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...
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Renewed investigations at Taung; 90 years after the discovery of Australopithecus africanus
- Kuhn, Brian F., Herries, Andy I.R., Price, Gilbert J., Baker, Stephanie E., Hopley, Philip, Menter, Colin, Caruana, Matthew V.
- Authors: Kuhn, Brian F. , Herries, Andy I.R. , Price, Gilbert J. , Baker, Stephanie E. , Hopley, Philip , Menter, Colin , Caruana, Matthew V.
- Date: 2016
- Subjects: Taung child , Geochronology , Australopithecus africanus
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/225421 , uj:22766 , Citation: Kuhn, B.F. et al. 2016. Renewed investigations at Taung ; 90 years after the discovery of Australopithecus africanus. Palaeontologia Africana, 51:10–26. , ISSN: 2410-4418
- Description: Abstract: 2015 marked the 90th anniversary of the description of the first fossil ofAustralopithecus africanus, commonly known as the Taung Child, which was unearthed during blasting at the Buxton-Norlim Limeworks (referred to as the BNL) 15 km SE of the town of Taung, South Africa. Subsequently, this site has been recognized as a UNESCOWorld Heritage site on the basis of its importance to southern African palaeoanthropology. Some other sites such as Equus Cave and Black Earth Cave have also been investigated; but the latter not since the 1940s. These sites indicate that the complex of palaeontological and archaeological localities at the BNL preserve a time sequence spanning the Pliocene to the Holocene. The relationship of these various sites and how they fit into the sequence of formation of tufa, landscapes and caves at the limeworks have also not been investigated or discussed in detail since Peabody’s efforts in the 1940s. In this contribution we mark the 90th anniversary of the discovery and description of the Taung Child by providing a critical review of previous work at Taung based on our recent preliminary work at the site. This includes a reassessment of the Taung Child Type Site, as well as renewed excavations at Equus Cave and the lesser-known locality and little-investigated Black Earth Cave. Preliminary results suggest that much of our previous understandings of the BNL’s formational history and site formation processes need to be reassessed. Only through detailed analysis on the BNL as a whole can we understand this complex depositional environment.
- Full Text:
- Authors: Kuhn, Brian F. , Herries, Andy I.R. , Price, Gilbert J. , Baker, Stephanie E. , Hopley, Philip , Menter, Colin , Caruana, Matthew V.
- Date: 2016
- Subjects: Taung child , Geochronology , Australopithecus africanus
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/225421 , uj:22766 , Citation: Kuhn, B.F. et al. 2016. Renewed investigations at Taung ; 90 years after the discovery of Australopithecus africanus. Palaeontologia Africana, 51:10–26. , ISSN: 2410-4418
- Description: Abstract: 2015 marked the 90th anniversary of the description of the first fossil ofAustralopithecus africanus, commonly known as the Taung Child, which was unearthed during blasting at the Buxton-Norlim Limeworks (referred to as the BNL) 15 km SE of the town of Taung, South Africa. Subsequently, this site has been recognized as a UNESCOWorld Heritage site on the basis of its importance to southern African palaeoanthropology. Some other sites such as Equus Cave and Black Earth Cave have also been investigated; but the latter not since the 1940s. These sites indicate that the complex of palaeontological and archaeological localities at the BNL preserve a time sequence spanning the Pliocene to the Holocene. The relationship of these various sites and how they fit into the sequence of formation of tufa, landscapes and caves at the limeworks have also not been investigated or discussed in detail since Peabody’s efforts in the 1940s. In this contribution we mark the 90th anniversary of the discovery and description of the Taung Child by providing a critical review of previous work at Taung based on our recent preliminary work at the site. This includes a reassessment of the Taung Child Type Site, as well as renewed excavations at Equus Cave and the lesser-known locality and little-investigated Black Earth Cave. Preliminary results suggest that much of our previous understandings of the BNL’s formational history and site formation processes need to be reassessed. Only through detailed analysis on the BNL as a whole can we understand this complex depositional environment.
- Full Text:
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