The role of northwest striking structures in controlling highgrade ore shoots at the Syama Gold Mine, Mali, West Africa
- Authors: Soro, Ali
- Date: 2020
- Subjects: Syama Gold Mine , Gold ores -- Geology -- Mali , Veins (Geology) -- Mali
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145209 , vital:38418
- Description: This study intended to investigate the relationship between the NW striking structures and the high-grade ore shoots at the Syama gold mine in Mali, West Africa. All structural data collected since 1987 from drill core have been integrated to allow the interpretation and modelling of these NW-SE structures. The structures collected were grouped into three main groups; foliations/shears/faults, veins and joints/contacts/fractures. Micromine software was used to plot the structures, printed out on A3 paper and interpreted manually using tracing paper. Analysis and interpretation of stereographic plots has shown that the majority of the high-grade zones are generally located at the intersection of the NNE structures and the NW structures. The observed cross-cutting relationship between the NNE and the NW structures suggests two different generation of faults. It is suggested that the NW structures were active during the D4 deformation event (Standing, 2007) and have played a role in reactivating earlier (D3) NNE structures, allowing greater fluid flow and enhancing the gold grade. These zones are mainly defined by brecciation and stockwork veining. The E-W structures are believed to be the latest and are attributed to the D5 event. Although gold mineralisation is grossly controlled by the NNE structures, the NW structures need to be considered as major gold enrichment upgrading factors at Syama. It is therefore strongly recommended that ongoing exploration at Syama specifically target the intersection of the NW and NNE structures as favourable zones for high-grade mineralisation.
- Full Text:
- Date Issued: 2020
- Authors: Soro, Ali
- Date: 2020
- Subjects: Syama Gold Mine , Gold ores -- Geology -- Mali , Veins (Geology) -- Mali
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145209 , vital:38418
- Description: This study intended to investigate the relationship between the NW striking structures and the high-grade ore shoots at the Syama gold mine in Mali, West Africa. All structural data collected since 1987 from drill core have been integrated to allow the interpretation and modelling of these NW-SE structures. The structures collected were grouped into three main groups; foliations/shears/faults, veins and joints/contacts/fractures. Micromine software was used to plot the structures, printed out on A3 paper and interpreted manually using tracing paper. Analysis and interpretation of stereographic plots has shown that the majority of the high-grade zones are generally located at the intersection of the NNE structures and the NW structures. The observed cross-cutting relationship between the NNE and the NW structures suggests two different generation of faults. It is suggested that the NW structures were active during the D4 deformation event (Standing, 2007) and have played a role in reactivating earlier (D3) NNE structures, allowing greater fluid flow and enhancing the gold grade. These zones are mainly defined by brecciation and stockwork veining. The E-W structures are believed to be the latest and are attributed to the D5 event. Although gold mineralisation is grossly controlled by the NNE structures, the NW structures need to be considered as major gold enrichment upgrading factors at Syama. It is therefore strongly recommended that ongoing exploration at Syama specifically target the intersection of the NW and NNE structures as favourable zones for high-grade mineralisation.
- Full Text:
- Date Issued: 2020
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
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
Petrography and geochemistry of the Masoke Iron Formation and its associated ferruginous counterparts, kanye basin Botswana
- Authors: Nkabelane, Ndifelani Oriel
- Date: 2019
- Subjects: Petrology -- South Africa , Geochemistry -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/115221 , vital:34101
- Description: A sequence of Transvaal Supergroup sediments extends into southern Botswana beneath Kalahari cover as the Kanye basin, these are known to host billions of tons @ 60>Fe. Masoke Iron Formation (Kanye Basin) which is stratigraphic correlative of The Ghaap Group and Chuniespoort Group of the Griqualand West basin and Transvaal basin, respectively. The Palaeoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa hosts high grade (>60% Fe) hematitic and specularitic iron and manganese mineralisation. It is therefore important to study and record the petrographic, mineralogy and geochemistry of Masoke Iron Formation, compare the results to the much known Kuruman and Griquatown Iron Formations. This study systematically investigate and record the petrography, mineralogy and geochemistry of all Masoke Iron Formation of Taupone Group in the Kanye Basin, which is stratigraphic correlative of The Ghaap Group and Chuniespoort Group of the Griqualand West basin and Transvaal basin, respectively. The further objective is to compare Masoke Iron Formation to the equivalent units in the Transvaal basin and Griqualand basin. In contrast to both Transvaal and Griqualand West Basin the Masoke iron Formation (Kanye Basin) has not been the subject of systematic scientific investigations. The study covers three main areas in the Kanye Basin: Keng Pan Area, Ukwi/Moretlwa hill and Janeng Hill Area. The mineralogy and geochemistry of these areas are presented in this study. Kanye Basin has a potential to host a large iron ore deposit, the geological setting in this area incorporates many of the elements necessary for iron ore formation. These include: banded iron formation (BIF), major unconformities with prolonged periods of weathering, carbonate sequences etc. In addition, several large deposits and mines are known from this area. This area can potentially have both hypogene and supergene enrichment of BIF. In this model, prospectively for new deposits is a function of the following: presence of iron formation units, proximity of mapped Asbestos Hills and Voëlwater BIF, thrust faulting (as indicated by the aero-magnetic interpretation), duplication of the ore horizon by folding, intersection of the BIF by major extensional fault, proximity of Olifantshoek/Waterberg outcrop, Gamagara unconformity, presence of carbonates (dolomites) and thin Kalahari sand cover. Major BIF units in the area of study include: the Masoke Iron Formation, equivalent to Kuruman Formation of the Asbestos Hills Subgroup, the Rooinekke iron formation of the Koegas Subgroup and the Hotazel Formation of the Voëlwater Subgroup. Supergene enrichment of these BIFs may occur wherever they are overlain by a major regional unconformity. The base of the Waterberg and the OlifantshoekSupergroups represent major unconformities in this regional target area. Potential for hypogene deposits is indicated by faulting (preferably extensional) proximal to BIF.
- Full Text:
- Date Issued: 2019
- Authors: Nkabelane, Ndifelani Oriel
- Date: 2019
- Subjects: Petrology -- South Africa , Geochemistry -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/115221 , vital:34101
- Description: A sequence of Transvaal Supergroup sediments extends into southern Botswana beneath Kalahari cover as the Kanye basin, these are known to host billions of tons @ 60>Fe. Masoke Iron Formation (Kanye Basin) which is stratigraphic correlative of The Ghaap Group and Chuniespoort Group of the Griqualand West basin and Transvaal basin, respectively. The Palaeoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa hosts high grade (>60% Fe) hematitic and specularitic iron and manganese mineralisation. It is therefore important to study and record the petrographic, mineralogy and geochemistry of Masoke Iron Formation, compare the results to the much known Kuruman and Griquatown Iron Formations. This study systematically investigate and record the petrography, mineralogy and geochemistry of all Masoke Iron Formation of Taupone Group in the Kanye Basin, which is stratigraphic correlative of The Ghaap Group and Chuniespoort Group of the Griqualand West basin and Transvaal basin, respectively. The further objective is to compare Masoke Iron Formation to the equivalent units in the Transvaal basin and Griqualand basin. In contrast to both Transvaal and Griqualand West Basin the Masoke iron Formation (Kanye Basin) has not been the subject of systematic scientific investigations. The study covers three main areas in the Kanye Basin: Keng Pan Area, Ukwi/Moretlwa hill and Janeng Hill Area. The mineralogy and geochemistry of these areas are presented in this study. Kanye Basin has a potential to host a large iron ore deposit, the geological setting in this area incorporates many of the elements necessary for iron ore formation. These include: banded iron formation (BIF), major unconformities with prolonged periods of weathering, carbonate sequences etc. In addition, several large deposits and mines are known from this area. This area can potentially have both hypogene and supergene enrichment of BIF. In this model, prospectively for new deposits is a function of the following: presence of iron formation units, proximity of mapped Asbestos Hills and Voëlwater BIF, thrust faulting (as indicated by the aero-magnetic interpretation), duplication of the ore horizon by folding, intersection of the BIF by major extensional fault, proximity of Olifantshoek/Waterberg outcrop, Gamagara unconformity, presence of carbonates (dolomites) and thin Kalahari sand cover. Major BIF units in the area of study include: the Masoke Iron Formation, equivalent to Kuruman Formation of the Asbestos Hills Subgroup, the Rooinekke iron formation of the Koegas Subgroup and the Hotazel Formation of the Voëlwater Subgroup. Supergene enrichment of these BIFs may occur wherever they are overlain by a major regional unconformity. The base of the Waterberg and the OlifantshoekSupergroups represent major unconformities in this regional target area. Potential for hypogene deposits is indicated by faulting (preferably extensional) proximal to BIF.
