Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis investigates questions surrounding the role that iron-rich colloids (nominally sized between 0.02 μm and 0.2 μm) and particulates (>0.2-0.45 μm) play in the context of the greater iron biogeochemical cycle. To this end, this study complements a review of reported size-fractionated iron (Fe) measurements with chemical and mineralogical data derived from synchrotron-based xray measurements. From an extensive literature review, the global surface ocean colloidal iron (cFe) pool is found to be highly dynamic, frequently exhibiting seasonal trends and nutrient-like behaviour. Spatial variability in surface ocean colloidal iron concentration is primarily a function of total iron supply, although the concentration and strength of iron-binding ligands, and inorganic thermodynamic constraints are additional influential factors. The size-fractionated study of colloidal Fe has rendered considerable evidence pointing towards direct or indirect biological utilization of this cFe pool; however, a more complete understanding of cFe-biological interaction necessarily requires better knowledge of cFe chemistry and mineralogy. To address these issues, this thesis documents the development of a novel x-ray microscopy and spectroscopy technique for determining the Fe speciation of individual Fe-rich particles under environmental conditions. Variations in the peak splitting in iron L3-edge XANES (X-ray Absorption Near-Edge Structure) spectra reflect changes in the local coordination environment surrounding the metal centre. Specifically, the energy splitting ( ΔeV) and intensity ratio of the split peaks at the L3-edge vary as a function of the Fe valence state, the number and chemistry of coordinating ligands and polyhedral distortion effects; and combinations of the two parameters are found to be characteristic of individual Fe minerals. To understand Fe speciation, the Δ eV versus intensity ratio plot was successfully applied to a variety of environmental Fe particles (greater than 20 nm diameter) collected from two ocean basins; the Southern Ocean and the south western Pacific Ocean. Speciation differences in Fe particles collected from the Southern Ocean show distinct compositional trends between the coasts of South Africa and Antarctica, with different Fe pools associated with the different oceanographic frontal zones. Despite the oxygenated nature of the seawater sampled, the presence of significant particle-hosted Fe(II) was observed in both the Southern Ocean at high latitudes, and at sampling sites proximal to the Kermadec Ridge in the Pacific Ocean. Ferrous iron particles at the latter study area were shown to be strongly associated with carbon functional groups, notably alcohol and carboxamine moieties. These findings, relating to particle chemical differences and associations with organic matter, have significant implications for our understanding of particle behaviour, their surface interactions and the role that they play in primary productivity and global elemental cycles. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek kwessies met betrekking tot die rol wat ysterryke kolloïede (van nominale groottes tussen 0.02 μm en 0.2 μm) en partikels (>0.2-0.45 μm) in die konteks van die groter ysterbiogeochemiese siklus speel. Vir hierdie doel bou die studie voort op ’n oorsig van aangemelde grootte-gefraksioneerde yster- (Fe-)metings met behulp van chemiese en mineralogiese data wat uit sinchrotrongebaseerde x-straalmetings verkry is. Na aanleiding van ’n uitvoerige literatuurstudie, blyk die globale poel kolloïdale yster (cFe) op die see-oppervlak hoogs dinamies te wees en toon dit dikwels seisoenale tendense en voedingstofagtige gedrag. Ruimtelike veranderlikheid in die cFekonsentrasie op die see-oppervlak is hoofsaaklik ’n funksie van totale ystervoorsiening, hoewel die konsentrasie en sterkte van ysterbindende ligande sowel as anorganiese termodinamiese beperkings ook ’n invloed kan hê. Die grootte-gefraksioneerde studie van kolloïdale Fe het beduidende bewyse opgelewer wat op die direkte of indirekte biologiese benutting van hierdie cFe-poel dui. Tog verg ’n vollediger begrip van cFe- biologiese interaksie noodwendig meer kennis van die chemie en mineralogie van cFe. Om hierdie kwessies te ondersoek, dokumenteer hierdie tesis die ontwikkeling van ’n innoverende X-straalmikroskopie- en X-straalspektroskopietegniek om die Fe-soortvorming van individuele Feryke partikels in omgewingsomstandighede te bepaal. Variasies in die pieksplitsing van yster-L3 rand-XANES- (“X-ray absorption near-edge structure”-)spektra weerspieël veranderlikheid in die lokale koördinasie-omgewing rondom die metaalkern. In die besonder wissel die energiesplitsing ( eV) en intensiteitsverhouding van die splitsingspieke by die L3-rand na gelang van die Fevalensietoestand, die getal en chemie van koördinasie-ligande, en poliëdriese distorsie-effekte, en kombinasies van die twee parameters blyk kenmerkend van individuele Fe-minerale te wees. Om Fe-soortvorming te verstaan, is die stipping van Δ eV versus intensiteitsverhouding suksesvol toegepas op ’n verskeidenheid Fe-omgewingspartikels (groter as 20 nm in deursnee) wat uit twee oseaankomme – die Suidelike Yssee en die suidwestelike Stille Oseaan – bekom is. Soortverskille in Fe-partikels wat uit die Suidelike Yssee bekom is, toon kenmerkende samestellingspatrone tussen die kus van Suid-Afrika en Antarktika, en verskillende Fe-poele word met die verskillende oseanografiese frontsones verbind. Ondanks die suurstofhoudende aard van die seewatermonsters, is beduidende Fe(II) in partikels opgemerk in die Suidelike Yssee by hoë breedteliggings sowel as op studieterreine naby die Kermadec-rif in die Stille Oseaan. Ysterhoudende partikels van laasgenoemde studieterrein het ’n sterk verband met koolstof- funksionele groepe, veral alkohol en karboksamien, getoon. Hierdie bevindinge met betrekking tot die chemiese verskille tussen partikels en die verband met organiese materie het beduidende implikasies vir ons begrip van partikelgedrag, die oppervlak-interaksies van partikels, en die rol wat dit in primêre produktiwiteit en globale elementsiklusse speel.

