The geological evolution of the eastern Richtersveld

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dc.contributor.advisorKroner, Aen_ZA
dc.contributor.advisorJoubert, Pen_ZA
dc.contributor.authorRitter, Ulrichen_ZA
dc.date.accessioned2015-03-04T18:59:47Z
dc.date.available2015-03-04T18:59:47Z
dc.date.issued1978en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractThe lithology of the early Proterozoic (-1950-1750 my) Richtersveld is characterised by predominantly calc-alkaline volcanics, (De Hoop Subgroup) overlain by and intercalated with quartzitic metasediments into which the mainly granodioritic rocks of the Vioolsdrif Intrusive Suite (VIS) were emplaced. Metavolcanics and sediments of the De Hoop Subgroup have been subdivided into formations, and their paleogeographic environments have been deduced from lithological criteria. In the north eastern Richtersveld systematic reconstruction permitted the recognition of four distinct depositional domains: (a) a high altitude volcanic terrain in the northeast, characterised by a great thickness of an entirely volcanic succession. (b) a synvolcanic graben structure in the southeast; infilled by melanocratic volcanics and immature sediments. (c) a low-lying volcanic terrain in the southwest, possibly representinga coastal plain, lithologically characterised by volcanic debris and redeposited volcanics of domain (a).d) marine quartzites in the south, indicating a marine ingression from the southwest towards the end of the volcanic cycle ,In the southeastern Richtersveld more strongly metamorphosed acid to intermediate volcanics overlie metasediments of the Namaqua Metamorphic Complex(NMC).Within the Vioolsdrif Intrusive Suite four intrusive phases can be distinguished. The oldest phase, a fine-grained granodiorite, is only tentatively assigned to the Vioolsdrif Intrusive Suite and probably constitutes a subvolcanic member of intermediate metavolcanics of the Kookrivier Formation. It was followed by syntectonic even-grained granodiorite and by posttectonic granite and leucogranite. Textural analysis of the undeformed granite phase provided information as to its intrusion and crystallisation history and the sequence of crystallisation. Since the latter allows the estimate of the water content of the initial magma, and as water content of the magma determines - according to some models -geological position and extent of porphyry ore deposits, predictions could be made as to the probable site and extent of possible porphyry ore deposits, which are in agreement with preliminary results obtained during field work. The metamorphic and tectonic development probably started soon after or even during deposition of the supracrustal rocks. Low grade metamorphism of low pressure type (andalusite-sillimanite facies series sensu Miyashiro, 1973) in the central northeastern Richtersveld (associated with tight to isoclinal Fi-folds of different magnitudes) and migmatisation in the south and northeast (mainly postdating F1) suggest an essentially zoned metamorphic complex with increasing grade of metamorphism towards the margins of the Richtersveld.en_ZA
dc.identifier.apacitationRitter, U. (1978). <i>The geological evolution of the eastern Richtersveld</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Geological Sciences. Retrieved from http://hdl.handle.net/11427/12564en_ZA
dc.identifier.chicagocitationRitter, Ulrich. <i>"The geological evolution of the eastern Richtersveld."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1978. http://hdl.handle.net/11427/12564en_ZA
dc.identifier.citationRitter, U. 1978. The geological evolution of the eastern Richtersveld. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Ritter, Ulrich AB - The lithology of the early Proterozoic (-1950-1750 my) Richtersveld is characterised by predominantly calc-alkaline volcanics, (De Hoop Subgroup) overlain by and intercalated with quartzitic metasediments into which the mainly granodioritic rocks of the Vioolsdrif Intrusive Suite (VIS) were emplaced. Metavolcanics and sediments of the De Hoop Subgroup have been subdivided into formations, and their paleogeographic environments have been deduced from lithological criteria. In the north eastern Richtersveld systematic reconstruction permitted the recognition of four distinct depositional domains: (a) a high altitude volcanic terrain in the northeast, characterised by a great thickness of an entirely volcanic succession. (b) a synvolcanic graben structure in the southeast; infilled by melanocratic volcanics and immature sediments. (c) a low-lying volcanic terrain in the southwest, possibly representinga coastal plain, lithologically characterised by volcanic debris and redeposited volcanics of domain (a).d) marine quartzites in the south, indicating a marine ingression from the southwest towards the end of the volcanic cycle ,In the southeastern Richtersveld more strongly metamorphosed acid to intermediate volcanics overlie metasediments of the Namaqua Metamorphic Complex(NMC).Within the Vioolsdrif Intrusive Suite four intrusive phases can be distinguished. The oldest phase, a fine-grained granodiorite, is only tentatively assigned to the Vioolsdrif Intrusive Suite and probably constitutes a subvolcanic member of intermediate metavolcanics of the Kookrivier Formation. It was followed by syntectonic even-grained granodiorite and by posttectonic granite and leucogranite. Textural analysis of the undeformed granite phase provided information as to its intrusion and crystallisation history and the sequence of crystallisation. Since the latter allows the estimate of the water content of the initial magma, and as water content of the magma determines - according to some models -geological position and extent of porphyry ore deposits, predictions could be made as to the probable site and extent of possible porphyry ore deposits, which are in agreement with preliminary results obtained during field work. The metamorphic and tectonic development probably started soon after or even during deposition of the supracrustal rocks. Low grade metamorphism of low pressure type (andalusite-sillimanite facies series sensu Miyashiro, 1973) in the central northeastern Richtersveld (associated with tight to isoclinal Fi-folds of different magnitudes) and migmatisation in the south and northeast (mainly postdating F1) suggest an essentially zoned metamorphic complex with increasing grade of metamorphism towards the margins of the Richtersveld. DA - 1978 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1978 T1 - The geological evolution of the eastern Richtersveld TI - The geological evolution of the eastern Richtersveld UR - http://hdl.handle.net/11427/12564 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/12564
dc.identifier.vancouvercitationRitter U. The geological evolution of the eastern Richtersveld. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1978 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/12564en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Geological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherGeologyen_ZA
dc.titleThe geological evolution of the eastern Richtersvelden_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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