- Full Text:
- Date Issued: 2019
Sulphide textures and compositions associated with the hydrothermal/magmatic system of the Twangiza gold deposit (South Kivu, DRC)
- Authors: Busane, Emmanuel Aganze
- Date: 2019
- Subjects: Gold mines and mining -- Congo (Democratic Republic) , Geology -- Congo (Democratic Republic) , Hydrothermal alteration -- Congo (Democratic Republic) , Sulphide minerals -- Congo (Democratic Republic) , Gold ores -- Geology -- Congo (Democratic Republic) , Geochemistry -- Congo (Democratic Republic) , Twangiza Mine (Congo (Democratic Republic))
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76588 , vital:30610
- Description: Twangiza mine is a gold deposit situated in the eastern Democratic Republic of Congo. The rock types at the Twangiza Mine consist of black shale, including carbonaceous mudstone and thin intercalated layers of siltstone, and feldspar-rich granitoid intrusive sills, referred to as albitite, folded into a major antiformal structure. The gold mineralization at the mine is commonly found associated with sulphides. The sulphide textures and compositions of mineralized and unmineralized samples of black shales, albitite sills and hydrothermal veins in the mine are considered for the understanding of the spatial association of gold with sulphides and gold mineralization history of the mine. The sulphides within the Twangiza mine consist of pyrite, arsenopyrite, pyrrhotite, chalcopyrite and rare cobaltite. The primary pyrite texture occurs in unmineralized black shale and is interpreted to be diagenetic. It consists of fine-grained anhedral pyrite crystals aggregating into spherical nodules and formed in replacement of organic material during the diagenesis process. The secondary pyrite textures resulted from the hydrothermal fluids activity and include (i) aggregates of annealed anhedral crystals into sulphide-rich lenses; (ii) elongated anhedral pyrite in the form of short stringers; (iii) fine-grained subhedral to euhedral pyrite randomly distributed within the rock matrix; (iv) euhedral zoned pyrite crystals occurring within veins; (v) aggregations of fine-grained anhedral pyrite, locally distributed in the matrix; (vi) abundant dissemination of fine-grained subhedral to anhedral pyrite crystals within the vein selvedge in the host rock; (vii) and coarse-grained massive pyrite bodies. The pyrite major elemental composition does not vary significantly in the different textures and sample types. The Fe content ranges from 44.57 to 46.40 wt. %, and the S content ranges from 53.75 to 55.25 wt. %. Pyrite from mineralized black shale and hydrothermal veins contains relatively higher concentrations of As (~ 1 wt. %) than pyrite from other sample types. The arsenopyrite commonly occurs as fine-grained anhedral crystals as inclusions within pyrite, medium-grained crystal intergrowing with pyrite and/or as coarse-grained massive arsenopyrite bodies in the massive sulphide veins. The arsenopyrite composition is uniform in all textural and sample type with Fe content ranging from 33.44 to 35.20 wt. %, S content ranging from 21.13 to 22.55 wt. % and As content ranging from 42.20 to 43.97 wt. %. In mineralized black shale and unmineralized black shale, the arsenopyrite shows, however, minor concentrations of Ni with 0.39 and 0.70 wt. % respectively. The pyrrhotite occurs as fine-grained anhedral patchy crystals randomly distributed within the rock matrix of unmineralized black shale and unmineralized granitoid, and / or as inclusions within pyrite in mineralized granitoid. The pyrrhotite shows a uniform composition in all samples and textural types, though minor concentrations of Ni (2.06 wt. %) content are reported in unmineralized granitoid. Chalcopyrite occurs as fine-grained crystals in inclusions within pyrite; and cobaltite occurs as rare fine-grained anhedral crystals occasionally disseminated in the albitite sill matrix. The chalcopyrite composition does not vary considerably in all sample and textural types, and cobaltite shows minor concentrations of Ni (4.55 wt. %) and Fe (3.45 wt. %). Native gold grains are commonly found associated with the secondary pyrite texture especially within the sulphide-rich lenses and in the massive sulphide veins, and are almost pure with ~97 wt. %. A Na-rich hydrothermal fluid from low-grade metamorphism associated with the E-W compressive tectonic event, which caused formation of the antiform structure which control the mineralization in the deposit area, led to the albitization of the deposit rocks and specially the alteration of the granitic assemblage to form albitite, and the deposition of aggregates of fine-grained anhedral crystals and growth and annealing of pyrite in sulphide-rich lenses. Afterward, the CO2-rich hydrothermal fluids influx circulated through reactivated structures, including quartz veins, and led to the precipitation of dolomite, ankerite, siderite and magnesite. They also led to the precipitation of pyrite of secondary textures as well as arsenopyrite, chalcopyrite and formation of pyrrhotite from the desulphurization of early pyrite. The CO2-rich hydrothermal fluids probably leached gold and other trace elements such as As, Co, etc. from the sedimentary host rocks and deposited them into suitable traps, such as the sulphide-rich lenses and massive sulphide bodies, preferably within the hinge zone of anticline axis constituting a hydrothermal fluid pathway.
