A study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibia

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dc.contributor.advisorFrimmel, Hartwig Een_ZA
dc.contributor.authorChadwick, Peter Jen_ZA
dc.date.accessioned2016-11-16T13:22:26Z
dc.date.available2016-11-16T13:22:26Z
dc.date.issued1993en_ZA
dc.descriptionBibliography: pages 131-138.en_ZA
dc.description.abstractThis study is focussed on the petrographic and isotopic aspects of the crystallization processes taking place in carbonate-hosted Berg Aukas-type Zn-Pb-V deposits of the Otavi Mountain Land in Northern Namibia. Numerous studies have shown that ore formation in Mississippi Valley-type deposits bears a close relationship with carbonate diagenesis and basin evolution. The application of isotope (Sr , O, C) techniques as regards to timing and mechanisms of ore-forming processes, as a possible tool in exploration, is especially emphasized in this study. Detailed petrographic and isotope-geochemical investigations were carried out in the Late Precambrian deposits of Berg Aukas, situated just north of the town of Grootfontein, in addition to the Odin Prospect situated to the east of Kombat Mine. Both ore deposits display many similarities, but also show differences concerning the facies-bound character of the host rock, which is related to the paleogeographic position and the tectonic framework. In spite of these differences, similar complex diagenetic textures and structures suggest a comparable diagenetic evolution. Isotope-geochemical analyses have been performed on samples of consecutive crystallization generations, or dolomite types. This was checked petrographically using cathodoluminescence, and sample homogeneity was monitored by means of X-ray diffraction. The results reveal significant isotopic trends, which are interpreted to reflect the diagenetic evolution of the respective basin. A consistent strontium isotope trend is noted, and in both cases studied, the later crystallization generations are enriched in radiogenic strontium, as compared to the earlier ones, which tend to approximate the strontium isotope composition of contemporaneous seawater. The increase in ⁸⁷Sr/⁸⁶Sr ratios in subsequent diagenetic generations is explained with the pore fluids evolving towards more radiogenic compositions with advancing diagenetic stages. The influence of basinal brines enriched in radiogenic strontium as a consequence of the reaction with Rb-bearing phases, especially detrital (clay) minerals hosted by underlying basement rocks, is considered to be most likely. Stable isotope investigations carried out on identical samples also show certain trends, though these are less pronounced compared to the strontium studies. In general, the later crystallization generations are depleted in the heavy isotope of carbon and oxygen, which is explained in terms of changing physico-chemical conditions of the system, in combination with changing fluid compositions during the course of diagenetic evolution. By combining petrographic and isotopic observations, the genetic hypothesis for the ore deposits at Berg Aukas and Odin can be significantly constrained. In both cases, a model is proposed based on basinal brine migration during advanced diagenetic stages. These brines were enriched in radiogenic strontium due to the interaction with basement rocks. Thus, the combination of petrographic and isotope-geochemical methods has proved to constitute a powerful tool in tracing the diagenetic evolution, and in an exploration sense may be used to identify imprints of fluid circulation, which mobilized and concentrated metals during various stages of basin evolution.en_ZA
dc.identifier.apacitationChadwick, P. J. (1993). <i>A study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibia</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Geological Sciences. Retrieved from http://hdl.handle.net/11427/22548en_ZA
dc.identifier.chicagocitationChadwick, Peter J. <i>"A study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibia."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1993. http://hdl.handle.net/11427/22548en_ZA
dc.identifier.citationChadwick, P. 1993. A study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibia. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Chadwick, Peter J AB - This study is focussed on the petrographic and isotopic aspects of the crystallization processes taking place in carbonate-hosted Berg Aukas-type Zn-Pb-V deposits of the Otavi Mountain Land in Northern Namibia. Numerous studies have shown that ore formation in Mississippi Valley-type deposits bears a close relationship with carbonate diagenesis and basin evolution. The application of isotope (Sr , O, C) techniques as regards to timing and mechanisms of ore-forming processes, as a possible tool in exploration, is especially emphasized in this study. Detailed petrographic and isotope-geochemical investigations were carried out in the Late Precambrian deposits of Berg Aukas, situated just north of the town of Grootfontein, in addition to the Odin Prospect situated to the east of Kombat Mine. Both ore deposits display many similarities, but also show differences concerning the facies-bound character of the host rock, which is related to the paleogeographic position and the tectonic framework. In spite of these differences, similar complex diagenetic textures and structures suggest a comparable diagenetic evolution. Isotope-geochemical analyses have been performed on samples of consecutive crystallization generations, or dolomite types. This was checked petrographically using cathodoluminescence, and sample homogeneity was monitored by means of X-ray diffraction. The results reveal significant isotopic trends, which are interpreted to reflect the diagenetic evolution of the respective basin. A consistent strontium isotope trend is noted, and in both cases studied, the later crystallization generations are enriched in radiogenic strontium, as compared to the earlier ones, which tend to approximate the strontium isotope composition of contemporaneous seawater. The increase in ⁸⁷Sr/⁸⁶Sr ratios in subsequent diagenetic generations is explained with the pore fluids evolving towards more radiogenic compositions with advancing diagenetic stages. The influence of basinal brines enriched in radiogenic strontium as a consequence of the reaction with Rb-bearing phases, especially detrital (clay) minerals hosted by underlying basement rocks, is considered to be most likely. Stable isotope investigations carried out on identical samples also show certain trends, though these are less pronounced compared to the strontium studies. In general, the later crystallization generations are depleted in the heavy isotope of carbon and oxygen, which is explained in terms of changing physico-chemical conditions of the system, in combination with changing fluid compositions during the course of diagenetic evolution. By combining petrographic and isotopic observations, the genetic hypothesis for the ore deposits at Berg Aukas and Odin can be significantly constrained. In both cases, a model is proposed based on basinal brine migration during advanced diagenetic stages. These brines were enriched in radiogenic strontium due to the interaction with basement rocks. Thus, the combination of petrographic and isotope-geochemical methods has proved to constitute a powerful tool in tracing the diagenetic evolution, and in an exploration sense may be used to identify imprints of fluid circulation, which mobilized and concentrated metals during various stages of basin evolution. DA - 1993 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1993 T1 - A study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibia TI - A study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibia UR - http://hdl.handle.net/11427/22548 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/22548
dc.identifier.vancouvercitationChadwick PJ. A study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibia. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1993 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/22548en_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.titleA study of the berg Aukas-type Pb-Zn-V deposits in the Otavi mountain land, Namibiaen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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