achieved in previous studies. This result points towards a strong shale influence in the ore-zone protolith. Expectedly, many of the enriched-zone trace elements and REE’s show far greater enrichment than what is observed in the ore-zone. Trace and Rare Earth Element profiles between the ore-zone and the enriched-zone are, however, generally correlative, with profiles reflecting similar enrichments and depletions for a given element - even within different rock units. This suggests that the hydrothermal fluid has moved in a general upward direction, reacting with host-rock units, and relinquishing elements carried in solution - wherever conditions have been favourable for the accommodation of these elements. This study has shed light on the relationship between the ore-zone and the enriched-zone, and results suggest that the process of alkali enrichment is not directly related to the process of upgrading of the iron ores. This is due to the extent of the alkali-enrichment below the ore-zone, as well as enrichment factors in some trace elements being superior to that of Fe2O3 in the ore- zone. Hence, both of these zones have both been affected by a later hydrothermal fluid. The source of the fluid is likely a mature basinal brine, of oxidized, alkaline nature - which leached elements (Ba, K, Na, Pb, Ca) from older rocks, and carried them in solution. On a local-scale, this fluid has exploited areas of weakness in the form of fractures, less consolidated conglomeratic material and crosscutting veins. Manganese and iron has been remobilized on a local scale - producing secondary textures and partitioning into phases such as Mn-rich calcite and serandite. Comparisons to other studies in the PMF and KMF have revealed very similar alkali-rich assemblages, bearing many of the same minerals observed in this study - even within more manganiferous deposits. These findings have led to suggestions of a possible regional-scale hydrothermal overprint, which may have imparted a similar geochemical signal over the entire region - with the assistance of faults and unconformities. Of course, proving this is no mean feat, but current work on the source of barium in barite, using Sr isotopes from samples across the region may shed light on the source of at least one key element of these deposits.
- Full Text:
- Date Issued: 2018
A reconciliation study of different resource estimation methods and drill hole spacing as applied to the Langer Heinrich calcrete-hosted uranium deposit, Namibia
- Authors: Baufeldt, Sven
- Date: 2018
- Subjects: Uranium -- Namibia , Calcretes -- Namibia , Carnotite -- Namibia , Uranium mines and mining -- Namibia , Uranium ores -- Geology -- Namibia , Langer-Heinrich Uranium mine
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62527 , vital:28203
- Description: The Langer Heinrich calcrete hosted uranium deposit is situated approximately 90 km to east of the coastal town of Swakopmund in Namibia. It is run by an Australian owned company, Paladin Energy Limited, along with China National Nuclear Corporation (CNNC) who maintain 25% of the shares. Production commenced in 2007 and has been ongoing. Carnotite is the primary and only ore mineral, and the nature of mineralisation within the Langer Heinrich palaeo channel dictates westward-directed continuous open pit mining. Smaller-scale 1micro pits target near-surface, high-grade, lenses toward the east. The high variability in uranium grade over relatively short distances complicates the grade estimation process. This combined with a low uranium price, and a study aimed at optimising of mine production is one of the key drivers for the research presented in this thesis. The efficacy of four resource estimation techniques, commonly used in the mining industry, are investigated by application to variable exploration, infill drilling and grade-control drill pattern spacing. The drill spacing includes regular grids of 50 m x 50 m, 25 m x 25 m and 12,5 m x 12,5 m exploration data. Also included is grade control drill data, drilled on a 4 m x 4 m spacing. The current selective mining unit (SMU) is 4mE x 4mN x 3mRl which is an indication of the minimum dimension whereby the loading equipment can separate ore from waste. The two datasets are processed by four estimation techniques: Inverse Distance Weighting (IDW, squared and cubed), Ordinary Kriging (OK), Multiple Indicator Kriging (MIK) and Conditional Simulation (CS). The two datasets consisted of real-time mining data from pit G1 (micro-pit) in the eastern parts of the mining licence, and pit H1 (continuous larger open pit) in the western area of the palaeo channel. The reconciliation project aims to provide results suitable for devising optimised mining strategies, particularly in future targets where drill spacing can perhaps be improved to provide suitable data with a greater cost saving strategy. Along with the optimal drill spacing or combination thereof, a preferred estimation technique can be suggested and recommended for future operations that involve mining of surficial calcrete-hosted uranium deposits. Results of this study show that 12,5 m x 12,5 m drill spacing provided estimation accuracies similar to that of the narrow 4 m x 4 m grade control spacing (blast hole drilling spacing). The 12,5 m x 12,5m spacing has potential for accurate grade estimations during mining, and could be supplemented by infill downhole radiometric logging on a 4 m x 4 m spacing when 1 Micro pit: Small pits within palaeo channel usually targeted for their near surface high-grade ore necessary. In general, Multiple Indicator Kriging (MIK) provided the most accurate and robust estimations on the wider spaced exploration data and conditional simulation (CS) proved more efficient on the narrow grade control data. These results correspond with current exploration practices for surficial uranium deposits world-wide. Deposit type, therefore complexity and hence SMU sizes play a pivotal role in drill hole planning and estimation accuracies.
- Full Text:
- Date Issued: 2018
- Authors: Baufeldt, Sven
- Date: 2018
- Subjects: Uranium -- Namibia , Calcretes -- Namibia , Carnotite -- Namibia , Uranium mines and mining -- Namibia , Uranium ores -- Geology -- Namibia , Langer-Heinrich Uranium mine
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62527 , vital:28203
- Description: The Langer Heinrich calcrete hosted uranium deposit is situated approximately 90 km to east of the coastal town of Swakopmund in Namibia. It is run by an Australian owned company, Paladin Energy Limited, along with China National Nuclear Corporation (CNNC) who maintain 25% of the shares. Production commenced in 2007 and has been ongoing. Carnotite is the primary and only ore mineral, and the nature of mineralisation within the Langer Heinrich palaeo channel dictates westward-directed continuous open pit mining. Smaller-scale 1micro pits target near-surface, high-grade, lenses toward the east. The high variability in uranium grade over relatively short distances complicates the grade estimation process. This combined with a low uranium price, and a study aimed at optimising of mine production is one of the key drivers for the research presented in this thesis. The efficacy of four resource estimation techniques, commonly used in the mining industry, are investigated by application to variable exploration, infill drilling and grade-control drill pattern spacing. The drill spacing includes regular grids of 50 m x 50 m, 25 m x 25 m and 12,5 m x 12,5 m exploration data. Also included is grade control drill data, drilled on a 4 m x 4 m spacing. The current selective mining unit (SMU) is 4mE x 4mN x 3mRl which is an indication of the minimum dimension whereby the loading equipment can separate ore from waste. The two datasets are processed by four estimation techniques: Inverse Distance Weighting (IDW, squared and cubed), Ordinary Kriging (OK), Multiple Indicator Kriging (MIK) and Conditional Simulation (CS). The two datasets consisted of real-time mining data from pit G1 (micro-pit) in the eastern parts of the mining licence, and pit H1 (continuous larger open pit) in the western area of the palaeo channel. The reconciliation project aims to provide results suitable for devising optimised mining strategies, particularly in future targets where drill spacing can perhaps be improved to provide suitable data with a greater cost saving strategy. Along with the optimal drill spacing or combination thereof, a preferred estimation technique can be suggested and recommended for future operations that involve mining of surficial calcrete-hosted uranium deposits. Results of this study show that 12,5 m x 12,5 m drill spacing provided estimation accuracies similar to that of the narrow 4 m x 4 m grade control spacing (blast hole drilling spacing). The 12,5 m x 12,5m spacing has potential for accurate grade estimations during mining, and could be supplemented by infill downhole radiometric logging on a 4 m x 4 m spacing when 1 Micro pit: Small pits within palaeo channel usually targeted for their near surface high-grade ore necessary. In general, Multiple Indicator Kriging (MIK) provided the most accurate and robust estimations on the wider spaced exploration data and conditional simulation (CS) proved more efficient on the narrow grade control data. These results correspond with current exploration practices for surficial uranium deposits world-wide. Deposit type, therefore complexity and hence SMU sizes play a pivotal role in drill hole planning and estimation accuracies.
- Full Text:
- Date Issued: 2018
Characterisation of the ultramafic and carbonatite components of the Schiel Alkaline Complex in the Limpopo Province of South Africa
- Authors: Mahomed, Uzayr
- Date: 2021-10-29
- Subjects: Ultrabasic rocks South Africa Limpopo , Carbonatites South Africa Limpopo , Geology South Africa Limpopo , Mica South Africa Limpopo , Biotite South Africa Limpopo , Magmatism , Schiel Alkaline Complex , Phoscorite , Glimmerite
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294768 , vital:57253
- Description: Owing to the poor documentation of the phoscorite-carbonatite association present in the Schiel Complex and the associated economic potential of other known phoscorite-bearing complexes, the Schiel Complex is widely thought to have similar economic potential. This complex is often compared to the lucrative Phalaborwa Complex, as it is thought to have crystallised from a common parental melt, with a similar age of emplacement. This study aims to provide clarity on the physical and chemical characterisation of the various rock types present in the Schiel Complex, with this study being the first petrological investigation based on fresh in-situ samples gathered from 3 borehole cores which were drilled by FOSKOR in the 1960s. The sampled sections of the ultramafics from the Schiel Complex are comprised of end-member rock compositions of either magmatic phoscorites or pyroxenites or metasomatic glimmerites, where gradational contacts between these various end-members produce rock varieties that contain characteristics of one or more end-member types. Carbonatite rocks are present as medium-grained, coarse-grained and banded calcio-carbonatite varieties where the carbonatite rocks are proposed as being the metasomatic medium for glimmerite production. Contrary to previous research, the structure of the ultramafic and carbonatite bodies are present as vein and veinlet structures which seem to originate from a single pipe-like body, from which these rock types intruded into the surrounding syenitic country-rock. Metasomatic alteration of the ultramafic sections of the Schiel Complex also show that the carbonatite rocks must have intruded after some ultramafic magmatism. The presence of the same minerals, with similar chemistries, in both the ultramafic and carbonatite rocks as well as similar REE chondrite-normalised plots show that the various rock types may have originated from a common parental magma, where the accumulation and crystallisation of minerals is the most likely factor in producing the various Schiel Complex rock varieties, causing silicate minerals to be present in the carbonate fraction of the magma, and carbonate minerals in the silicate fraction of the magma. Apatite is the expected rare earth element (REE) mineralising mineral in phoscorites, but is shown to be depleted in REE content in the Schiel Complex due to metasomatic fluid infiltration causing the scavenging and dissipation of REEs. These rocks have also crystallised containing no significant copper-bearing mineralisation, contrary to that which is seen in the Phalaborwa Complex. A comparison of mica minerals between the Schiel Complex rocks and the Phalaborwa Complex rocks show that the two complexes have undergone unique emplacement processes and should not be considered as sister complexes. Efforts to date the glimmerite and carbonatite rocks based on zircon grain U/Pb geochronology proved unsuccessful in constraining the current ages of emplacement provided by previous researchers, but rock relationships show that the current accepted sequence of events cannot be correct, providing scope for further research. This study provides an update on the chemical and physical characteristics, based on the only available sample suite of the ultramafic and carbonatite components, of the Schiel Complex, increasing the depth of documentation of these rare rock types and aiding in refuting some conclusions on the genesis, emplacement and evolution of the Schiel Complex proposed by previous research. , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mahomed, Uzayr
- Date: 2021-10-29
- Subjects: Ultrabasic rocks South Africa Limpopo , Carbonatites South Africa Limpopo , Geology South Africa Limpopo , Mica South Africa Limpopo , Biotite South Africa Limpopo , Magmatism , Schiel Alkaline Complex , Phoscorite , Glimmerite
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294768 , vital:57253
- Description: Owing to the poor documentation of the phoscorite-carbonatite association present in the Schiel Complex and the associated economic potential of other known phoscorite-bearing complexes, the Schiel Complex is widely thought to have similar economic potential. This complex is often compared to the lucrative Phalaborwa Complex, as it is thought to have crystallised from a common parental melt, with a similar age of emplacement. This study aims to provide clarity on the physical and chemical characterisation of the various rock types present in the Schiel Complex, with this study being the first petrological investigation based on fresh in-situ samples gathered from 3 borehole cores which were drilled by FOSKOR in the 1960s. The sampled sections of the ultramafics from the Schiel Complex are comprised of end-member rock compositions of either magmatic phoscorites or pyroxenites or metasomatic glimmerites, where gradational contacts between these various end-members produce rock varieties that contain characteristics of one or more end-member types. Carbonatite rocks are present as medium-grained, coarse-grained and banded calcio-carbonatite varieties where the carbonatite rocks are proposed as being the metasomatic medium for glimmerite production. Contrary to previous research, the structure of the ultramafic and carbonatite bodies are present as vein and veinlet structures which seem to originate from a single pipe-like body, from which these rock types intruded into the surrounding syenitic country-rock. Metasomatic alteration of the ultramafic sections of the Schiel Complex also show that the carbonatite rocks must have intruded after some ultramafic magmatism. The presence of the same minerals, with similar chemistries, in both the ultramafic and carbonatite rocks as well as similar REE chondrite-normalised plots show that the various rock types may have originated from a common parental magma, where the accumulation and crystallisation of minerals is the most likely factor in producing the various Schiel Complex rock varieties, causing silicate minerals to be present in the carbonate fraction of the magma, and carbonate minerals in the silicate fraction of the magma. Apatite is the expected rare earth element (REE) mineralising mineral in phoscorites, but is shown to be depleted in REE content in the Schiel Complex due to metasomatic fluid infiltration causing the scavenging and dissipation of REEs. These rocks have also crystallised containing no significant copper-bearing mineralisation, contrary to that which is seen in the Phalaborwa Complex. A comparison of mica minerals between the Schiel Complex rocks and the Phalaborwa Complex rocks show that the two complexes have undergone unique emplacement processes and should not be considered as sister complexes. Efforts to date the glimmerite and carbonatite rocks based on zircon grain U/Pb geochronology proved unsuccessful in constraining the current ages of emplacement provided by previous researchers, but rock relationships show that the current accepted sequence of events cannot be correct, providing scope for further research. This study provides an update on the chemical and physical characteristics, based on the only available sample suite of the ultramafic and carbonatite components, of the Schiel Complex, increasing the depth of documentation of these rare rock types and aiding in refuting some conclusions on the genesis, emplacement and evolution of the Schiel Complex proposed by previous research. , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-10-29
Chemostratigraphy of the lowermost iron-manganese cycle of the Hotazel Formation, and implications for its primary depositional environment
- Authors: Masoabi, Ntseka Thomas
- Date: 2022-10-14
- Subjects: Chemostratigraphy , Great Oxygenation Event , Manganese ores Geology South Africa Northern Cape , Banded iron formation
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362938 , vital:65376