- Full Text:
- Date Issued: 2019
- Authors: Busane, Emmanuel Aganze
- Date: 2019
- Subjects: Gold mines and mining -- Congo (Democratic Republic) , Geology -- Congo (Democratic Republic) , Hydrothermal alteration -- Congo (Democratic Republic) , Sulphide minerals -- Congo (Democratic Republic) , Gold ores -- Geology -- Congo (Democratic Republic) , Geochemistry -- Congo (Democratic Republic) , Twangiza Mine (Congo (Democratic Republic))
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76588 , vital:30610
- Description: Twangiza mine is a gold deposit situated in the eastern Democratic Republic of Congo. The rock types at the Twangiza Mine consist of black shale, including carbonaceous mudstone and thin intercalated layers of siltstone, and feldspar-rich granitoid intrusive sills, referred to as albitite, folded into a major antiformal structure. The gold mineralization at the mine is commonly found associated with sulphides. The sulphide textures and compositions of mineralized and unmineralized samples of black shales, albitite sills and hydrothermal veins in the mine are considered for the understanding of the spatial association of gold with sulphides and gold mineralization history of the mine. The sulphides within the Twangiza mine consist of pyrite, arsenopyrite, pyrrhotite, chalcopyrite and rare cobaltite. The primary pyrite texture occurs in unmineralized black shale and is interpreted to be diagenetic. It consists of fine-grained anhedral pyrite crystals aggregating into spherical nodules and formed in replacement of organic material during the diagenesis process. The secondary pyrite textures resulted from the hydrothermal fluids activity and include (i) aggregates of annealed anhedral crystals into sulphide-rich lenses; (ii) elongated anhedral pyrite in the form of short stringers; (iii) fine-grained subhedral to euhedral pyrite randomly distributed within the rock matrix; (iv) euhedral zoned pyrite crystals occurring within veins; (v) aggregations of fine-grained anhedral pyrite, locally distributed in the matrix; (vi) abundant dissemination of fine-grained subhedral to anhedral pyrite crystals within the vein selvedge in the host rock; (vii) and coarse-grained massive pyrite bodies. The pyrite major elemental composition does not vary significantly in the different textures and sample types. The Fe content ranges from 44.57 to 46.40 wt. %, and the S content ranges from 53.75 to 55.25 wt. %. Pyrite from mineralized black shale and hydrothermal veins contains relatively higher concentrations of As (~ 1 wt. %) than pyrite from other sample types. The arsenopyrite commonly occurs as fine-grained anhedral crystals as inclusions within pyrite, medium-grained crystal intergrowing with pyrite and/or as coarse-grained massive arsenopyrite bodies in the massive sulphide veins. The arsenopyrite composition is uniform in all textural and sample type with Fe content ranging from 33.44 to 35.20 wt. %, S content ranging from 21.13 to 22.55 wt. % and As content ranging from 42.20 to 43.97 wt. %. In mineralized black shale and unmineralized black shale, the arsenopyrite shows, however, minor concentrations of Ni with 0.39 and 0.70 wt. % respectively. The pyrrhotite occurs as fine-grained anhedral patchy crystals randomly distributed within the rock matrix of unmineralized black shale and unmineralized granitoid, and / or as inclusions within pyrite in mineralized granitoid. The pyrrhotite shows a uniform composition in all samples and textural types, though minor concentrations of Ni (2.06 wt. %) content are reported in unmineralized granitoid. Chalcopyrite occurs as fine-grained crystals in inclusions within pyrite; and cobaltite occurs as rare fine-grained anhedral crystals occasionally disseminated in the albitite sill matrix. The chalcopyrite composition does not vary considerably in all sample and textural types, and cobaltite shows minor concentrations of Ni (4.55 wt. %) and Fe (3.45 wt. %). Native gold grains are commonly found associated with the secondary pyrite texture especially within the sulphide-rich lenses and in the massive sulphide veins, and are almost pure with ~97 wt. %. A Na-rich hydrothermal fluid from low-grade metamorphism associated with the E-W compressive tectonic event, which caused formation of the antiform structure which control the mineralization in the deposit area, led to the albitization of the deposit rocks and specially the alteration of the granitic assemblage to form albitite, and the deposition of aggregates of fine-grained anhedral crystals and growth and annealing of pyrite in sulphide-rich lenses. Afterward, the CO2-rich hydrothermal fluids influx circulated through reactivated structures, including quartz veins, and led to the precipitation of dolomite, ankerite, siderite and magnesite. They also led to the precipitation of pyrite of secondary textures as well as arsenopyrite, chalcopyrite and formation of pyrrhotite from the desulphurization of early pyrite. The CO2-rich hydrothermal fluids probably leached gold and other trace elements such as As, Co, etc. from the sedimentary host rocks and deposited them into suitable traps, such as the sulphide-rich lenses and massive sulphide bodies, preferably within the hinge zone of anticline axis constituting a hydrothermal fluid pathway.
- Full Text:
- Date Issued: 2019
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, 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
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
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
Primary controls on iron and manganese distribution in sphalerite of the Gams Formation, Gamsberg zinc deposit, Namaqualand, South Africa
- Authors: Poignant-Molina, Léo
- Date: 2018
- Subjects: Sphalerite , Sphalerite South Africa Gamsberg , Manganese South Africa Gamsberg , Zinc mines and mining South Africa Gamsberg , Geochemistry South Africa Gamsberg , Metamorphism (Geology) , Electron probe microanalysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63775 , vital:28488
- Description: The Gamsberg deposit is a 200 Mt zinc reserve belonging to the world class base metalrich Aggeneys-Gamsberg mining district. A rifting environment permitted the development of four proximal SEDEX-type deposits whereby Gamsberg is localized in the eastern side of the district and characterised by a peculiar enrichment in manganese. This study investigates the geochemistry of sphalerite in the Gams Formation holding the economic units of the deposit. Microscopic petrography revealed that most of primary textures have been overprinted by recrystallization, alteration, replacement and deformational textures produced during the polyphase metamorphism of the Namaquan Orogeny. Therefore, EPMA analysis provided the bulk of information to define the geochemical distribution of sphalerite. A lateral variation was noticed throughout the Gams Formation, whereby the North orebody presents Zn-rich and Fe+Mn-poor sphalerite while the West and East orebodies contain Zn-poor and Fe-Mn-rich sphalerite. This feature has been interpreted as the association of a chemocline and a variation in the basin topography defining deep Mn+Fe-rich zones and shallow Mn+Fe-poor zones in the primitive basin. It is suggested that mineralized hot brines mixed with seawater developed the chemocline. The uneven topography shaped the geochemical variation between the actual orebodies.
- Full Text:
- Date Issued: 2018
- Authors: Poignant-Molina, Léo
- Date: 2018
- Subjects: Sphalerite , Sphalerite South Africa Gamsberg , Manganese South Africa Gamsberg , Zinc mines and mining South Africa Gamsberg , Geochemistry South Africa Gamsberg , Metamorphism (Geology) , Electron probe microanalysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63775 , vital:28488
- Description: The Gamsberg deposit is a 200 Mt zinc reserve belonging to the world class base metalrich Aggeneys-Gamsberg mining district. A rifting environment permitted the development of four proximal SEDEX-type deposits whereby Gamsberg is localized in the eastern side of the district and characterised by a peculiar enrichment in manganese. This study investigates the geochemistry of sphalerite in the Gams Formation holding the economic units of the deposit. Microscopic petrography revealed that most of primary textures have been overprinted by recrystallization, alteration, replacement and deformational textures produced during the polyphase metamorphism of the Namaquan Orogeny. Therefore, EPMA analysis provided the bulk of information to define the geochemical distribution of sphalerite. A lateral variation was noticed throughout the Gams Formation, whereby the North orebody presents Zn-rich and Fe+Mn-poor sphalerite while the West and East orebodies contain Zn-poor and Fe-Mn-rich sphalerite. This feature has been interpreted as the association of a chemocline and a variation in the basin topography defining deep Mn+Fe-rich zones and shallow Mn+Fe-poor zones in the primitive basin. It is suggested that mineralized hot brines mixed with seawater developed the chemocline. The uneven topography shaped the geochemical variation between the actual orebodies.