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2010. / ENGLISH SUMMARY: Regional mapping of the Stinkbank granite in the south Central Zone of the Damara Belt, focused on an area of ca. 150 km2 in the SW parts of the granite along well exposed sections of the Khan River to the SW of the town of Usakos. The granite forms part of the regionally widespread granite suite of Salem-type granites that intruded at ca. 550-540 Ma into amphibolite-facies rocks of the Damara Supergroup. The Stinkbank granite is intrusive into the regional-scale, NE-trending D2 Kransberg syncline, cored by schists of the Kuiseb Formation and surrounded by marble units of the Karibib Formation. The granite comprises three major lithotypes that have intruded in sequence. The earliest granites are represented by biotite-rich megacrystic granites, followed by leucocratic megacrystic granites and a final stage of voluminous, garnetiferous and tourmaline-bearing, medium-grained leucogranites. Contact relationships with the wall rocks are, for the most part, concordant, documenting the largely sheet-like geometry of the granites. Internal contacts between different granite phases are well preserved and indicate that the granites have intruded as shallowly-dipping, largely concordant sheets. Intrusive contact relationships and petrographic and geochemical characteristics indicate that each of the three major granite phases represented a distinct emplacement pulse. Successive emplacement of the granite sheets point to the assembly of the Stinkbank granite from the top down, with younger sheets intruding structurally below earlier emplaced granite sheets. This has created a pseudostratigraphy within the Stinkbank granite. The mapping of the internal contacts shows that the granite sheets were progressively folded into NE-trending, upright folds, parallel to D2 folds in the surrounding wall rocks. NE-trending magmatic and solid-state foliations in all granite phases are axial planar to the folds and underline the syntectonic emplacement of the Stinkbank granite during the D2 NW-SE subhorizontal shortening. Based on the intrusive relationships and the progressive deformation of granite phases, an intrusive sequence can be developed for the Stinkbank granite. The earliest granite phases were emplaced during the onset of the regional D2 deformation, parallel to the subhorizontal bedding. Continued granite sheeting led to the vertical growth of the sheet-like granite and bending of the wall rocks above the inflating granite sheets, leading to the laccolithic geometry of the SW parts iii of the Stinkbank granite. Progressive deformation, folding of the granite sheets and fold amplification resulted in fold interference patterns in the SW parts of the Stinkbank granite. The Stinkbank granite represents a mid-crustal granite with well-preserved granite sheeting that was assembled during regional deformation. Granite sheeting and progressive deformation illustrate the interplay between (1) regional strains, and (2) the orientation and presence of pre-existing wall-rock anisotropies (bedding) and their significance for the magmatic assembly and progressive deformation of the granite. / AFRIKAANSE OPSOMMING: Regionale kartering van die Stinkbank graniet in die suidelike Sentrale Sone (sSS) van die Damara Gordel. Die studie fokus op die area van ongeveer 150 km2 in die SW dele van die graniet, langs n goed blootgestelde seksie van die Khan Rivier, SW van Usakos. Die graniet vorm deel van n wydverspreide suite van Salem- tipe graniete wat tussen 550-540 Ma in die amfiboliet fasies gesteentes van die Damara Supregroep ingedring het. Die Stinkbank graniet kom voor in regionale –skaal , NE – neigende D2 Kransberg Sinklinorium, wat bestaan uit skis van die Kuiseb Formasie en marmer van die Karibib Formasie. Die graniet bestaan uit drie hoof fases wat in volgorde ingedring het. Die oudste graniet is die biotiet-ryke megakristiese graniet, gevolg deur die leukokratiese megakristiese graniet en laastens die leukograniet. Kontak verhoudings met die wandgesteentes is grootendeels konkordant en dit dui op die feit dat die graniet uit lae bestaan. Die interne kontakte tussen die verskillende graniete is goed preserveer en dui aan dat die graniete voorkom as vlak lêende lae. Kontakverhoudings, petrografie en geochemiese karakteristieke dui aan dat elk van die die drie tiepes graniet uniek is. Die volgorde van intrusie van die Stinkbank graniet het voorgekom van bo na onder. Dit het n “skyn-stratigrafie” tot gevolg gehad. Kartering van die interne kontakte tussen die graniete het getoon dat die graniet lae is deurentyds gevou na NE- neigende, regop voue, parallel aan die D2 voue in die omringende wandegesteentes. NE- neigende magmatiese en soliede stadium foliasies in al die graniete is asvlak planêr aan die voue en dui ook op die syn-tektoniese intrusie van die Stinkbank graniet gedurende die D2 , NW-SE subhorisontale verkorting. Intrusiewe verhoudings en die progressiewe deformasie van die graniet, dui dat n volgorde verkry kan word vir die Stinkbank graniet. Die oudste graniet fase het ingedring gedurende die begin van die streekse D2 deformasie, parallel aan die subhorisontale gelaagdheid. Aanhoudende graniet-lae intrusies het gely tot die groei van n laag-ryke graniet en die buiging van die omliggende wangesteentes om dit n lakoliet vorm te gee in die SW dele van die Stinkbank graniet. Progressiewe deformasie, vouing van graniet lae en vergroting van voue het tot vou-interferensie patrone in die SW dele van die Stinkbank graniet tot gevolg gehad. Die Stinkbank graniet stel n middel- kors graniet met goed gepreserveerde gelaagdheid, wat gedurende regional deformasie ingedring het, voor. Graniet lae en progressiewe deformasie illustreer die verhouding tussen (1) regionale spanning en (2) die orientasie en teenwoordigheid van voorafbestaande wandgesteente anisotropie (gelaagdheid) en hulle belangrikheid vir die opbou en deformasie van die graniet.

Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Fan System 5 forms the uppermost submarine fan system of the Permian-age Tanqua Fan Complex (Ecca Group) of the southwestern Karoo Basin. It is the most widespread system and represents the final phase of fan deposition in the Tanqua sub-basin. Depositional characteristics differ markedly from the rest of the fan systems, mainly because it lacks sedimentary features indicative of a single point source basin floor fan. The entire system consists of six different stages of fan growth and development in the lower slope settings. A hypothetical model was composed for Fan System 5 to understand the spatial/temporal distribution of reservoir and seal facies in slope turbidite settings. The facies vary from massive amalgamated sandstone beds to thin-bedded, ripple cross-laminated sand and siltstone beds. A thick shale unit identified as a regional marker layer overlies Fan System 5. lts base is defined by the presence of a regionally developed 20 cm thick hemipelagic shale unit. Six sand-rich units with channel-complexes are present in the Klein Hangklip, Groot Hangklip, Kalkgat, Tongberg, Skoorsteenberg and Blauwkop localities. The facies characteristics in the southernmost outcrops of Fan System 5 (Groot Hangklip, Tongberg and Kalkgat) reflect deposition in a lower slope setting where local structural control seems to have played a major role in the distribution and regional development of channel-fill and overbank depositional elements. The channel-fills are arranged in vertical to off-set stacking patterns and are comprised of massive, amalgamated [me to very fine-grained sandstone units up to 30 m in thickness. They are separated by thinner sandstone/siltstone units of varying thickness. The channelization displayed by the more proximal outcrops are interpreted to represent an upper fan, deposited in a lower- to mid-slope setting. In contrast to the channel-fill deposits at Skoorsteenberg, Klein Hangklip and Groot Hangklip, ripple cross-laminated overbank deposits, associated with smaller channel-fill units, predominate in the northeastern and eastern parts of the outcrop area. Massive- and thinbedded frontal sheet sandstones constitute the down-dip extensions to the most northern outcrops of Fan System 5. Highly erosive, stacked base-of-slope channel complexes, seemingly controlled by subtle early structural features, were able to construct significant thicknesses of regionally well-developed overbank deposits, marginal to the channel complexes. These facies changes occur over relatively short distances, which hold significant implications for the prediction of and the heterogeneity of reservoir facies in slope settings. Gradients are much steeper in the lower slope to mid-slope area than on the proximal basin floor. The occurrence of soft-sediment deformation in the overbank and upper parts of the channel-fill deposits supports a slope origin. Weakly developed wave-ripple marks in the uppermost layers of Fan System 5 further indicate that water depths approached wave base prior to deposition of the upper markerbed shales. Paleotransport for Fan System 5 was towards the north, northeast and east. The palaeocurrent directions of the channel-fill complexes in Klein- and Groot Hangklip seem to roughly correspond to the structural trend of synclinal depressions in this area. However, the effect and influences of basin floor topography and structural features on deposition were determined to be minimal on the regional development and local facies control of the fan. / AFRIKAANSE OPSOMMING: Waaiersisteem 5 vorm die laaste submarine waaiersisteem van die Perm-ouderdom Tankwa Waaierkompleks (Ecca Groep) in die suidwestelike Karoo-kom. Dit vorm die mees wydverspreide sisteem en verteenwoordig ook die fmale fase van waaierafsetting in die Tankwa sub-kom. Afsettingseienskappe verskil aansienlik van die onderliggende waaiersisteme, omdat kenmerkende sedimentêre eienskappe van 'n enkele toevoer bron ontbreek. Die hele sisteem bestaan uit ses verskillende periodes van waaiergroei en ontwikkeling in die laer kornhelling omgewmgs. 'n Voorspellingsmodel is opgestel vir Waaiersisteem 5 om die ruimtelike/temporele verspreiding van die reservoir en seël fasies in kornhelling turbidiet omgewings te kan verstaan. Hierdie fasies varieer van massiewe, geamalgameerde sandsteen tot dun gelaagde riffel- lamineerde sand- en sliksteenlae. 'n Dik regionale skalie eenheid oorlê Waaiersisteem 5 en vorm die boonste merkerlaag. Die basis word onderlê deur 'n 20 cm dik regionaalontwikkelde hemipelagiese skalie laag wat die onderste merkerlaag vorm. Ses sandige eenhede met geassosieerde kanaalkomplekse is onderskeidelik teenwoordig in: Klein Hangklip, Groot Hangklip, Kalkgat, Tongberg, Skoorsteenberg en Blauwkop omgewings. Die fasies-eienskappe van die mees suidelike dagsome van Waaiersisteem 5 (Tongberg, Groot Hangklip en Kalkgat) toon afsetting in 'n laer kornhelling omgewing, waar plaaslike tektoniese effekte moontlik 'n groot rol gespeel het in die verspreiding en regionale ontwikkeling van die kanaalvulsels en geassosieerde oewerwal-afsettings. Die gestapelde, wegstand kanaalvulsels-afsettings bestaan uit massiewe, geamalgameerde fyn tot baie fynkorrelrige sandsteen eenhede, wat diktes tot ongeveer 30 m kan bereik. Dit word van mekaar geskei deur dun sandsteenlsliksteen eenhede van afwisselende diktes. Die kanaal komplekse in die mees proksimale dagsome word interpreteer as 'n bo-waaier, wat afgeset is in 'n laer- tot middel kornhelling