O estágio pós-colisional Neoproterozoico no sul do Brasil é marcado por intenso magmatismo granítico controlado por zonas de cisalhamento transcorrentes, relacionadas ao Cinturão de Cisalhamento Sul-brasileiro (CCSb). O CCSb controlou a ascensão e o posicionamento de magmas crustais e mantélicos. Neste contexto, O Granito Corre-mar (GCM) representa uma pequena intrusão posicionado em uma zona de baixa deformação localizada entre dois importantes segmentos do CCSb: as Zonas de Cisalhamento Major Gercino e Itajaí- Perimbó. O GCM possui um diagnóstico par de foliações subevetical que forma um par S-C sinistral, presente em todas as intrusões, independentemente do tamanho, e foi posicionado em um sistema conjugado, onde um cisalhamento sinistral de direção NNE, e uma extensão na direção NW-SE, gerando espaço ao longo da direção NE. Deformação de estado sólido associada ao cisalhamento NNE é atestado por microestruturas como recristalização de feldspatos e caudas de recristalização assimétricas. A abertura é atribuída à dinâmica regional destral transcorrente das zonas de cisalhamento Major Gercino e Itajaí-Perimbó, sendo que o posicionamento foi controlado essencialmente pela componente de estensão NW-SE. A idade de cristalização em zircão U-Pb LAMC- ICP-MS do GCM de 615 ± 4 Ma, muito próxima a outros granitos regionais, como as idades de 611 Ma do Granito Serra dos Macacos (GSM) e de 620 Ma do Granito Rio Pequeno (GRP) sugere que esses três corpos graníticos são sincrônicos. As fortes feições de deformação presents no GCM, diferentemente dos granitos Neoproterozoicos próximos, demonstra que o espaço, mais do que o tempo, pode explicar a diferença dos padrões estruturais identificados no GCM. Assinaturas geoquímicas e de isótopos de Sr-Nd, como caráter levemente peraluminoso, altos conteúdos de K, altas razões de ETRL/ETRP, moderados conteúdos de Rb, Nb, Zr e ETR em relação à SiO2, juntamente com baixas razões de 86Sr/87Sri e valores de εNdt fortemente negativos, indicam que o GCM é derivado de fontes crustais antigas, possivelmente relacionadas à rochas quartzofeldspáticas ortognáissicas Paleoproterozoicas do Complexo Camboriú. A relaçãodas das idades das heranças Arqueanas a Paleoproterozoicas do GCM com as idades dos eventos de migmatização identificados no Complexo Camboriú, além da relação das idades de cristalização de ~615-611 Ma dos granitos crustais da área com o último evento de migmatização em 640-610, reforça a conexão genética entre eles. As idades TDM paleoproterozoicas, as assinaturas geoquímicas e isotópicas, a cristalização e as idades de heranças do GCM e do GSM atestam que eles representam pulsos graníticos contemporâneos e comagmáticos, com uma conexão genética com o evento de migmatização Neoproterozoico do Complexo Camboriú. / The Neoproterozoic post-collisional stage in south Brazil is marked by intense granitic magmatism controlled by transcurrent shear zones all related to the Southern Brazilian Shear Belt (SBSB). The SBSB controls the ascent and emplacement of crustal and mantle magmas. In such scenario, the Corre-mar Granite (CMG), represent a small intrusion emplaced in a low strain zone located between two important segments of the SBSB: the Major Gercino and Itajaí-Perimbó Shear Zones. The CMG have a diagnostic subvertical foliation pair that form a sinistral S-C pair, present in all intrusions regardless of their size, and was emplaced within a conjugate system, where sinistral NNE shearing and NW-SE extension were both active, generating space along the NE direction. Solid state deformation associated to the NNE shearing is attested by microstructures as feldspar recrystallization and asymmetric recrystallization tails. The opening is attributed to the regional dextral transcurrent dynamics of the Major Gercino and Itajaí-Perimbó shear zones and magma emplacement was essentially conditioned by the NW extension component. The zircon U-Pb LA-MC-ICP-MS crystallization age of CMG at 615 ± 4 Ma, very close to other regional granites, as the 611 Ma Serra dos Macacos (SMG) and 620 Ma Rio Pequeno Granite (RPG) points these three granitic bodies as quite synchronous. The strong deformation features present in the CMG, as opposed to the other nearby Neoproterozoic granites (RPG and SMG) demonstrate that space, rather than time, must be called upon to explain the difference in the structural patterns identified in the CMG. Geochemical and Sr-Nd isotopic signatures, as slight peraluminous character, high-K contents, high LREE/HREE ratios, moderate Rb, Nb, Zr, and REE contents to regular SiO2, together with low 86Sr/87Sri and the strongly negative εNdt values indicate that the CMG is derived from old crustal sources possibly related to the Paleoproterozoic Camboriú Complex quartz-feldspatic orto-gneissic rocks. The match of the Archean to Paleoproterozoic inheritance ages of the CMG with the migmatization event ages identified in the Camboriú Complex and moreover the match of the crystallization ages of ~615-611 Ma of the crustalderived granites with the last migmatization event at 640-610 Ma reinforces the genetic link between them. The Paleoproterozoic TDM ages, the geochemical and isotopic signatures, the crystallization and inheritance ages resemblance of the CMG and the SMG attest that they represent comagmatic and contemporaneous granitic pulses with a genetic connection with the Neoproterozoic migmatization event in the Camboriu Complex.

