Die geologie van die gebied Rooinekke-Matsap-Wolhaarkop in Noord-Kaapland met spesiale verwysing na die Koega-subgroep, Transvaal-supergroep
- Authors: Van Wyk, Jacob Pieter
- Date: 2014-05-26
- Subjects: Geology - South Africa - Northern Cape
- Type: Thesis
- Identifier: uj:11202 , http://hdl.handle.net/10210/10796
- Description: M.Sc. (Geology) , Please refer to full text to view abstract
- Full Text:
- Authors: Van Wyk, Jacob Pieter
- Date: 2014-05-26
- Subjects: Geology - South Africa - Northern Cape
- Type: Thesis
- Identifier: uj:11202 , http://hdl.handle.net/10210/10796
- Description: M.Sc. (Geology) , Please refer to full text to view abstract
- Full Text:
Multi-pronged approach to constrain the age of the Molopo Farms layered igneous complex, Northern Cape Province and Southeastern Botswana
- Authors: Ravhura, Livhuwani Given
- Date: 2016
- Subjects: Geochronology , Geology - Botswana , Geology - South Africa - Northern Cape , Igneous rocks - Botswana , Igneous rocks - South Africa - Northern Cape , Molopo Farms Complex (Botswana and South Africa)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235897 , uj:24133
- Description: M.Sc. (Geology) , Abstract: This study presents the first detailed major- and trace element geochemical and geochronological studies of the Molopo Farms Complex (MFC), situated in the Northern Cape Province, South Africa and south eastern Botswana. The rocks of the MFC are gabbro, serpentinite, pyroxenite and intrudes into sedimentary host rocks, these rocks are medium- to coarse grained. The mafic igneous rocks of the MFC are dominantly sub-alkaline tholeiitic in composition and characterized as basaltic andesite. The MFC is completely covered by Cenozoic sediments of the Kalahari Formation and it is only known through intersection in exploration drill core and geophysical data. It is thought that the MFC has intruded the sedimentary succession of the Paleoproterozoic Transvaal Supergroup. Unlike other layered complexes (Bushveld Complex, Stillwater Complex, etc.), no detailed geochemical studies have been done on the MFC. At present, the available age is the poorly constrained at 2044±24 Ma (Rb-Sr errorchron age) and for that reason, and the fact that it is a layered igneous complex it has been correlated with Bushveld Complex. However, this age and correlation are poorly constrained. This study provides additional data on the geochemical composition of the igneous rocks to fully understand the geochemical signature of the igneous rocks of the MFC, a baddeleyite age on a gabbro from the complex and also detrital zircon age data on the sedimentary country rocks. The geochemical signature of the MFC has been compared to that of other magmatic events (Bushveld Complex, Moshaneng dykes and Post Waterberg sills) to evaluate the similarities in composition. The MFC is characterized by an enrichment in LREE relative to the HREE and shows negative Eu, Nb(Ta), P, Ti and positive K, Pb and U anomalies. This geochemical signature compares well with that of the B1-magma of the Bushveld Complex. An age of 2052±16 Ma, obtained from U-Pb baddeleyite dating, has been interpreted to be the emplacement age of the MFC. This age is within error with the 2054.4±1.3 Ma accepted age of the Bushveld Complex. The maximum age of sedimentary country rock into which MFC intrudes has been better constrained by U-Pb detrital zircon dating. The youngest concordant zircon ages obtained are between 2018±39 and...
