D.Phil. (Geology) / Please refer to full text to view abstract

Field and laboratory spectroscopy are sub-fields of remote sensing, where the radiometric data of materials are individually measured either where the materials occur in situ or in a controlled laboratory environment. Both applications require the use of a spectroradiometer to record this reflected electromagnetic radiation. The spectral properties of rocks from the Mambulu Complex in the Natal Belt have not been studied previously. Four dominant rock types, namely, massif-type anorthosite, leuco-gabbro, pyroxenite and magnetitite were sampled from the Mambulu Complex and their spectral reflectances measured. Absorption features were determined after continuum removal was applied to the spectra. Anorthosite showed absorption features at 480-490, 592, 603, 608, 627-726, 765, 1410, 1905-1955, 2200, 2250 and 2330nm. For leuco-gabbro absorption features were observed at 481, 950-1010, 1407, 1917, 2206, 2252, and 2300-2340nm. Magnetitite displayed absorption features at 414, 460-515, 620-715, 982, 1380-1480, 1800, 1905-1930 and 2145-2330nm. For medium-grained pyroxenite absorption features were present at 410-420, 483, 680, 977-993, 1410-1415, 1800, 1920, 2205, 2250, 2307, 2400 and 2430nm. Coarse-grained pyroxenite showed absorption features at 460-727, 979, 1000, 1401, 1422, 1800, 1913, 1930, 2203, 2258, 2321, 2388 and 2421nm. ANOVAs and Bonferroni tests were applied to the spectral data to calculate significant spectral differences and between which pairs of rocks these significant differences occurred. Results showed that there were significant spectral differences between all the rock types of the Mambulu Complex. The variability of spectral characteristics within rock species was attributed to the difference in composition of fresh and weathered surfaces; and the significant spectral differences between rock samples can be attributed primarily to differences in mineral composition. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2012.

D.Phil. (Geology) / Please refer to full text to view abstract

Thesis (DSc (Geology))--Stellenbosch University, 1948. / 375 leaves printed on single pages, preliminary pages and numbered pages1-312. Includes bibliography, figures and photos. / Digitized at 330 dpi color PDF format (OCR), using KODAK i 1220 PLUS scanner.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Diamictites are sedimentary deposits that originate from a number of different environments, the most common being associated with a glacial environment. Although this association is not, in all cases correct, it is still being used due to the lack of knowledge to confidently identify, classify and interpret a depositional environment for diamictite deposits. During the late Carboniferous to early Permian, two diamictite deposits formed during the development of the Cape Basin and Main Karoo Basin in the southern margins of South Africa. These deposits are known as the Miller diamictite and Dwyka diamictite. The latter is well known and was deposited during the Karoo-deglaciation. The Dwyka diamictite is often referred to as Dwyka Tillite. This is an inappropriate reference owing to that not all of the Dwyka deposits are directly formed as a result of glacial contact. The origin of the Miller diamictite is uncertain, but there are suggestions that its origin can be traced to either a glacial or debris flow deposit formed in a deltaic environment, thus referred to by some as a tillite and others as a diamictite. To establish the sedimentary environments of the above mentioned diamictite deposits in the study area, two facies models were presented with a notable bias for the second model. The first model represents a continuous sedimentation cycle between the closing of the Cape Basin and opening of the Main Karoo Basin, whereas the second model demonstrates an erosional break (hiatus) between the depositions of the above mentioned basins. Derived from the use of the second model, it can be concluded that the Miller diamictite can indeed be classified as a diamictite from a textural interpretation. Both diamictites (Miller and Dwyka) cannot be referred to as tillite deposits since none show evidence of direct glacial contact. The Miller and the Dwyka are both diamictites, but were formed in different sedimentary environments. The Miller diamictite is a product of debris flow deposits from the slope of a braided delta, whereas the Dwyka diamictite represents distal glacio-marine “rain-out” deposits. / AFRIKAANSE OPSOMMING: Diamiktiete is sedimentêre neerslae afkomstig vanaf verskillende omgewings en dit word meestal met n glasiale omgewing geassosieer. Alhoewel hierdie assosiasie nie in alle gevalle korrek is nie, word dit nog steeds gemaak as gevolg van die gebrek aan kennis om diamiktiete met selfvertroue te identifiseer, te klassifiseer en 'n afsettingsomgewing vir die sedimente te interpreteer. Gedurende die laat Karboon tot vroeë Permiese tydperk het twee diamiktiet afsettings gevorm gedurende die vorming van die Kaap Supergroep Kom en Karoo Kom in die suidelike grense van Suid-Afrika. Die afsetting staan bekend as die Miller diamiktiet en Dwyka diamiktiet. Laasgenoemde is redelik bekend en is gedurende die Karoo gletser ontvormings tydperk gesedimenteer. Die Dwyka diamiktiet word dikwels Dwyka Tilliet genoem, wat onvanpas is aangesien nie al die Dwyka neerslae direk gevorm het as gevolg van direkte glasiale kontak nie. Die oorsprong van die Miller diamiktiet is egter onseker. Dit word veronderstel dat die Miller diamiktiet óf deur 'n gletser, of puin vloei neerslag gevorm het in 'n deltaiese omgewing, dus word daarna verwys as 'n tilliet of ʼn diamiktiet. Om die sedimentêre omgewings van die twee bogenoemde diamiktiet afsettings in die studie area te bevestig, is twee fasies modelle aangebied met 'n voorkeur aan die tweede model. Die eerste fasies model verteenwoordig n siklus van ongebroke sedimentasie tydens die sluiting van die Kaapse Kom en die opening van die Karoo Kom. Die tweede fasies model verteenwoordig n hiatus tussen die afsetting van die bogenoemde komme. Gegrond op sy teksturele samestelling kan die Miller diamiktiet inderdaad as 'n diamiktiet geklassifiseer word. Beide diamiktiete (Miller en Dwyka) kan nie as tilliet neerslae beskou word nie, aangesien geen bewyse gelewer kan word van afsetting as gevolg van direkte glasiale kontak nie. Die Miller en Dwyka is n diamiktiet, maar is gevorm in verskillende afsettingsomgewings. Die Miller diamiktiet is 'n produk van die puin vloei neerslag vanaf die helling van ‘n delta, terwyl die Dwyka diamiktiet verteenwoordig ‘n afgeleë glasio-mariene “uit-reen” neerslae.