- Full Text:
- Date Issued: 2018
Sulphur isotope study of pyrite from the Twangiza-Namoya Gold Belt, (South Kivu, DRC): a proxy of gold provenance
- Moloto, Thapelo Refiloe Patience
- Authors: Moloto, Thapelo Refiloe Patience
- Date: 2018
- Subjects: Isotope geology -- Congo (Democratic Republic) , Pyrites -- Congo (Democratic Republic) , Gold mines and mining -- Congo (Democratic Republic) , Sulfur -- Isotopes -- Congo (Democratic Republic) , Hydrothermal deposits -- Congo (Democratic Republic) , Twangiza-Namoya Gold Belt, (South Kivu, DRC)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60552 , vital:27793
- Description: Gold in the highly prospective Twangiza-Namoya Gold Belt (TNGB) in the eastern Democratic Republic of Congo (DRC), with its four main deposits at Twangiza, Kamituga, Lugushwa and Namoya, appears to be correlated with the presence of sulphide minerals. Sulphur isotopic compositions of pyrite in the metasedimentary host rocks and in hydrothermal veins are used to identify the possible primary sources of hydrothermal sulphur and, by proxy, hydrothermal gold. The sulphur isotope signatures of the pyrites from the TNGB deposits show an overall range from -18.4%o to +22.6%o. S34 values in host rock pyrite are: -2.2%o to +3.0%o (Twangiza deposit), -4.2%o to -0.6% (Kamituga deposit), -18.4% to -12.7% (Lugushwa deposit), and +12.4% to +22.6% (Namoya deposit). The sulphur isotopic signature of vein pyrite is -5.2% to +3.0% (Twangiza deposit), -9.1% to -7.4% (Kamituga deposit), -0.3% to +3.2% (Lugushwa deposit) and +1.3% to +20.4% (Namoya deposit). The isotopic data indicate a primary sedimentary to evaporitic source of sulphur in the host rock pyrite. Pyrite from metadiorites shows magmatic S isotope compositions. Native gold was found in both sedimentary host rock and vein samples. This indicates that native gold was present in the primary metasedimentary sequence of the TNGB. Some vein pyrites in the TNGB have isotopic signatures that are similar to that of the host rock pyrite. These veins have formed from fluids extracted from the hosting metasedimentary sequence. Conversely, other vein pyrite shows different S34S values compared to the host rock pyrite, suggesting a fluid source that is different from the sedimentary source. Possibly, particularly in the Lugushwa deposit, an igneous source may have released sulphur and possibly gold bearing fluids in addition to those extracted from the sedimentary sequences in the TNGB. However, there is abundant evidence for sulphur and gold mobilised in the sedimentary host rocks and precipitated in the hydrothermal system of the TNGB.
- Full Text:
- Date Issued: 2018
- Authors: Moloto, Thapelo Refiloe Patience
- Date: 2018
- Subjects: Isotope geology -- Congo (Democratic Republic) , Pyrites -- Congo (Democratic Republic) , Gold mines and mining -- Congo (Democratic Republic) , Sulfur -- Isotopes -- Congo (Democratic Republic) , Hydrothermal deposits -- Congo (Democratic Republic) , Twangiza-Namoya Gold Belt, (South Kivu, DRC)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60552 , vital:27793
- Description: Gold in the highly prospective Twangiza-Namoya Gold Belt (TNGB) in the eastern Democratic Republic of Congo (DRC), with its four main deposits at Twangiza, Kamituga, Lugushwa and Namoya, appears to be correlated with the presence of sulphide minerals. Sulphur isotopic compositions of pyrite in the metasedimentary host rocks and in hydrothermal veins are used to identify the possible primary sources of hydrothermal sulphur and, by proxy, hydrothermal gold. The sulphur isotope signatures of the pyrites from the TNGB deposits show an overall range from -18.4%o to +22.6%o. S34 values in host rock pyrite are: -2.2%o to +3.0%o (Twangiza deposit), -4.2%o to -0.6% (Kamituga deposit), -18.4% to -12.7% (Lugushwa deposit), and +12.4% to +22.6% (Namoya deposit). The sulphur isotopic signature of vein pyrite is -5.2% to +3.0% (Twangiza deposit), -9.1% to -7.4% (Kamituga deposit), -0.3% to +3.2% (Lugushwa deposit) and +1.3% to +20.4% (Namoya deposit). The isotopic data indicate a primary sedimentary to evaporitic source of sulphur in the host rock pyrite. Pyrite from metadiorites shows magmatic S isotope compositions. Native gold was found in both sedimentary host rock and vein samples. This indicates that native gold was present in the primary metasedimentary sequence of the TNGB. Some vein pyrites in the TNGB have isotopic signatures that are similar to that of the host rock pyrite. These veins have formed from fluids extracted from the hosting metasedimentary sequence. Conversely, other vein pyrite shows different S34S values compared to the host rock pyrite, suggesting a fluid source that is different from the sedimentary source. Possibly, particularly in the Lugushwa deposit, an igneous source may have released sulphur and possibly gold bearing fluids in addition to those extracted from the sedimentary sequences in the TNGB. However, there is abundant evidence for sulphur and gold mobilised in the sedimentary host rocks and precipitated in the hydrothermal system of the TNGB.
- Full Text:
- Date Issued: 2018
A bulk and fraction-specific geochemical study of the origin of diverse high-grade hematitic iron ores from the Transvaal Supergroup, Northern Cape Province, South Africa
- Authors: Moloto, William
- Date: 2017
- Subjects: Iron ore -- South Africa -- Transvaal Supergroup , Hematite -- South Africa -- Transvaal Supergroup , Transvaal Supergroup (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50546 , vital:25998
- Description: The Paleoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa is host to high-grade, Banded Iron Formation-hosted hematite iron-ore deposits and is the country’s most important source of iron to date. Previous studies suggest the origin of these iron ores to be ancient supergene, and that the ore forming process would have therefore pre-dated deposition of the basal Mapedi shales of the Olifansthoek Supergroup that unconformably overlies the Transvaal strata. The nature of the protolith to the ores has been suggested to be largely BIF of the Asbestos Hills Subgroup, and mainly the Kuruman BIF. The work presented in this thesis seeks to provide insights into the diversity of processes that are likely to have been involved during the genesis of these high-grade iron ores, in the context of constraining the pre-ore lithologies and the relative role of supergene-style, largely residual enrichment processes versus any possible metasomatic hydrothermal effects. This study had as primary focus the application of combined bulk and fraction-specific geochemical applications on representative iron-ore samples from four different localities in the Northern Cape Province, namely King/Khumani, Beeshoek, Heuninkranz and Hotazel. The collected samples show a variety of textures and also capture different pre-unconformity stratigraphic sections of BIF. The key objective was to assess whether the fraction-specific analytical results could provide any firm constraints for the origin of the ferrous and non-ferrous matrix fractions of the ores, namely whether they represent any combinations of protolith residue, allochtonously-introduced detritus or hydrothermally-derived material, and whether the results are comparable and consistent across all samples studied. In particular, constraints were sought as to whether the ore protolith was exclusively BIF or may potentially have contained at least a fraction of other lithologic types, such as shale; and whether there is sufficient evidence to support solely a supergene model for the ores or the data suggest other more epigenetic models of ore formation involving the action of hydrothermal fluids Bulk-rock geochemical analyses reveal the overwhelming dominance of Fe-oxide (as hematite) in all samples, at concentrations as high as 99 wt.% Fe2O3. Major and trace-element abundances of all samples were re-calculated assuming only iron addition from the postulated protolith (average BIF and shale), and the results revealed atypical enrichments in the iron ores by comparison to average BIF, and more shale-like relative abundances when normalised against the Post-Archaean Average Shale (PAAS). Specifically, BIF-normalised diagrams show relative enrichments by as much as 53-95% for Al2O3; 11-86% for TiO2; and 4-60% for P2O5. By contrast, PAAS-normalised values display enrichments of 1-3% for Al2O3, 0.2-3% for TiO2, and 3-13% for P2O5. Similar observations can be made for the greatest majority of trace elements when normalised against average BIF as compared to normalisation against PAAS. A suite of trace element that include alkali earths (e.g. Ba, Sr) and transition metals (e.g. Ni, Zn) show enrichments that are unrelated to the apparently detrital siliciclastic fraction of the ores, and are therefore linked to a possible hydrothermal input. Fraction-specific extractions were performed via the adaptation of existing dissolution protocols using oxalic acid (iron-oxide fraction) followed by HF digestion (silicate-fraction). The analyses of the produced aliquots using ICP-MS techniques, focused mainly on the REE abundances of the separated ferrous and non-ferrous matrix fractions and their comparisons to bulk-rock REE signatures. The results lend further support to the suggestion that the ore samples contain a predominant shale-like signal which does not directly compare to published REE signatures for supergene or hydrothermal BIF-hosted iron-ore deposits alike. The data therefore collectively point to a post-unconformity epigenetic hydrothermal event/s of iron ore-formation that would have exploited not only BIF but also shale as suitable pre-ore protolith.