- Description: The giant Kalahari Manganese Field (KMF), located in the Northern Cape Province, South Africa, comprises approximately half of the world’s manganese resources, estimated at about eight billion tons at grades ranging from 20-48 wt%. The KMF is linked to a period in geological time when the Earth’s atmospheric and oceanic conditions underwent a major transition from oxygen-deficient to oxygen-enriched conditions – an event famously referred to as the Great Oxidation Event (GOE) that occurred around 2.4 Ga. The KMF deposits are hosted in Banded Iron Formation (BIF) of the Paleoproterozoic Hotazel Formation in the uppermost Transvaal Supergroup. The sedimentary Mn ores are interbedded with Hotazel BIF in the form of three alternating depositional cycles of BIF, transitional hematite lutite and laminated, carbonate-rich manganese ore. The lowermost and thickest of the three cycles is the most economically significant and has been mined for several decades on a large scale from the southernmost KMF. In this study, two drill cores from the southern KMF were inspected, logged and sampled at a high resolution of approximately half-meter interval per sample. The selected cores, namely G774, capturing the lower portion of the Hotazel Formation from the Mamatwan locality, and MP-56, capturing the corresponding portion from the Middleplaats locality, are geographically proximal to each other, with a horizontal distance of roughly 3 km separating the two of them. The G774 drill core is characterized by a conspicuously thick manganese layer covering a thickness of 50 m, with the overlying BIF reaching a total thickness of 11 m. The MP-56 drill core, on the other hand, has a relatively thinner corresponding manganese layer of 30 m in thickness, while the overlying BIF layer exhibits a thickness of 24 m. The extent of sampling up-section was constrained by an apparently coeval black shale layer which represents the chosen upper stratigraphic marker for the lower part of the Hotazel section in the broader area that is under investigation in this thesis. That way, a high resolution chemostratigraphic approach was employed to elucidate the potential factors contributing to the relative sedimentary lateral thickness variations seen across the southernmost KMF. High-resolution geochemical data were used to explore relationships and signals that might constrain relative precipitation rates for iron and manganese against detrital species, fluctuating redox conditions in the original environment of deposition, and chemostratigraphic correlation. All geochemical data (i.e., major oxides, minor and trace elements and carbonate carbon isotopes) were obtained respectively through employing X-ray Fluorescence (XRF), Laser Ablation Inductively Coupled Mass Spectrometry (ICP-MS), and Gas-source mass spectrometry. Comparative considerations made between the bulk geochemistry of the two sequences (i.e., Mamatwan and Middleplaats sections) reveal that periods of high-Mn deposition in the Hotazel Formation appear to be very Ca-carbonate rich (as indicated by high CaO, LOI and Sr concentrations). This, in turn, suggests that the Mn abundance is in the Hotazel ores is controlled mainly by the silicate phase braunite and is diluted by the deposition of Ca-carbonate through time. Bulk-rock concentration results for trace elements of the High Field Strength Element (HFSE) group (namely Zr, Hf, Y, Nb and Sc) were utilized to constrain the rates of either clastic and/or volcanic detrital inputs, as they traditionally represent refractory mineral particles of a common detrital/volcanic origin. The two chemosedimentary sequences preserve these elements in very low and thus quantitatively negligible concentrations – suggesting that the Hotazel depositional environment received very low and insignificant influx of a terrigeneous detrital component. A selection of these elements was therefore used to deduce, with caution, the relative as opposed to absolute precipitation rate of the major chemical constituents (i.e., Fe + Si vs Mn + carbonate), assuming a constant detrital flux through time. It was found that the relative abundances of Zr, Y and Nb is roughly 1.5 – 2 times as high in the BIF lithofacies relative to the Mn ones at both localities. This led to the inference that the Mn-enriched portion of the sediment must have been deposited at approximately twice the rate that the Fe-rich (BIF) portion was originally deposited. In terms of redox-sensitive elements, the elements Co and Mo seem to reveal the most valuable insights into the redox environment of primary chemical deposition. Cobalt displays a unique pattern in that its highest concentration is attained at the hematite lutite transitions (similarly with the REE in this regard), while very low and seemingly invariant concentration is exhibited within the core of the main orebodies. The same pattern seems to be reproduced to a degree by the corresponding bulk MgO component, whereby MgO abundance maxima are associated with the basal hematite lutite and the hematitic flanks of the Mn-ore zone, while the core of the Mn-rich layer attains relatively low and essentially invariant MgO concentrations. This implicates a close and direct association of Co with the hematite fraction of the rocks and a concurrent enrichment in Mn-rich carbonate (dolomite). On the other hand, Mo seems to have a direct and clear association with peak MnO2 content of the rocks, which in turn presents a high possibility of Mo having adsorbed onto primary Mn-oxyhydroxides in the water column, thus providing evidence that Mn-oxide must have acted as an important Mo sink, at least locally. Finally, the carbonate-carbon isotope results provide a useful tool that brings the two stratigraphic sections “together“, in conjunction with other correlatable chemostratigraphic parameters (e.g. Co, Mg). The results demonstrate that bulk carbon fluxes and isotopic signals in the sediments must reflect primary processes of deposition, and that correlation across two apparently disparate lithostratigraphic sections can be effected. The key finding is that, at times, manganese deposition in one part of a vii stratified basin was evidently accompanied by simultaneous BIF deposition at another, thus painting a very complex picture of massive primary chemical precipitation of Fe and Mn at the dawn of the GOE. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Masoabi, Ntseka Thomas
- Date: 2022-10-14
- Subjects: Chemostratigraphy , Great Oxygenation Event , Manganese ores Geology South Africa Northern Cape , Banded iron formation
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362938 , vital:65376
- Description: The giant Kalahari Manganese Field (KMF), located in the Northern Cape Province, South Africa, comprises approximately half of the world’s manganese resources, estimated at about eight billion tons at grades ranging from 20-48 wt%. The KMF is linked to a period in geological time when the Earth’s atmospheric and oceanic conditions underwent a major transition from oxygen-deficient to oxygen-enriched conditions – an event famously referred to as the Great Oxidation Event (GOE) that occurred around 2.4 Ga. The KMF deposits are hosted in Banded Iron Formation (BIF) of the Paleoproterozoic Hotazel Formation in the uppermost Transvaal Supergroup. The sedimentary Mn ores are interbedded with Hotazel BIF in the form of three alternating depositional cycles of BIF, transitional hematite lutite and laminated, carbonate-rich manganese ore. The lowermost and thickest of the three cycles is the most economically significant and has been mined for several decades on a large scale from the southernmost KMF. In this study, two drill cores from the southern KMF were inspected, logged and sampled at a high resolution of approximately half-meter interval per sample. The selected cores, namely G774, capturing the lower portion of the Hotazel Formation from the Mamatwan locality, and MP-56, capturing the corresponding portion from the Middleplaats locality, are geographically proximal to each other, with a horizontal distance of roughly 3 km separating the two of them. The G774 drill core is characterized by a conspicuously thick manganese layer covering a thickness of 50 m, with the overlying BIF reaching a total thickness of 11 m. The MP-56 drill core, on the other hand, has a relatively thinner corresponding manganese layer of 30 m in thickness, while the overlying BIF layer exhibits a thickness of 24 m. The extent of sampling up-section was constrained by an apparently coeval black shale layer which represents the chosen upper stratigraphic marker for the lower part of the Hotazel section in the broader area that is under investigation in this thesis. That way, a high resolution chemostratigraphic approach was employed to elucidate the potential factors contributing to the relative sedimentary lateral thickness variations seen across the southernmost KMF. High-resolution geochemical data were used to explore relationships and signals that might constrain relative precipitation rates for iron and manganese against detrital species, fluctuating redox conditions in the original environment of deposition, and chemostratigraphic correlation. All geochemical data (i.e., major oxides, minor and trace elements and carbonate carbon isotopes) were obtained respectively through employing X-ray Fluorescence (XRF), Laser Ablation Inductively Coupled Mass Spectrometry (ICP-MS), and Gas-source mass spectrometry. Comparative considerations made between the bulk geochemistry of the two sequences (i.e., Mamatwan and Middleplaats sections) reveal that periods of high-Mn deposition in the Hotazel Formation appear to be very Ca-carbonate rich (as indicated by high CaO, LOI and Sr concentrations). This, in turn, suggests that the Mn abundance is in the Hotazel ores is controlled mainly by the silicate phase braunite and is diluted by the deposition of Ca-carbonate through time. Bulk-rock concentration results for trace elements of the High Field Strength Element (HFSE) group (namely Zr, Hf, Y, Nb and Sc) were utilized to constrain the rates of either clastic and/or volcanic detrital inputs, as they traditionally represent refractory mineral particles of a common detrital/volcanic origin. The two chemosedimentary sequences preserve these elements in very low and thus quantitatively negligible concentrations – suggesting that the Hotazel depositional environment received very low and insignificant influx of a terrigeneous detrital component. A selection of these elements was therefore used to deduce, with caution, the relative as opposed to absolute precipitation rate of the major chemical constituents (i.e., Fe + Si vs Mn + carbonate), assuming a constant detrital flux through time. It was found that the relative abundances of Zr, Y and Nb is roughly 1.5 – 2 times as high in the BIF lithofacies relative to the Mn ones at both localities. This led to the inference that the Mn-enriched portion of the sediment must have been deposited at approximately twice the rate that the Fe-rich (BIF) portion was originally deposited. In terms of redox-sensitive elements, the elements Co and Mo seem to reveal the most valuable insights into the redox environment of primary chemical deposition. Cobalt displays a unique pattern in that its highest concentration is attained at the hematite lutite transitions (similarly with the REE in this regard), while very low and seemingly invariant concentration is exhibited within the core of the main orebodies. The same pattern seems to be reproduced to a degree by the corresponding bulk MgO component, whereby MgO abundance maxima are associated with the basal hematite lutite and the hematitic flanks of the Mn-ore zone, while the core of the Mn-rich layer attains relatively low and essentially invariant MgO concentrations. This implicates a close and direct association of Co with the hematite fraction of the rocks and a concurrent enrichment in Mn-rich carbonate (dolomite). On the other hand, Mo seems to have a direct and clear association with peak MnO2 content of the rocks, which in turn presents a high possibility of Mo having adsorbed onto primary Mn-oxyhydroxides in the water column, thus providing evidence that Mn-oxide must have acted as an important Mo sink, at least locally. Finally, the carbonate-carbon isotope results provide a useful tool that brings the two stratigraphic sections “together“, in conjunction with other correlatable chemostratigraphic parameters (e.g. Co, Mg). The results demonstrate that bulk carbon fluxes and isotopic signals in the sediments must reflect primary processes of deposition, and that correlation across two apparently disparate lithostratigraphic sections can be effected. The key finding is that, at times, manganese deposition in one part of a vii stratified basin was evidently accompanied by simultaneous BIF deposition at another, thus painting a very complex picture of massive primary chemical precipitation of Fe and Mn at the dawn of the GOE. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
Constraints on Cr-PGE Mineralisation Models: Geochemical and petrological studies in the Middle Group 1 and 3 Chromitites, Western Limb, Bushveld Complex, South Africa
- Authors: Arunachellan, Yogendran
- Date: 2022-10-14
- Subjects: Chromite South Africa Bushveld Complex , Mineralogy South Africa Bushveld Complex , Geochemical surveys South Africa Bushveld Complex
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362730 , vital:65357
- Description: The Bushveld Complex in South Africa has been of interest in various research groups for decades, along with diverse theories regarding its origin, formation, and emplacement. These theories include magma mixing, contamination, and changes in the chamber's ephemeral parameters. Of interest for our current study is the formation of the middle group chromitite layers in the Western Limb. In this research, we aimed to determine the emplacement mechanism of the MG group chromitites by scrutinising the MG 1 and MG 3 layers. In core KD 151, the focus was placed on the MG 3 and MG 1 chromitite layers and their associated silicate rocks; on these regions of the core, time was spent for detailed observations. The differences and similarities of these layers were explored as the study advanced. The objectives were to determine the in-situ or proximal crystallisation of the chromitite by evaluating mineral textures and compositions. This required that we determine the characteristics of the immediate HW (hanging wall) and FW (footwall) to these chromitites, with insights into the relationship that anorthositic zones may offer and examine the PGE profiles of the chromitites in contrasting lithological settings. The sampled borehole was in the Western Limb of the Bushveld Complex; the immediate HW, chromitite layers and FW were divided into sections (2.5 x 5 cm) along selected horizons for a microscale study. The preliminary results of a study on the sub-economic Middle Group (MG) layers within the Critical Zone (CZ), contrasting the MG 1 (Lower CZ) and MG 3 (Upper CZ) chromitite layers of the Rustenburg Layered Suite of the Bushveld Complex, South Africa were analysed. The MG 3 and 1 suites of silicate rocks show disequilibrium textures between the pyroxenes and plagioclase, forming discontinuous olivine rims. These reaction rims are interpreted as products of magmatic aqueous fluid-facilitated reactions with minerals in a sub-solidus state. Deformation of the plagioclase was also noted in MG 1; this fracturing indicates either the transportation of these minerals or compaction by an overlying crystal mush. The MG 3 package of plagioclase, pyroxene and chromite compositions range from An67-78, En71-86 and Cr# of 68-84, respectively. The MG 1 package of plagioclase, pyroxene and chromite compositions are An64-91, En79-88 and Cr# of 70-80, respectively. The Cu/Pd ratio decreases from the base of the FW as it approaches the base of the chromitite, then remains low within the chromitite layer and finally increases upwards in the HW. These trends are observed in both the MG 3 and 1 package, therefore not influenced by the sulphide control. There is a decrease in both IPGE and PPGE upwards as the HW progresses into the chromitite. The FW levels of Ir and Ru increase upwards immediately adjacent to the FW contact, while Pd and Rh concentrations decrease. The whole-rock Mg# indicates a decrease in the MG 3 with a uniform increase in the HW and an erratic upward increase observed in the FW. The chondrite normalised PGE plots show a bell-shaped curve which is evident for the En content of the pyroxenes and the content of plagioclase with the highest values in the chromitite layer itself. The Cr# of the chromite decreases upwards with the highest values along the FW. The Cu/Pd ratio for MG 1 indicates chromitite control rather than sulphide control of the PGE. The whole-rock Mg# decreases in MG 1 with higher uniform values observed in the HW and FW. The geochemical and petrological data from the MG group study revealed that in situ fractional crystallisation seems unlikely as the sole mechanism for their formation in the CZ. A model is suggested in which the migration and transport of a magmatic slurry type suspension with accompanying hydrous fluids would likely have resulted in the emplacement of these chromitite packages along with the PGE mineralisation of the chromitites. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Arunachellan, Yogendran
- Date: 2022-10-14
- Subjects: Chromite South Africa Bushveld Complex , Mineralogy South Africa Bushveld Complex , Geochemical surveys South Africa Bushveld Complex
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362730 , vital:65357