omgewmg. In teenstelling met die kanaalvulsels in die Skoorsteenberg, Klein Hangklip en Groot Hangklip omgewings, domineer riffel kruisgelamineerde oewerwal-afsettings, geassoseer met klein kanaalvulsels, die noordoostelike en oostelike dagsome van Waaiersisteem 5. Massiewe en dungelaagde frontale plaat sandstene, kom voor in die distale helling-omgewings in die mees noordelike dagsome van Waaiersisteem 5. Hoogs eroderende, gestapelde kanaalkomplekse, aan die basis van die komhelling wat moontlik beheer is deur vroeë komvloer topografie, was die oorsaak vir regionaal goed-ontwikkelde oewerwalafsettings. Hierdie fasies-verandering vind plaas oor 'n baie kort afstand wat betekenisvolle gevolge inhou vir die voorspelling van heterogeniteit van petroleum reservoir fasies in komhelling afsetting-omgewings. Die gradiënt vir die laer komhelling tot mid-komhelling omgewings is baie steiler as die distale komvloer omgewings. Die voorkoms van sagte-sediment deformasies in die oewerwal en boliggende dele van die kanaalvulsels weerspeël 'n moontlike komhelling omgewing. Swakontwikkelde golfriffelmerke in die boonste lae van Waaiersisteem 5 dui 'n waterdiepte aan wat nabyaan golf-basis is, voordat dit deur diepmariene skalies oorlê word. Paleovloeirigtings vir Waaiersisteem 5 was in 'n noord, noordoostelike en oostelike rigting. Die paleovloeirigting vir die Klein- en Groot Hangklip kanaalkomplekse stem min of meer ooreen met die strukturele grein van die sinklinale laagtes in die omgewing. Die effek en beheer van komvloer topografie en ander strukturele faktore op afsetting was minimaalop die regionale ontwikkeling en plaaslike fasies verspreiding van die waaier.

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 (DSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: This study has examined the 3 kbar partial melting behaviour of 4 metapelites collected from the highest grade rocks occurring below the anatectic zone of the Mt Stafford area, Arunta Inlier, central Australia. In this area, metasediments are interpreted to have undergone partial melting within the andalusite stability field, possibly as a result of a lowering of the metapelite solidus by the presence of boron in the rocks. Two of the samples were two mica metapelites (MTS70 and MTS71) that both contained significant quantities of tourmaline and were thus boron enriched. The other two samples were biotite metapelites. One of these rocks contains only a trace of tourmaline (MTS8) and the other is tourmaline free (MTS7). Despite expectations that muscovite in the two mica samples would break down via a subsolidus reaction, muscovite was stable to above 750 C due to the incorporation of Ti, phengitic and possibly F components into its structure. Between 750 and 800 C, muscovite melted out completely via a coupled muscovite + biotite fluid-absent incongruent reaction. In the most mica-rich sample this reaction produced ~ 60 % melt at 800 C. In the biotite metapelites, biotite melting began at a temperature below 800 C and was accompanied by very modest melt production at this low temperature. In contrast to the two mica metapelites, the main pulse of melt production in these samples occurred at a temperature between 850 and 950 C. In both these samples biotite + melt coexistence persisted for a temperature range in excess of 150 C, and in MTS8, biotite was still in the run products at 950 C. The very refractory nature of these evolved biotite compositions is most likely a consequence of both the presence of a Ti buffering phase in the assemblage (ilmenite) and the essentially plagioclase-free nature of the starting compositions. Under the fluid-absent conditions of this study tourmaline is clearly a reactant in the partial melting process, but does not appear to shift the fluid-absent incongruent melting reactions markedly. Neither quartz, nor andalusite was completely consumed in the melting reactions, indicating the metastable persistence of andalusite to higher than the wet solidus temperatures. The assemblages do not change much with increasing temperature and mimic the field relationships. The fluid-absent melting experiments indicated that the main pulse of melting occurred between 850 and 950 °C, significantly higher than indicated by the field evidence of 600 to 675 °C, therefor disequilibrium in the experiments can not be ruled out. The presence of a fluid during partial melting at Mt Stafford provides therefor an explanation of the low temperatures at which melting occurred. / AFRIKAANSE OPSOMMING: Die 3 Mpa vloeistof-vrye gedeeltelike smelting van 4 metapeliete, gekollekteer van die hoogste graad rotse net onder die anatektiese sone van die Mt Stafford area, Arunta inlêer, sentraal Australië, is bestudeer. Die metapeliete van hierdie area word geinterpreteer dat hulle gedeeltelike smelting in die andalusiet stabiliteitsveld ondergaan het, moontlik as 'n resultaat van die verlaging van die metapeliet solidus as gevolg van die teenwoordigheid van boor. Twee van die monsters bestudeer was twee-mika metapeliete (MTS70 en MTS71) met beduidende hoeveelhede toermalyn en is dus boor-verryk. Die ander twee monsters was biotiet metapeliete, waarvan een spoorhoeveelhede toermalyn (MTS8) bevat het en die ander toermalyn vry was (MTS7). Ten spyte van verwagtinge dat muskoviet in die twee mika monsters sou afbreek via 'n subsolidus reaksie, was dit stabiel tot bo 750°C as gevolg van die vervanging van Ti, fengitiese en moontlik F komponente in die muskoviet struktuur. Tussen 750 en 800°C het muskoviet heeltemal gesmelt