This study lias initiated with the aim of identifying the existence of any geochemical criteria which may be used to distinguish between the various volcanic formations within the Witwatersrand triad. The Witwatersrand triad comprises three sequences: the Dominion Group at the base, the Witwatersrand Supergroup in the middle, and the Ventersdorp Supergroup at the top. It is underlain by Archaean basement rocks, and covered by rocks of the Transvaal sequence. The Dominion Group consists of the sedimentary Rhenosterspruit quartzite Formation at the base, overlain by a bimodal component of the Syferfontein Porphyry succession of lavas. Basaltic lavas are the major component of the Rhenosterhoek Formation, while the overlying Formation consists primarily of dacitic porphyries. Intercalations of one lava type within the other are common, however, so each formation is not the exclusive domain of only one lava type. The Witwatersrand Supergroup, a predominantly argillaceous and arenaceous sequence, contains two narrow volcanic horizons, one of wbich, the Jeppestown Amygdaloid (now Crown Formation), consisting of tholeiitic andesites, occurs in the study area. The overlying Ventersdorp Supergroup has, at its base, the basaltic Klipriviersberg Group, of which four out of six formations are present in the study area, namely, the Alberton, Orkney, Loraine and Edenville Formations. This group is succeeded unconformably by the PIatberg Group, consisting of the sedimentary Kameel doorns Formation, followed by the (informal) Goedgenoeg, Makwassie Quartz Porphyry and Rietgat Formations. The Goedgenoeg and Rietgat Formations are basaltic, whil e the Mawassie rocks range from basaltic to dacitic, the majority being tholeiitic andesites and andesites . The Pniel sequence at the top of the Ventersdorp Supergroup consists of the sedimentary Bothaville Formation, and the Allarridge Formation, the lavas of which are basaltic with some andesitic tendencies. A well-defined geochemical stratigraphy was found to exist. From the eleven volcanic formations examined, nine distinct geochemical units emerged, as the Loraine and Edenville Formations were found to have the same geochemical characteristics, as did the Goedgenoeg and Rietgat Formations. Despite having undergone law-grade greenschist facies metamorphism, very clear variation patterns with height are displayed by the immobile elements Ti, P, Kb, Zr and Y, and the light rare earth elements La, Ce and Nd. In contrast, much scatter was observed in the variation patterns of Na, K, Mn, Ba and Rb. Three techniques were employed to effect discrimination between formations - orthosonal discrimination, interelement and ratio vs ratio plots, and discriminant analysis. Confidence limits placed on normal probability plots served to isolate outlier samples for further examination by the various discrimination techniques. A successful test of the efficacy of the discrimination techniques was afforded when fourteen samples from an unknown succession were positively identified as representative of the Klipriviersberg Group