- Full Text:
- Authors: Ravhura, Livhuwani Given
- Date: 2016
- Subjects: Geochronology , Geology - Botswana , Geology - South Africa - Northern Cape , Igneous rocks - Botswana , Igneous rocks - South Africa - Northern Cape , Molopo Farms Complex (Botswana and South Africa)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235897 , uj:24133
- Description: M.Sc. (Geology) , Abstract: This study presents the first detailed major- and trace element geochemical and geochronological studies of the Molopo Farms Complex (MFC), situated in the Northern Cape Province, South Africa and south eastern Botswana. The rocks of the MFC are gabbro, serpentinite, pyroxenite and intrudes into sedimentary host rocks, these rocks are medium- to coarse grained. The mafic igneous rocks of the MFC are dominantly sub-alkaline tholeiitic in composition and characterized as basaltic andesite. The MFC is completely covered by Cenozoic sediments of the Kalahari Formation and it is only known through intersection in exploration drill core and geophysical data. It is thought that the MFC has intruded the sedimentary succession of the Paleoproterozoic Transvaal Supergroup. Unlike other layered complexes (Bushveld Complex, Stillwater Complex, etc.), no detailed geochemical studies have been done on the MFC. At present, the available age is the poorly constrained at 2044±24 Ma (Rb-Sr errorchron age) and for that reason, and the fact that it is a layered igneous complex it has been correlated with Bushveld Complex. However, this age and correlation are poorly constrained. This study provides additional data on the geochemical composition of the igneous rocks to fully understand the geochemical signature of the igneous rocks of the MFC, a baddeleyite age on a gabbro from the complex and also detrital zircon age data on the sedimentary country rocks. The geochemical signature of the MFC has been compared to that of other magmatic events (Bushveld Complex, Moshaneng dykes and Post Waterberg sills) to evaluate the similarities in composition. The MFC is characterized by an enrichment in LREE relative to the HREE and shows negative Eu, Nb(Ta), P, Ti and positive K, Pb and U anomalies. This geochemical signature compares well with that of the B1-magma of the Bushveld Complex. An age of 2052±16 Ma, obtained from U-Pb baddeleyite dating, has been interpreted to be the emplacement age of the MFC. This age is within error with the 2054.4±1.3 Ma accepted age of the Bushveld Complex. The maximum age of sedimentary country rock into which MFC intrudes has been better constrained by U-Pb detrital zircon dating. The youngest concordant zircon ages obtained are between 2018±39 and...
- Full Text:
Petrography and geochemistry of the Hotazel Formation on Mukulu 265, Kalahari Manganese Field, Northern Cape Province
- Authors: Vafeas, Nicholas Andrew
- Date: 2016
- Subjects: Geology - South Africa - Northern Cape , Manganese ores - Kalahari Desert , Iron ores
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124793 , uj:20960
- Description: Abstract: With the need for steel ever increasing, the Kalahari Manganese Deposit is a resource of great economic importance and as such, the need for accurate data and comprehensive studies on the manganese and iron ores are vital. The Mukulu 265 project area is positioned along the border of the high (Wessels-type) to low (Mamatwan-type) grade manganese ore and like the neighbouring N’chwaning and Wessels mines, is subject to: intrusions by diabase dykes; thrusting and subsequent overlapping of strata; normal faulting and associated Wessels event enrichment; and erosion along two separate unconformities, namely the Mapedi/Gamagara and the Kalahari unconformities. As a result of these structural evolutionary events, both the iron and the manganese ores vary in grade, mineralogy and texture from north to south and east to west. This variation is the result of contact metamorphism and associated igneousrelated hydrothermal fluids; supergene alteration along the Mapedi/Gamagara unconformity; and metasomatic alteration along the reactivated north-south striking normal faults. The latter is responsible for the systematic residual enrichment in manganese content and the increase in high-grade minerals in the manganese ore, as well as the subsequent leaching of carbonates and silicates that is witnessed in the northern section of Mukulu 265. Based on varying degrees of alteration from south to north on Mukulu 265, the banded iron formation, hematite lutite and manganese ores have been broadly categorised into three classes, namely least altered (LA), partially altered (PA) and highly altered (HA). The LA rock-types are considered to be closest to the primary rock-types found on Mukulu 265 and show relatively little alteration compared to the PA and HA samples. From the LA to the HA manganese ore samples, there is a clear increase in manganese oxides such as hausmannite, predominantly at the expense of carbonates such and kutnohorite and dolomite, particularly within the ovoids. Sampling and analysing the manganese ore by visually distinguishing common subzones, reveals a distinct pattern within the lower manganese ore beds of the selected boreholes that shows a lateral geochemical trend. This geochemical trend exhibits higher concentrations in manganese with lower concentrations in undesired elements such as iron within the lowercentral portion of the lower manganese ore bed. The geochemical pattern exhibited by the ore zones forms the basis by which the ore grade changes with depth and thus underpins its importance for selective mining processes. An interpretation of the ore genesis based on geochemical and mineralogical results for the lower manganese ore bed, suggests that the... , M.Sc. (Geology)