deur die vloeistof-vrye gekoppelde muskoviet+biotiet reaksie. In die monster met die meeste mika het hierdie reaksie ~ 60 % gesmelt by 80°C en lae hoeveelhede smelt is by hierdie lae temperature geproduseer. In kontras met die twee-mika metapeliete het die hoof puls van smeltproduksie in hierdie monsters plaasgevind tussen 850 en 950°C. In beide hierdie monsters het biotiet+smelt 150°C. Biotiet was steeds ongesmelt in MTS8 by 950°. Die hoë refraktoriese natuur van hierdie biotiet samestellings is hoogs waarskynlik 'n gevolg van die teenwoordigheid van 'n Ti-bufferende fase (ilmenite) en die afwesigheid van plagioklaas in die begin samestellings. Toermalyn is duidelik 'n reaktant in hierdie vloeistof-vrye gedeeltelike smelting studie, maar dra nie beduidend by tot die verlaging van die inkongruente smeltingsreaksies nie. Nie kwarts of andalusiet het heeltemal gesmelt oor die temperatuurreeks nie, wat aandui dat die andalusiet stabiel is by temperature hoër as die nat solidus. Die mineraalverspreidings verander nie veel met verhoging in temperatuur nie en mimiek dus die veld verwantskappe. Die vloeistof-vrye smeltings eksperimente het aangedui dat die hoofpuls van smelting tussen 850 en 950°C geskied het, wat aansienlik hoër is soos aangedui uit die veldgetuienis van 600 tot 675°C, dus is die moontlikheid van disekwilibrium gedurende die eksperimente 'n moontlikheid. Die moontlikheid dat vloeistof teenwoordig was tydens die smeltproses by Mt Stafford verskaf dus 'n oplossing vir die lae temperature wat tydens smelting bereik is.

Thesis (PhD (Earth Sciences))--University of Stellenbosch, 2010. / ENGLISH SUMMARY: S-type granite intrusions are extremely common in the continental crust and form from the partial melting of metasediments. Compositions of S-type granite range from leucogranite to granodiorite and have trace element contents that globally increase with increasing maficity (Fe + Mg). Models proposed for the formation of S-type granite do not answer satisfactorily all petrological and compositional requirements. In this study, S-type granite of the Cape Granite Suite (CGS), South Africa is used to discriminate between potential sources of compositional variation. Experimental studies show that melt produced from the partial melting of sediment is exclusively leucocratic. On this basis, the entrainment of up to 20 wt.% of peritectic garnet within S-type melt can be established to produce the observed major element variations. S-type CGS locally contains garnet. This garnet is in equilibrium with granite composition at P-T conditions (5kb and 750 C for the core of the garnet and 3kb and 720 C for the rim) well below conditions recorded by xenoliths from the same granite (10 kb and 850 C from a metabasite). From this result it seems that the originally entrained garnet no longer exists in the Stype CGS and it have been replaced by newly formed minerals (garnet, cordierite and biotite). Considering the short time necessary to emplace granites (about 100 000 years), it appears that garnet has been compositionnally re-equilibrated through a dissolution-precipitation process. The study of trace element variations in S-type CGS shows that most leucocratic compositions are undersaturated in Zr and Ce compared to predictions from experimental models for dissolution of accessory zircon and monazite in their source regions. Thus, S-type melts are likely to be formed in disequilibrium with respect to accessory phase stability. As a result the observed increase in trace element content with increasing maficity indicates that accessory minerals such as zircon and monazite are co-entrained with peritectic garnet in melt to produce the observed trace element variation in S-type granite. Trace element disequilibrium in the CGS S-type granitoids requires particularly short times of residence of melt within the source region. Together, these results provide for the first time, a fully comprehensive model for major and trace elements variations. Compositional variation in CGS S-type granite results from source processes by a selective entrainment of peritectic and accessory minerals. After entrainment, these minerals are likely to be re-equilibrated within the magma, through a dissolution-reprecipitation process. In addition, it appears that the construction of large S-type granitic bodies occurs through successive addition of magma batches of different composition that originates directly from the source region. / AFRIKAANSE OPSOMMING: S-tipe granietinstrusies is baie algemeen in die kontinentale kors en vorm deur die gedeeltelike smelting van metasedimente. Samestellings van S-tipe graniete strek vanaf leukograniet tot granodioriet en het spoorelementsamestellings wat global toeneem met ’n toenemende mafiese component (Fe + Mg). Modelle wat voorgestel is vir die formasie van S-tipe graniete beantwoord nie bevredigend al die petrologiese en komposisionele benodigdhede nie. In hierdie studie word S-tipe graniete van die Kaapse Graniet Suite (CGS), Suid Afrika, gebruik om te diskrimineer tussen potensiele bronne van komposisionele variasie. Eksperimentele studies wys dat smelt, geproduseer van die gedeeltelike smelting van sedimente, uitsluitlik leukokraties is. Op hierdie basis kan bewys word, dat die optel-en-meevoering van tot 20 wt% van peritektiese granaat in S-tipe smelt, die waargeneemde hoofelement variasies kan produseer. S-tipe CGS bevat lokale granaat. Hierdie granaat is in ekwilibrium met die graniet samestelling by P-T kondisies (5kb en 750circC vir die kern van