- Description: The Bushveld Complex in South Africa has been of interest in various research groups for decades, along with diverse theories regarding its origin, formation, and emplacement. These theories include magma mixing, contamination, and changes in the chamber's ephemeral parameters. Of interest for our current study is the formation of the middle group chromitite layers in the Western Limb. In this research, we aimed to determine the emplacement mechanism of the MG group chromitites by scrutinising the MG 1 and MG 3 layers. In core KD 151, the focus was placed on the MG 3 and MG 1 chromitite layers and their associated silicate rocks; on these regions of the core, time was spent for detailed observations. The differences and similarities of these layers were explored as the study advanced. The objectives were to determine the in-situ or proximal crystallisation of the chromitite by evaluating mineral textures and compositions. This required that we determine the characteristics of the immediate HW (hanging wall) and FW (footwall) to these chromitites, with insights into the relationship that anorthositic zones may offer and examine the PGE profiles of the chromitites in contrasting lithological settings. The sampled borehole was in the Western Limb of the Bushveld Complex; the immediate HW, chromitite layers and FW were divided into sections (2.5 x 5 cm) along selected horizons for a microscale study. The preliminary results of a study on the sub-economic Middle Group (MG) layers within the Critical Zone (CZ), contrasting the MG 1 (Lower CZ) and MG 3 (Upper CZ) chromitite layers of the Rustenburg Layered Suite of the Bushveld Complex, South Africa were analysed. The MG 3 and 1 suites of silicate rocks show disequilibrium textures between the pyroxenes and plagioclase, forming discontinuous olivine rims. These reaction rims are interpreted as products of magmatic aqueous fluid-facilitated reactions with minerals in a sub-solidus state. Deformation of the plagioclase was also noted in MG 1; this fracturing indicates either the transportation of these minerals or compaction by an overlying crystal mush. The MG 3 package of plagioclase, pyroxene and chromite compositions range from An67-78, En71-86 and Cr# of 68-84, respectively. The MG 1 package of plagioclase, pyroxene and chromite compositions are An64-91, En79-88 and Cr# of 70-80, respectively. The Cu/Pd ratio decreases from the base of the FW as it approaches the base of the chromitite, then remains low within the chromitite layer and finally increases upwards in the HW. These trends are observed in both the MG 3 and 1 package, therefore not influenced by the sulphide control. There is a decrease in both IPGE and PPGE upwards as the HW progresses into the chromitite. The FW levels of Ir and Ru increase upwards immediately adjacent to the FW contact, while Pd and Rh concentrations decrease. The whole-rock Mg# indicates a decrease in the MG 3 with a uniform increase in the HW and an erratic upward increase observed in the FW. The chondrite normalised PGE plots show a bell-shaped curve which is evident for the En content of the pyroxenes and the content of plagioclase with the highest values in the chromitite layer itself. The Cr# of the chromite decreases upwards with the highest values along the FW. The Cu/Pd ratio for MG 1 indicates chromitite control rather than sulphide control of the PGE. The whole-rock Mg# decreases in MG 1 with higher uniform values observed in the HW and FW. The geochemical and petrological data from the MG group study revealed that in situ fractional crystallisation seems unlikely as the sole mechanism for their formation in the CZ. A model is suggested in which the migration and transport of a magmatic slurry type suspension with accompanying hydrous fluids would likely have resulted in the emplacement of these chromitite packages along with the PGE mineralisation of the chromitites. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
Controls of lateral and vertical variations in the geochemistry of the Hotazel Fe-Mn Formation at Nchwaning and Gloria mines, Kalahari Manganese Field, South Africa
- Authors: Dorbor Jr., Stephen Baysah
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424621 , vital:72169
- Description: The Paleoproterozoic Kalahari manganese field (KMF) in the Northern Cape Province, South Africa, hosts a large resource of manganese ores that has been of great interest over many decades. The Kalahari Manganese deposit (KMD), which is the largest of five erosional relics of the Hotazel Formation in the KMF, hosts three beds of Mn ores with alternating layers of banded iron formation (BIF) and hematite lutite. These three rock types are all evaluated for their mineralogy and geochemistry in this study, with emphasis on lateral and vertical distributions across the Gloria and Nchwaning Mines in the northernmost KMF, an area of high-grade, hydrothermally altered Mn mineralisation. The Mn ores of the Hotazel formation are traditionally categorised into two types. The carbonate-rich low Mn grade (Mn≤40 wt. %) ores (Mamatwan-type) domninates the largest part of the KMD, while carbonate-free, high Mn grade (Mn≥ 45 wt.%) ore (Wessels-type) occurs in the northernmost KMD. The Wessels-type ores are considered as the hydrothermally altered product of Mamatwan-type ores, and as indicated above, are the focus of this study. Five drill cores containing Wessels-type ores from the Nchwaning and Gloria area of the northern KMD were analysed to help understand the petrographic and particularly the geochemical variations in the Hotazel Fe-Mn Formation, both laterally for a given Mn layer of the three, and vertically across Mn layers as captured in specific drillcores. Petrographic and whole-rock geochemical results obtained from the three rock types of the Hotazel Formation show variations in their mineralogical and geochemical compositions, especially in the high-grade Mn ores themselves. Most of the samples of the BIFs layers are dominated by hematite and chert occurring in banded fashion, which is typical of a normal carbonate-free altered BIF discussed in this thesis. The BIFs can also be locally enriched in hematite (ferruginised), occurring as massive hematite ores usually at the top of the stratigraphic profiles. The presence of aegirine-rich assemblages is also noted occurring in some of the BIF and hematite lutite sections immediately above and below the Mn ore beds. The high-grade Mn ore beds vary greatly in mineralogy and texture of the ores laterally and even within a single drill core. In an extreme case, a single drillcore sampled from the Gloria mine (GL57) contains high-grade Wessels-type ore in the upper Mn bed and low-grade, Mamatwan-type ore in the lower Mn layer. Geochemically, the Mn ore bodies also show substantial geochemical variability, although a net increase in the Mn grade downward is usually characterised by a corresponding depletion in mainly bulk Ca, Si and carbonate. However, the Fe content appears to be consistently higher in the upper ore bodies of the drillcores than the lower ones, and the increase in the concentration of the Fe-oxide expectedly causes a relative decrease in the bulk Mn-oxide concentration, usually expressed as an antithetic relationship between the two elements. In terms of trace element distributions, this appears to be more significant in the Mn ores than the other two rock types affected by the same alteration process, probably due to the presence of Mn phases such as hausmannite and braunite serving as good hosts to several trace elements. Cu, Zn, Pb and to a lesser extent Mo are trace metals that appear to show elevated concentration levels (net enrichments) in high-grade Mn ore by comparison to the presumed Mamatwan-type protolith. Ba is an additional element of clear enrichment, manifested mainly as the mineral barite. The Northern KMD has a complex post-depositional history, which includes the intrusion of NE-SW-trending dykes, formation of the Mapedi/Gamagara erosional unconformity, normal faulting associated with the Wessels event and major thrust faults in the western part of the northern KMD. These structural events all have the potential to have contributed to the alteration and subsequent enrichment of the Mn ores in the Nchwaning and Gloria area. As such, the mineralogical, textural, and geochemical variations observed here can tentatively be attributed to the different structural features in the northern KMD. Classic interpretations suggest that normal N-S-trending fault structures have acted as fluid conduits for hydrothermal fluids, which led to the metasomatic alteration of the Mn ore body laterally. Drill cores proximal to and evidently affected by fault-controlled alteration in the SE and SW-portions of the Nchwaning area, have comparable mineralogical and geochemical characteristics for both ore bodies (upper and lower) with subdued alteration effects from the unconformed contact above. Fluids associated with the Mapedi/Gamagara unconformity, would have percolated down-stratigraphy causing oxidative ferruginisation, which led to the formation of massive hematite ores in the top BIF layers and ferruginised Mn ores in the Mn ore beds. This alteration effect appears more prominent in a drill core from the northern part of the study area where the unconformity contact appears more proximal to the upper Mn bed. Drill cores located in the western part of the Nchwaning area seem to also capture evidence of fluid alteration with enrichment in Na recorded in the local abundance of the mineral aegirine. Finally, the dyke structures appear to have acted as impermeable fluid barriers to both lateral and possibly down-dip fluid-flow. , Thesis (MSc) -- Faculty of Science, Geology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Dorbor Jr., Stephen Baysah
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424621 , vital:72169
- Description: The Paleoproterozoic Kalahari manganese field (KMF) in the Northern Cape Province, South Africa, hosts a large resource of manganese ores that has been of great interest over many decades. The Kalahari Manganese deposit (KMD), which is the largest of five erosional relics of the Hotazel Formation in the KMF, hosts three beds of Mn ores with alternating layers of banded iron formation (BIF) and hematite lutite. These three rock types are all evaluated for their mineralogy and geochemistry in this study, with emphasis on lateral and vertical distributions across the Gloria and Nchwaning Mines in the northernmost KMF, an area of high-grade, hydrothermally altered Mn mineralisation. The Mn ores of the Hotazel formation are traditionally categorised into two types. The carbonate-rich low Mn grade (Mn≤40 wt. %) ores (Mamatwan-type) domninates the largest part of the KMD, while carbonate-free, high Mn grade (Mn≥ 45 wt.%) ore (Wessels-type) occurs in the northernmost KMD. The Wessels-type ores are considered as the hydrothermally altered product of Mamatwan-type ores, and as indicated above, are the focus of this study. Five drill cores containing Wessels-type ores from the Nchwaning and Gloria area of the northern KMD were analysed to help understand the petrographic and particularly the geochemical variations in the Hotazel Fe-Mn Formation, both laterally for a given Mn layer of the three, and vertically across Mn layers as captured in specific drillcores. Petrographic and whole-rock geochemical results obtained from the three rock types of the Hotazel Formation show variations in their mineralogical and geochemical compositions, especially in the high-grade Mn ores themselves. Most of the samples of the BIFs layers are dominated by hematite and chert occurring in banded fashion, which is typical of a normal carbonate-free altered BIF discussed in this thesis. The BIFs can also be locally enriched in hematite (ferruginised), occurring as massive hematite ores usually at the top of the stratigraphic profiles. The presence of aegirine-rich assemblages is also noted occurring in some of the BIF and hematite lutite sections immediately above and below the Mn ore beds. The high-grade Mn ore beds vary greatly in mineralogy and texture of the ores laterally and even within a single drill core. In an extreme case, a single drillcore sampled from the Gloria mine (GL57) contains high-grade Wessels-type ore in the upper Mn bed and low-grade, Mamatwan-type ore in the lower Mn layer. Geochemically, the Mn ore bodies also show substantial geochemical variability, although a net increase in the Mn grade downward is usually characterised by a corresponding depletion in mainly bulk Ca, Si and carbonate. However, the Fe content appears to be consistently higher in the upper ore bodies of the drillcores than the lower ones, and the increase in the concentration of the Fe-oxide expectedly causes a relative decrease in the bulk Mn-oxide concentration, usually expressed as an antithetic relationship between the two elements. In terms of trace element distributions, this appears to be more significant in the Mn ores than the other two rock types affected by the same alteration process, probably due to the presence of Mn phases such as hausmannite and braunite serving as good hosts to several trace elements. Cu, Zn, Pb and to a lesser extent Mo are trace metals that appear to show elevated concentration levels (net enrichments) in high-grade Mn ore by comparison to the presumed Mamatwan-type protolith. Ba is an additional element of clear enrichment, manifested mainly as the mineral barite. The Northern KMD has a complex post-depositional history, which includes the intrusion of NE-SW-trending dykes, formation of the Mapedi/Gamagara erosional unconformity, normal faulting associated with the Wessels event and major thrust faults in the western part of the northern KMD. These structural events all have the potential to have contributed to the alteration and subsequent enrichment of the Mn ores in the Nchwaning and Gloria area. As such, the mineralogical, textural, and geochemical variations observed here can tentatively be attributed to the different structural features in the northern KMD. Classic interpretations suggest that normal N-S-trending fault structures have acted as fluid conduits for hydrothermal fluids, which led to the metasomatic alteration of the Mn ore body laterally. Drill cores proximal to and evidently affected by fault-controlled alteration in the SE and SW-portions of the Nchwaning area, have comparable mineralogical and geochemical characteristics for both ore bodies (upper and lower) with subdued alteration effects from the unconformed contact above. Fluids associated with the Mapedi/Gamagara unconformity, would have percolated down-stratigraphy causing oxidative ferruginisation, which led to the formation of massive hematite ores in the top BIF layers and ferruginised Mn ores in the Mn ore beds. This alteration effect appears more prominent in a drill core from the northern part of the study area where the unconformity contact appears more proximal to the upper Mn bed. Drill cores located in the western part of the Nchwaning area seem to also capture evidence of fluid alteration with enrichment in Na recorded in the local abundance of the mineral aegirine. Finally, the dyke structures appear to have acted as impermeable fluid barriers to both lateral and possibly down-dip fluid-flow. , Thesis (MSc) -- Faculty of Science, Geology, 2023
- Full Text:
- Date Issued: 2023-10-13
Exploration potential for copperbelt - style mineralisation in NW Province, Zambia; soil geochemistry as a targeting tool
- Authors: Mwamba, John
- Date: 2018
- Subjects: Mineralogy -- Zambia -- Copperbelt Province , River sediments -- Zambia -- Copperbelt Province , Soils -- Sampling -- Zambia -- Copperbelt Province , Prospecting -- Geophysical methods , Landsat satellites , Lufilian fold belt
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62538 , vital:28204
- Description: The NW Province of Zambia is fast becoming a major significant mining district challenging to usurp the economic importance of the traditional Copperbelt Province that has been mined for nearly a century. With latest developments at Kansanshi, Lumwana and Kalumbila mines exploration efforts in the search for Copperbelt style mineralisation have doubled up in the province in recent months. Traditional methods of stream sediment and soil sampling, geophysics, aerial photo and Landsat imagery interpretations have been employed in exploration targeting campaigns. This thesis asks the question: Can we use the Copperbelt geochemical footprint as a proxy to finding new copper deposits in NW Province? The challenge faced in such studies is that few geochemical datasets for old mines exist and the little that does is proprietary information. In some mines this dataset is entirely nonexistent - at least not in the public domain. Attempting to run orientation geochemical trials on such mines is not feasible at present due to maturity of mining and the levels of contamination of the natural environment that have occurred over several decades of mining. However, in tackling this question few Copperbelt geochemical datasets from Baluba, Nkana, Mimbula, Nchanga, Bwana Mkubwa, Mufulira West and Lufubu North were used. The findings presented in this report are that for Copperbelt style mineralisation Cu/Co, Cu/Ni, Cu/Ag ratios in soil geochemistry data should be in the ranges of 0.25 to 0.48 provided geochemical studies occurred in residual soils. These ratios hold true for sediment hosted copper-cobalt mineralisation hosted at various stratigraphic levels within the Roan Group or in upper levels elsewhere on the Central African Copperbelt. Geochemical dataset for the study areas presented in this report show that the soil geochemistry footprint in the province is not dissimilar to the soil geochemistry footprint of the traditional Copperbelt Province. This means there is great potential for finding Copperbelt style mineralisation in the province and other styles of mineralisation in which copper is associated with cobalt, lead, zinc, nickel, vanadium and molybdenum. The areas of study also possess requisite geological factors that are conducive to hosting Copperbelt style deposits. These factors include: favourable structural traps with similar trends to existing mines in the province, geophysical characteristics comparable to other deposits in the province, right geological package known to host multi-type deposits in the Katangan stratigraphic sequence, and similar geochemical footprints observed on other deposits within the Lufilian fold belt. For this reason, geochemical dataset must not be looked at in isolation but should be treated in considerations with other factors and geological environment.