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 (PhD) -- Stellenbosch Univesrsity, 1972. / The Darling batholith is characterised by large scale hybridisation, but mainly consists of the coarsely porphyritic Darling granite. This granite changes gradationally into a biotite-rich variety which occupies a roughly elliptical area with a major, northwesterly trending axis of 30 km. The biotite granite envelops a large irregular body of hybrid granodiorite. Small intrusions of younger granite occur within the batholith namely the Klipberg and Contreberg granites and possibly the biotite-rich Dassenberg granite. Dassen Island is underlain by fine-grained granite which could be related to either the younger or coarsely porphyritic granites. A prominent northwesterly trending mylonite zone can be traced through Darling to Swartberg, and ultimately to Trekoskraal in the Saldanha batholith, but is not continuous since it occasionally changes into gneissic granite and is also interrupted by the younger intrusives. Quantitative mapping included measurement of matrix grain size, average maximum phenocryst length, xenolith distribution density, quartz nodule distribution density and average size, lineation, dark mineral index and gneissosity. On Dassen Island the distribution of tourmaline nodules was , determined. The results are displayed as small scale contour maps which show strong correlation between the various parameters. The average values of matrix grain size, average phenocryst length and xenolith distribution density are respectively 2-5mm, 20-60mm and 0-1,5 per m² for the Darling granite, and 1-2 mm, 5-20 mm and 1-9 per m² for the hybrid granodiorite. It was found that the matrix grain size decreases with increase in hybridisation. The spotty distribution pattern of tourmaline nodules on Dassen Island indicates addition of boron by assimilation of metamorphites and a late stage liquid immiscibility process. The granites :.have normal mineralogy and the K-feldspar of the phenocrysts is maximum microcline (Δ = 0,9 - 1,0). The hybrid granodiorite contains much pinitised cordierite and locally garnet. The deeply pleochroic bioti te is probably of the 2M1 polytype and has a higher Fe:Mg ratio in the hybrid granodiorite than in the granite (2,8 - 3,0 vs. 2,2 - 2,3). The intimately associated chlorite seems to be of the Ia polytype. The cordierite is of the normal and low temperature type with average intensity index of 2,7 , distortion index of 0,3 and 2 a of 63°. The xenoliths are predominantly quartzitic metagraywackes, but lime-rich types holding sphene and diopside were occasionally encountered. Thirteen new chemical analyses and thirty-one previously published analyses are used to calculate average composite analyses of the various rock types. The results of calculations employing Barth standard cell values indicate that the hybrid granodiorite could have originated by reaction between granite magma and Malmesbury quartzitic metagraywacke and pe-lite with a little limestone. A "granite differentiation index" based on weight percentages of (Ti02 + MgO + FeO + Fe2O3) and (Si02 + Na2O + K2O) shows a linear relationship between the granites in probable order of age. The magmatic differentiation trend is separated from the hybridisation trend on a 6alk - 2(al - alk) - (100 - 2al) diagram. Mesonorms and their cordierite variants are used to effect comparison with the experimental granitic system of von Platen (1965). The Darling and Contreberg granites plot near the relevant cotectic surfaces. A pilot experimental study of melting behaviour indicates that the Contreberg granite is closer to a minimum melt composition than the Darling granite. Comparison of alkali values with a M Na2O - M K2O Schreinemakers diagram of Korzhinskii (1959), shows that the alkali ratio of the older analyses may be incorrect, and indicates that the dark minerals have a greater effect on plagioclase composition than the amount of K-feldspar. The classification of granites by means of Harpum diagrams is shown to have little relevance to the reconstruction of the ancient thermodynamical variants. The Darling granite is correlated with the Hoedjies Point granite of the Saldanha batholith and on geochronological evidence probably corresponds in age (500- 600 m.y.) with the Cape Peninsula granite. The younger granites of Darling are tentatively correlated with the Cape Columbine granite of the Saldanha batholith. The northeastern boundary of the Darling batholith is a major fault, the Colenso fault, which is considered to extend as far as Northwest Bay, Saldanha. It is proposed that the Darling batholith occupies a down-faulted block within a graben and that the hybrid granodiorite represents a remnant synform of the roof rocks intruded by the granite. The younger granites constitute only four percent by volume of the batholith and may represent anatectic melts from a nearby subjacent source.