die granaat en 3kb en 720circC vir die rand) ver onder kondisies waargeneem by xenoliete van dieselfde granite (10kb en 850circC van ’n metabasiet). Van hierdie resultaat kan afgelei word dat die oorspronklike opgetel-en-meegevoerde graniet bestaan nie meer in die S-tipe CGS en dat dit vervang is deur nuutgevormde minerale (granaat, kordieriet en biotiet). As in ag geneem word die kort tyd wat nodig is om graniete in te plaas (omtrent 100 000 jaar), wil dit voorkom dat granaat se samestelling geherekwilibreer word deur ’n oplossings-presipitasie proses. Die studie van spoorelement variasies in S-tipe CGS wys dat meeste leukokratiese samestellings is onderversadig in Zr en Ce in vergelyking met voorspellings deur eksperimentele modelle vir die oplossing van bykomstige zircon en monasiet in hulle brongebiede. Dus is S-tipe smelte meer geneig om gevorm te word in disekwilibrium in verhouding tot bykomstige mineraalstabilileit. Met die gevolg is dat die waargenome toename in spoorelementinhoud met toename in mafiese component wys dat bykomstige minerale, soos zirkoon en monasiet, word saam opgetel-enmeegevoer met peritektiese granaat in smelt om die waargenome spoorelement variasie in S-tipe graniete te verklaar. Spoorelement disekwilibrium in die CGS S-tipe granitoide benodig veral kort tye van residensie van die smelt binne die brongebied. Saam gee hierdie resultate vir die eerste keer ’n algehele antwoord vir hoof- en spoorelement variasies. Variasie in samestelling in CGS S-tipe graniete is die resultaat van bronprosesse deur ’n selektiewe optel-en-meevoer van peritektiese en bykomstige minerale. Na die optel-en-meevoer van hierdie minerale word hulle geherekwilibreer binne die magma deur ’n oplossings-presipitasie proses. Addisioneel wil dit voorkom of die konstruksie van groot S-tipe granietliggame plaasvind deur opeenvolgende toevoegings van magma lotte van verskillende samestellings wat direk uit die brongebied kom.

Thesis (DSc.)--Stellenbosch University, 1952. / ENGLISH ABSTRACT: The ideal geological column of the Kimberley-Elsburg Series in the East Rand Basin is described, with particular reference to the IQrnberley group of sediments. A system of nomenclature has been devised, and it is suggested that it could'also be used in other parts of the large structural basin, stretching from Johannesburg'in the north to near Theunissen in the south,. and from .Klerksdorp in the west to Greylingstad in the east. The stratigraphy of individual areas in the East Rand Basin is described in detail, and it is shown that certain stratigraphic.units display a remarkable regularity, maintaining their lithologica~ characteristics bver large areas, persisting also into the Greylingstad- Balfour district, the Central Rand, the West and Far West Rand, the Klerksdorp area, and into the Orange Free State goid field. In the East Rand Basin the May Reef is the principal gold carrier, and is of economic importance in certain mines. In the Orange Free State gold field the lowermost Kimberley reef is also of economic importance. Three regional unconformities have been recognised in the part of the column extending from below the Kimberley Shales to above the May Reef. The May Reef covers the upper one', and owes its existence to this period of erosion. The history of this reef could be traced back to its parent rock~ in this case, stratigraphically older auriferous gravels. The author believes that the unconformity below the May Reef developed as a result of sub-aqueous erosion. The. oldest erosion surface probably developed in the same way. The middle one developed largely on the land, but was subsequently submerged. It is concluded that the sediments of the Kimberley-Elsburg Series were deposited in the marine neritic environment, i.e. in a sea of substantial but not excessive depth. A few remarks have been added on the metamorphism of the System. An interesting feature in this connection is the occurrence of ubiquitous authigenic rutile in the form of minute needles and knee-shaped twins. It appears that the rutile developed as a stress mineral, ilmenite having been the original detrital constituent. / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The ~2.67 Ga Matok pluton comprises calc‐alkaline pyroxene (px)‐bearing and px‐free granitoids. The pluton was constructed by means of two episodes of intrusion each of which had co‐magmatic px‐bearing and px‐free granitoid groups. All the granitoid groups (px‐bearing and px‐free) are characterised by non‐porphyritic and porphyritic varieties. The phenocrysts in both episodes of intrusion are plagioclase ± alkali feldspar and are aligned parallel to the trend of the Limpopo Belt, attesting to a syntectonic emplacement. The time gap between the first and second intrusion is insignificant and magma was most likely stored in the chamber after the first intrusion. Petrography and geochemical signature of both px‐bearing and px‐free granitoid samples have been studied and a petrogenetic model which accounts for the coeval px‐bearing and px‐free granitoids is proposed. The relevance of the syntectonic emplacement of the Matok pluton ie n the Limpopo Belt is also addrssed. Px‐bearing granitoids always have clinopyroxene but orthopyroxene is not always present. Magnetite and ilmenite are present in both px‐bearing and px‐free granitoids but are more abundant in the px‐bearing granitoids and subordinate in the px‐free granitoids. Plagioclase in both px‐bearing and px‐free granitoids is of oligoclase (An12‐30) composition but is relatively more calcic and increases in modal abundance in the px‐bearing granitoids. Alkali feldspar is more dominant in the px‐free granitoids. Hornblende is present in all the px‐bearing granitoids and the px‐free granitoids with ≤71 wt.