- Full Text:
- Date Issued: 2018
- Authors: Mwamba, John
- Date: 2018
- Subjects: Mineralogy -- Zambia -- Copperbelt Province , River sediments -- Zambia -- Copperbelt Province , Soils -- Sampling -- Zambia -- Copperbelt Province , Prospecting -- Geophysical methods , Landsat satellites , Lufilian fold belt
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62538 , vital:28204
- Description: The NW Province of Zambia is fast becoming a major significant mining district challenging to usurp the economic importance of the traditional Copperbelt Province that has been mined for nearly a century. With latest developments at Kansanshi, Lumwana and Kalumbila mines exploration efforts in the search for Copperbelt style mineralisation have doubled up in the province in recent months. Traditional methods of stream sediment and soil sampling, geophysics, aerial photo and Landsat imagery interpretations have been employed in exploration targeting campaigns. This thesis asks the question: Can we use the Copperbelt geochemical footprint as a proxy to finding new copper deposits in NW Province? The challenge faced in such studies is that few geochemical datasets for old mines exist and the little that does is proprietary information. In some mines this dataset is entirely nonexistent - at least not in the public domain. Attempting to run orientation geochemical trials on such mines is not feasible at present due to maturity of mining and the levels of contamination of the natural environment that have occurred over several decades of mining. However, in tackling this question few Copperbelt geochemical datasets from Baluba, Nkana, Mimbula, Nchanga, Bwana Mkubwa, Mufulira West and Lufubu North were used. The findings presented in this report are that for Copperbelt style mineralisation Cu/Co, Cu/Ni, Cu/Ag ratios in soil geochemistry data should be in the ranges of 0.25 to 0.48 provided geochemical studies occurred in residual soils. These ratios hold true for sediment hosted copper-cobalt mineralisation hosted at various stratigraphic levels within the Roan Group or in upper levels elsewhere on the Central African Copperbelt. Geochemical dataset for the study areas presented in this report show that the soil geochemistry footprint in the province is not dissimilar to the soil geochemistry footprint of the traditional Copperbelt Province. This means there is great potential for finding Copperbelt style mineralisation in the province and other styles of mineralisation in which copper is associated with cobalt, lead, zinc, nickel, vanadium and molybdenum. The areas of study also possess requisite geological factors that are conducive to hosting Copperbelt style deposits. These factors include: favourable structural traps with similar trends to existing mines in the province, geophysical characteristics comparable to other deposits in the province, right geological package known to host multi-type deposits in the Katangan stratigraphic sequence, and similar geochemical footprints observed on other deposits within the Lufilian fold belt. For this reason, geochemical dataset must not be looked at in isolation but should be treated in considerations with other factors and geological environment.
- Full Text:
- Date Issued: 2018
Gem-bearing granitic pegmatites in Malawi: their mineralogy, geochemistry, age, and fluid compositional variations
- Kankuzi, Charles Frienderson
- Authors: Kankuzi, Charles Frienderson
- Date: 2019
- Subjects: Granite , Pegmatites , Geochemistry , Fluid inclusions , Nonferrous metals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/97905 , vital:31505 , DOI https://doi.org/10.21504/10962/97905
- Description: The gem bearing granitic pegmatites from different pegmatite fields across Malawi intrude all important geological entities from the Palaeoproterozoic in the north, the Mesoproterozoic in central Malawi and the Pan-African basement in the south. U/Pb zircon and Rb/Sr mineral isochron ages indicate pegmatite emplacement from the Palaeoproterozoic to Pan-African and Mesozoic time. Most pegmatites are related to the Pan-African cycle; no Mesoproterozoic pegmatites were observed in this study. Within the Pan-African pegmatite groups there are two important subgroups. Some pegmatites show Sr isotopic compositions that indicate mantle components contributing to the parental granites from which the pegmatites evolved. Others show higher Sr initials, indicating crustal granites as primary pegmatite sources or significant crustal contamination. Only for few pegmatites, such as the Palaeoproterozoic and Ordovician gem tourmaline pegmatites in the Chitipa and Dowa Districts, the granitic source is evident from their field context. For all others the granitic origin is interpreted by mineralogical and geochemical evidence. All analysed pegmatites belong to either the Rare Element Class or the Miarolitic Class, but they vary in their degree of fractionation. The more evolved pegmatites are more enriched in incompatible elements such as Be, Li, B, and Ta, which resulted in the formation of gem minerals such as beryl, aquamarine, tourmaline and topaz, which may or may not be associated with tantalite. The Rare Element pegmatites can be further subdivided into the REL-Li subclass, beryl type, beryl-columbite subtype, and in the complex type and elbaite subtype. The Miarolitic pegmatites include Mi-Li subclass and beryl-topaz type. Fluid inclusion studies (heating-cooling stage, Raman spectroscopy) identified a variety of fluid compositions that were present at different times and different places, indicating a variety of fluid sources. They range from aqueous-saline to CO2–rich carbonic fluids (CO2 +C3H8+ N2), or aqueous-carbonic fluids (H2O-CO2-CH4 and H2O-CO2-H2-H2S-CH4). The dominant solutes and species for the pegmatites show genetic variations over time and orogen (Paleo-/Meso-/Neoproterozoic). Uniform homogenisation temperatures and salinities in individual samples indicate that the gem-bearing pegmatites contained homogeneous fluids at the time of their capturing in quartz. Based on fluid inclusion data, the estimated trapping conditions of inclusions in quartz for all studied pegmatites except for one pegmatite suggest low pressures between 0.9 to 2.6 kb at temperatures of 400-600 C. The other pegmatite formed at slightly higher pressures of 2.2 to 3.6 kb. However, the pressure range for all the pegmatites is in agreement with the known liquidus conditions of Rare-Element pegmatite crystallisation. The shallow crustal emplacement level (3.4-9.8 km) and the greater depth (8.3 to 13.6 km) favoured the formation of gemstones. , Thesis (PhD) -- Faculty of Science, Geology, 2019
- Full Text: false
- Date Issued: 2019
- Authors: Kankuzi, Charles Frienderson
- Date: 2019
- Subjects: Granite , Pegmatites , Geochemistry , Fluid inclusions , Nonferrous metals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/97905 , vital:31505 , DOI https://doi.org/10.21504/10962/97905
- Description: The gem bearing granitic pegmatites from different pegmatite fields across Malawi intrude all important geological entities from the Palaeoproterozoic in the north, the Mesoproterozoic in central Malawi and the Pan-African basement in the south. U/Pb zircon and Rb/Sr mineral isochron ages indicate pegmatite emplacement from the Palaeoproterozoic to Pan-African and Mesozoic time. Most pegmatites are related to the Pan-African cycle; no Mesoproterozoic pegmatites were observed in this study. Within the Pan-African pegmatite groups there are two important subgroups. Some pegmatites show Sr isotopic compositions that indicate mantle components contributing to the parental granites from which the pegmatites evolved. Others show higher Sr initials, indicating crustal granites as primary pegmatite sources or significant crustal contamination. Only for few pegmatites, such as the Palaeoproterozoic and Ordovician gem tourmaline pegmatites in the Chitipa and Dowa Districts, the granitic source is evident from their field context. For all others the granitic origin is interpreted by mineralogical and geochemical evidence. All analysed pegmatites belong to either the Rare Element Class or the Miarolitic Class, but they vary in their degree of fractionation. The more evolved pegmatites are more enriched in incompatible elements such as Be, Li, B, and Ta, which resulted in the formation of gem minerals such as beryl, aquamarine, tourmaline and topaz, which may or may not be associated with tantalite. The Rare Element pegmatites can be further subdivided into the REL-Li subclass, beryl type, beryl-columbite subtype, and in the complex type and elbaite subtype. The Miarolitic pegmatites include Mi-Li subclass and beryl-topaz type. Fluid inclusion studies (heating-cooling stage, Raman spectroscopy) identified a variety of fluid compositions that were present at different times and different places, indicating a variety of fluid sources. They range from aqueous-saline to CO2–rich carbonic fluids (CO2 +C3H8+ N2), or aqueous-carbonic fluids (H2O-CO2-CH4 and H2O-CO2-H2-H2S-CH4). The dominant solutes and species for the pegmatites show genetic variations over time and orogen (Paleo-/Meso-/Neoproterozoic). Uniform homogenisation temperatures and salinities in individual samples indicate that the gem-bearing pegmatites contained homogeneous fluids at the time of their capturing in quartz. Based on fluid inclusion data, the estimated trapping conditions of inclusions in quartz for all studied pegmatites except for one pegmatite suggest low pressures between 0.9 to 2.6 kb at temperatures of 400-600 C. The other pegmatite formed at slightly higher pressures of 2.2 to 3.6 kb. However, the pressure range for all the pegmatites is in agreement with the known liquidus conditions of Rare-Element pegmatite crystallisation. The shallow crustal emplacement level (3.4-9.8 km) and the greater depth (8.3 to 13.6 km) favoured the formation of gemstones. , Thesis (PhD) -- Faculty of Science, Geology, 2019
- Full Text: false
- Date Issued: 2019
Genetic connectivity of the roundjaw bonefish (Albula glossodonta) in the Southwest Indian Ocean
- Talma, Sheena Claudia Aisa Lydie
- Authors: Talma, Sheena Claudia Aisa Lydie
- Date: 2021-10-29
- Subjects: Bonefish Mauritius , Bonefish Seychelles , Bonefish Genetics , Bonefish Habitat , Bonefish Geographical distribution , Bonefish Larvae Dispersal , Genetic markers , Cytochrome b , Fish populations Mauritius , Fish populations Seychelles , Marine ecotourism , Saltwater fly fishing , Bonefish fisheries Catch effort
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192174 , vital:45202
- Description: The Southwest Indian Ocean (SWIO) islands of Mauritius and Seychelles are both highly dependent on tourism and fisheries for their economies. One of the growing ecotourism sectors is saltwater fly fishing, an industry based on catch-and-release fishing for a host of species, including bonefishes. Bonefishes (Albula spp.) have received significant research attention in the Pacific and Atlantic Oceans, with only sporadic research conducted in the Indian Ocean. My project aimed to investigate the genetic connectivity of the roundjaw bonefish (Albula glossodonta) in two island states (Seychelles and Mauritius) within the SWIO using a mitochondrial genetic marker (cyt-b) and next generation sequencing (ddRADseq). Samples collected were grouped based on their spatial distribution. The Seychelles consisted of four island groups (Inner Island Group, Aldabra Group, Amirantes and Alphonse Group, and Farquhar Group) whereas Mauritius was represented by one island group (Saint Brandon). Genetic analyses were undertaken between and within each of these groups. Mitochondrial cytochrome-b identified two species of bonefish: Albula glossodonta and Albula oligolepis; the latter was only genetically identified from the Inner Island Group. I hypothesise that this is due to habitat partitioning, with A. oligolepis being a deeper dwelling bonefish species compared to A. glossodonta, which occupies shallow water habitats such as sand flats, atoll lagoons and reef flats. Neutral SNP loci revealed a panmictic pattern of distribution for A. glossodonta throughout the Seychelles Island groups but showed a pattern of weak structure between Seychelles and Mauritius. Genetic diversity indices such as allelic richness, showed low diversity across the sampling sites (AR range: 1.761-1.889). Population structure tests such as pairwise FST showed low but significant population structure. The highest FST indices were recorded between the Aldabra and Farquhar Groups, as well as the Aldabra and Saint Brandon Groups (0.044 ± 0.000 and 0.040 ± 0.000, respectively). Descriptive tests such as PCA and DAPC showed similar trends, whereby Saint Brandon clustered separately from the other samples from the Seychelles Island groups. However, these trends were Abstract seen at very low variations (PCA axes 1 and 2 accounted for only 2.0 and 1.9 % of the total variation, respectively). A population assignment test grouped the individuals as one ancestral population. A spatial principal component analysis showed that Saint Brandon was dissimilar to the Seychelles Island groups. Like other Elopomorph species, bonefishes have leptocephalus larvae capable of long-distance dispersal which may explain the well-mixed genetic population observed within the Seychelles islands. Although currents within the Indian Ocean, especially on a mesoscale, are not well understood, the South Equatorial Current likely facilitates connectivity between the Seychelles islands while also limiting gene flow between Seychelles and Mauritius. Understanding population structure is important for informing the appropriate management and conservation strategies, especially in oceanic nations where data informing important industries like tourism and fisheries are often limited. The bonefish fly fishing industry is well-known to be a lucrative sector, generating, for example US$ 1.4 million a year in the Bahamas. This study recognised that there are numerous knowledge gaps relevant to the bonefish industry that need to be addressed, including: 1) understanding the socio-economic importance of fly fishing to island states like Seychelles, 2) estimating the abundance and species distribution of bonefishes within Seychelles, 3) understanding effectiveness of MPAs for recreational fishery species like bonefish and, lastly, 4) generating more fishery-relevant biological information on the heavily targeted fly fishing species within Seychelles. These needs must be met to inform management plans and to better manage the fly fishing ventures that target species like bonefish. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Talma, Sheena Claudia Aisa Lydie
- Date: 2021-10-29
- Subjects: Bonefish Mauritius , Bonefish Seychelles , Bonefish Genetics , Bonefish Habitat , Bonefish Geographical distribution , Bonefish Larvae Dispersal , Genetic markers , Cytochrome b , Fish populations Mauritius , Fish populations Seychelles , Marine ecotourism , Saltwater fly fishing , Bonefish fisheries Catch effort
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192174 , vital:45202