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Large areas of the earth’s surface are covered by soils that are susceptible to large decreases in bulk volume when they become saturated. These soils are termed collapsing soils and are very common in parts of the USA, Asia, South America and Southern Africa. This study is concerned with the occurrence of these collapsible soils in the residual granites of the Stellenbosch area. The study was undertaken as relatively little is known about the collapse phenomenon in the problematic weathered granites of the Western Cape. The majority of research thus far has been carried out on the deep residual soils formed on basement-granite in the Transvaal areas, whereas little attention has been paid to the Cape granites. The aim of the study was achieved through the experimental work which included double oedometer testing, indicator analyses and shear strength testing. Double oedometer tests were performed to quantify the potential collapse settlement of the soils from the demarcated study area. To provide a better understanding of the collapse behaviour of the soils, indicator analysis, which included Atterberg limits and particle size distributions, were performed. Direct shear tests were further carried out on saturated and natural moisture content specimens to establish the effect of collapsibility on shear strength and whether substantial additional settlement of the saturated soils would occur during shear. It was found that collapsible soils are prevalent in the demarcated study area as the majority of soils showed a potential collapse settlement of 1% or more. Collapse exceeding 5% were calculated in a few instances proving some soils to be highly collapsible. The double oedometer and indicator analysis results were used in an attempt to obtain a relationship between collapse settlement and a combination of easily determined properties such as dry density (void ratio), moisture content and grading, but no meaningful conclusions have emerged. The shear strength tests indicated that a clear correlation does not exist between collapsibility and shear strength. It was further established that a relationship between collapse settlement determined during the double oedometer testing and the volume change during shear strength testing cannot be assumed. It can thus be concluded that soils can be very unpredictable and further research on the collapse phenomenon is indicated. / AFRIKAANSE OPSOMMING: Groot dele van die aarde se oppervlakte is bedek deur grondtipes wat geneig is tot ‘n afname in volume as dit deurweek word. Hierdie gronde word swigversakkende gronde genoem en dit word algemeen teëgekom in dele van die VSA, Asië, Suid-Amerika en Suider-Afrika. In hierdie studie word die voorkoms van swigversakkende gronde in die residuele graniet in die Stellenbosch area ondersoek. Die studie is onderneem aangesien relatief min i.v.m. die swigversakking-verskynsel in die problematiese verweerde graniet van die Weskaap bekend is. Die meeste van die navorsing sover is onderneem op die diep residuele gronde wat gevorm is op die Argaïese graniet in die Transvaal gebied, en betreklik min aandag is geskenk aan die Kaapse graniet. Tydens die studie is eksperimente wat dubbele oedometer toetse, indikator analises, en skuifsterkte toetse insluit, uitgevoer. Dubbele oedometer toetse is uitgevoer om die potensiële swigversakking van die grond in die afgebakende studiegebied te kwantifiseer. In ‘n poging om die swigversakking-verskynsel van die grond beter te verstaan, is indikator analises wat Atterberg grense en partikel grootte verspreiding insluit, uitgevoer. Direkte skuiftoetse is ook uitgevoer op deurweekte grondmonsters en op monsters wat natuurlike vog bevat, om sodoende die effek van swigversakking op skuifsterkte vas te stel en om uit te vind of aansienlike addisionele sakking van die deurweekte gronde tydens skuif plaasvind. Daar is gevind dat swigversakkende gronde die oorheersende grondtipe in die afgebakende studiegebied is waar meeste van die gronde ‘n potensiële swigversakking van meer as 1% toon. ‘n Swigversakking van meer as 5% is in ‘n paar gevalle bereken, wat bewys dat sommige grondtipes hoogs versakkend is. Die resultate van die dubbele oedometer en indikator analises is gebruik in ‘n poging om te bewys dat daar ‘n verhouding bestaan tussen swigversakking en ‘n kombinasie van kenmerke wat maklik vasgestel kan word soos droë digdheid (ruimte verhouding), voginhoud en gradering, maar daar kon nie tot ‘n sinvolle slotsom gekom word nie. Die skuifsterkte toetse toon dat daar nie ‘n duidelike korrelasie bestaan tussen swigversakking en skuifsterkte nie. Daar is verder vasgestel dat dit nie moontlik is om te aanvaar dat daar ‘n verhouding bestaan tussen swigversakking soos vasgestel tydens die dubbele oedometer toetsing, en die verandering in volume tydens skuifsterkte toetsing nie. Daar is dus tot die slotsom gekom dat grond baie onvoorspelbaar kan wees en dat verdere navorsing na die swigversakking-verskynsel nodig is.