- Full Text:
- Authors: Vafeas, Nicholas Andrew
- Date: 2016
- Subjects: Geology - South Africa - Northern Cape , Manganese ores - Kalahari Desert , Iron ores
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124793 , uj:20960
- Description: Abstract: With the need for steel ever increasing, the Kalahari Manganese Deposit is a resource of great economic importance and as such, the need for accurate data and comprehensive studies on the manganese and iron ores are vital. The Mukulu 265 project area is positioned along the border of the high (Wessels-type) to low (Mamatwan-type) grade manganese ore and like the neighbouring N’chwaning and Wessels mines, is subject to: intrusions by diabase dykes; thrusting and subsequent overlapping of strata; normal faulting and associated Wessels event enrichment; and erosion along two separate unconformities, namely the Mapedi/Gamagara and the Kalahari unconformities. As a result of these structural evolutionary events, both the iron and the manganese ores vary in grade, mineralogy and texture from north to south and east to west. This variation is the result of contact metamorphism and associated igneousrelated hydrothermal fluids; supergene alteration along the Mapedi/Gamagara unconformity; and metasomatic alteration along the reactivated north-south striking normal faults. The latter is responsible for the systematic residual enrichment in manganese content and the increase in high-grade minerals in the manganese ore, as well as the subsequent leaching of carbonates and silicates that is witnessed in the northern section of Mukulu 265. Based on varying degrees of alteration from south to north on Mukulu 265, the banded iron formation, hematite lutite and manganese ores have been broadly categorised into three classes, namely least altered (LA), partially altered (PA) and highly altered (HA). The LA rock-types are considered to be closest to the primary rock-types found on Mukulu 265 and show relatively little alteration compared to the PA and HA samples. From the LA to the HA manganese ore samples, there is a clear increase in manganese oxides such as hausmannite, predominantly at the expense of carbonates such and kutnohorite and dolomite, particularly within the ovoids. Sampling and analysing the manganese ore by visually distinguishing common subzones, reveals a distinct pattern within the lower manganese ore beds of the selected boreholes that shows a lateral geochemical trend. This geochemical trend exhibits higher concentrations in manganese with lower concentrations in undesired elements such as iron within the lowercentral portion of the lower manganese ore bed. The geochemical pattern exhibited by the ore zones forms the basis by which the ore grade changes with depth and thus underpins its importance for selective mining processes. An interpretation of the ore genesis based on geochemical and mineralogical results for the lower manganese ore bed, suggests that the... , M.Sc. (Geology)
- Full Text:
A petrographical and geochemical analysis of the upper and lower manganese ore bodies from the Kalahari Manganese Deposit, Northern Cape, South Africa – controls on hydrothermal metasomatism and metal upgrading
- Authors: Blignaut, Lauren Cher
- Date: 2017
- Subjects: Geology - South Africa - Northern Cape , Geochemistry - South Africa - Northern Cape , Mineralogy - South Africa - Northern Cape , Petrology - South Africa - Northern Cape , Manganese ores - Geology - South Africa - Northern Cape
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233924 , uj:23893
- Description: Ph.D. (Geology) , Abstract: The Paleoproterozoic Kalahari Manganese Field (KMF) is the largest known land-based manganese (Mn) deposit on Earth. Of the five erosional relics that the KMF comprises within the Hotazel Formation, the Kalahari Manganese Deposit (KMD) is the largest. The Mn ores within the KMD are hosted in three beds that alternate with banded iron-formation (BIF) and hematite lutite. The low-grade ore (<38 wt% Mn), is mostly quartz-free and carbonate-rich, whereas the high-grade ore (>44 wt% Mn), is a carbonate-free, Mn oxide-rich ore. The drill cores analysed incorporate the Nchwaning (I, II and III), Belgravia and Gloria mines, as well as the Black Rock outcrop. This study provides a correlation of petrographical, mineralogical and geochemical data, in order to characterise and interpret the protolith, low-grade and high-grade ores of both the upper and lower Mn ore bodies. The source, transport, deposition, diagenesis, metamorphism, as well as hydrothermal alteration of the Mn ores have been addressed. The spatial distribution of the mineral assemblages, the mechanism of Mn enrichment, fluid characteristics and fluid-rock interactions, as well as the