- Description: The Southwest Indian Ocean (SWIO) islands of Mauritius and Seychelles are both highly dependent on tourism and fisheries for their economies. One of the growing ecotourism sectors is saltwater fly fishing, an industry based on catch-and-release fishing for a host of species, including bonefishes. Bonefishes (Albula spp.) have received significant research attention in the Pacific and Atlantic Oceans, with only sporadic research conducted in the Indian Ocean. My project aimed to investigate the genetic connectivity of the roundjaw bonefish (Albula glossodonta) in two island states (Seychelles and Mauritius) within the SWIO using a mitochondrial genetic marker (cyt-b) and next generation sequencing (ddRADseq). Samples collected were grouped based on their spatial distribution. The Seychelles consisted of four island groups (Inner Island Group, Aldabra Group, Amirantes and Alphonse Group, and Farquhar Group) whereas Mauritius was represented by one island group (Saint Brandon). Genetic analyses were undertaken between and within each of these groups. Mitochondrial cytochrome-b identified two species of bonefish: Albula glossodonta and Albula oligolepis; the latter was only genetically identified from the Inner Island Group. I hypothesise that this is due to habitat partitioning, with A. oligolepis being a deeper dwelling bonefish species compared to A. glossodonta, which occupies shallow water habitats such as sand flats, atoll lagoons and reef flats. Neutral SNP loci revealed a panmictic pattern of distribution for A. glossodonta throughout the Seychelles Island groups but showed a pattern of weak structure between Seychelles and Mauritius. Genetic diversity indices such as allelic richness, showed low diversity across the sampling sites (AR range: 1.761-1.889). Population structure tests such as pairwise FST showed low but significant population structure. The highest FST indices were recorded between the Aldabra and Farquhar Groups, as well as the Aldabra and Saint Brandon Groups (0.044 ± 0.000 and 0.040 ± 0.000, respectively). Descriptive tests such as PCA and DAPC showed similar trends, whereby Saint Brandon clustered separately from the other samples from the Seychelles Island groups. However, these trends were Abstract seen at very low variations (PCA axes 1 and 2 accounted for only 2.0 and 1.9 % of the total variation, respectively). A population assignment test grouped the individuals as one ancestral population. A spatial principal component analysis showed that Saint Brandon was dissimilar to the Seychelles Island groups. Like other Elopomorph species, bonefishes have leptocephalus larvae capable of long-distance dispersal which may explain the well-mixed genetic population observed within the Seychelles islands. Although currents within the Indian Ocean, especially on a mesoscale, are not well understood, the South Equatorial Current likely facilitates connectivity between the Seychelles islands while also limiting gene flow between Seychelles and Mauritius. Understanding population structure is important for informing the appropriate management and conservation strategies, especially in oceanic nations where data informing important industries like tourism and fisheries are often limited. The bonefish fly fishing industry is well-known to be a lucrative sector, generating, for example US$ 1.4 million a year in the Bahamas. This study recognised that there are numerous knowledge gaps relevant to the bonefish industry that need to be addressed, including: 1) understanding the socio-economic importance of fly fishing to island states like Seychelles, 2) estimating the abundance and species distribution of bonefishes within Seychelles, 3) understanding effectiveness of MPAs for recreational fishery species like bonefish and, lastly, 4) generating more fishery-relevant biological information on the heavily targeted fly fishing species within Seychelles. These needs must be met to inform management plans and to better manage the fly fishing ventures that target species like bonefish. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Genetic relationships between migmatites and the Swartoup Pluton in the Swartoup Hills (central Namaqua Belt)
- Authors: Schmeldt, Graeme Alvin
- Date: 2021-10-29
- Subjects: Migmatite South Africa Northern Cape , Intrusions (Geology) South Africa , Metamorphic rocks South Africa Northern Cape , Metamorphism (Geology) South Africa Northern Cape , Onseepkans (South Africa) , Namaqualand (South Africa) , Anatexis , Swartoup , Koenap
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192162 , vital:45201
- Description: The central Namaqua Metamorphic Complex can be characterised by long-standing high-temperature (up to granulite/amphibolite facies) conditions between _ 1300 and 1100Ma, inevitably resulting in widespread metamorphism and plutonism. Hosted within a NW–SE striking antiformal structure about 40 km east of Onseepkans, Northen Cape, South Africa, in the Swartoup Hills, lies the Swartoup Pluton. The Swartoup Pluton was sampled and described in hand specimen and thin section. The study area was photographed, with all data presented in this study. The various rock types are readily discerned in the field due to their characteristic weathering colours and overall fabrics. The Swartoup granodioritic body is hosted within metasediments of the Bysteek and Koenap Formations, of the Arribees Group. The package was later intruded by another later granitoid, the Polisiehoek Granite-gneiss. The Bysteek Formation, a wall rock to the S-type Swartoup Pluton, reacted at the contact with the igneous body resulting in localised feldspathic granites and granodiorites with prominent, often euhedral, garnet, pryoxene and titanite. The Swartoup Pluton is divided into two subgroups. The first is characterised by higher P2O5 contents, _ 0.3 – 0.4 wt.%, shown with a narrower constraint on its Rb contents, _ 80 – 160 ppm, than the second, with _ 0.14 – 0.4 wt.% P2O5 and 20 – 310 ppm Rb. Meanwhile the Polisiehoek Granite-gneiss shows _ 50 – 420 ppm Rb and _ 0.04 – 0:1 wt% P2O5. As a whole, the Swartoup Pluton is characterised by somewhat elevated CaO concentrations (_ 1.5 – 6.0 wt.%), relative to calculated averages of granites (1.8 wt.% CaO, Le Maitre, 1976) and granodiorites (3.9 wt.% CaO, Le Maitre, 1976). Whilst most of the Swartoup specimens were classified as granodiorites, some orthopyroxene-bearing monzodiorite and orthopyroxenebearing monzonite were locally found and sampled. However, much of the body appears to be granodioritic to granitic in composition. The Polisiehoek Granite-gneiss is characterised by its orange-brown weathering colour in the field, sheared texture, lower P2O5 and higher total alkali content than the Swartoup Pluton. The Polisiehoek Granite-gneiss is a highly fractionated S-type granite, as shown by plots of (a) (Na2O + K2O)/CaO and (b) FeOT/MgO versus Zr + Nb + Ce + Y (Whalen et al., 1987; Zhang et al., 2019) and also of (c) (Al2O3 + CaO)/(FeOT + Na2O + K2O) versus 100 × (MgO + FeOT + TiO2)/SiO2 (after Sylvester, 1989). Classification schemes identify the Polisiehoek Granite-gneiss as either a granite (TAS diagram, after Middlemost, 1994) or alkali granite (R1R2 diagram, after De la Roche et al., 1980). , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Schmeldt, Graeme Alvin
- Date: 2021-10-29
- Subjects: Migmatite South Africa Northern Cape , Intrusions (Geology) South Africa , Metamorphic rocks South Africa Northern Cape , Metamorphism (Geology) South Africa Northern Cape , Onseepkans (South Africa) , Namaqualand (South Africa) , Anatexis , Swartoup , Koenap
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192162 , vital:45201
- Description: The central Namaqua Metamorphic Complex can be characterised by long-standing high-temperature (up to granulite/amphibolite facies) conditions between _ 1300 and 1100Ma, inevitably resulting in widespread metamorphism and plutonism. Hosted within a NW–SE striking antiformal structure about 40 km east of Onseepkans, Northen Cape, South Africa, in the Swartoup Hills, lies the Swartoup Pluton. The Swartoup Pluton was sampled and described in hand specimen and thin section. The study area was photographed, with all data presented in this study. The various rock types are readily discerned in the field due to their characteristic weathering colours and overall fabrics. The Swartoup granodioritic body is hosted within metasediments of the Bysteek and Koenap Formations, of the Arribees Group. The package was later intruded by another later granitoid, the Polisiehoek Granite-gneiss. The Bysteek Formation, a wall rock to the S-type Swartoup Pluton, reacted at the contact with the igneous body resulting in localised feldspathic granites and granodiorites with prominent, often euhedral, garnet, pryoxene and titanite. The Swartoup Pluton is divided into two subgroups. The first is characterised by higher P2O5 contents, _ 0.3 – 0.4 wt.%, shown with a narrower constraint on its Rb contents, _ 80 – 160 ppm, than the second, with _ 0.14 – 0.4 wt.% P2O5 and 20 – 310 ppm Rb. Meanwhile the Polisiehoek Granite-gneiss shows _ 50 – 420 ppm Rb and _ 0.04 – 0:1 wt% P2O5. As a whole, the Swartoup Pluton is characterised by somewhat elevated CaO concentrations (_ 1.5 – 6.0 wt.%), relative to calculated averages of granites (1.8 wt.% CaO, Le Maitre, 1976) and granodiorites (3.9 wt.% CaO, Le Maitre, 1976). Whilst most of the Swartoup specimens were classified as granodiorites, some orthopyroxene-bearing monzodiorite and orthopyroxenebearing monzonite were locally found and sampled. However, much of the body appears to be granodioritic to granitic in composition. The Polisiehoek Granite-gneiss is characterised by its orange-brown weathering colour in the field, sheared texture, lower P2O5 and higher total alkali content than the Swartoup Pluton. The Polisiehoek Granite-gneiss is a highly fractionated S-type granite, as shown by plots of (a) (Na2O + K2O)/CaO and (b) FeOT/MgO versus Zr + Nb + Ce + Y (Whalen et al., 1987; Zhang et al., 2019) and also of (c) (Al2O3 + CaO)/(FeOT + Na2O + K2O) versus 100 × (MgO + FeOT + TiO2)/SiO2 (after Sylvester, 1989). Classification schemes identify the Polisiehoek Granite-gneiss as either a granite (TAS diagram, after Middlemost, 1994) or alkali granite (R1R2 diagram, after De la Roche et al., 1980). , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-10-29
Geological study and economic evaluation of the Paardeplaats Coal Exploration Project
- Authors: Gcayi, Gcobani
- Date: 2017
- Subjects: Coal Geology South Africa Mpumalanga , Coal Prospecting South Africa Mpumalanga , Coal mines and mining South Africa Mpumalanga , Geology, Economic South Africa , Coal reserves South Africa Mpumalanga
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59183 , vital:27452
- Description: For a coal mining company the coal resources are an important asset, and they are acquired in a number of different ways, such as obtaining a prospecting permit from government or an existing permit from another entity and or purchasing an operating colliery from another entity. The Paardeplaats Project is a brownfields project located approximately 7 km south west of the town of Belfast in Mpumalanga Province, South Africa, on the far eastern edge of the Witbank Coalfield. The project is located adjacent to an operating mine, Glisa Colliery, owned by Eyesizwe Coal. Eyesizwe Coal was awarded the prospecting permit in 2006 by the Department of Mineral Resources. Subsequent exploration activities, which included airborne magnetic survey and borehole drilling, were conducted between 2008 and 2010. The results of the drilling confirmed the presence of coal resources, which are classified in the Measured, Indicated and Inferred categories. Mining and beneficiation methods from the adjacent Glisa Colliery, which has similar geology to the project area, were assumed in order to generate a coal reserve statement. The Coal Reserve qualities are suitable to the domestic market, particularly Eskom. South Africa’s coal supply is demand driven, primarily from Eskom for electricity generation followed by the export market and thirdly by Sasol for synthetic fuel generation. The majority of Eskom’s existing coal-fired power stations are located in the Mpumalanga Province, which provides a viable market for coal projects in Mpumalanga when considering existing transport infrastructure and transportation costs. Eskom’s continued demand for coal in the Mpumalanga region, at least until 2040, provides a future market for advanced coal projects in the region. A valuation of the project using the Cash Flow Approach showed the project to be economically viable. , Thesis (MSc) -- Faculty of Faculty of Science, Geology, 2017
- Full Text:
- Date Issued: 2017
- Authors: Gcayi, Gcobani
- Date: 2017
- Subjects: Coal Geology South Africa Mpumalanga , Coal Prospecting South Africa Mpumalanga , Coal mines and mining South Africa Mpumalanga , Geology, Economic South Africa , Coal reserves South Africa Mpumalanga
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59183 , vital:27452
- Description: For a coal mining company the coal resources are an important asset, and they are acquired in a number of different ways, such as obtaining a prospecting permit from government or an existing permit from another entity and or purchasing an operating colliery from another entity. The Paardeplaats Project is a brownfields project located approximately 7 km south west of the town of Belfast in Mpumalanga Province, South Africa, on the far eastern edge of the Witbank Coalfield. The project is located adjacent to an operating mine, Glisa Colliery, owned by Eyesizwe Coal. Eyesizwe Coal was awarded the prospecting permit in 2006 by the Department of Mineral Resources. Subsequent exploration activities, which included airborne magnetic survey and borehole drilling, were conducted between 2008 and 2010. The results of the drilling confirmed the presence of coal resources, which are classified in the Measured, Indicated and Inferred categories. Mining and beneficiation methods from the adjacent Glisa Colliery, which has similar geology to the project area, were assumed in order to generate a coal reserve statement. The Coal Reserve qualities are suitable to the domestic market, particularly Eskom. South Africa’s coal supply is demand driven, primarily from Eskom for electricity generation followed by the export market and thirdly by Sasol for synthetic fuel generation. The majority of Eskom’s existing coal-fired power stations are located in the Mpumalanga Province, which provides a viable market for coal projects in Mpumalanga when considering existing transport infrastructure and transportation costs. Eskom’s continued demand for coal in the Mpumalanga region, at least until 2040, provides a future market for advanced coal projects in the region. A valuation of the project using the Cash Flow Approach showed the project to be economically viable. , Thesis (MSc) -- Faculty of Faculty of Science, Geology, 2017
- Full Text:
- Date Issued: 2017
Gold mineralization in a high grade metamorphic terrane in the Handeni District, Eastern Tanzania
- Bitesigirwe, Godfrey Stephen
- Authors: Bitesigirwe, Godfrey Stephen
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54756 , vital:26609