- Full Text:
- Date Issued: 2017
- Authors: Moloto, William
- Date: 2017
- Subjects: Iron ore -- South Africa -- Transvaal Supergroup , Hematite -- South Africa -- Transvaal Supergroup , Transvaal Supergroup (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50546 , vital:25998
- Description: The Paleoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa is host to high-grade, Banded Iron Formation-hosted hematite iron-ore deposits and is the country’s most important source of iron to date. Previous studies suggest the origin of these iron ores to be ancient supergene, and that the ore forming process would have therefore pre-dated deposition of the basal Mapedi shales of the Olifansthoek Supergroup that unconformably overlies the Transvaal strata. The nature of the protolith to the ores has been suggested to be largely BIF of the Asbestos Hills Subgroup, and mainly the Kuruman BIF. The work presented in this thesis seeks to provide insights into the diversity of processes that are likely to have been involved during the genesis of these high-grade iron ores, in the context of constraining the pre-ore lithologies and the relative role of supergene-style, largely residual enrichment processes versus any possible metasomatic hydrothermal effects. This study had as primary focus the application of combined bulk and fraction-specific geochemical applications on representative iron-ore samples from four different localities in the Northern Cape Province, namely King/Khumani, Beeshoek, Heuninkranz and Hotazel. The collected samples show a variety of textures and also capture different pre-unconformity stratigraphic sections of BIF. The key objective was to assess whether the fraction-specific analytical results could provide any firm constraints for the origin of the ferrous and non-ferrous matrix fractions of the ores, namely whether they represent any combinations of protolith residue, allochtonously-introduced detritus or hydrothermally-derived material, and whether the results are comparable and consistent across all samples studied. In particular, constraints were sought as to whether the ore protolith was exclusively BIF or may potentially have contained at least a fraction of other lithologic types, such as shale; and whether there is sufficient evidence to support solely a supergene model for the ores or the data suggest other more epigenetic models of ore formation involving the action of hydrothermal fluids Bulk-rock geochemical analyses reveal the overwhelming dominance of Fe-oxide (as hematite) in all samples, at concentrations as high as 99 wt.% Fe2O3. Major and trace-element abundances of all samples were re-calculated assuming only iron addition from the postulated protolith (average BIF and shale), and the results revealed atypical enrichments in the iron ores by comparison to average BIF, and more shale-like relative abundances when normalised against the Post-Archaean Average Shale (PAAS). Specifically, BIF-normalised diagrams show relative enrichments by as much as 53-95% for Al2O3; 11-86% for TiO2; and 4-60% for P2O5. By contrast, PAAS-normalised values display enrichments of 1-3% for Al2O3, 0.2-3% for TiO2, and 3-13% for P2O5. Similar observations can be made for the greatest majority of trace elements when normalised against average BIF as compared to normalisation against PAAS. A suite of trace element that include alkali earths (e.g. Ba, Sr) and transition metals (e.g. Ni, Zn) show enrichments that are unrelated to the apparently detrital siliciclastic fraction of the ores, and are therefore linked to a possible hydrothermal input. Fraction-specific extractions were performed via the adaptation of existing dissolution protocols using oxalic acid (iron-oxide fraction) followed by HF digestion (silicate-fraction). The analyses of the produced aliquots using ICP-MS techniques, focused mainly on the REE abundances of the separated ferrous and non-ferrous matrix fractions and their comparisons to bulk-rock REE signatures. The results lend further support to the suggestion that the ore samples contain a predominant shale-like signal which does not directly compare to published REE signatures for supergene or hydrothermal BIF-hosted iron-ore deposits alike. The data therefore collectively point to a post-unconformity epigenetic hydrothermal event/s of iron ore-formation that would have exploited not only BIF but also shale as suitable pre-ore protolith.
- Full Text:
- Date Issued: 2017
A stratigraphic, petrographic and geochemical study of the gamagara formation at the maremane dome, Northern Cape province, South Africa
- Authors: Cousins, David Patrick
- Date: 2017
- Subjects: Iron ores -- Geology -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape , Mineralogy -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4679 , vital:20711
- Description: Between 80 and 90 percent of the potential iron ore reserves in the Griqualand West basin in the Northern Cape province of South Africa is situated in the Asbesheuwels Iron-formation immediately below an unconformity that separates it from the Gamagara Formation of the Olifantshoek Supergroup. This extensive regional unconformity marks a lengthy period of non-deposition and erosion which preceded the deposition of the Gamagara Formation. Due to the nature of the intimate relationship between the shales and iron ore body, specifically on the Maremane dome, new insights into the Gamagara Formation were required. The thesis provides a renewed stratigraphic, petrographic and geochemical study on the Gamagara Formation and relates it to previous studies done on the lateral correlative Mapedi Formation, some 70 km north of the Maremane dome. The use of 10 newly available drill-cores selected from across the Maremane Dome allows for regional correlations to be made in a study which employs petrographic/mineralogical investigations using transmitted/reflected light microscopy, XRD and EPMA, complimented by traditional whole-rock geochemical analysis of majors, traces, rare earth elements and Nd isotopes. At the base of the Gamagara lie conglomerates representing an alluvial fan deposit, overlying this, shale and quartzite successions represent progradational delta lobes. The deltas are interpreted to be tide- dominated as indicated by a combination of features including: microbial mat growth, intertidal deposition in the delta top, sand bars and flaser laminations in the upward coarsening quartzite units of the delta front. Transgression is indicated by periodic transgressive lag deposits. A variety of sedimentary structures and textural features are described that can be interpreted as the results of microbial mat colonization on the sediment surface. Although in none of the described features can it irrefutably be proven that they are microbial mat deposits, the observed features are consistent with such an interpretation and should be considered indicators of possible microbial mat presence in the Gamagara Formation. Hydrothermal modifications are identified in various units of the Gamagara Formation and seem to occur as separate events. Basal white shales show mobility of Al and slight HFSE enrichments, while overlying red shales record HFSE, K and Fe enrichments. K-metasomatism has been known to occur in the underlying paleoweathering profile of the Transvaal Supergroup (Ongeluk lavas) a unit which is interpreted as the most likely provenance for the mid-to-upper shale lithofacies of the Gamagara Formation. Highly alkaline F-bearing brines had the ability to mobilize titania and fluorapatite, reset Nd isotope systematics and ultimately enriched HFSE concentrations in the red shales of the Gamagara Formation. As the same enrichment is evident in the Mapedi Formation, the event possibly represents unconformity related fluid flow on a regional scale (~140 km). Nd-isotopes record an isotopic disturbance concurrent with the HFSE enrichment and Tdm model ages suggest disruption (and enrichment) occurred between 1.73 and 1.86 Ga. Following this, Fe-addition occurred by epigenetic mechanisms similar to those of MVT-type deposits. Although gaps in the current understanding of the modifications of the Gamagara Formation exist, such events may have far reaching implications for the underlying iron ore bodies and the possibility arises that the genesis and/or epigenetic modification of the ore bodies of the Transvaal Supergroup may be casually linked to the same fluid-migration event/s.