influence of epigenetic alteration processes and the erosional unconformity on the quality of the ore has been discussed. The fluid-rock interaction leads to the presence of boron (B), which is considered highly detrimental to the steel quality. Thus, the spatial distribution, location and the source of the B, as well as ways of dealing with its presence has been addressed. A regional model for the alteration of the Mn ores, based on the above results, has been produced. Five distinct drill core groups, based on mineralogical associations, textural features and geochemical characteristics were distinguished. The diagenetic textural features are comprised of carbonate minerals, and generally preserved within the lower grade ores. The higher grade ores show replacement of the carbonates with oxides and ‘secondary’ carbonate minerals, whilst the highest grade ore is almost completely devoid of the textural features. The upper ore bodies display higher Fe and Si contents, whereas the lower ore bodies show enrichment in Mn and Ca. This suggests pervasive and incipient oxidation, as well as carbonate leaching from the upper to the lower bed. An increase in grade is characterised by enrichment in Mn, Fe, Cu, Pb, Zn, Ni and Co, and depletion in Ca, Mg and Si. The high-grade ores are enriched in Ba, Sr, Li and B, with the upper ore beds generally exhibiting higher abundances of these elements relative to the lower ore bodies. Boron is mineralogically controlled and hosted by braunite, braunite-II, gaudefroyite, tephroite and the carbonate- and serpentine-group minerals. The trace elements were redistributed and locally concentrated
- Full Text:
- Authors: Blignaut, Lauren Cher
- Date: 2017
- Subjects: Geology - South Africa - Northern Cape , Geochemistry - South Africa - Northern Cape , Mineralogy - South Africa - Northern Cape , Petrology - South Africa - Northern Cape , Manganese ores - Geology - South Africa - Northern Cape
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233924 , uj:23893
- Description: Ph.D. (Geology) , Abstract: The Paleoproterozoic Kalahari Manganese Field (KMF) is the largest known land-based manganese (Mn) deposit on Earth. Of the five erosional relics that the KMF comprises within the Hotazel Formation, the Kalahari Manganese Deposit (KMD) is the largest. The Mn ores within the KMD are hosted in three beds that alternate with banded iron-formation (BIF) and hematite lutite. The low-grade ore (<38 wt% Mn), is mostly quartz-free and carbonate-rich, whereas the high-grade ore (>44 wt% Mn), is a carbonate-free, Mn oxide-rich ore. The drill cores analysed incorporate the Nchwaning (I, II and III), Belgravia and Gloria mines, as well as the Black Rock outcrop. This study provides a correlation of petrographical, mineralogical and geochemical data, in order to characterise and interpret the protolith, low-grade and high-grade ores of both the upper and lower Mn ore bodies. The source, transport, deposition, diagenesis, metamorphism, as well as hydrothermal alteration of the Mn ores have been addressed. The spatial distribution of the mineral assemblages, the mechanism of Mn enrichment, fluid characteristics and fluid-rock interactions, as well as the influence of epigenetic alteration processes and the erosional unconformity on the quality of the ore has been discussed. The fluid-rock interaction leads to the presence of boron (B), which is considered highly detrimental to the steel quality. Thus, the spatial distribution, location and the source of the B, as well as ways of dealing with its presence has been addressed. A regional model for the alteration of the Mn ores, based on the above results, has been produced. Five distinct drill core groups, based on mineralogical associations, textural features and geochemical characteristics were distinguished. The diagenetic textural features are comprised of carbonate minerals, and generally preserved within the lower grade ores. The higher grade ores show replacement of the carbonates with oxides and ‘secondary’ carbonate minerals, whilst the highest grade ore is almost completely devoid of the textural features. The upper ore bodies display higher Fe and Si contents, whereas the lower ore bodies show enrichment in Mn and Ca. This suggests pervasive and incipient oxidation, as well as carbonate leaching from the upper to the lower bed. An increase in grade is characterised by enrichment in Mn, Fe, Cu, Pb, Zn, Ni and Co, and depletion in Ca, Mg and Si. The high-grade ores are enriched in Ba, Sr, Li and B, with the upper ore beds generally exhibiting higher abundances of these elements relative to the lower ore bodies. Boron is mineralogically controlled and hosted by braunite, braunite-II, gaudefroyite, tephroite and the carbonate- and serpentine-group minerals. The trace elements were redistributed and locally concentrated
- Full Text:
Mineralogical and geochemical modification of manganese ore in response to fluid flow through the Hotazel Formation of the Kalahari Manganese Field, Northern Cape Province, South Africa
- Authors: Vafeas, Nicholas Andrew
- Date: 2018
- Subjects: Geology - South Africa - Northern Cape , Mineralogical chemistry - South Africa - Northern Cape , Manganese ores - South Africa - Northern Cape
