List of Titles

Application of geophysical methods to investigate the subsurface geology of Kuruman and Kono areas in Griqualand West Basin, South Africa

- Mthintweni, Sylvia Lwandisa

Authors: Mthintweni, Sylvia Lwandisa
Date: 2021-05
Subjects: Geology , Soil surveys--Geophysical methods
Language: English
Type: Master's theses , text
Identifier: http://hdl.handle.net/10353/22555 , vital:52456
Description: Kono and Kuruman areas belong to the geology of the Campbell Rand and Asbestos Hills Subgroups, Ghaap Group in the Griqualand West Basin. Campbell Rand Subgroup comprises interbedded chert, limestone and dolomite rocks of dominantly the Kogelbeen Formation covered with a thick regolith of red sand and weathered material. The Asbestos Hills Subgroup consists of a banded iron formation (BIF) of the Kuruman Formation overlain by the Kalahari sands. Petrographic and mineralogical analyses and various geophysical methods were utilised to investigate the surface and subsurface conditions of the study areas. This study was done to characterize and understand the geology of Kuruman and Kono and identify the structural lineaments. Rock samples of varying lithology were collected in the field for laboratory analyses that include preparation of thin sections and petrographic analyses and density and porosity determinations. Both the petrographic results and XRF analyses revealed that iron oxide (Fe2O3) and silica (SiO2) are the most abundant minerals in BIF. Iron oxide and silica percentages range between 21.17-39.97 wt % and 59.03-78.01 wt %, respectively. BIF has an average density of 3.0 g/cm3 and porosity of 2.51% and dolomite has an average density of 2.8 g/cm3 and porosity of 0.17%. The Bouguer anomaly values range between - 119.00 mGal and -1 17.29 mGals. High gravity anomalies are attributed to shallow fresh bedrock and this was confirmed by the seismic line that cuts across the map. The gravity high observed in the Kuruman profile coincides with the thick BIF body observed in the field. The gravity analytic signal indicates a width of about 1125 m for the BIF and inferred two normal faults at about 675 m and 1500 m. The high magnetic anomalies in the ground magnetic map correspond to chert rich dolomite ridges in the field and the intermediate to lows correspond to dolomitic terrains. A geological map was superimposed on an aeromagnetic map to correlate the two. The linear magnetic high trending from NW – SE coincide with BIF. Older dykes trending east-west were intruded by younger dykes trending north-south. The total counts channel map for Kono area shows the measured total gamma radiation count in the study area and the concentrations of radioelements range between 51.84 and 94.64 counts/sec. The concentrations of potassium, thorium and uranium range from 0.12 – 0.51%, 0.83 – 5.23 ppm and 0.06 – 2.27 ppm, respectively. A high concentration of radiometric elements cutting through the central part of the map stretching from northwest to southeast was observed in a ternary map and this could be associated with chert rich dolomite outcrops. Seismic refraction tomography (SRT) cross-section for study area 1 in Kono revealed 3 different layers. The topmost layer comprises sand and loose material and has a velocity ranging from 614 – 1194 m/s. It is underlain by highly to slightly weathered dolomite with a velocity that ranges from 1774 – 2354 m/s. Layer 3 is the fresh bedrock dolomite and has a velocity of 2934 m/s. Three layers were observed in study area 2 for Kuruman. Layer 1 had a velocity of 300 – 750 m/s, the second layer had a velocity of 1200 – 2100 m/s and the bottom layer’s velocity was 2500 – 2999 m/s. An inferred fault is indicated on the western side of the seismic section at about 650 m. The dipole-dipole resistivity model for the main survey line in Kono revealed that the area is underlain by fractured bedrock with high resistivity in places. A thick conductive stratum was observed at the beginning of the line. The resistivity models for the sinkhole in Kono were characterized into three resistivity zones. High resistivity values (1000 – 134202 Ωm) are due to slightly weathered to fresh bedrock, intermediate values (24 – 5770 Ωm) are interpreted to be due to highly weathered dolomite and compacted dolomitic soils and very low resistivity zones (4 – 397 Ωm) are inferred to be karstic cavities. , Thesis (MSc) -- Faculty of Science and Agriculture, 2021
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Date Issued: 2021-05

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The petrogenesis of the volcanic rocks of the Witwatersrand triad in the Klerksdorp area, Transvaal