M.Sc. / Certain carbonate bearing formations in the Paleoproterozoic Pretoria Group and its Griqualand West equivalent exhibit remarkable geochemical and stable isotopic signatures. The 8'3Ccarb isotopic signatures from the Duitschland and Silverton Formations exhibit large positive excursions, which seemingly coincide with a significant increase in atmospheric oxygen between 2.4 and 2.0 Ga. The Duitschland Formation with its distinctive basal unconformity is composed primarily of limestone and dolomite units, interbedded with two compositionally different shale units and quartzite. Toward the base of the formation there is a distinct conglomeratic quartzite which forms a sequence boundary above which isotopic and geochemical signatures change dramatically. Normal marine isotopic signatures characterize the lower portion of the succession while above the sequence boundari, the carbonates are enriched in "C. This enrichment, however, appears to be the result of local processes occurring within a closed basin. Furthermore it is apparent that the Duitschland Formation (with its three distinct marker beds) is the equivalent of the Rooihoogte Formation and therefore constitutes the base of the Pretoria Group. The Mooidraai Dolomite Formation which outcrops only locally in the Northern Cape Province, is characterized by fenestral and microbially laminated dolomite. The geochemical properties are relatively homogeneous with increases in the FeO and MnO concentrations, resulting from post depositional diagenesis. The stable isotope signatures of these dolomites represent normal marine signatures. There is, however, a depletion in the 813C and 8180 signatures in the ankeritic and sideritic lithofacies, which suggests that this succession was deposited from a stratified water column with respect to the total dissolved CO2. The positive 6 13C excursion present in the carbonates of the Lucknow Formation in Griqualand West, traditionally grouped with the Olifantshoek Group can be correlated with carbonates near the top of the Silverton Formation in the Transvaal area. The latter also displays distinctly positive 6 43C values. One possibility is that if these successions were deposited in closed anoxic basins and that the isotopic anomalies are the result of local processes such as fermentive diagenesis and methanogenesis. However, the close association of the carbonates with shallow marine orthoquartzites suggests that these were deposited in an open marine system and that the positive 8 !3C values reflect a shift in the composition of the ocean water at the time of deposition of the carbonates at 2.2 Ga. Other carbonates present in the Pretoria Group, namely from the Vermont and Houtenbek Formations, display normal open marine 8' 3C values of close to zero. A systematic stratigraphic compilation of all 6 43C values available from the Transvaal Supergroup indicates that two clear-cut positive 5' 3C excursions are present. These excursions were apparently short-lived and well defined and did not occur over an extended period of time as suggested by earlier studies based on global compilations with large uncertainties in radiometric ages of deposits.

D.Phil. Geology) / This study presents detailed petrographic, mineral-chemical and geochemical characteristics ofmafic intrusions from three iron oremining areas - Thabazimbi, Sishen and Hotazel - in southern Africa In addition, as themafic intrusions at the Thabazimbi, Sishen and Hotazel mines occur in close spatial association with iron and manganese ore, this study addresses the aspect of whether these intrusions have a bearing on the localization of these ores. Precise geochronologic data of these previously undated mafic dykes and sills is presented to classify them into a regional context. particularly in considering whether these dykes and sills are part of known Large Igneous Provinces (LIPs) in sonthem Africa. The Thabazimbi dykes are coarse grained dolerites while the sills are diabases. The dykes are younger than the sills. Composition wise, sills are dominantly basaltic andesites, while the dykes are dominantly hasaltic. Different to the sills, the dykes are characterized byrestriction of olivine, higher HFSE and LREE as well as less prominent negative Bu" anomaly. Geochemical and isotope chemical characteristics of the Thabazimhi dykes and sills are explained in terms of a combined partial melting, followed by fractional crystallization and crustal contamination with differentiation model. with the dykes showing greater crustal assimilation. The petrogenetic characteristics of the Sishen dolerite dykes in many ways resemble both the Colombia River Basalts and the typical Umkondo dolerites, and point to significant crustal contamination, typical of continental tholeiites. Geochemical characteristics of the Sishen dolerites is acconnted by the partial melting followed by fractional crystallization and crustal contamination, but unlike the Thabazimbi dykes and sills crustal assimilation is significant. At Hotazel, the petrographyand geochemistry of 'bostonites' bas been used to define their true composition while at the same time highlighting the presence of a -2 - 3 m thick iron ore unit associated with banded iron formation and manganese ore. Geochemically, the Hotazel 'bostonites' are "basaltic andesites' while textnra1ly, the Hotazel <bostonites' are essentially diabases. Regarding the iron ores that occurs in the Hotazel Formation at the base of the Pre-Mapedi nnconformity, they are composed of various forms of hematite with variable minor chlorite. quartz and carbonates. Iron ore genesis is attributed to supergene processes similar to those that have affected Sishentype iron ore below the Gamagara unconformity on the Maremane Dome. A U-Pb 2046.6±3.4 Ma age has been obtained for the crystallization of a Thabazimbi sill by dating titanite. This is interpreted to indicate that while the mafic/ultramafic component ofthe Bushveld Complex may have been emplaced over a short period, there was later magmatic activity at 2046 Ma, represented by the Thabazimbi sill and other late Bushveld Complex related intrusions such as the Uitkomst Complex at 2044 Ma. The 1044.3±7.5 Ma age obtained for the Sishen dolerites has resulted into two major interpretations. Firstly. the age is interpreted to be the minimum age for Umkondo LIP. The age shows that while large sections of the Umkondo LIP may have been emplaced within a short time interval, emplacement of end members ofthis LIP was in progress at least - 50 Ma later. Secondly. the age of these dolerites shows that they were emplaced subsequent to major iron ore genesis at Sishen. The new age. coupled with the limited extent ofthese intrusions shows that they played a no part in the origin ofthe bulk ofthe iron ore at the mine.