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/292777 , uj:31822
- Description: Abstract: The Kalahari Manganese Field hosts the largest land based manganese resource in the world, comprising several variants of manganese ore-types including diagenetic/Mamatwan-type, supergene, hydrothermal/Wessels-type and thrust-related manganese ore. The lower manganese ore bed of the Hotazel Formation from five mines was investigated and analysed petrographically. Four of the five mines were further analysed geochemically and include Mamatwan mine in the south of the lower Kalahari Manganese Field, Sebilo Manganese Resources and United Kalahari Manganese mine in the central lower Kalahari Manganese Field and Gloria mine in the north of the lower Kalahari Manganese Field. The lower manganese ore bed from these mines is structurally located below the N-S trending Blackridge Thrust Fault and comprises diagenetic, low-grade, high carbonate-bearing ore. The ore from Mamatwan mine bears the closest similarities to a proposed original protolith comprising abundant kutnohoritic and calcitic ovoidal concretions, ribbons and lenses that are variably distributed within a braunite I and kutnohorite matrix. The highest manganese content is found within the lower half of the lower manganese ore bed and exhibits a Mn2O3 content of 30-45 wt %. In the central part of the lower Kalahari Manganese Field, diagenetic ore is located at shallow depths just below the Kalahari unconformity and as a result is subjected to the effects of classic supergene alteration. These effects have resulted in the replacement of much of the diagenetic carbonate and oxides by supergene oxyhydroxides, including cryptomelane, psilomelane and pyrolusite. The development of these phases, coupled with the removal of carbonates has increased the manganese content to 40-55 wt %. In addition, the precipitation of classic supergene phases resulted in an increase in bulk chemical potassium and barium abundances within the ore, as well as the residual enrichment of vanadium. The manganese ore in the area of Mukulu is positioned above the Blackridge Thrust Fault and as such, has been displaced several tens of kilometres eastwards. The resultant ore exhibits signs of Wessels event alteration, reaching Mn2O3 abundances of 60-80 wt % and is significantly coarse-grained relative to the diagenetic ore. Three stages of alteration were identified in the Thrust Manganese ore i.e. Stages 1, 2 and 3, and closely resemble the... , Ph.D. (Geology)
- Full Text:
- Authors: Vafeas, Nicholas Andrew
- Date: 2018
- Subjects: Geology - South Africa - Northern Cape , Mineralogical chemistry - South Africa - Northern Cape , Manganese ores - South Africa - Northern Cape
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/292777 , uj:31822
- Description: Abstract: The Kalahari Manganese Field hosts the largest land based manganese resource in the world, comprising several variants of manganese ore-types including diagenetic/Mamatwan-type, supergene, hydrothermal/Wessels-type and thrust-related manganese ore. The lower manganese ore bed of the Hotazel Formation from five mines was investigated and analysed petrographically. Four of the five mines were further analysed geochemically and include Mamatwan mine in the south of the lower Kalahari Manganese Field, Sebilo Manganese Resources and United Kalahari Manganese mine in the central lower Kalahari Manganese Field and Gloria mine in the north of the lower Kalahari Manganese Field. The lower manganese ore bed from these mines is structurally located below the N-S trending Blackridge Thrust Fault and comprises diagenetic, low-grade, high carbonate-bearing ore. The ore from Mamatwan mine bears the closest similarities to a proposed original protolith comprising abundant kutnohoritic and calcitic ovoidal concretions, ribbons and lenses that are variably distributed within a braunite I and kutnohorite matrix. The highest manganese content is found within the lower half of the lower manganese ore bed and exhibits a Mn2O3 content of 30-45 wt %. In the central part of the lower Kalahari Manganese Field, diagenetic ore is located at shallow depths just below the Kalahari unconformity and as a result is subjected to the effects of classic supergene alteration. These effects have resulted in the replacement of much of the diagenetic carbonate and oxides by supergene oxyhydroxides, including cryptomelane, psilomelane and pyrolusite. The development of these phases, coupled with the removal of carbonates has increased the manganese content to 40-55 wt %. In addition, the precipitation of classic supergene phases resulted in an increase in bulk chemical potassium and barium abundances within the ore, as well as the residual enrichment of vanadium. The manganese ore in the area of Mukulu is positioned above the Blackridge Thrust Fault and as such, has been displaced several tens of kilometres eastwards. The resultant ore exhibits signs of Wessels event alteration, reaching Mn2O3 abundances of 60-80 wt % and is significantly coarse-grained relative to the diagenetic ore. Three stages of alteration were identified in the Thrust Manganese ore i.e. Stages 1, 2 and 3, and closely resemble the... , Ph.D. (Geology)
- Full Text:
- «
- ‹
- 1
- ›
- »