- Bowen, Michael Peter

Authors: Bowen, Michael Peter
Date: 1985
Subjects: Volcanic rocks , Witwatersrand triad , Klerksdorp , Transvaal , Northwest Province , South Africa , Chemical analysis , Magma , Geology
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:4909 , http://hdl.handle.net/10962/d1001569
Description: Several hundred chemical analyses of early Proterozoic lavas of the Witwatersrand triad (incorporating the Dominion Group, Witwatersrand Supergroup and Ventersdorp Supergroup) in the Klerksdorp area, have revealed the presence of various distinct magma types. These essentially correspond to formally defined lithostratigraphic units, but several inconsistencies have necessitated the use of informal nomenclature. The lavas have been regionally metamorphosed to low-grade, greenschist facies assemblages. Original igneous textures are preserved, despite a metamorphic overprint. Metamorphism has resulted in a certain degree of random chemical remobilization. Ba, Sr, Rb, K₂0, Na₂0 and CaO have been highly mobile, and their usefulness in petrogenetic modelling is extremely limited. In contrast, Zr, Nb, Y, LREE's, Cr, Ni, Ti0₂ P₂0₅ and Al₂0₃ have remained immobile. Ti/Zr and Ti/P ratios together constitute efficient discriminating variables for characterizing the different magma types. Lava compositions range from primitive Mg-rich tholeiites to rhyolites, the bulk being tholeiitic andesites. Al₂0₃ contents do not exceed 15%, a feature which reflects the tholeiitic, as opposed to calcalkaline, character of these lavas. Two magma-types are present within the Dominion Group, which is a typical example of bimodal volcanism. The Dominion basic lavas are overlain by the Dominion acid porphyries, with a limited amount of interfingering. The basic lava suite is highly fractionated, with compositions ranging from Mg-, Cr- and Ni-rich tholeiites (close to primary mantle melts) to evolved tholeiitic andesites. The most primitive liquids evolved by 45% fractional crystallization of hornblende, followed by a further 70% crystallization of an orthopyroxene-plagioclase assemblage containing up to 3% sulphides. The Dominion porphyries are rhyolitic, display very limited compositional variation, and probably represent a crustal melt related to the same magmatic event which produced the basic lavas. The only lavas from the Witwatersrand Supergroup present in the Klerksdorp area are those of the Crown Formation (Jeppestown amygdaloid). These are tholeiitic dacites which display extremely limited compositional variation, and are unrelated to any of the other magmas of the Witwatersrand triad. The Ventersdorp Supergroup comprises 4 magma-types: The Kliprivierberg Group lavas at the base are subdivisible into 3 sub-types on the basis of Zr contents. (Zr>11Oppm) are the most evolved. They are tholeiitic andesites which display fairly limited compositional variation. It is likely that more evolved compositions are present in other areas where the porphyritic lavas which characterize this unit are better developed. The overlying Orkney lavas are characterized by 110ppm>Zr>90ppm. They are tholeiitic andesites of similar composition to the Alberton lavas, but have lower incompatible element levels, higher siderophile element levels, and are of extremely uniform composition. The uppermost Loraine/Edenville lavas range from magnesian tholeiites to tholeiitic andesites. They are distinguished by Zr< 90ppm, and contain the most primitive magmas af the Witwatersrand triad, with up to 17,5% MgO, 2600ppm Cr, 600ppm Ni and M-values up to 77. The most primitive liquids evolved by 38% fractional crystallization of orthopyroxene ∓ chromite, followed by 35% fractional crystallization of an extract containing clinopyroxene and plagioclase. The absence of olivine precipitation is a result of the inherently high Si0₂ content of the magma. The Loraine/Edenville, Orkney and Alberton lavas do not lie on a common liquid line of descent, but are probably consanguinous. The Platberg Group overlies the Kliprivierberg Group, and has a coarse-clastic sedimentary unit, the Kameeldoorns Formation, at the base. Three petrographically distinct porphyritic lava sequences overlie the Kameeldoorns Formation, namely the informal "Goedgenoeg formation", the Makwassie quartz-feldspar porphyries and the Rietgat Formation. Despite petrographic differences, the Goedgenoeg and Rietgat lavas are chemically indistinguishable and thus form a single magma-type. The Makwassie porphyries are dacitic in composition with a high proportion of feldspar and quartz phenocrysts. Rational variation trends are attributed to a nett loss of Si0₂ during secondary alteration. The porphyries are probably of crustal origin. The Goedgenoeg/Rietgat lavas display unusual chemistry and a broad, irrational compositional spectrum. They contain very high incompatible element levels, high nonnative quartz, as well as high MgO, M-values, Cr and Ni relative to the other tholeiitic andesites of the Witwatersrand triad. It is tentatively suggested that they are hybrid magmas containing both crust and mantle components, the former possibly represented by the Makwassie porphyries. Field evidence suggests that Platberg volcanism commenced directly after Klipriviersberg volcanism ceased, and was accompanied by a period of enhanced tectonic activity. The Platberg lavas thus probably reflect a crustal melting cycle associated with the Klipriviersberg magmatic event. The Allanridge lavas are the youngest rocks of the Witwatersrand triad. They are separated from the Platberg Group by a unit of flat-lying sediments, the Bothaville Formation, which was deposited after an extended period of peneplanation. The Allanridge lavas form a separate magma-type. They are tholeiitic andesites of similar composition to the Alberton lavas, but have higher incompatible element levels and are not consanguinous. The compositional similarities amongst the basic magma-types of the Witwatersrand triad suggests that all were generated in an hydrous mantle. Interelement ratio differences between the various magma-types nevertheless support the concept that the mantle was chemically heterogeneous during the early Proterozoic.
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Date Issued: 1985

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Geology and mine planning

- Maturana-Bascope, M

Authors: Maturana-Bascope, M
Date: 1983
Subjects: Geology , Mining geology , Geology, Economics
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:5027 , http://hdl.handle.net/10962/d1006896
Description: From introduction: This dissertation aims to review the main aspects involved in mine planning, in order to provide the geologists with the main criteria to obtain a preliminary estimate of the minability of an in situ orebody, and to make the geologists aware of the information they can contribute to the planning engineers. Furthermore, an understanding of the basic principles behind mine planning may help the exploration geologist to select more realistic targets of exploration.
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Date Issued: 1983

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A review of the geology of primary tin deposits with emphasis on the factors that control grade and tonnage

- Archer, Paul D

Authors: Archer, Paul D
Date: 1981
Subjects: Tin ores , Granite , Geology , Tonnage
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:4912 , http://hdl.handle.net/10962/d1001572
Description: "The purpose of this dissertation is ... to review the economic geology of primary tin deposits and the geological factors that control grade and tonnage . The work concludes with a discussian of the implications of these geological controls on evaluation"-- Introd., p. 1
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Date Issued: 1981

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