Isotopic resetting of zircon : influence of age, temperature and chemical environment
- Authors: Magwaza, Boniswa Nolwazi
- Date: 2019
- Subjects: Sedimentation and deposition - South Africa , Geology - South Africa
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/417502 , uj:35360
- Description: Abstract: To assess the causes and extent of isotopic resetting of zircon, U-Pb and Lu-Hf analyses have been performed on zircons from Archean and Bushveld granites as well as Transvaal sediments which have been intruded by magmas of the Bushveld Complex, Pilanesberg Complex, Spitskop Complex, Goudini Complex, and Karoo dolerites in the vicinity of Bushveld Complex using laser ablation multi-collector inductively coupled plasma source mass spectrometry (LA-MC-ICPMS). U-Pb results for zircon analyses from both Archean granites and Transvaal sedimentary rocks indicate that they have undergone partial Pb loss and age resetting. Pb loss was influenced by radiation damage in zircons and metamorphism. Contributions from the Bushveld Complex thermal overprint cannot be excluded, based on evidence from concordia diagrams and 207Pb/206Pb ages; two samples of Magaliesberg sandstones (MEMG 3, 4), closest to the contact with the Marginal Zone, are affected the most. The presence of common Pb and its correction also contributed in shifting the data towards younger 207Pb/206Pb ages. Younger alkaline intrusions as well as Karoo dolerites did not have much influence on zircon signatures. There are only small differences in initial Hf ratios of analyses within the same sample, indicating that the Lu-Hf isotope system remained undisturbed. There are no appreciable effects on trace element concentrations to support that disturbance in U-Pb signatures of zircons is accompanied by their modifications. .. , M.Sc. (Geology)
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- Authors: Magwaza, Boniswa Nolwazi
- Date: 2019
- Subjects: Sedimentation and deposition - South Africa , Geology - South Africa
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/417502 , uj:35360
- Description: Abstract: To assess the causes and extent of isotopic resetting of zircon, U-Pb and Lu-Hf analyses have been performed on zircons from Archean and Bushveld granites as well as Transvaal sediments which have been intruded by magmas of the Bushveld Complex, Pilanesberg Complex, Spitskop Complex, Goudini Complex, and Karoo dolerites in the vicinity of Bushveld Complex using laser ablation multi-collector inductively coupled plasma source mass spectrometry (LA-MC-ICPMS). U-Pb results for zircon analyses from both Archean granites and Transvaal sedimentary rocks indicate that they have undergone partial Pb loss and age resetting. Pb loss was influenced by radiation damage in zircons and metamorphism. Contributions from the Bushveld Complex thermal overprint cannot be excluded, based on evidence from concordia diagrams and 207Pb/206Pb ages; two samples of Magaliesberg sandstones (MEMG 3, 4), closest to the contact with the Marginal Zone, are affected the most. The presence of common Pb and its correction also contributed in shifting the data towards younger 207Pb/206Pb ages. Younger alkaline intrusions as well as Karoo dolerites did not have much influence on zircon signatures. There are only small differences in initial Hf ratios of analyses within the same sample, indicating that the Lu-Hf isotope system remained undisturbed. There are no appreciable effects on trace element concentrations to support that disturbance in U-Pb signatures of zircons is accompanied by their modifications. .. , M.Sc. (Geology)
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The stratigraphy, sedimentology and petrography of the number 2 coal seam in the northern portion of the Permian Highveld Coalfield, Karoo Basin, South Africa
- Authors: Francis, Fabian Anthony
- Date: 2019
- Subjects: Geology, Stratigraphic , Coal - Geology - South Africa , Sedimentation and deposition - South Africa
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/417413 , uj:35349
- Description: Abstract: This study focusses on the stratigraphy, sedimentology and petrography of the No. 2 depositional sequence in the northern portion of the Permian Highveld Coalfield, Karoo Basin, South Africa. A database comprising 7 000 vertical boreholes was utilised to create series of elevation, thickness, quality and petrographic distributions (called grids) across a 4 500 km2 study area. The primary aim of this study is to develop a palaeoenvironmental and depositional model for the No. 2 depositional sequence, from the base of the Dwyka Group up to the top of the No. 2 Coal Seam (C2 Seam). This study provides a sub-regional database of the C2 Seam, its physical attributes (proximate analyses), general petrographic composition and overall distribution of the coal relative to its interpreted depositional environment, should this seam ever be mined. An investigation of this scale has never been done before in the Highveld Coalfield... , M.Sc. (Geology)
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- Authors: Francis, Fabian Anthony
- Date: 2019
- Subjects: Geology, Stratigraphic , Coal - Geology - South Africa , Sedimentation and deposition - South Africa
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/417413 , uj:35349
- Description: Abstract: This study focusses on the stratigraphy, sedimentology and petrography of the No. 2 depositional sequence in the northern portion of the Permian Highveld Coalfield, Karoo Basin, South Africa. A database comprising 7 000 vertical boreholes was utilised to create series of elevation, thickness, quality and petrographic distributions (called grids) across a 4 500 km2 study area. The primary aim of this study is to develop a palaeoenvironmental and depositional model for the No. 2 depositional sequence, from the base of the Dwyka Group up to the top of the No. 2 Coal Seam (C2 Seam). This study provides a sub-regional database of the C2 Seam, its physical attributes (proximate analyses), general petrographic composition and overall distribution of the coal relative to its interpreted depositional environment, should this seam ever be mined. An investigation of this scale has never been done before in the Highveld Coalfield... , M.Sc. (Geology)
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