% SiO2 but is absent in the px‐free granites with >71 wt.% SiO2. Both magmatic epidote and titanite occur exclusively in the px‐free granitoids with ≤71 wt.% SiO2 and are absent in all the px‐bearing granitoids as well as the px‐free gra nites with >71 wt.% SiO2. Px‐bearing granitoids are mainly of dioritic and granodioritic and have subordinate granitic composition while px‐free granitoids are mainly of granitic and granodioritic and have subordinate dioritic composition. All the rocks define well correlated variation of SiO2 with the rest of the major elements. However, there is always a hiatus between the granites with >71 wt.% SiO2 and all other rocks. Px‐bearing and px‐free granitoids at the same SiO2 concentrations tend to have approximately equal concentrations of MgO, CaO and TiO2, whereas K2O concentration is distinctively higher for the px‐free granitoids. The distribution of the high field strength elements (HFSE; Nb, Ta, Zr and Hf) and rare earth elements (REE) is similar in both px‐bearing and px‐free granitoids. On contrary, Th, U, Cs and Rb are characteristically higher in the px‐free granitoids. All granitoids are characterised by negative anomalies of the HFSE (Nb, Ta and Ti) and the LILE (Th, U and Sr) on primitive mantle normalised diagrams. On the one hand, concentrations of compatible elements (Cr, Ni and Mg) in the Matok pluton granitoids are rather low for a mantle source. On the other hand, all the granitoids have superchondtritic Nb/Ta ratios that overlap with those of the Ventersdorp continental flood basalts which extruded in the Kaapvaal Craton at ~2.7 Ga. The continental crust typically has subchondritic Nb/Ta ratio, and superchondtritic Nb/Ta ratios are widely accepted to resemble a mantle source. The implication is that the Matok pluton granitoids had inherited the superchondtritic Nb/Ta ratio from their source; juvenile underplated mafic magmas that had ponded owing to the impact of the Ventersdorp mantle plume. The large volumes of ponded magma s probably induced the high grade metamorphism in the Limpopo Belt. All the granitoids of the Matok pluton are probably products of one partial melting event. One possible way to account for the co‐existence of px‐bearing and px‐free granitoids in the Matok pluton is by means of, at least, two magma chambers; one which was filled with anhydrous magma and the other which was filled with hydrous magma. An alternative model would be that in which there was only one chamber. In the one chamber scenario, the magma was hydrodynamically sorted into zones that differed mostly in fH2O and concentrations of highly fluid‐mobile elements but conserved the uniformity in fluid immobile elements. Regardless of the number of chambers, magma batches intruded in the form of feeder dikes which minimally interacted, thus avoiding the hydration of pyroxene in the px‐bearing granitoids. / SELELEKELA: Plutone ya Matok e fumanehang profinsing ya Limpopo sebakeng seo ho digeologist se tsebahalang ka hore ke Lebanta la Limpopo e ile ya aheya dilemong tse 2.67 biliyone tse fetileng. Plutone ena eile ya aheya ka mekgahlelo e mmeli, mme mokgahlelo ka mong o ne o bopilwe ka majwe a nang le pyroxene le a senang yona. Majwe kaofela ke a mofuta wa calc‐alkaline. Phapang e kgolo dipakeng tsa mefuta ena e mmedi ya majwe ke boteng ba pyroxene le boteng ba epidote le titanite majweng a nang le pyroxene le a senang pyroxene ka ho latellana. Ha e le diminerale tse ding kaofela tsona ha likgethe mofuta wa lejwe; liteng mefuteng ya majwe ka bobedi. Kgonahalo ya hore plutone ya Matok e ahwe ka mefuta ena e mmedi (px‐bearing and px‐free) e tlile ka mekgoa e mmedi kapa o mong wa mekgwa ena yo ka bobedi e ka etsahalang. (1)Tlaase semelong sa lesheleshele moralla (magma) hone ho ena le didiba tse pedi, seseng se tshetse lesheleshele le chesang haholo ebile le le metsi a fokolang (anhydrous magma) ha se seng se ne se tshetse lesheleshele le metsi a mangata (hydrous magma). Ho tloheng moo didibeng tse pedi ho tla moo plutone ea Matok eleng teng kajeno masheleshele ana a ne a tla ka mokgwa wa di‐dike tseo kaofela phello ya tsona e neng e le sebakeng se le seng‐plutone ya Matok. (2) Mokgwa wa bobedi ke haeba ho ne ho ena le sediba se le seng sa lesheleshele moralla, mme ka sedibeng ka moo ho ne ho ena le maqulwana (zones) a neng a fapane ka bongata ba metsi. Ho tloha sedibeng moo masheleshele ana a ne a tloha ka bona boqulwana boo entse ele ka mokhwa wa di‐dike, mme kaofela phello ya di‐dike ene ele plutone ya Matok. Kaofela majwe a plutone ya Matok a na le feldspar eo boholo ba nako e patlameng ho ya nqa bophirimela‐bochabela (W‐E), e leng nqa eo Lebanta la Limpopo le phatlaletseng ka teng. Hona ho tiisa hore plutone ya Matok e aheile nakong yo Lebanta la Limpopo le neng le ntse le aheya le lona. Ke dilemong tse kabang 2.7 biliyone tse fetileng ha dikarolong tse ding tsa Cratone ya Kaapvaal ho ne ho aheya majwe a moralla a Ventersdorp. Majwe ana ke a hlahang tlaase botebong ba lefatshe (mantle), mme a susumeditswe ke plumo. Karolo boholo ya lesheleshele moralla hae ya ka ya nyoloha ho fihla hodimo lefatsheng. Empa mofuthu o mongata ho nyoloha leshelesheleng moo ke ona oileng wa 'pheha' majwe ho phatlalla le Lebanta la Limpopo. Ho nyoloha hona ha plumo ho etsahetse ka nako e lengwe le ho tsukutleha ho hoholo ho potapota le Cratone ya Kalahari, mme bobedi diketsahalo tsena diile tsa tswala Lebanta la Limpopo. Hobane plutone ya Matok e aheile hanghang ka mora hore lesheleshele la moralla le dule tlaase ho lekgapetla la lefatshe (crust), dielemente tse ratang haholo diminerale tsa ditemperetjha tse hodimo diile tsa feela jwalo di nkile lefa hotswa lesheleshele moralleng la Ventersdorp.