- Description: Most orogenic type gold deposits are formed under low greenschist facies to mid amphibolite facies metamorphic conditions and deposition is either structurally or lithologically controlled. A few known gold deposits found in high grade metamorphic terranes include those in the Yilgarn craton in Australia, Renco in Zimbabwe, Hemlo in Canada and the recently discovered Handeni deposit in Tanzania. Within Tanzania, gold deposits are mainly hosted in Archaean low grade metamorphic rocks commonly known as the Lake Victoria greenstone belt. The greenstone belts of Tanzania are of Nyanzian age (> 2.5Ga) and are located to the south and east of Lake Victoria on the Tanzania craton. The Tanzania Craton is surrounded by Usagaran 1.9 Ga rocks (the east African orogenic belt (EAO) better known as the Mozambique belt) to the east and the Ubendian belt to the south and west. Published reports show that the eastern part of the Tanzania Craton is dominated by the fragments of Archaean rocks. Metamorphism along East Africa and the Tanzania Craton is due to several geological events. These geological events include the intrusion of granites in the Archaean Tanzania Craton (3 Ga), subduction of ocean plate resulted to the formation of Usagaran belt (1.9 Ga), opening and closure of Mozambique Ocean, which resulted in the formation of the Mozambique belt between 700 – 800 Ma and the Pan African orogeny at 640 – 620 Ma, which is associated with the formation of Gondwana. It is believed that fragments from the Archaean Tanzania craton were re - metamorphosed during these events. The Handeni project (the focus of this thesis) is located in the northern portion of the eastern part of the Usagaran belt (1.9 Ga) comprising the eastern part of Archaean Tanzania Craton. The area is characterized by Proterozic rocks of basaltic composition. The documented 2.7 Ga rocks at the Kilindi Handeni Superterrane at the northern part of the Usagaran belt correlate well with 2.7 Ga of Nyanzian rocks of Archaean Tanzania craton. The Handeni project area is geologically dominated by metamorphosed and deformed units of quartzofeldspathic gneisses, migmatitic gneiss, garnet silicified rock, garnetiferous amphibolite, garnetiferous granulite, graphitic schist and hornblende pyroxenite. Intensive deformation features that were developed include folds (sheath folds, micro and macro scales), faults, shears and regional thrusts. This thesis focuses on identifying the protolith of the rocks, alteration minerals, and metamorphic assemblages in the project area in order to understand the timing of gold mineralization. Geological investigation of core, ore petrology and mineralogy, mineral composition by using JEOL microprobe analysis and XRF analysis of bulk rocks were utilized. All the analytical work was done at the Geology laboratory, Rhodes University. Petrographic analysis shows that the rocks sampled in the study area are characterized by alteration minerals such as calcite, dolomite and sericite. Sulphide minerals including chalcopyrite, pyrrhotite, pyrite, pentlandite and gersdorffite were identified. Gold mineralization is associated with disseminated sulphides in association with trace amounts of base metals. Four rock types were proposed as host rocks for the mineralization, namely garnet silicified rock with superimposed quartz veins, garnetiferous amphibolite, garnetiferous granulite and hornblende pyroxenite. Fold troughs, filled fractures associated with episodes of folding, quartz veins and shear zones are suggested as gold precipitation sites. The presence of high grade metamorphic rocks containing gold, intermediate to low grade assemblages with sulphides and associated hydrothermal alteration as well as a complex deformation history suggests that the Handeni mineralization took place over an extended time period stretching from a ductile to a brittle environment.
- Full Text:
- Date Issued: 2014
- Authors: Bitesigirwe, Godfrey Stephen
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54756 , vital:26609
- Description: Most orogenic type gold deposits are formed under low greenschist facies to mid amphibolite facies metamorphic conditions and deposition is either structurally or lithologically controlled. A few known gold deposits found in high grade metamorphic terranes include those in the Yilgarn craton in Australia, Renco in Zimbabwe, Hemlo in Canada and the recently discovered Handeni deposit in Tanzania. Within Tanzania, gold deposits are mainly hosted in Archaean low grade metamorphic rocks commonly known as the Lake Victoria greenstone belt. The greenstone belts of Tanzania are of Nyanzian age (> 2.5Ga) and are located to the south and east of Lake Victoria on the Tanzania craton. The Tanzania Craton is surrounded by Usagaran 1.9 Ga rocks (the east African orogenic belt (EAO) better known as the Mozambique belt) to the east and the Ubendian belt to the south and west. Published reports show that the eastern part of the Tanzania Craton is dominated by the fragments of Archaean rocks. Metamorphism along East Africa and the Tanzania Craton is due to several geological events. These geological events include the intrusion of granites in the Archaean Tanzania Craton (3 Ga), subduction of ocean plate resulted to the formation of Usagaran belt (1.9 Ga), opening and closure of Mozambique Ocean, which resulted in the formation of the Mozambique belt between 700 – 800 Ma and the Pan African orogeny at 640 – 620 Ma, which is associated with the formation of Gondwana. It is believed that fragments from the Archaean Tanzania craton were re - metamorphosed during these events. The Handeni project (the focus of this thesis) is located in the northern portion of the eastern part of the Usagaran belt (1.9 Ga) comprising the eastern part of Archaean Tanzania Craton. The area is characterized by Proterozic rocks of basaltic composition. The documented 2.7 Ga rocks at the Kilindi Handeni Superterrane at the northern part of the Usagaran belt correlate well with 2.7 Ga of Nyanzian rocks of Archaean Tanzania craton. The Handeni project area is geologically dominated by metamorphosed and deformed units of quartzofeldspathic gneisses, migmatitic gneiss, garnet silicified rock, garnetiferous amphibolite, garnetiferous granulite, graphitic schist and hornblende pyroxenite. Intensive deformation features that were developed include folds (sheath folds, micro and macro scales), faults, shears and regional thrusts. This thesis focuses on identifying the protolith of the rocks, alteration minerals, and metamorphic assemblages in the project area in order to understand the timing of gold mineralization. Geological investigation of core, ore petrology and mineralogy, mineral composition by using JEOL microprobe analysis and XRF analysis of bulk rocks were utilized. All the analytical work was done at the Geology laboratory, Rhodes University. Petrographic analysis shows that the rocks sampled in the study area are characterized by alteration minerals such as calcite, dolomite and sericite. Sulphide minerals including chalcopyrite, pyrrhotite, pyrite, pentlandite and gersdorffite were identified. Gold mineralization is associated with disseminated sulphides in association with trace amounts of base metals. Four rock types were proposed as host rocks for the mineralization, namely garnet silicified rock with superimposed quartz veins, garnetiferous amphibolite, garnetiferous granulite and hornblende pyroxenite. Fold troughs, filled fractures associated with episodes of folding, quartz veins and shear zones are suggested as gold precipitation sites. The presence of high grade metamorphic rocks containing gold, intermediate to low grade assemblages with sulphides and associated hydrothermal alteration as well as a complex deformation history suggests that the Handeni mineralization took place over an extended time period stretching from a ductile to a brittle environment.
- Full Text:
- Date Issued: 2014
Graphite: origin, deposits and economics : an exploration study of the Orom Graphite project
- Van den Berg, Jacobus Petrus
- Authors: Van den Berg, Jacobus Petrus
- Date: 2018
- Subjects: Graphite , Ore deposits , Geophysics , Graphite mines and mining Economic aspects Africa, East , Trenches , Project management
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63786 , vital:28489
- Description: Developing exploration projects successfully requires that the Reasonable Prospects for Eventual Economic Extraction (RPEEE) be confirmed and based on the global market perception and trend. The exploration methods applied in the attempt to establish this RPEEE must be based on a key management framework that assures the results, and eventually the conclusion, are obtained with best practical and technical approaches whilst managing the risks and capitalizing on each result. The Orom Graphite project is located within the East African Orogenic belt, a suture zone between the Congo craton and the SLAMIN shield, formed during the formation of Gondwana during the late Proterozoic to early-Phanerozoic era. The closing of the Mozambique ocean, and the eventual collision between the craton and shield, occurred along the paleo-earths equator and migrated towards lower latitudes. This, along with the period’s biodiversity boom, provided the perfect deposition environment for carbonaceous sediments which were later metamorphosed to amphibolite and granulites grade metamorphism, resulting in the carbonization and the eventual graphitization of these carbonaceous sediments. The project is located within a poorly developed part of Uganda with the closest port situated some 1 500 km to the east in Kenya. The poorly developed infrastructure along with probable high logistical cost assigns a low competitivity index if compared to the economic costs of peer projects. However, the potential resources of the Orom Graphite project suggest that the Life of Mine (LOM) can rival the largest resource currently reported within the market. The current market conditions suggest that a possible oversupply of graphite concentrate will dominate the market within the next 4 to 10 years. This suggests that new graphite projects such as the Orom Graphite project are likely to develop into the production phase once the global supply and demand stabilize. This requires the Orom Graphite project to develop from its current scoping study level to a project development study level associated with a definitive feasibility study. To date, the project developed through mapping, reconnaissance drilling, geophysical survey and trenching programs increasing the Net Present Value (NPV) considerably based upon a Cost-Based Valuation approach using Prospectivity Enhancement Multiplier (PEM). The metallurgical studies could however not produce a graphite concentrate product within industrial grade standards. The risk associated with developing the project further into the Mineral Resource Estimation (MRE) phase was quantified and risk was evaluated by implementing a point decision tree and calculating the Expected Monetary Value (EMV). Due to the unfavourable metallurgical results obtained to date, the risk associated with undertaking an additional metallurgical test is considerable with a slight chance of producing a negative project value estimated at 65%. JP van den Berg Rhodes University Overall, the Orom Graphite project contains favourable geological formations with a potential large resource. Market trends indicate that a considerable resource is currently being developed and can supply the global market for the next 4 to 10 years. The project’s location within a landlocked country decreases its economic competitiveness with peer project and the unfavourable, but not conclusive, metallurgical results obtained during the scoping phase do not instil confidence that the project will develop into a productive mine soon. Managing the project development with future graphite demand in mind is the key to determining whether the project still has future value.
- Full Text:
- Date Issued: 2018
- Authors: Van den Berg, Jacobus Petrus
- Date: 2018
- Subjects: Graphite , Ore deposits , Geophysics , Graphite mines and mining Economic aspects Africa, East , Trenches , Project management
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63786 , vital:28489
- Description: Developing exploration projects successfully requires that the Reasonable Prospects for Eventual Economic Extraction (RPEEE) be confirmed and based on the global market perception and trend. The exploration methods applied in the attempt to establish this RPEEE must be based on a key management framework that assures the results, and eventually the conclusion, are obtained with best practical and technical approaches whilst managing the risks and capitalizing on each result. The Orom Graphite project is located within the East African Orogenic belt, a suture zone between the Congo craton and the SLAMIN shield, formed during the formation of Gondwana during the late Proterozoic to early-Phanerozoic era. The closing of the Mozambique ocean, and the eventual collision between the craton and shield, occurred along the paleo-earths equator and migrated towards lower latitudes. This, along with the period’s biodiversity boom, provided the perfect deposition environment for carbonaceous sediments which were later metamorphosed to amphibolite and granulites grade metamorphism, resulting in the carbonization and the eventual graphitization of these carbonaceous sediments. The project is located within a poorly developed part of Uganda with the closest port situated some 1 500 km to the east in Kenya. The poorly developed infrastructure along with probable high logistical cost assigns a low competitivity index if compared to the economic costs of peer projects. However, the potential resources of the Orom Graphite project suggest that the Life of Mine (LOM) can rival the largest resource currently reported within the market. The current market conditions suggest that a possible oversupply of graphite concentrate will dominate the market within the next 4 to 10 years. This suggests that new graphite projects such as the Orom Graphite project are likely to develop into the production phase once the global supply and demand stabilize. This requires the Orom Graphite project to develop from its current scoping study level to a project development study level associated with a definitive feasibility study. To date, the project developed through mapping, reconnaissance drilling, geophysical survey and trenching programs increasing the Net Present Value (NPV) considerably based upon a Cost-Based Valuation approach using Prospectivity Enhancement Multiplier (PEM). The metallurgical studies could however not produce a graphite concentrate product within industrial grade standards. The risk associated with developing the project further into the Mineral Resource Estimation (MRE) phase was quantified and risk was evaluated by implementing a point decision tree and calculating the Expected Monetary Value (EMV). Due to the unfavourable metallurgical results obtained to date, the risk associated with undertaking an additional metallurgical test is considerable with a slight chance of producing a negative project value estimated at 65%. JP van den Berg Rhodes University Overall, the Orom Graphite project contains favourable geological formations with a potential large resource. Market trends indicate that a considerable resource is currently being developed and can supply the global market for the next 4 to 10 years. The project’s location within a landlocked country decreases its economic competitiveness with peer project and the unfavourable, but not conclusive, metallurgical results obtained during the scoping phase do not instil confidence that the project will develop into a productive mine soon. Managing the project development with future graphite demand in mind is the key to determining whether the project still has future value.
