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.

The emplacement of continental flood basalt provinces is often ascribed to fissure eruption. However, in many provinces the locations of actual vent complexes remains illusive. In southern Africa, the Karoo continental flood basalt province was erupted during the Jurassic between 183 and 179 Ma. The southernmost outcrop of the Karoo continental flood basalt lavas is the Lesotho remnant; and is comprised of the Drakensberg Group which forms the uppermost portion of the Karoo Supergroup. The geochemical stratigraphy for the Drakensberg Group is well established. At the base, there are a number of small volume compositionally diverse units, which form the Barkly East Formation, overlying which, there are larger volume, compositionally less variable units of the Lesotho Formation, which form the bulk of the volcanic sequence. The Lesotho remnant is associated with an abundance of dykes in the adjacent vicinity. This suggests that the lavas were fed from local rather than distal eruption sites. This study presents whole rock major and trace element data for 94 dykes and three sills from the northern Lesotho - northeastern Free State region and demonstrates that on the basis of geochemistry, all 97 intrusions can be correlated with various units of the northern Barkly East and Lesotho Formations. In addition, the petrographical; characteristics, orientation and distribution of the dykes do not correlate with geochemistry. Geochemical discrimination diagrams have been used to identify five compositionally diverse dykes, which are similar to the northern Barkly East Formation units. Three dykes are characteristic of the Letele unit and two are compositionally similar to the Wonderkop unit. Although the geochemical characteristics of the Lesotho Formation units are rather well constrained, the composition of these units is typified by considerable overlap in composition. Therefore, since unambiguous classification of dykes with geochemical similarities to the various units of the Lesotho Formation is unachievable using an empirical approach, the multivariate forward-stepwise discriminant function analysis (DFA) technique was used to facilitate the classification of the remaining 89 dykes and three sills. Forward-stepwise DFA classified 23 dykes as having compositional similarities to the Mafika Lisiu unit, 29 as having compositions of the Maloti or Senqu types; and 32 as having the composition of the Mothae type. In addition, eight dykes are compositionally similar to the Oxbow dykes, which intrude the Senqu unit in northern Lesotho. These results suggest that that the Lesotho remnant was fed from local eruption sites and that long distance magma transport for the bulk of the Lesotho remnant basalt lavas is unlikely.

Les processus internes et externes qui ont formé et structuré la croûte de la planète Mars au début de son histoire sont actuellement mal connus. Le canyon de Valles Marineris représente la plus grande coupe naturelle à la surface de Mars, où affleure la croûte moyenne et supérieure. L'étude de cette région clé a été abordée minéralogiquement et morphologiquement à partir de données hyperspectrales CRISM, et des images à haute résolution HiRISE de la mission MRO (NASA, 2006). La base du canyon est constituée de roches massives, fracturées, à fort albédo, riches en pyroxènes pauvres en calcium, pénétrées par des dikes verticaux riches en olivine. Ces roches sont interprétées comme des affleurements de croûte primitive, préservée et exposée dans son contexte originel. Les plateaux bordant le canyon sont couverts d’une formation de 100m d’épaisseur d’argiles ferromagnésiennes, recouvertes d’argiles alumineuses. Cette formation géologique visible sur plus de 106km2 traduit un niveau d’altération de la croûte sous un climat humide. Enfin, les dépôts stratifiés centraux de la région de Capri Chasma, d'épaisseur plurikilométrique, sont riches en sulfates monohydratés et polyhydratés, corrélés à des groupes de strates distincts. Ces sédiments se sont déposés durant l’Hespérien et ont ensuite été érodés par des processus fluviatiles. Ces résultats permettent de reconstituer la succession d’événements suivants : I) formation de la croûte primitive témoin d’un océan magmatique primitif, II) recouvrement de cette croûte primitive par un empilement volcanique, III) Altération de surface à grand échelle, IV) Ouverture du canyon de Valles Marineris, V) dépôts et érosion de niveaux stratifiés riches en sulfates. / Valles Marineris is a unique vertical section through the uppermost kilometers of the martian crust; its location, east of Tharsis bulge, and its water-related history suggest a great diversity of rock types in this area. High resolution morphologic (HiRISE) and mineralogic (CRISM) data from the MRO mission (NASA, 2006) available over the area were investigated. A typical succession of horizontal units of distinct morphologies and mineralogies was observed in the Eastern part of Valles Marineris, including basaltic lavas, phyllosilicate-rich boulders and a LCP (Low-Calcium Pyroxene)-rich basement. This basement, interpreted as being a uniquely preserved outcrop of pristine Noachian crust, is intruded by olivine-rich dikes, which are valuable witnesses of early magmatic and tectonic processes. A thin light-toned formation, enriched in Fe/Mg smectites at its base, and Al-phyllosilicates at its top, is draping the Noachian plateaus around the canyons. This widespread unit could have formed by alteration under a wet climate, and is akin to pedogenesis. Finally, kilometer-thick layered deposits that are filling most of the canyons were analyzed in the area of Capri Chasma, at the outlet of Valles Marineris. These Hesperian-aged deposits are enriched in monyhydrated and polyhydrated sulfates and appear to have been eroded by younger fluvial processes. Both spectral types are associated with different units of distinct morphologies, at different elevations. All these observations were combined to propose the following succession of events: I- Formation of the pristine crust by crystallization in a magma ocean, II- Piling of lava flows on the top of this crust and dike activity, III- Widespread surficial alteration, IV- Opening of Valles Marineris, V- deposition and erosion of the sulfate-rich layered deposits.