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The Central Zone (CZ) of the Damara belt in central Namibia is underlain by voluminous Pan-African granites and is host to numerous pegmatite occurrences, some of which have economic importance and have been mined extensively. This study discusses the occurrence, geometry, relative timing and emplacement mechanisms for the Usakos pegmatite field, located between the towns of Karibib and Usakos and within the core of the regional-scale Kranzberg syncline. Lithological mapping of the Kuiseb Formation in the core of the Kranzberg syncline identified four litho-units that form an up to 800 m thick succession of metaturbidites describing an overall coarsening upward trend. This coarsening upwards trend suggests sedimentation of the formation’s upper parts may have occurred during crustal convergence and basin closure between the Kalahari and Congo Cratons, rather than during continued spreading as previously thought. The Kranzberg syncline is a regional-scale NW verging, NE-SW trending, strongly non-cylindrical structure that consists of a moderately SE dipping, normal NW limb and a steep- to overturned SE limb. First- and lower-order folds show relatively consistent E - SE plunges at moderate angles and stretching lineations and boudinage of competent layers point to a fold-parallel stretch during folding. Folding is associated with a moderate- to steep SE dipping transecting foliation that shows a consistent anticlockwise rotation with respect to the axial plane of the fold. The transecting cleavage and a component of non-coaxial shear along the overturned limb suggest that folding was accomopanied by a dextral component of shear thought to be related to the SW-directed extrusion of the adjacent Usakos dome during regional NW-SE directed shortening. It is further suggested that the Kranzberg syncline evolved within the overall regional pattern of regional dome and syncline structures in the sCZ, and not as a forced fold in response to the formation of neighbouring dome structures. Based on cross-cutting relationships and deformation, four main generations of bedding-concordant sills and bedding-discordant pegmatite dykes were identified. Along the normal limb, shallowly-dipping sills dominate, highlighting the significance of bedding anisotropies for sheet propagation. Along the overturned limb, interconnected dyke and sill geometries co-exist. Here, pegmatite emplacement appears to have been influenced by (1) the regional strain, (2) differing wall rock rheologies; (3) the orientation of pre-existing anisotropies; and (4) driving melt pressures. Dykes within the Usakos pegmatite field formed within dilational sites, at high angles to the regional stretch, whereas sills formed at high angles to the regional shortening strain and in contractional sites. Where driving pressures for melt ascent were high enough, an interconnectivity of dykes and sills and subsequent melt transfer from contractional into dilational sites is developed. Where melt pressures dropped below a critical value pegmatites were arrested, thus preserving the ascent pathways of the melts. These complex intersecting melt pathways are developed throughout the Kranzberg syncline. This suggests the existence of fairly stable melt networks in the continental crust. This geometrical complexity also accounts for the stockwork-like structures observed in pegmatite fields. / AFRIKAANSE OPSOMMING: Die Sentrale Sone (CZ) van die Damara gordel in sentrale Namibië is onder lê deur volumineuse Pan-Afrikaanse graniete en speel gasheer vir talle pegmatiet voorkomste, waarvan party van ekonomiese belang is en is ekstensief ontgin. Hierdie studie bespreek die voorkoms, geometrie, relatiewe tydsberekening en inplasing meganismes vir die Usakos pegmatiet gebied, wat tussen die stede van Karibib en Usakos en wat binne die kern van die regionale-skaal Kranzberg sinklien geleë is. Litologiese kartering van die Kuiseb Formasie in die kern van die Kranzberg sinklien het vier lito-eenhede geidentifiseer. Hierdie eenhede, wat saam tot 'n 800 m dik opeenvolging van metaturbidiete vorm, beskryf ‘n algemene opwaartse vergrowwing neiging. Hierdie tendens dui aan dat sedimentasie van die Formasie se boonste dele tydens die aardkorst konvergensie en kom sluiting tussen die Kalahari en die Kongo kratons voorgekom het, eerder as in 'n oseaanvloerverbreiding omgewing soos voorheen gedink was. Die Kranzberg sinklien is 'n regionale-skaal struktuur met ‘n NW vergensie, ‘n NOSW koersing, wat sterk nie-silindries is en wat uit 'n matige SO helling, normale NW flank en 'n steil-tot omgeslaande SO flank bestaan. Eerste-en laer-orde plooie vertoon relatief konsekwent matige O - SO duikings en strek lineasies en boudinage van kompetent lae dui 'n plooi parallel strek tydens plooiing aan. Plooiing is geassosieer met 'n ongeveer aksiale planêre, matig- tot steil SO helling foliasie wat omstandig waargeneem word om 'n konsekwente antikloksgewyse rotasie met betrekking tot die aksiale vlak van die plooi te hê. Hierdie antikloksgewyse rotasie is ‘n bewyse vir 'n komponent van nie-koaksiale regse skuifskeur deur die omgekeerde flank en dui dit ook aan dat 'n regse komponent van skeer gedurend of na plooiing plaasgevind het. Daar is gedink dat die regse komponent van skeur in verband met die laterale, SW-gerig extrusie van die aangrensende Usakos koepel gedurende plaaslike NW-SO verkorting ontwikkel het. Dit is verder voorgestel dat die Kranzberg sinklien binne die totale patroon van plaaslike koepel en sinklien strukture in die sCZ geontwikkel het, en nie as 'n gedwonge plooi in reaksie op die formasie van die naburige koepel strukture (bv. Usakos koepel). Gebaseer op kruis-sny verhoudings en deformasie, was vier generasies van gelaagdheid-konkordant plate en gelaagdheid-diskordant pegmatiet dyke geïdentifiseer. In die normale flank, vlak-helling plate oorheers, wat die belangerikheid van die laagvlak-anisotropiese op plaat voortplanting beklemtoon. In die steil, omgekeerde flank, bestaan onderlinge verbinde dyk en plaat geometrië gelyktydig. Hier is pegmatiet inplasing blykbaar beïnvloed deur (1) die regionale span; (2) verskillende wandgesteentes reologië; (3) die oriëntasies van anisotropie (ie. gelaagdheid ); en (4) smeltsel druk. Dyke in die Usakos pegmatiet gebied het binne dilatasionele liggings, teen hoë hoeke aan die regionale strek gevorm, terwyl plate teen hoë hoeke aan die plaaslike verkorting span en in kontraksionele liggings gevorm het. Waar smeltsel druk hoog genoeg was, is 'n onderlinge verbinding van dyke en plate, en die daaropvolgende smeltsel oordrag van kontraksionele liggings na dilatasionele liggings behou. In teenstelling, waar smeltsel druk onder 'n kritieke waarde geval het, word die pegmatiete geblokeer, en dus kan die behoude smeltsel styging paaie waargeneem word. Hierdie snyende smeltsel geometrië, in beide kontraksionele en dilatasionele liggings dui aan dat redelik stabiele smeltsel netwerke in die kontinentale kors kan bestaan en verder kan en verklaar die algemene stokwerk-agtige strukture wat in pegmatiet velde van ander mid-korstige omgewings waargeneem word.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: To date, the only volcanic rocks described from the Cape Granite Suite are ignimbrites that crop out along the western margin of Langebaan lagoon, to the south of Saldahna. These ignimbrites, with an age of 515 ± 3 Ma, represent the youngest rocks within the Suite. This study aims to investigate the petrogenesis of fine grained granitic rocks exposed to the north of Langebaan lagoon, as well as to reassess the classification of these rocks as a sub-volcanic quartz porphyritic intrusive. These rocks exhibit a dark grey to brown micro- to crypto-crystalline matrix containing prominent feldspar and quartz phenocrysts that are often embayed and broken. Phenocrysts of biotite and orthopyroxene (Fs50-70) can be identified microscopically, as can replacement of both phases by chlorite. Ilmenite commonly occurs in close association with the orthopyroxene phenocrysts. A second generation of poikiloblastic biotite overgrows the matrix and is clearly formed through sub-solidus reaction. The feldspar phenocrysts are commonly microcline microperthite. Contact exposures can be observed in the study area which indicates that the finer grained rock intruded older coarser grained granites. The predominance of broken phenocrysts as well as the presence of fiamme present in outcrop in rocks with a microcrystalline matrix is indicative of a volcanic origin, suggesting that these rocks be classified as ignimbrite as opposed to quartz porphyry. The foregoing observations and features could be interpreted to represent a welded ignimbrite deposit which is underlain by coarse grained granite. The finer grained ignimbrite would then represent a subsequent intrusion by a later pulse of similar magma along the contact with the coarser grained granite. The ignimbrites are silicic with SiO2 ranging between 69 and 76 wt. %; they are mildly peraluminous with values for ASI (ASI = mol. Al2O3/ (CaO+Na2O+K2O)) ranging from 1.02 to 1.09; and ASI is negatively correlated with Mg + Fe (hereafter maficity). Tight to very tight inter-element correlations exist for several major elements as well as trace elements when plotted against maficity. The following R² values apply: Al =0.94; Ca = 0.98; Si = 0.97; Ti = 1.00; Na =0.90; Zr =0.95; La = 0.87. These elements are all positively correlated with maficity, except for Si which is negatively correlated. Orthopyroxene and ilmenite represent early formed, high temperature minerals in the magma. In the biotite-poor rocks, ilmenite represents the main reservoir of titanium whilst orthopyroxene represents the main MgO and FeO reservoir. The exceptionally tight Ti: maficity correlation requires that both these minerals always be present at the same molecular ratio in the magma, despite the significant range in maficity portrayed by the rocks and despite the fact that these minerals have different size-density relationships. This exceptionally tight correlation can be readily interpreted to reflect entrainment of a peritectic assemblage consisting of ilmenite and orthopyroxene. The Al, Ca and Na correlations require the entrainment of peritectic plagioclase. The decreasing trend for ASI requires the entrainment of peritectic clionopyroxene. A near perfect match with the concentrations of these elements in the ignimbrites is produced by modelling entrainment of a peritectic assemblage consisting of plagioclase, ilmenite, orthopyroxene and clionopyroxene in stoichiometric proportions dictated by the melting reaction. A peritectic assemblage formed by these phases’ points to the partial melting of a source undergoing coupled biotite and hornblende fluid-absent melting, with hornblende being subordinate. The opx- and ilmenite-rich micro-domains in the rocks represent zones in the magma rich in original peritectic orthopyroxene and ilmenite. In contrast, the peritectic plagioclase demanded by the chemistry of the rocks has melted during ascent due to overheating and decreasing water solubility in the melt. The phenocrystic potassium feldspar observed in the rocks crystallised after significant cooling and the physical behaviour of these crystals does not shape the chemistry of the magma. K contents of the ignimbrites are however not well replicated by this modelling, which predicts a significant K decrease due to dilution. K in the rocks is not correlated with maficity. This may reflect the fact that the K behaviour represents two slightly different source protoliths with differing K contents. / AFRIKAANSE OPSOMMING: Tot op hede is die enigste vulkaniese rots van die Kaapse Granietgroep wat al beskryf is ignimbriete wat teen die westelike grens van die Langebaan-lagune, na die suide van Saldanha, aan die oppervlak kom. Hierdie ignimbriete, met ’n ouderdom van 515 ± 3 Ma, verteenwoordig die jongste gesteentes in die Groep. Die doel van hierdie studie was om die petrogenese van fynkorrelrige granietrots wat na die noorde van die Langebaan-lagune blootgestel is, te ondersoek, en ook die klassifikasie van hierdie rotse as ’n subvulkaniese kwartsporfier- intrusiewe gesteentes te assesseer. Hierdie gesteentes toon ’n donker grys tot bruin mikro- tot kriptokristalvormige matriks wat prominente veldspaat en kwartsfenokriste bevat wat dikwels bogtig en gebreek is. Fenokriste van biotiet en ortopirokseen (Fs50-70) asook vervanging van albei fases deur chloriet kan mikroskopies geïdentifiseer word. Ilmeniet kom dikwels naby ortopirokseenfenokriste voor. ’n Tweede generasie poikiloblastiese biotiet groei die matriks toe en is duidelik deur subsolidusreaksie gevorm. Die veldspaatfenokriste is gewoonlik mikroklien-mikropertiet. Kontakblootstelling kan in die studiegebied waargeneem word, wat aantoon dat die fynkorrelrige rots ander grofkorrelrige granietgesteentes intrudeer het. Die oorheersing van gebroke fenokriste asook die teenwoordigheid van ‘fiamme’ strukture in die rotsdagsoom met ’n mikrokristalvormige matriks dui op vulkaniese oorsprong, wat aan die hand doen dat hierdie gesteentes as ignimbriete eerder as kwartsporfier geklassifiseer kan word. Hierdie waarnemings en eienskappe kan geïnterpreteer word as verteenwoordigend van ’n gelaste ignimbriet-afsetting wat deur grofkorrelrige graniet onderlê word. Die fynkorrelrige ignimbriet stel dan ’n daaropvolgende intrusie voor deur ’n latere puls van soortgelyke magma teen die kontak met die grofkorrelrige graniet af. Die ignimbriete is silisies met SiO2 wat wissel tussen 69 en 76 wt. %; hulle is matig peralumineus met waardes vir ASI (ASI = mol. Al2O3/ (CaO+Na2O+K2O)) wat wissel van 1.02 tot 1.09; en ASI is negatief gekorreleer met Mg + Fe (hierná mafiese komponent). Nou tot baie nou inter-elementkorrelasies bestaan vir verskeie groot elemente asook spoorelemente wanneer dit teen die mafiese komponent gestip word. Die volgende R²-waardes is van toepassing: Al =0.94; Ca = 0.98; Si = 0.97; Ti = 1.00; Na =0.90; Zr =0.95; La = 0.87. Hierdie elemente is almal positief met die mafiese komponent gekorreleer, buiten