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The common presence of large volumes of coarse-grained olivine in kimberlite magmas has been proposed to attest to the volume of mantle xenolith material that has been disaggregated during the ascent of the magma. Orthopyroxene should constitute 10-50 vol% of mantle xenoliths in kimberlites, some of which must be disaggregated into the kimberlite, yet it is typically absent. This work tests the stability of orthopyroxene in ascending kimberlite magma by conducting experiments at pressures between 2.0 and 3.5 GPa and temperatures between 1100 and 1300°C. The starting material consisted of natural hypabyssal kimberlite that is close in composition to primary group I kimberlite magma with 5wt% orthopyroxene sourced from a natural peridotite added. At higher temperatures and pressures it is seen that orthopyroxene quantities exceed that of the starting material, but at lower temperatures and pressures it is absent. These results indicate that orthopyroxene is not stable in the magma composition investigated within the shallower part of the sub-continental lithospheric mantle. Based on increased olivine volumes in the experiments where orthopyroxene disappeared, as well as textural relationships between olivine and orthopyroxene, it is found that orthopyroxene dissolution is incongruent along the reaction Mg2Si2O6 (opx) = Mg2SiO4 (ol) + SiO2 (in the liquid). It is concluded that this reaction leads to a maximum addition of 5.5 vol% peritectic olivine to the kimberlite as it ascends through the depths equivalent to a pressure window of 2.0 to 3.5 GPa. / AFRIKAANSE OPSOMMING: The common presence of large volumes of coarse-grained olivine in kimberlite magmas has been proposed to attest to the volume of mantle xenolith material that has been disaggregated during the ascent of the magma. Orthopyroxene should constitute 10-50 vol% of mantle xenoliths in kimberlites, some of which must be disaggregated into the kimberlite, yet it is typically absent. This work tests the stability of orthopyroxene in ascending kimberlite magma by conducting experiments at pressures between 2.0 and 3.5 GPa and temperatures between 1100 and 1300°C. The starting material consisted of natural hypabyssal kimberlite that is close in composition to primary group I kimberlite magma with 5wt% orthopyroxene sourced from a natural peridotite added. At higher temperatures and pressures it is seen that orthopyroxene quantities exceed that of the starting material, but at lower temperatures and pressures it is absent. These results indicate that orthopyroxene is not stable in the magma composition investigated within the shallower part of the sub-continental lithospheric mantle. Based on increased olivine volumes in the experiments where orthopyroxene disappeared, as well as textural relationships between olivine and orthopyroxene, it is found that orthopyroxene dissolution is incongruent along the reaction Mg2Si2O6 (opx) = Mg2SiO4 (ol) + SiO2 (in the liquid). It is concluded that this reaction leads to a maximum addition of 5.5 vol% peritectic olivine to the kimberlite as it ascends through the depths equivalent to a pressure window of 2.0 to 3.5 GPa.

Thesis (MSc (Earth Sciences))--Stellenbosch University, 2008. / Detailed geological mapping and a structural analysis of auriferous quartz veins were undertaken in the Karibib region of the Pan-African Damara belt in central Namibia. The study focuses on the formation and controls of quartz-vein sets and associated lodegold mineralization in heterogeneous, siliciclastic- and marble- dominated amphibolitefacies host rocks around the Navachab gold mine and adjacent areas. Two main arrays of shallowly-dipping quartz veins can be distinguished that form a conjugate set. Steep, bedding-parallel and high-angle cross-cutting veins also occur, but play a subordinate role for mineralization. The orientation of the main conjugate set and progressive deformation of these quartz veins indicate that veining occurred during the late stages of the main phase of NW-SE directed, subhorizontal shortening (D2) and associated NW-verging folding and top-to-the-NW thrusting. Cross-cutting relationships with plutonic rocks indicate a timing of ca. 540 Ma for the mineralization. The quartz veins sets show a consistent orientation irrespective of their location with respect to NE-trending, NW-verging first-order fold structures that were previously considered to be pertinent for the mineralization. The quartz vein sets also cross-cut different lithologies at high angles. This suggests that the regional strain (D2) was the first-order control of quartz vein formation. More localized lithological and/or structural controls played, however, an important factor for the formation of economicgrade mineralization. Thick and closely spaced quartz veins in steeply dipping rocks of the Navachab open pit form a more than 150m thick economic-grade vein swarm. In this structural situation and during layer-normal subhorizontal shortening, the host rocks experienced high extensional strains in a vertical direction, favouring the formation of subhorizontal extension fractures.