- Full Text:
- Date Issued: 2018
Ilmenite megacryst-hosted melt inclusions from the Monastery kimberlite: implications for kimberlite origins
- Authors: Van Huyssteen, Aiden
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/178387 , vital:42935
- Description: Polymineralic inclusions encapsulating a daughter assemblage of crystalline phases (including silicates, oxides, and carbonates) and an amorphous glass phase, hosted in ilmenite megacrysts from the Monastery kimberlite, were investigated texturally and geochemically in order to constrain their melt origin, modeof formation, and evolution prior to quenching. The isolated nature of the melt inclusions within the ilmenite megacrysts provides an opportunity to study components of primary kimberlitic magma captured within the SCLM (4.5–6 GPa) that has been isolated from pervasive modifying processes that are common in kimberlites. The common daughter phase assemblage within the melt inclusions comprises serpentine, phlogopite, calcite, spinel, kassite, perovskite, ilmenite, and glass. The glass is Si-Mg-Fe-rich, with low Al2O3 contents. It is also K2O- and TiO2-free, with variably depleted REE. In composition, serpentine forms a crystalline equivalent to the glass. However, these phases are optically distinct. Serpentine represents two modes of formation: (i) discrete euhedral grains set within a glass matrix that represent a primary phase, crystallising directly from the entrapped melts, and (ii) as patches of partially crystallised glass that represent a secondary phase formed by the devitrification of the glass. Spinel and phlogopite form along early kimberlitic evolutionary trends and record the depletion of the melt in TiO2, Al2O3, and K2O, which typically decreases from the core to the rim of the crystals. Volatile and alkali-bearing minerals (calcite, apatite, phlogopite) crystallised within the melt inclusions from the captured alkali-rich carbonated-silicate kimberlite melt. The daughter mineral assemblage initially crystallised as euhedral and subhedral grains with a uniform composition under equilibrium conditions. Subsequent crystallisation formed grains that exhibit magmatic zoning due to their crystallisation in a progressively depleted melt. Lastly, the crystallisation of skeletal oxide grains occurred under disequilibrium conditions, at a stage of magma ascent with rapidly changing variables including temperature, melt viscosity, and diffusivity. Prior to complete crystallisation, the residual Si-Mg-Fe melt of this crystallisation process was quenched to form the observed glass. The phases that constitute the common daughter assemblage show large variations in modal proportions, forming a continuum from silicate-rich to carbonate-rich endmember inclusions, with certain daughter phases absent in some inclusions. This suggests that the melt was heterogenous at the time of capture and comprised immiscible silicic/oxidic and carbonate melts. Phase separation, therefore, may have started prior to capturing of magma batches as inclusions in ilmenite, but further segregation and crystallisation continued after these batches had become isolated from the megacryst matrix as melt inclusions. The immiscibility and co-existence of the silicic/oxidic and carbonate melts is preserved by textural features between calcite and glass, such as rounded globules of calcite grains set within a silicate glass matrix, calcite forming the matrix for euhedral silicate and oxide minerals, and calcite occupying the interior void of skeletal oxide grains set within a silicate glass matrix. Furthermore, spherulitic globular domains of Ca- and Ti-rich glasses set within a matrix of the Si-Mg-Fe glass suggest that the silicic/oxidic melt underwent further segregation into oxide-rich (Ca-Ti) and silicate-rich (Si-Mg-Fe-Al-K-Ti) melts, potentially crystallising the oxide and silicate minerals of the daughter assemblage, respectively. The abundance of incompatible trace elements and the Cr-poor composition of secondary low-Mg ilmenite as a daughter mineral within the melt inclusions (~1400 ppm Nb; <0.1 wt% Cr2O3; <0.1 wt% MgO), in addition to the Cr-poor composition of the other daughter phases within the inclusions (i.e. <0.1 wt% Cr2O3 for phlogopite and spinel), indicate that they crystallised from a similar melt as the Cr-poor, but high Mg-ilmenite megacrysts (~1400 ppm Nb; <0.1 wt% Cr2O3; ~10 wt% MgO). Furthermore, the melt inclusions are randomly distributed and no textural and/or geochemical evidence for melt infiltration of the ilmenite megacrysts was associated with the melt inclusions. These features are consistent with a primary origin for the melt inclusions which implies a cognate relationship between the megacrysts and the captured kimberlite melt. , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Van Huyssteen, Aiden
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/178387 , vital:42935
- Description: Polymineralic inclusions encapsulating a daughter assemblage of crystalline phases (including silicates, oxides, and carbonates) and an amorphous glass phase, hosted in ilmenite megacrysts from the Monastery kimberlite, were investigated texturally and geochemically in order to constrain their melt origin, modeof formation, and evolution prior to quenching. The isolated nature of the melt inclusions within the ilmenite megacrysts provides an opportunity to study components of primary kimberlitic magma captured within the SCLM (4.5–6 GPa) that has been isolated from pervasive modifying processes that are common in kimberlites. The common daughter phase assemblage within the melt inclusions comprises serpentine, phlogopite, calcite, spinel, kassite, perovskite, ilmenite, and glass. The glass is Si-Mg-Fe-rich, with low Al2O3 contents. It is also K2O- and TiO2-free, with variably depleted REE. In composition, serpentine forms a crystalline equivalent to the glass. However, these phases are optically distinct. Serpentine represents two modes of formation: (i) discrete euhedral grains set within a glass matrix that represent a primary phase, crystallising directly from the entrapped melts, and (ii) as patches of partially crystallised glass that represent a secondary phase formed by the devitrification of the glass. Spinel and phlogopite form along early kimberlitic evolutionary trends and record the depletion of the melt in TiO2, Al2O3, and K2O, which typically decreases from the core to the rim of the crystals. Volatile and alkali-bearing minerals (calcite, apatite, phlogopite) crystallised within the melt inclusions from the captured alkali-rich carbonated-silicate kimberlite melt. The daughter mineral assemblage initially crystallised as euhedral and subhedral grains with a uniform composition under equilibrium conditions. Subsequent crystallisation formed grains that exhibit magmatic zoning due to their crystallisation in a progressively depleted melt. Lastly, the crystallisation of skeletal oxide grains occurred under disequilibrium conditions, at a stage of magma ascent with rapidly changing variables including temperature, melt viscosity, and diffusivity. Prior to complete crystallisation, the residual Si-Mg-Fe melt of this crystallisation process was quenched to form the observed glass. The phases that constitute the common daughter assemblage show large variations in modal proportions, forming a continuum from silicate-rich to carbonate-rich endmember inclusions, with certain daughter phases absent in some inclusions. This suggests that the melt was heterogenous at the time of capture and comprised immiscible silicic/oxidic and carbonate melts. Phase separation, therefore, may have started prior to capturing of magma batches as inclusions in ilmenite, but further segregation and crystallisation continued after these batches had become isolated from the megacryst matrix as melt inclusions. The immiscibility and co-existence of the silicic/oxidic and carbonate melts is preserved by textural features between calcite and glass, such as rounded globules of calcite grains set within a silicate glass matrix, calcite forming the matrix for euhedral silicate and oxide minerals, and calcite occupying the interior void of skeletal oxide grains set within a silicate glass matrix. Furthermore, spherulitic globular domains of Ca- and Ti-rich glasses set within a matrix of the Si-Mg-Fe glass suggest that the silicic/oxidic melt underwent further segregation into oxide-rich (Ca-Ti) and silicate-rich (Si-Mg-Fe-Al-K-Ti) melts, potentially crystallising the oxide and silicate minerals of the daughter assemblage, respectively. The abundance of incompatible trace elements and the Cr-poor composition of secondary low-Mg ilmenite as a daughter mineral within the melt inclusions (~1400 ppm Nb; <0.1 wt% Cr2O3; <0.1 wt% MgO), in addition to the Cr-poor composition of the other daughter phases within the inclusions (i.e. <0.1 wt% Cr2O3 for phlogopite and spinel), indicate that they crystallised from a similar melt as the Cr-poor, but high Mg-ilmenite megacrysts (~1400 ppm Nb; <0.1 wt% Cr2O3; ~10 wt% MgO). Furthermore, the melt inclusions are randomly distributed and no textural and/or geochemical evidence for melt infiltration of the ilmenite megacrysts was associated with the melt inclusions. These features are consistent with a primary origin for the melt inclusions which implies a cognate relationship between the megacrysts and the captured kimberlite melt. , Thesis (MSc) -- Faculty of Science, Geology, 2021
- Full Text:
- Date Issued: 2021-04
Lateral and vertical mineral-chemical variation in high-grade ores of the Kalahari Manganese Field, and implications for ore genesis and geometallurgy
- Authors: Motilaodi, Donald
- Date: 2022-10-14
- Subjects: Manganese ores , Geometallurgy , Hydrothermal alteration , Petrology , Mineralogy , Geochemistry
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362972 , vital:65379
- Description: The Kalahari Manganese Field (KMF) is a world-class resource of manganese ore hosted by the Paleoproterozoic Hotazel banded iron formation. KMF ores are categorised into two main types, i.e., low-grade, carbonate rich, braunitic ore (Mn≤40wt%) and carbonate-free, high-grade, Ca-braunite+hausmannite ore (Mn≥44wt%). High-grade ores, also known as Wessels type from the homonymous mine in the northernmost KMF, are thought to have formed from variable degrees of hydrothermal carbonate and silica leaching from a low-grade ore precursor, termed Mamatwan-type after the homonymous mine in the southernmost KMF. This project aims to conduct a mineralogical and mineral-chemical study of representative manganese ore samples from a suite of drillcores intersecting both the upper and the lower layers in the northern KMF, covering the areas of Wessels, N’chwaning and Gloria mines. Petrographically, the high-grade Mn ore displays great variability in three-dimensional space. Texturally, the ores exhibit a great variety of textures which may or may not show preservation of the laminated and ovoidal textures that typify the postulated low-grade protore. There is also significant variation in the mineralogical and geochemical characteristics of the high-grade Mn ores both vertically and laterally. Vertical variation includes, probably for the first time, variability between the upper and lower ore layers within individual drillcores of the Hotazel sequence. Mineralogically, the ores contain variable modal abundances of the ore-forming minerals braunite (I, II, “new”) and hausmannite, and much less so of bixbyite, marokite and manganite. Common accessories include andradite, barite and low-Mn carbonate minerals. Chemically, the dominant ore minerals braunite and hausmannite, contain Fe up to 22 and 15wt% respectively, which accounts for the bulk of the iron contained in the ores. Braunite compositions also exhibit a large range with respect to their ratio of Ca/Si. Mineral-specific trace element concentrations for the same minerals measured by LA-ICP-MS, reveal generally large variations from one element to the other. When normalized against the trace element composition of bulk low-grade precursor ore, strong enrichments are recorded for both hausmannite and braunite in selected alkali/alkali earth elements, transition metals and lanthanides, such as Sc, Co, Zn, Cu, Pb, La, and Ce. These are akin to enrichments recorded in average high-grade ore. Although there is also no obvious relationship between Fe content in both hausmannite and braunite and their trace element abundances, the drillcore that captures high-grade ore with the highest trace element concentrations appears to be located most proximal to a major fault. Results collectively suggest that high-grade Mn ores of the KMF have undergone a complex hydrothermal history with a clear and significant metasomatic addition of trace elements into ore-forming minerals. First order trends in the mineralogical and mineral-chemical distribution of the ores in space, suggest hausmannite-dominated ores near the Hotazel suboutcrop, and an apparent decline in ore quality with braunite II-andradite-barite-calcite ores as the major graben fault is approached in a southwesterly direction. The latter trend appears to be at odds with prevailing fault-controlled alteration models. Elucidating that hydrothermal history of the Wessels-type high grade Mn ores of the KMF, will be crucial to understanding the compositional controls of these ores in space, and the potential impact thereof in terms of geometallurgy. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Motilaodi, Donald
- Date: 2022-10-14
- Subjects: Manganese ores , Geometallurgy , Hydrothermal alteration , Petrology , Mineralogy , Geochemistry
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362972 , vital:65379
- Description: The Kalahari Manganese Field (KMF) is a world-class resource of manganese ore hosted by the Paleoproterozoic Hotazel banded iron formation. KMF ores are categorised into two main types, i.e., low-grade, carbonate rich, braunitic ore (Mn≤40wt%) and carbonate-free, high-grade, Ca-braunite+hausmannite ore (Mn≥44wt%). High-grade ores, also known as Wessels type from the homonymous mine in the northernmost KMF, are thought to have formed from variable degrees of hydrothermal carbonate and silica leaching from a low-grade ore precursor, termed Mamatwan-type after the homonymous mine in the southernmost KMF. This project aims to conduct a mineralogical and mineral-chemical study of representative manganese ore samples from a suite of drillcores intersecting both the upper and the lower layers in the northern KMF, covering the areas of Wessels, N’chwaning and Gloria mines. Petrographically, the high-grade Mn ore displays great variability in three-dimensional space. Texturally, the ores exhibit a great variety of textures which may or may not show preservation of the laminated and ovoidal textures that typify the postulated low-grade protore. There is also significant variation in the mineralogical and geochemical characteristics of the high-grade Mn ores both vertically and laterally. Vertical variation includes, probably for the first time, variability between the upper and lower ore layers within individual drillcores of the Hotazel sequence. Mineralogically, the ores contain variable modal abundances of the ore-forming minerals braunite (I, II, “new”) and hausmannite, and much less so of bixbyite, marokite and manganite. Common accessories include andradite, barite and low-Mn carbonate minerals. Chemically, the dominant ore minerals braunite and hausmannite, contain Fe up to 22 and 15wt% respectively, which accounts for the bulk of the iron contained in the ores. Braunite compositions also exhibit a large range with respect to their ratio of Ca/Si. Mineral-specific trace element concentrations for the same minerals measured by LA-ICP-MS, reveal generally large variations from one element to the other. When normalized against the trace element composition of bulk low-grade precursor ore, strong enrichments are recorded for both hausmannite and braunite in selected alkali/alkali earth elements, transition metals and lanthanides, such as Sc, Co, Zn, Cu, Pb, La, and Ce. These are akin to enrichments recorded in average high-grade ore. Although there is also no obvious relationship between Fe content in both hausmannite and braunite and their trace element abundances, the drillcore that captures high-grade ore with the highest trace element concentrations appears to be located most proximal to a major fault. Results collectively suggest that high-grade Mn ores of the KMF have undergone a complex hydrothermal history with a clear and significant metasomatic addition of trace elements into ore-forming minerals. First order trends in the mineralogical and mineral-chemical distribution of the ores in space, suggest hausmannite-dominated ores near the Hotazel suboutcrop, and an apparent decline in ore quality with braunite II-andradite-barite-calcite ores as the major graben fault is approached in a southwesterly direction. The latter trend appears to be at odds with prevailing fault-controlled alteration models. Elucidating that hydrothermal history of the Wessels-type high grade Mn ores of the KMF, will be crucial to understanding the compositional controls of these ores in space, and the potential impact thereof in terms of geometallurgy. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
Mineral paragenesis of olmiite/poldevaartite and rhodochrosite/shigaite occurrences in the Kalahari Manganese Field, and their relation to the formation of high-grade manganese ore of Nchwaning II mine, Black Rock, South Africa
- Authors: Opperman, Alicia
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422448 , vital:71943
- Description: Access restricted. Access embargoed until 2025. , Thesis (MSc) -- Faculty of Science, Geology, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Opperman, Alicia
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422448 , vital:71943
- Description: Access restricted. Access embargoed until 2025. , Thesis (MSc) -- Faculty of Science, Geology, 2023
- Full Text:
- Date Issued: 2023-03-29
Mineralogical and geochemical constraints on the origin, alteration history and metallogenic significance of the Manganore iron-formation, Northern Cape Province, South Africa
- Authors: Papadopoulos, Vlassis
- Date: 2017
- Subjects: Banded iron formation , Transvaal Supergroup (South Africa) , Groups (Stratigraphy) South Africa , Lithostratigraphy , Petrology South Africa , Geochemistry South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65189 , vital:28702
- Description: The Manganore iron-formation (MIF) of the Transvaal Supergroup is host to the most important high-grade iron ore bodies in South Africa. Prevailing models for ore genesis invoke supergene processes performing during a long period of erosion, oxidation and weathering under tropical lateritic conditions while the role of potential hydrothermal processes is not addressed. Lack of detailed petrographical and geochemical data necessitated reexamination of the MIF through new and existing drill core exploration material. Thorough petrographical investigation revealed a multi-event complex alteration history involving hydrothermal activity. Iron and silica mobility during alteration is demonstrated by a series of replacement, overprinting, crosscutting textures, extensive silicification and hematitization. Metasomatized textures such as pseudomorphs of primary magnetite, carbonate minerals and chert pods/lenses point to an alteration occurring in layer- controlled fronts and link stratigraphically the MIF to Kuruman and Griquatown iron- formations. Whole-rock geochemical data verify textural observations suggesting strong enrichment of iron or silica in meter-scale horizons, expressed by different generations of quartz and hematite. High-grade iron ore is highly enriched in TiO2 and Al2O3 compared to the protolith while both BIF and iron ore display highly increased concentrations of trace elements (transition metals and HFSE). Oxygen isotopes from different quartz textures reveal little to none isotopic exchangement during alteration whereas O isotopes from hematite are in concert to values from literature and suggest two different generations of hematite. A total of 20 minerals apart from quartz and hematite were documented. An earlier alkali/HFSE alteration event that is believed to have affected the overlying Gamagara shales is recorded in the BIF by the presence of muscovite, apatite, rutile, zircon and xenotime. A later and possibly ongoing event of succeeding hydrothermal pulses involves mainly sulphates (gypsum, baryte, celestine), pyrite, carbonates (siderite, calcite) and silicates (berthierine and tourmaline). Alkali-bearing brines persistently exploit the BIF mainly through karstification-related secondary porosity, are evidently carrying iron and are proposed to participate in or control the iron enrichment by facilitating removal of silica. The source of metals, sulfur and carbon is attributed to the underlying Campbellrand dolomites and especially to the upper Gamogaan Formation. The unconformable contact between BIF and the overlying shales is suggested as a suitable fluid conduit for the development of the observed BIF and shale-derived high-grade hematite iron ore.