A plug-like intrusion of Karroo dolerite, near Dordrecht in the Eastern Cape of the Republic, is described. Field mapping with the, aid of aerial photographs has revealed that the contact of the intrusion, for the most part, dips very steeply outwards. In the south- eastern and eastern areas, however, sheet- or sill-like forms appear to be given off from the main intrusion. In plan view the intrusion is roughly oval shaped, its longer axis being aligned in a north-westerly direction. Its surface area measures approximately 60 square kilometres (24 square miles). A large number of xenoliths composed exclusively of Stormberg sediments, pyroclastic rocks and minor lavas, are to be found cropping out within the dolerite intrusion. These xenoliths, many of which occur in positions far above or below their normal stratigraphic elevation, are extremely variable in size - the largest having an area of approximately 15 square kilometres (6 square miles). The xenoliths represent fragments of the original "roof" of sediments and pyroclastics which have collapsed into and been engulfed by the dolerite magma. This type of dolerite intrusion is known as a "belljar" intrusion. A superficial classification of the dolerites, based chiefly on textural and certain mineralogical features, is presented. In the area surrounding the main intrusion are a number of dolerite dikes and sheets. The youngest phase of igneous activity is represented by the Dragon's Back dike, which cuts across the complex in a north-westerly direction. Several veining phenomena, as well as an interesting variety of metamorphic and metasomatic rocks, are associated with the main dolerite intrusion. Six diatremes are situated in the vicinity of the intrusion. Pyroclastic rocks are represented by a variety of types, and are to be found outside the area of the intrusion, and as xenoliths within it. A tentative interpretation of the mechanism of formation of the intrusion, which appears to be related to volcanic activity and cauldron subsidence, is presented.

Boreholes NG1 and NG2 were drilled on the farm Nooitgedacht 406 KQ to intersect the lower Critical and lower Zones of the western Bushveld Complex. The aim of this study is to describe the textural features and chemical characteristics of the olivine-bearing rocks in the intersections, as determined by petrographic studies, XRF analysis and microprobe analysis. The olivine-bearing rocks are dunites, harzburgites and olivine pyroxenites. They comprise olivine and orthopyroxene, with minor chromite, clinopyroxene and plagioclase, and their textures vary between adcumulate, mesocumulate and poikilitic. The sequence intersected can be broadly correlated with that in the eastern Bushveld Complex. Of the whole-rock inter-element ratios, the MMF (MgO)/[MgO+FeO])ratio is the clearest indicator of cyclicity. The olivine-rich rocks are more primitive than the associated rocks, and seem to become more primitive with height in most intervals. The plagioclase in the olivine-bearing rocks is unusually sodic in corrposition, having a maximum Na₂0 content of 8.12%. A comparison of olivine and plagioclase compositions with those in other intrusions has revealed that the only other major intrusion with sodic plagioclase is the Kiglapait intrusion of Canada. In the Kiglapait intrusion the sodic plagioclase occurs in conjunction with fayalitic olivine as opposed to the forsteritic variety of this study. Chemical variations in the rocks sampled indicate that periodic replenishment of the magma from which the rocks crystallised must have occurred. In some of the olivine-bearing intervals where little fractionation is evident, replenishment seems to have been continuous. In other intervals fractionation appears to have continued uninterrupted for significant periods, prior to rejuvenation by fresh influxes of magma.