- Full Text:
- Date Issued: 2017
- Authors: Cousins, David Patrick
- Date: 2017
- Subjects: Iron ores -- Geology -- South Africa -- Northern Cape , Geology -- South Africa -- Northern Cape , Mineralogy -- South Africa -- Northern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4679 , vital:20711
- Description: Between 80 and 90 percent of the potential iron ore reserves in the Griqualand West basin in the Northern Cape province of South Africa is situated in the Asbesheuwels Iron-formation immediately below an unconformity that separates it from the Gamagara Formation of the Olifantshoek Supergroup. This extensive regional unconformity marks a lengthy period of non-deposition and erosion which preceded the deposition of the Gamagara Formation. Due to the nature of the intimate relationship between the shales and iron ore body, specifically on the Maremane dome, new insights into the Gamagara Formation were required. The thesis provides a renewed stratigraphic, petrographic and geochemical study on the Gamagara Formation and relates it to previous studies done on the lateral correlative Mapedi Formation, some 70 km north of the Maremane dome. The use of 10 newly available drill-cores selected from across the Maremane Dome allows for regional correlations to be made in a study which employs petrographic/mineralogical investigations using transmitted/reflected light microscopy, XRD and EPMA, complimented by traditional whole-rock geochemical analysis of majors, traces, rare earth elements and Nd isotopes. At the base of the Gamagara lie conglomerates representing an alluvial fan deposit, overlying this, shale and quartzite successions represent progradational delta lobes. The deltas are interpreted to be tide- dominated as indicated by a combination of features including: microbial mat growth, intertidal deposition in the delta top, sand bars and flaser laminations in the upward coarsening quartzite units of the delta front. Transgression is indicated by periodic transgressive lag deposits. A variety of sedimentary structures and textural features are described that can be interpreted as the results of microbial mat colonization on the sediment surface. Although in none of the described features can it irrefutably be proven that they are microbial mat deposits, the observed features are consistent with such an interpretation and should be considered indicators of possible microbial mat presence in the Gamagara Formation. Hydrothermal modifications are identified in various units of the Gamagara Formation and seem to occur as separate events. Basal white shales show mobility of Al and slight HFSE enrichments, while overlying red shales record HFSE, K and Fe enrichments. K-metasomatism has been known to occur in the underlying paleoweathering profile of the Transvaal Supergroup (Ongeluk lavas) a unit which is interpreted as the most likely provenance for the mid-to-upper shale lithofacies of the Gamagara Formation. Highly alkaline F-bearing brines had the ability to mobilize titania and fluorapatite, reset Nd isotope systematics and ultimately enriched HFSE concentrations in the red shales of the Gamagara Formation. As the same enrichment is evident in the Mapedi Formation, the event possibly represents unconformity related fluid flow on a regional scale (~140 km). Nd-isotopes record an isotopic disturbance concurrent with the HFSE enrichment and Tdm model ages suggest disruption (and enrichment) occurred between 1.73 and 1.86 Ga. Following this, Fe-addition occurred by epigenetic mechanisms similar to those of MVT-type deposits. Although gaps in the current understanding of the modifications of the Gamagara Formation exist, such events may have far reaching implications for the underlying iron ore bodies and the possibility arises that the genesis and/or epigenetic modification of the ore bodies of the Transvaal Supergroup may be casually linked to the same fluid-migration event/s.
- Full Text:
- Date Issued: 2017
Characterization of the distribution of platinum group elements in sulphide ores within the Merensky Reef at Modikwa and Two Rivers Platinum Mines, Eastern Bushveld Complex, South Africa
- Authors: Zilibokwe, Nosibulelo Julie
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7938 , vital:21326
- Description: The distribution of the platinum group element (PGE), in the Merensky Reef was characterized by, first determining the occurrence of the platinum group minerals (PGM), then by establishing the PGE concentration in the base metal sulphides (BMS) associated with the PGE mineralization in the Merensky Reef from selected borehole intersections, at the Two Rivers (TRP) and Modikwa Platinum Mines in the Eastern Bushveld Complex. A mineral liberation analyser (MLA) was then used to identify the PGM phases; their silicate and base metal associations; and their grain size distribution. Electron microprobe quantitative analysis and mapping were then used to determine the compositional variation of the PGM and the PGE elemental distribution in the BMS, respectively. The study showed that the BMS including pyrrhotite, pentlandite, and chalcopyrite were the principal sulphides, where pyrrhotite was most prominent with minor quantities of pyrite. Orthopyroxene, clinopyroxene and plagioclase were the most abundant primary silicate minerals identified, while secondary silicates identified included talc, serpentine and amphibole. Platinum group minerals showed three distinct groups with respect to the mineralogical association with the PGE; (i) BMS association; (ii) chromite association; and (iii) silicate association. Of the BMS, chalcopyrite showed the most dominant association with the PGMs. All samples from both mines exhibited a wide range of PGMs, including maslovite, braggite, cooperate, laurite and PGE alloys such as ferroplatinum as well as other unidentified platinum and palladium sulphides, arsenides and bismuthides, while gold was present as electrum. The PGMs ranged in size from less than a micron to about 125 microns with an average of 20 microns. The close association of PGM with BMS along the margins of sulphides indicates that the PGMs were derived from the sulphide melt. PGE distribution in the sulphides at Modikwa showed pentlandite contained the highest concentrations of palladium (up to 379 ppm) and chalcopyrite hosting the highest rhodium concentrations (up to 793 ppm). Samples from Two Rivers revealed pentlandite as the principal host to both palladium and rhodium, with concentrations reaching up to 695 and 930 ppm, respectively. Magnetite at both Modikwa and Two Rivers showed significant rhodium content, reaching up to 982 and 930 ppm, respectively. The pyrrhotite compared to other sulphides contained all the elements found in the platinum group (PPGE), namely, platinum, palladium and rhodium, with all the platinum identified found in the pyrrhotite. The concentrations for the iridium group (IPGE) namely, iridium, osmium, and ruthenium were below the detection limit. The PGE mineralization in the stratigraphy varied within each mine. The mineralization revealed top loading in the central sector (Modikwa) and bottom loading in the southern sector (Two Rivers). The sequence of the Merensky Reef at the two sectors of the Eastern Bushveld Complex showed a remarkable similarity in their mineralogy suggesting that these two sectors were formed from the same liquid or formed simultaneously within a single magma chamber; however the PGE distribution within the stratigraphy may have been controlled by the presence of cumulate sulphides.
- Full Text:
- Date Issued: 2017
- Authors: Zilibokwe, Nosibulelo Julie
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7938 , vital:21326
- Description: The distribution of the platinum group element (PGE), in the Merensky Reef was characterized by, first determining the occurrence of the platinum group minerals (PGM), then by establishing the PGE concentration in the base metal sulphides (BMS) associated with the PGE mineralization in the Merensky Reef from selected borehole intersections, at the Two Rivers (TRP) and Modikwa Platinum Mines in the Eastern Bushveld Complex. A mineral liberation analyser (MLA) was then used to identify the PGM phases; their silicate and base metal associations; and their grain size distribution. Electron microprobe quantitative analysis and mapping were then used to determine the compositional variation of the PGM and the PGE elemental distribution in the BMS, respectively. The study showed that the BMS including pyrrhotite, pentlandite, and chalcopyrite were the principal sulphides, where pyrrhotite was most prominent with minor quantities of pyrite. Orthopyroxene, clinopyroxene and plagioclase were the most abundant primary silicate minerals identified, while secondary silicates identified included talc, serpentine and amphibole. Platinum group minerals showed three distinct groups with respect to the mineralogical association with the PGE; (i) BMS association; (ii) chromite association; and (iii) silicate association. Of the BMS, chalcopyrite showed the most dominant association with the PGMs. All samples from both mines exhibited a wide range of PGMs, including maslovite, braggite, cooperate, laurite and PGE alloys such as ferroplatinum as well as other unidentified platinum and palladium sulphides, arsenides and bismuthides, while gold was present as electrum. The PGMs ranged in size from less than a micron to about 125 microns with an average of 20 microns. The close association of PGM with BMS along the margins of sulphides indicates that the PGMs were derived from the sulphide melt. PGE distribution in the sulphides at Modikwa showed pentlandite contained the highest concentrations of palladium (up to 379 ppm) and chalcopyrite hosting the highest rhodium concentrations (up to 793 ppm). Samples from Two Rivers revealed pentlandite as the principal host to both palladium and rhodium, with concentrations reaching up to 695 and 930 ppm, respectively. Magnetite at both Modikwa and Two Rivers showed significant rhodium content, reaching up to 982 and 930 ppm, respectively. The pyrrhotite compared to other sulphides contained all the elements found in the platinum group (PPGE), namely, platinum, palladium and rhodium, with all the platinum identified found in the pyrrhotite. The concentrations for the iridium group (IPGE) namely, iridium, osmium, and ruthenium were below the detection limit. The PGE mineralization in the stratigraphy varied within each mine. The mineralization revealed top loading in the central sector (Modikwa) and bottom loading in the southern sector (Two Rivers). The sequence of the Merensky Reef at the two sectors of the Eastern Bushveld Complex showed a remarkable similarity in their mineralogy suggesting that these two sectors were formed from the same liquid or formed simultaneously within a single magma chamber; however the PGE distribution within the stratigraphy may have been controlled by the presence of cumulate sulphides.
