A geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabwe

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dc.contributor.advisorGurney, John Jen_ZA
dc.contributor.authorMuusha, Miracleen_ZA
dc.date.accessioned2016-07-04T08:42:03Z
dc.date.available2016-07-04T08:42:03Z
dc.date.issued1997en_ZA
dc.descriptionBibliography: pages 52-56.en_ZA
dc.description.abstractThe River Ranch kimberlite is a 5.2 hectare diatreme from which the original surficial crater facies material has been removed by erosion. Proof of the prior existence of such a feature is provided by down rafted blocks of epiclastic and pyroclastic rocks exposed in the diatreme during open pit mining operations. Six intrusive kimberlite phases have been recognised in the diatreme by careful mapping and confirmed by petrographic observations, particularly variations in groundmass mineralogy. Subsequent to emplacement, the diatreme has been cut by intrusive tholeitic dolerites of apparently Karoo age. The River Ranch occurrence is classified as a Group I kimberlite although the definitive isotopic evidence is lacking due to pervasive alteration of the exposed rocks. The absence of megacrystic and groundmass ilmenite and the presence of groundmass diopside are unusual for the group of rocks. However the presence of monticellite and the low abundance of phlogopite argue against a Group II classification. The overwhelmingly peridotitic nature of the mantle mineral macrocrysts in the kimberlite is consistent with the observations of Kopylova et al (1995) that the diamonds at River Ranch are predominantly peridotitic and are likely to have formed in a single process. The approximate equilibration temperature for a small suite of coarse grained lherzolite from the kimberlites is 1200°C, suggesting a geothermal gradient rather higher than seen in the Kaap-Vaal craton. The diamonds at River Ranch are predominantly brown, strongly resorbed and have less than average value. It is predicted that a combination of kimberlite petrography, micro-diamond measurements and mantle macrocryst studies should be a valuable aid to grade control and mine planning.en_ZA
dc.identifier.apacitationMuusha, M. (1997). <i>A geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabwe</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Geological Sciences. Retrieved from http://hdl.handle.net/11427/20191en_ZA
dc.identifier.chicagocitationMuusha, Miracle. <i>"A geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabwe."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1997. http://hdl.handle.net/11427/20191en_ZA
dc.identifier.citationMuusha, M. 1997. A geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabwe. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Muusha, Miracle AB - The River Ranch kimberlite is a 5.2 hectare diatreme from which the original surficial crater facies material has been removed by erosion. Proof of the prior existence of such a feature is provided by down rafted blocks of epiclastic and pyroclastic rocks exposed in the diatreme during open pit mining operations. Six intrusive kimberlite phases have been recognised in the diatreme by careful mapping and confirmed by petrographic observations, particularly variations in groundmass mineralogy. Subsequent to emplacement, the diatreme has been cut by intrusive tholeitic dolerites of apparently Karoo age. The River Ranch occurrence is classified as a Group I kimberlite although the definitive isotopic evidence is lacking due to pervasive alteration of the exposed rocks. The absence of megacrystic and groundmass ilmenite and the presence of groundmass diopside are unusual for the group of rocks. However the presence of monticellite and the low abundance of phlogopite argue against a Group II classification. The overwhelmingly peridotitic nature of the mantle mineral macrocrysts in the kimberlite is consistent with the observations of Kopylova et al (1995) that the diamonds at River Ranch are predominantly peridotitic and are likely to have formed in a single process. The approximate equilibration temperature for a small suite of coarse grained lherzolite from the kimberlites is 1200°C, suggesting a geothermal gradient rather higher than seen in the Kaap-Vaal craton. The diamonds at River Ranch are predominantly brown, strongly resorbed and have less than average value. It is predicted that a combination of kimberlite petrography, micro-diamond measurements and mantle macrocryst studies should be a valuable aid to grade control and mine planning. DA - 1997 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1997 T1 - A geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabwe TI - A geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabwe UR - http://hdl.handle.net/11427/20191 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/20191
dc.identifier.vancouvercitationMuusha M. A geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabwe. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1997 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/20191en_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.otherGeological Sciencesen_ZA
dc.titleA geological study of the River Ranch kimberlite pipe and associated diamonds and mantle minerals : Limpopo Mobile Belt, Zimbabween_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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