Si, wat negatief gekorreleer is. Ortopirokseen en ilmeniet verteenwoordig vroeg gevormde, hoëtemperatuur-minerale in die magma. In die biotiet-arme rotse stel ilmeniet die hoofreservoir van titaan voor, terwyl ortopirokseen die vernaamste MgO- en FeO-reservoir voorstel. Die buitengewoon nou Ti: mafiese-korrelasie vereis dat albei hierdie minerale altyd in dieselfde molekulêre verhouding in die magma teenwoordig moet wees, ondanks die beduidende omvang van die mafiese komponent wat deur die gesteentes getoon word en ondanks die feit dat hierdie minerale verskillende grootte–digtheidsverhoudings het. Hierdie buitengewoon nou korrelasie kan geredelik geïnterpreteer word om meesleping van ’n peritektiese groep te weerspieël wat uit ilmeniet en ortopirokseen bestaan. Die Al-, Ca- en Na-korrelasies vereis die meesleping van peritektiese plagioklaas. Die verminderende neiging tot ASI vereis die meesleping van peritektiese klionopirokseen. ’n Byna perfekte passing met die konsentrasies van hierdie elemente in die ignimbriete word voortgebring deur die modellering van meesleping van ’n peritektiese groep bestaande uit plagioklaas, ilmeniet, ortopirokseen en klionopirokseen in stoïgiometriese verhoudings wat deur die smeltreaksie bepaal word. ’n Peritektiese groep wat deur hierdie fases gevorm word, dui op die gedeeltelike smelting van ’n bron wat gekoppelde biotiet- en horingblende- vloeistofafwesige smelting ondergaan, met horingblende wat ondergeskik is. Die ortopirokseen- en ilmeniet-ryke mikrodomeins in die gesteentes verteenwoordig sones in die magma wat ryk is aan oorspronklike peritektiese ortopirokseen en ilmeniet. Hierteenoor het die peritektiese plagioklaas wat deur die chemie van die gesteentes vereis word tydens styging gesmelt weens oorverhitting en dalende wateroplosbaarheid in die smeltsel. Die fenokristiese kaliumveldspaat wat in die rotse waargeneem is wat ná aanmerklike afkoeling gekristalliseer het en die fisiese gedrag van hierdie kristalle vorm nie die chemie van die magma nie. Die K-inhoud van die ignimbriete word egter nie goed deur hierdie modellering gerepliseer nie, wat ’n aanmerklike K-afname weens verdunning voorspel. K in die rotse is nie met mafiese komponente gekorreleer nie. Dit kan die feit weerspieël dat die K-gedrag twee effens verskillende bronprotoliete met verskillende K-inhoud voorstel.

published_or_final_version / Applied Geosciences / Master / Master of Science

Geotechnical characterization of crystalline rock is often dependent upon the influence of the rock's fracture system. To test ensemble fracture behavior in situ, a series of cross-hole and single-hole electrical conductivity measurements were made within saturated Oracle granite. The tests were conducted with a point source and a point reference electrode and employed electrode separations ranging from 8 inches to over 100 feet. A volume of rock approximately 50 x 50 x 150 feet was tested (as bounded by the vertical test borings). Analysis of the data in terms of an equivalent homogeneous material showed that the effective electrical conductivity increased with electrode separation. The cross-hole data indicate that the rock can be treated as a non-homogeneous, isotropic material. Further, the spatial variation of measured conductivities along a line can be fit to a fractal model (fractional Brownian motion), implying that the scale-dependence is a result of a fractal process supported by the fracture system. Scale-dependence exists at the upper scale limit of the measurements, hence a classical representative elemental volume was not attained. Two directions were taken to understand the scale-dependence. The rock mass is treated in terms of a disordered material, a continuum with spatially varying conductivity. First, a percolation-based model of a disordered material was examined that relates the conductivity pathways within the rock to the backbone of a critical percolation cluster. Using the field data, a fractal dimension of 2.40 was derived for the dimensionality of the subvolume within the rock that supports current flow. The second approach considers an analytic solution for a non-homogeneous, isotropic material known as the alpha center model (Stefanescu, 1950). This model, an analytic solution for a continuously varying conductivity in three dimensions, is a non-linear transform to Laplace's equation. It is employed over a regular grid of support points as an alternative to spatially discretized (piece-wise continuous) numerical methods. The model is shown to be capable of approximating the scale-dependent behavior of the field tests. Scaling arises as a natural consequence of the disordered electrical structure caused by the fracture system.