- Full Text:
- Date Issued: 2017
Evolution of Fe-Ti-V oxides from the main magnetite layer, Upper Zone, Bushveld Complex, South Africa: a comparison across the Western, Northern and Eastern Lobes
- Authors: Iorga-Pavel, Adina
- Date: 2017
- Subjects: Magnetite -- South Africa -- Bushveld Complex , Mineralogy -- South Africa -- Bushveld Complex , Oxides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7357 , vital:21248
- Description: The Main Magnetite Layer (MML) from the Northern, Eastern and Western lobes of the Bushveld Complex shows significant differences in textures and in mineral chemistry. The MML in the Eastern and Western lobes is massive, with rare, small and altered pyroxene inclusions. By contrast, the MML in the Northern Lobe is more heterogeneous, and it is made of anastomosed and sometimes imbricated, thin layers of magnetitite, magnetite-rich and silicate-rich rocks, where the inclusions in Ti-magnetite are more numerous and consist of mainly altered subhedral and anhedral plagioclase. The comparison of the maximum values of the oxides shows that the MML in the Northern Lobe has the highest content of V2O3 (1.97 wt%), TiO2 (22.49 wt%) and MgO (2.92 wt%), while the MML in the Eastern Lobe has the highest content of Cr2O3 (2.92 wt%) and Al2O3 (9.80 wt%), but lowest V2O3 (0.52 wt%). The lower TiO2 content and higher V2O3 content in the MML of the Northern and Western Lobes suggest lower oxidising conditions during the crystallization of oxides. The MML in all three studied lobes consists of two layers of magnetitite, suggesting that MML was formed by two separate magma influxes, probably on a diverse and complex type of magma chamber floor. The high TiO2 content in magnetite, together with the negative correlation between TiO2 and V2O3 suggest that the maximum V content should represent a “less evolved” and less oxidized melt. In this respect, higher concentrations V2O3 in magnetite can be expected in magnetitite layers with lower TiO2. It can be inferred that the Ti-magetite in the MML from the Eastern Lobe was formed from a more evolved (TiO2 and FeO enriched) and more oxidized (lower V2O3) melt, compared with the MML from the Northern and Western lobes. These findings can be used to illustrate: a) that high fO2 can be responsible for the relatively low V content in magnetite from Fe-Ti oxide ores and b) the vanadium in magnetite decreases significantly in more evolved cumulates, due to a decreasing fO2 with differentiation. Compositional profiles of Ti- magnetite along the stratigraphic height of the MML in the Eastern Lobe (composed of two layers, separated in the outcrop by a parting plane) depicts a cryptic variation with depth in each of the two layers, where each layer can be divided into four sublayers, labelled upwards as A, B, C (with C1, C2, C3 and C4) and D based on Cr, Mg, Ti, Al and V variation. Small scale reversals of the mentioned elements and the repetition of A, B, C and D sub-layers in each layer suggest that MML formed from two successive influxes of magma (indicated by relatively elevated values of MgO), which evolved by crystallization and cooling in a similar manner, to produce the A to D variation. Based on these observations and theoretical considerations, this study dismisses several models for the genesis of the MML: the immiscibility, the increased oxygen fugacity, the relative increase of H2O content of the melt, pressure variation within the magma chamber, magma mixing, and crustal rock contamination. The model proposed here for MML genesis involves the crystallization of both Ti-magnetite and ilmenite from a Fe-Ti-Ca-Al-rich melt (ferro-diorite) along its line of descent, and gravitational settling of oxides in a dynamic regime. The factor which triggered the crystallization of magnetite is a critical saturation of melt in magnetite (attaining saturation of magnetite and ilmenite in the melt after some silicates crystallized). The difference between the nature of silicate inclusions in magnetite and the nature of the magnetite floor, suggest that the Fe-rich magma was not in equilibrium with the cumulates from the present floor, but rather it was emplaced laterally on long distances, the melt being disrupted from its own cumulates. The absence of correlation between the Cr2O3 in magnetite and co-existing ilmenite can indicate than no in-situ fractional crystallization took place at the moment of magnetite accumulation, but rather that magnetite and ilmenite gravitationally accumulated and the grains mechanically mixed from a flowing magma. The model presented herein proposes a five stage model of MML formation: Stage 1 is represented by the intrusion of a Fe-T-Ca-Al-rich magma which expands laterally within a flat and thin magma chamber. Oxides start to crystallize within a dynamic regime of the magma. Stage 2 is given by the accumulation of oxides at the bottom of the new floor. Some plagioclase starts to crystallize (e.g. subhedral plagioclase in the MML of the Northern Lobe). Stage 3 is a short living static regime, where both plagioclase and magnetite crystallized, without fractionation, forming the thin magnetite-anorthosite layer separating the MML into two layers. Stage 4 is represented by a new influx of Fe-Ti-Ca-Al-rich magma which is emplaced above the magnetite-bearing anorthosite, flushing out the liquid which was in equilibrium with the anorthosite. The oxides started crystallizing in a dynamic regime, as in Stage 1. In stage 5, the accumulation of oxides produced the upper layer of the MML. Our interpretation is that the flow of the magma was more dynamic (probably more turbulent on long distances) in the MML of the Northern Lobe, compared to the MML in the Western and Eastern lobes, producing highly heterogeneous and imbricated thin layers of magnetitite and silicates. The presence of olivine corona around orthopyroxene suggests the incongruent melting of orthopyroxene, which points out towards a local re-heating of existing silicate layers, this being a strong argument for multiple injections in generation of MML. Massive crystallization of oxides produced the sulphur saturation of the magma and caused the precipitation of the igneous sulphides, which nucleated on the existing oxides. Later hydrothermal fluids (and/or late magmatic volatiles?) percolated the MML, producing chloritization of the included silicates, remobilization of igneous sulphides and precipitation of hydrothermal sulphides.