D.Phil. (Geology) / The structural history and mechanisms of bedding-parallel faulting associated with the Ventersdorp Contact Reef (VCR) on the Kloof Gold Mine are discussed. Pre-VCR deformation is determined by folding of the Booysens Shale Formation and the Turffontein Subgroup. Extension of Ventersdorp age (± 2700 Ma) probably took place by the simultaneous operation of normal, strike-slip and oblique slip faults (mixed-mode extension). Because the strikeslip and oblique-slip faults were extensional, they could be utilised as conduits for dykes, forming "Fault and Dyke Zones". Northwestward directed thrusting, which postdates the normal faulting, resulted in positive inversion. The thrust faults have a ramp-flat symmetry with ramps forming in the VCR horizon and the overlying Alberton Formation and flats forming in the underlying Booysens Shale Formation and along the contact between the VCR and the Alberton Formation. The thrust faults follow complex deformation paths, indicated by out-of-sequence thrusting, simultaneous folding and thrusting, underthrusting and compressed boudins. Hanging-wall ripouts, which can be related to this thrust event, are introduced as a shear sense indicator. No northwestward verging thrust faults of post-Transvaal age (post 2430 Ma) could be identified, indicating that this compressional event occurred prior to the deposition of the Black Reef Quartzite Formation. The minimum amount of shortening due to northwestward directed thrusting was estimated as 37 % with the help of restored sections. However, due to the out-of-sequence propagation of thrust faults, a control of the strain estimation was possible and true shortening probably exceeded the calculated amount of shortening considerably. The restoration of sections with out-of sequence thrusts is discussed in detail. Sheath fold-like structures in pseudotachylyte can be related to northwestward directed thrusting and are introduced as a new shear sense indicator.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21353号 / 工博第4512号 / 新制||工||1703(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 藤田 正治, 教授 中川 一, 准教授 竹林 洋史 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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No description available.

羅杜芳. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 210-215) / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in Chinese and English. / Luo Dufang.

L'érosion de contact est un type d'érosion interne qui se développe à l'interface entre deux couches de matériaux de granulométries différentes. Les particules d'un sol fin (sable, limon, argile…) sont détachées par l'écoulement et entraînées à travers les pores du sol grossier au contact (gravier…). Bien que l'on suspecte sa présence dans de nombreux ouvrages, ce processus d'érosion a été peu étudié jusqu'à présent. Aussi ce travail de thèse s'est attaché à mieux le comprendre pour parvenir à le modéliser. A l'échelle du pore, l'écoulement à l'interface entre deux milieux poreux a été caractérisé, grâce à un dispositif expérimental développé au Cemagref d'Aix-en-Provence qui combine fluorescence induite par laser, méthode PIV et milieu iso-indice. L'importance de la variabilité des sollicitations hydrauliques a ainsi été soulignée. A l'échelle de l'échantillon, des essais sur sols réels et sols reconstitués ont été menés au LTHE, afin d'identifier les phénomènes en jeu. Ont également été obtenues sur ce dispositif des mesures du taux d'érosion en fonction de l'intensité de l'écoulement, pour différents types de sols fins et de sols grossiers. Une modélisation stochastique de ces essais a ensuite été proposée. Enfin, des essais à grande échelle ont été conduits au laboratoire de la Compagnie Nationale du Rhône pour étudier l'éventuelle influence d'effets d'échelle ainsi que les conséquences de cette érosion de contact sur le comportement global et l'intégrité d'un ouvrage. Il a ainsi été mis en évidence la possibilité qu'une érosion de conduit soit initiée par érosion de contact. Cette thèse a été réalisée dans le cadre du projet ERINOH (ERosion INterne dans les Ouvrages Hydrauliques), en convention CIFRE avec le Centre d'Ingénierie Hydraulique d'EDF. / Contact erosion is a type of internal erosion which occurs at the interface between two soil layers of different particle sizes. Particles from the fine soil (sand, silt, clay…) are pulled and driven by the flow through the pores of the surrounding coarse soil (gravel ...). Although its presence is suspected in many earthfill embankments, this process has been little studied so far. The aim of this thesis was to better understand and, possibly, to model contact erosion. At pore scale, the flow at the interface between two porous media was characterized thanks to an experimental device, developed in Cemagref, combining Planar Laser Induced Fluorescence, PIV method and Refractive Index Matching. The spatial variability of flow shear stress has been emphasized. At sample scale, several tests on real and reconstituted soils were carried out in LTHE, in order to identify the phenomena involved in contact erosion. Erosion rates as a function of flow magnitude have also been measured for different types of fine and coarse soils. Then, a stochastic model was proposed to account for these experiments. Finally, large scale tests were conducted in the laboratory of Compagnie National du Rhône, to study the influence of scale effects as well as the consequences of contact erosion on global behavior and integrity of the embankment structure. The possibility of piping initiation by contact erosion was underlined. This thesis is part of the project ERINOH project and was funded by EDF-CIH.

No abstract available. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2013.