The objective of this thesis was to design a canister for the disposal of spent nuclear fuel and other high-level waste in deep borehole repositories using currently available and proven oil, gas, and geothermal drilling technology. The canister is suitable for disposal of various waste forms, such as fuel assemblies and vitrified waste. The design addresses real and perceived hazards of transporting and placing high-level waste, in the form of spent reactor fuel, into a deep igneous rock environment with particular emphasis on thermal performance. The proposed boreholes are 3 to 5 km deep, in igneous rock such as granite. The rock must be in a geologically stable area from a volcanic and tectonic standpoint, and it should have low permeability, as shown in recent data taken from a Russian deep borehole. Although deep granite should remain dry, water in flooded boreholes is expected to be reducing, but potentially corrosive to steel. However, the granite and plug are the containment barrier, not the canister itself. The canisters use standard oil drilling casings. The inner diameter is 315.32mm in order to accommodate a PWR assembly with a width of 214mm. At five meters tall, each canister holds one PWR assembly. The canister thickness is 12.19mm, with an outer diameter of 339.7mm. A liner can extend to the bottom of the emplacement zone to aid in retrievability. The liner has an outer diameter of 406.4mm and a thickness of 9.52mm. The standard drill bit used with a liner of this size has an outer diameter of 444.5mm. / Contract number: N62271-97-6-0026. / US Navy (USN) author.

The Mourne Mountains situated in County Down, Northern Ireland, mainly consists of solidified granite magma chambers that intruded ~ 56 million years ago into the surrounding greywacke. How granite magma chambers are emplaced in the crust has for years been a debate amongst scientist of volcanology, and is referred to as the ‘space problem’ debate. There are two principle theories in how the granite magma chambers in the Mourne Mountains were formed; either the magma chambers were forcefully emplaced by doming the greywacke host-rock or the magma chambers were emplaced by passively by magma filling the space over a subsiding block of host-rock. In this study rock samples from Luke’s Mt. dyke has been investigated with anisotropy of magnetic susceptibility (AMS). AMS measures the orientation of magnetic minerals in a rock sample and thereby shows the magma movement. These measurements indicated that the magma in the studied Luke’s Mt dyke flowed into the connected magma chamber and thus are a feeding ring-dyke. This implies that the granite bodies of the Mourne Mountains were emplaced by a passive process like cauldron subsidence. / Mätningar av magnetiska mineral har visat att den stelnade magman i en granitgång tillhörande Mournebergen i Nordirland en gång flödat in mot granitmagmakammarna. Med den här vetskapen kan tolkningar göras över hur de stora Mournebergen en gång formades. Sedan länge har den så kallade ’space problem’ debatten pågått bland forskare inom vulkanologi. Debatten diskuterar huruvida magma intruderar och placeras i jordskorpan. Mournebergen består huvudsakligen av granitmagmakammare som intruderat in i omkringliggande bergarten gråvacka för cirka 56 miljoner år sedan. Är magmakammarna ett resultat av deformation i omkringliggande gråvacka eller tvärtom? AMS (anisotropy of magnetic susceptibility) är en metod där magnetiska mineral och dess magnetiska susceptibilitet mäts för att ta reda på dess orientering i en stelnad magma. Vid ett pålagt magnetiskt fält kommer de magnetiska mineralen visa på en viss magnetisk susceptibilitet i olika orienteringar. Det här kan representeras som tre axlar på en ellipsoid. Axlarna på ellipsoiden ger information om hur mineralen flödat med magman. AMS-mätningar av stenprover från den studerade granitgången Luke’s Mt Dyke i Mournebergen visar på att graniterna som utgör största delen av bergen troligen är resultat av ett så kallat passivt bildande av magmakammare och därmed har omkringliggande bergarten gråvacka inte deformerats av granitmagmakammarna.