- Full Text:
- Date Issued: 2017
- Authors: Iorga-Pavel, Adina
- Date: 2017
- Subjects: Magnetite -- South Africa -- Bushveld Complex , Mineralogy -- South Africa -- Bushveld Complex , Oxides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7357 , vital:21248
- Description: The Main Magnetite Layer (MML) from the Northern, Eastern and Western lobes of the Bushveld Complex shows significant differences in textures and in mineral chemistry. The MML in the Eastern and Western lobes is massive, with rare, small and altered pyroxene inclusions. By contrast, the MML in the Northern Lobe is more heterogeneous, and it is made of anastomosed and sometimes imbricated, thin layers of magnetitite, magnetite-rich and silicate-rich rocks, where the inclusions in Ti-magnetite are more numerous and consist of mainly altered subhedral and anhedral plagioclase. The comparison of the maximum values of the oxides shows that the MML in the Northern Lobe has the highest content of V2O3 (1.97 wt%), TiO2 (22.49 wt%) and MgO (2.92 wt%), while the MML in the Eastern Lobe has the highest content of Cr2O3 (2.92 wt%) and Al2O3 (9.80 wt%), but lowest V2O3 (0.52 wt%). The lower TiO2 content and higher V2O3 content in the MML of the Northern and Western Lobes suggest lower oxidising conditions during the crystallization of oxides. The MML in all three studied lobes consists of two layers of magnetitite, suggesting that MML was formed by two separate magma influxes, probably on a diverse and complex type of magma chamber floor. The high TiO2 content in magnetite, together with the negative correlation between TiO2 and V2O3 suggest that the maximum V content should represent a “less evolved” and less oxidized melt. In this respect, higher concentrations V2O3 in magnetite can be expected in magnetitite layers with lower TiO2. It can be inferred that the Ti-magetite in the MML from the Eastern Lobe was formed from a more evolved (TiO2 and FeO enriched) and more oxidized (lower V2O3) melt, compared with the MML from the Northern and Western lobes. These findings can be used to illustrate: a) that high fO2 can be responsible for the relatively low V content in magnetite from Fe-Ti oxide ores and b) the vanadium in magnetite decreases significantly in more evolved cumulates, due to a decreasing fO2 with differentiation. Compositional profiles of Ti- magnetite along the stratigraphic height of the MML in the Eastern Lobe (composed of two layers, separated in the outcrop by a parting plane) depicts a cryptic variation with depth in each of the two layers, where each layer can be divided into four sublayers, labelled upwards as A, B, C (with C1, C2, C3 and C4) and D based on Cr, Mg, Ti, Al and V variation. Small scale reversals of the mentioned elements and the repetition of A, B, C and D sub-layers in each layer suggest that MML formed from two successive influxes of magma (indicated by relatively elevated values of MgO), which evolved by crystallization and cooling in a similar manner, to produce the A to D variation. Based on these observations and theoretical considerations, this study dismisses several models for the genesis of the MML: the immiscibility, the increased oxygen fugacity, the relative increase of H2O content of the melt, pressure variation within the magma chamber, magma mixing, and crustal rock contamination. The model proposed here for MML genesis involves the crystallization of both Ti-magnetite and ilmenite from a Fe-Ti-Ca-Al-rich melt (ferro-diorite) along its line of descent, and gravitational settling of oxides in a dynamic regime. The factor which triggered the crystallization of magnetite is a critical saturation of melt in magnetite (attaining saturation of magnetite and ilmenite in the melt after some silicates crystallized). The difference between the nature of silicate inclusions in magnetite and the nature of the magnetite floor, suggest that the Fe-rich magma was not in equilibrium with the cumulates from the present floor, but rather it was emplaced laterally on long distances, the melt being disrupted from its own cumulates. The absence of correlation between the Cr2O3 in magnetite and co-existing ilmenite can indicate than no in-situ fractional crystallization took place at the moment of magnetite accumulation, but rather that magnetite and ilmenite gravitationally accumulated and the grains mechanically mixed from a flowing magma. The model presented herein proposes a five stage model of MML formation: Stage 1 is represented by the intrusion of a Fe-T-Ca-Al-rich magma which expands laterally within a flat and thin magma chamber. Oxides start to crystallize within a dynamic regime of the magma. Stage 2 is given by the accumulation of oxides at the bottom of the new floor. Some plagioclase starts to crystallize (e.g. subhedral plagioclase in the MML of the Northern Lobe). Stage 3 is a short living static regime, where both plagioclase and magnetite crystallized, without fractionation, forming the thin magnetite-anorthosite layer separating the MML into two layers. Stage 4 is represented by a new influx of Fe-Ti-Ca-Al-rich magma which is emplaced above the magnetite-bearing anorthosite, flushing out the liquid which was in equilibrium with the anorthosite. The oxides started crystallizing in a dynamic regime, as in Stage 1. In stage 5, the accumulation of oxides produced the upper layer of the MML. Our interpretation is that the flow of the magma was more dynamic (probably more turbulent on long distances) in the MML of the Northern Lobe, compared to the MML in the Western and Eastern lobes, producing highly heterogeneous and imbricated thin layers of magnetitite and silicates. The presence of olivine corona around orthopyroxene suggests the incongruent melting of orthopyroxene, which points out towards a local re-heating of existing silicate layers, this being a strong argument for multiple injections in generation of MML. Massive crystallization of oxides produced the sulphur saturation of the magma and caused the precipitation of the igneous sulphides, which nucleated on the existing oxides. Later hydrothermal fluids (and/or late magmatic volatiles?) percolated the MML, producing chloritization of the included silicates, remobilization of igneous sulphides and precipitation of hydrothermal sulphides.
- Full Text:
- Date Issued: 2017
Fraction-specific geochemistry across the Asbestos Hills BIF of the Transvaal Supergroup, South Africa: implications for the origin of BIF and the history of atmospheric oxygen
- Oonk, Paul Bernardus Hendrikus
- Authors: Oonk, Paul Bernardus Hendrikus
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/50721 , vital:26021
- Description: Banded iron formations (BIF), deposited prior to and concurrent with the Great Oxidation Event (GOE) at ca. 2.4 Ga, record changes in oceanic and atmospheric chemistry during this critical time interval. Four previously unstudied drill-cores from the Griqualand West Basin, South Africa, capturing the rhythmically mesobanded, deep-water Kuruman BIF and the overlying granular, shallower Griquatown BIF, were sampled every ca. 10 m along core depth. Mineralogically, these BIFs consist of three iron-bearing fractions: (1) Fe-Ca-Mg-Mn carbonates, (2) magnetite with/without minor hematite and (3) Fe-silicates. These fractions are typically fine-grained on a sub-μm scale and their co-occurrence in varying amounts means that bulk-rock or microanalytical geochemical and stable isotope data are influenced by mineralogy.
- Full Text:
- Date Issued: 2017
- Authors: Oonk, Paul Bernardus Hendrikus
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/50721 , vital:26021
- Description: Banded iron formations (BIF), deposited prior to and concurrent with the Great Oxidation Event (GOE) at ca. 2.4 Ga, record changes in oceanic and atmospheric chemistry during this critical time interval. Four previously unstudied drill-cores from the Griqualand West Basin, South Africa, capturing the rhythmically mesobanded, deep-water Kuruman BIF and the overlying granular, shallower Griquatown BIF, were sampled every ca. 10 m along core depth. Mineralogically, these BIFs consist of three iron-bearing fractions: (1) Fe-Ca-Mg-Mn carbonates, (2) magnetite with/without minor hematite and (3) Fe-silicates. These fractions are typically fine-grained on a sub-μm scale and their co-occurrence in varying amounts means that bulk-rock or microanalytical geochemical and stable isotope data are influenced by mineralogy.
- Full Text:
- Date Issued: 2017
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
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 variation in the basal Upper Zone, Bushveld Igneous Complex, South Africa: implications for ore genesis and mineral extraction
- Van Huyssteen, Darryn Ashley
- Authors: Van Huyssteen, Darryn Ashley
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5060 , vital:20762
- Full Text:
- Date Issued: 2017
- Authors: Van Huyssteen, Darryn Ashley
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5060 , vital:20762
- Full Text:
- Date Issued: 2017