- Full Text:
- Date Issued: 2017
- Authors: Papadopoulos, Vlassis
- Date: 2017
- Subjects: Banded iron formation , Transvaal Supergroup (South Africa) , Groups (Stratigraphy) South Africa , Lithostratigraphy , Petrology South Africa , Geochemistry South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65189 , vital:28702
- Description: The Manganore iron-formation (MIF) of the Transvaal Supergroup is host to the most important high-grade iron ore bodies in South Africa. Prevailing models for ore genesis invoke supergene processes performing during a long period of erosion, oxidation and weathering under tropical lateritic conditions while the role of potential hydrothermal processes is not addressed. Lack of detailed petrographical and geochemical data necessitated reexamination of the MIF through new and existing drill core exploration material. Thorough petrographical investigation revealed a multi-event complex alteration history involving hydrothermal activity. Iron and silica mobility during alteration is demonstrated by a series of replacement, overprinting, crosscutting textures, extensive silicification and hematitization. Metasomatized textures such as pseudomorphs of primary magnetite, carbonate minerals and chert pods/lenses point to an alteration occurring in layer- controlled fronts and link stratigraphically the MIF to Kuruman and Griquatown iron- formations. Whole-rock geochemical data verify textural observations suggesting strong enrichment of iron or silica in meter-scale horizons, expressed by different generations of quartz and hematite. High-grade iron ore is highly enriched in TiO2 and Al2O3 compared to the protolith while both BIF and iron ore display highly increased concentrations of trace elements (transition metals and HFSE). Oxygen isotopes from different quartz textures reveal little to none isotopic exchangement during alteration whereas O isotopes from hematite are in concert to values from literature and suggest two different generations of hematite. A total of 20 minerals apart from quartz and hematite were documented. An earlier alkali/HFSE alteration event that is believed to have affected the overlying Gamagara shales is recorded in the BIF by the presence of muscovite, apatite, rutile, zircon and xenotime. A later and possibly ongoing event of succeeding hydrothermal pulses involves mainly sulphates (gypsum, baryte, celestine), pyrite, carbonates (siderite, calcite) and silicates (berthierine and tourmaline). Alkali-bearing brines persistently exploit the BIF mainly through karstification-related secondary porosity, are evidently carrying iron and are proposed to participate in or control the iron enrichment by facilitating removal of silica. The source of metals, sulfur and carbon is attributed to the underlying Campbellrand dolomites and especially to the upper Gamogaan Formation. The unconformable contact between BIF and the overlying shales is suggested as a suitable fluid conduit for the development of the observed BIF and shale-derived high-grade hematite iron ore.
- Full Text:
- Date Issued: 2017
Mineralogical, geochemical and lead isotopic analysis of the lead mineralization of the Skorpion Deposit, south western Namibia
- Authors: Uazeua, Kakunauua
- Date: 2019
- Subjects: Zinc ores -- Namibia , Formations (Geology) -- Namibia , Mineralogy -- Namibia , Lead -- Metallurgy -- Namibia , Lead -- Isotopes -- Namibia
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68391 , vital:29250
- Description: The Skorpion none-sulphide Zinc Deposit is located in the para-autochtonous Port Nolloth Zone of the Gariep Belt, which overlays the Lower-Proterozoic Orange River Group basement rocks (Corrans et al., 1993). Situated in close proximity to the larger Rosh Pinah Zn-Pb deposit, the Skorpion Deposit contained a resource of 24.6 Mt at 10.6 % Zn and unquantified Cu and Pb prior to mining. To date, zinc has been the only metal exploited, with minor amounts of copper as a by-product. This study aims at understanding the mineralogical composition of the Skorpion lead mineralization and understanding the relationship between lead and the major metals such as zinc and copper in order to form a basis for further work that could determine the potential of processing lead as a by-product. As part of the study, work was also done on lead isotopes mainly with the aim of understanding the mineralization genesis and to determine the differences between the Skorpion and Rosh Pinah deposit which rationalize the inferior economic potential of the Skorpion lead mineralization. Results of the study have shown that majority of the lead mineralization is hosted by the felsic metavolcanics as galena and subordinately in the metasiliciclastics as pyromorphite, a lead manganese phosphate. In terms of the mineral textures, the lead minerals appear to be mainly secondary phases that have been remobilized and reprecipitated around pyrite, within pyrite cracks and intergrown with minerals such as chalcocite and greenockite. Lead has been mainly concentrated along fault zones. The elevated pyromorphite concentrations tend to occur within gossanous zones in close association with iron and manganese oxides. These textures represent supergene enrichment of a sulphide proto ore. However, contrary to copper and zinc mineralization, lead was not remobilized far from the proto ore merely as a function of its poor mobility in acidic fluids (Reddy et al., 1995). This substantiates the concentration of secondary lead in the felsic metavolcanics and to a much lesser extent, in the metasiliciclastics. Both secondary zinc and copper were reprecipitated in the metasiliciclastics, further away from the sulphide proto ore, hosted mainly by the felsic metavolcanics. The average lead isotope ratios of 206Pb/204Pb (17.26), 207Pb/204Pb (15.60) and 208Pb/204Pb (37.42) resemble results provided by Frimmel (2004) for both the Skorpion and Rosh Pinah deposits. For the Skorpion samples from Frimmel (2004) had the following average ratios: 206Pb/204Pb (17.29), 207Pb/204Pb (15.59) and 208Pb/204Pb (37.51). The Rosh Pinah samples had the following average ratios: 206Pb/204Pb (17.17), 207Pb/204Pb (15.61) and 208Pb/204Pb (37.45). These results indicate lead derivation from the lower 2.0 Ga Eburnean pre-Gariep basement in agreement with and Frimmel et al. (2004). The host felsic metavolcanics might have been derived from melting of the basement rocks during the formation of the Adamastor Ocean. In comparison to the Rosh Pinah deposit lead isotope signatures, the Skorpion lead isotopes overlap with the Rosh Pinah deposit isotopes, but have a much narrower range. This is an indication of a much shorter lived and potentially faster mineralization event contrary to the SEDEX type Rosh Pinah deposit. The smaller tonnage of the Skorpion deposit, its inferior lead concentrations and the elevated radiogenic lead isotopes point toward a VMS deposit which was formed in a small graben fed by shallow conduits during a short lived mineralization event. Sedimentary rocks covered the forming deposit at a fast rate and impaired the deposit advancement. The interaction between the upper crustal rocks and the mineralizing fluids is what may have resulted in the elevated radiogenic lead signature. In contrast to this, SEDEX deposits such as the Rosh Pinah Deposit, are generally fed by deep seated conduits that allow more longer lived leaching of metals from the underlying basement rocks and generally allow minor influence from upper crustal rocks.
- Full Text:
- Date Issued: 2019
- Authors: Uazeua, Kakunauua
- Date: 2019
- Subjects: Zinc ores -- Namibia , Formations (Geology) -- Namibia , Mineralogy -- Namibia , Lead -- Metallurgy -- Namibia , Lead -- Isotopes -- Namibia
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68391 , vital:29250
- Description: The Skorpion none-sulphide Zinc Deposit is located in the para-autochtonous Port Nolloth Zone of the Gariep Belt, which overlays the Lower-Proterozoic Orange River Group basement rocks (Corrans et al., 1993). Situated in close proximity to the larger Rosh Pinah Zn-Pb deposit, the Skorpion Deposit contained a resource of 24.6 Mt at 10.6 % Zn and unquantified Cu and Pb prior to mining. To date, zinc has been the only metal exploited, with minor amounts of copper as a by-product. This study aims at understanding the mineralogical composition of the Skorpion lead mineralization and understanding the relationship between lead and the major metals such as zinc and copper in order to form a basis for further work that could determine the potential of processing lead as a by-product. As part of the study, work was also done on lead isotopes mainly with the aim of understanding the mineralization genesis and to determine the differences between the Skorpion and Rosh Pinah deposit which rationalize the inferior economic potential of the Skorpion lead mineralization. Results of the study have shown that majority of the lead mineralization is hosted by the felsic metavolcanics as galena and subordinately in the metasiliciclastics as pyromorphite, a lead manganese phosphate. In terms of the mineral textures, the lead minerals appear to be mainly secondary phases that have been remobilized and reprecipitated around pyrite, within pyrite cracks and intergrown with minerals such as chalcocite and greenockite. Lead has been mainly concentrated along fault zones. The elevated pyromorphite concentrations tend to occur within gossanous zones in close association with iron and manganese oxides. These textures represent supergene enrichment of a sulphide proto ore. However, contrary to copper and zinc mineralization, lead was not remobilized far from the proto ore merely as a function of its poor mobility in acidic fluids (Reddy et al., 1995). This substantiates the concentration of secondary lead in the felsic metavolcanics and to a much lesser extent, in the metasiliciclastics. Both secondary zinc and copper were reprecipitated in the metasiliciclastics, further away from the sulphide proto ore, hosted mainly by the felsic metavolcanics. The average lead isotope ratios of 206Pb/204Pb (17.26), 207Pb/204Pb (15.60) and 208Pb/204Pb (37.42) resemble results provided by Frimmel (2004) for both the Skorpion and Rosh Pinah deposits. For the Skorpion samples from Frimmel (2004) had the following average ratios: 206Pb/204Pb (17.29), 207Pb/204Pb (15.59) and 208Pb/204Pb (37.51). The Rosh Pinah samples had the following average ratios: 206Pb/204Pb (17.17), 207Pb/204Pb (15.61) and 208Pb/204Pb (37.45). These results indicate lead derivation from the lower 2.0 Ga Eburnean pre-Gariep basement in agreement with and Frimmel et al. (2004). The host felsic metavolcanics might have been derived from melting of the basement rocks during the formation of the Adamastor Ocean. In comparison to the Rosh Pinah deposit lead isotope signatures, the Skorpion lead isotopes overlap with the Rosh Pinah deposit isotopes, but have a much narrower range. This is an indication of a much shorter lived and potentially faster mineralization event contrary to the SEDEX type Rosh Pinah deposit. The smaller tonnage of the Skorpion deposit, its inferior lead concentrations and the elevated radiogenic lead isotopes point toward a VMS deposit which was formed in a small graben fed by shallow conduits during a short lived mineralization event. Sedimentary rocks covered the forming deposit at a fast rate and impaired the deposit advancement. The interaction between the upper crustal rocks and the mineralizing fluids is what may have resulted in the elevated radiogenic lead signature. In contrast to this, SEDEX deposits such as the Rosh Pinah Deposit, are generally fed by deep seated conduits that allow more longer lived leaching of metals from the underlying basement rocks and generally allow minor influence from upper crustal rocks.
- Full Text:
- Date Issued: 2019