2 fold. maps and reprint of Journal article in end pocket of vol. 2. / 2 v. : photos., diags., maps ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Mineralogy, 1979

Copies of author's previously published articles inserted. / Bibliography: leaves 142-159. / xiv, 159, [47] leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Focuses on understanding the controls of distribution of continental deformation from the perspective of structural and metamorphic investigations, using the 500 Ma Adelaide Fold Belt in South Australia as a case study. Of particular interest is the relative roles of compositional, thermal and structural controls on the distribution of deformation at the scale of an orogen. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1999?

Iron-formations are ferruginous sedimentary rocks which have their source from fumarolic activity associated with submarine volcanism, with deposition of iron as oxides, hydroxides, and hydrous oxide-silicate minerals in shallow and/or deep marine sedimentary systems. The Precambrian ironformations of southern Africa have a wide age range, but are more prominently developed before 1.SGa. These iron formations occur in greenstone belts of the Kaapvaal and Zimbabwean cratons, in the Limpopo mobile belt, in cratonic basins and in the Damara mobile belt. The Archaean-Proterozoic sedimentary basins and greenstone belts host iron ore deposits in iron-formation. Iron formations have a lengthy geological history. Most were subjected to intense, and on occasions repeated, tectonic and metamorphic episodes which also included metasomatic processes at times to produce supergene/hypogene high grade iron ores. Iron-formations may be enriched by diagenetic, and metamorphic processes to produce concentrating-grade ironformations. Uplift, weathering and denudation, have influenced the mineral association and composition of the ores, within which magnetite, haematite and goethite constitute the major ore minerals. The iron resources of the southern Africa region include the Sishen deposits, hosting to about 1200 Mt of high grade direct shipping ore, at >63% Fe. Deposits of Zimbabwe have more than 33 000 Mt of beneficiable iron-formation. The evaluation of an iron ore prospect involves many factors which must be individually assessed in order to arrive at an estimate of the probable profitability of the deposit. Many of these are geological and are inherent in the deposit itself. Other factors are inherent aspects of the environment in which the ore is formed. Although the geological character of the ore does not change, technological advances in the processing techniques may have a great effect on the cost of putting the ore into marketable form. Geochemical, geophysical and remote sensing methods would be used for regional exploration. Chip sampling and drilling are useful for detailed exploration. Purely geological exploration techniques are applicable on a prospect scale in the exploration of iron ore deposits. Regional exploration targeting should choose late Archaean greenstone belts containing oxide facies iron-formation or Early Proterozoic basins located at craton margins as they are both known to host high-grade haematite orebodies formed by supergene/hypogene enrichment. Most types of iron ore deposits in southern Africa are described and classified. An attempt is made to emphasize the major controls on mineralisation, in the hope that these may be applicable to exploration both in the southern African region and within analogous settings around the world.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1971. / Vita. / Includes bibliograpies. / Ph.D.

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Alleghanian-aged deformation and grain size reduction of quartzofeldspathic and mafic rocks of the Late Precambrian Ponaganset Gneiss proceeded at amphibolite grade conditions ( 600°C, 4-6 kb), and were accompanied by considerable mobility of Si, Na, K, Ca, Fe and Mg. Fluids present during and after ductile deformation facilitated hydration reactions within a narrow ( > 10 cm), foliation-parallel mafic layer composed largely of clinopyroxene and albitic plagioclase (An₃). The final product of these reactions was a K-feldspar/plagioclase (An₉)-rich amphibolite. Mass balance relations show that the amphibolite-forming reactions required an influx of Fe²⁺ and Mg²⁺ cations, and expulsion of Na⁺ into the surrounding gneisses. The source for Fe²⁺ and Mg²⁺ was probably the adjacent, actively-deforming quartzofeldspathic mylonite which, with reference to the protolith gneisses less than 30 cm from the gneiss-amphibolite contact, is reduced by 60% of its original concentration of these elements. Where no amphibolite layer is present, quartzofeldspathic mylonites display a similar depletion in Fe and Mg, but also carry textural and geochemical evidence for fluid flow on a millimeter to centimeter scale (e.g. foliation-parallel quartz veins walled by monomineralic layers of plagioclase or K-feldspar, and pronounced cm scale gradients in whole rock K, Na and Si concentrations). Despite the evidence in favor of fluid flow, reaction progress calculations in the amphibolite layer suggest that minimum volumetric fluid-rock ratios never exceeded 0.05 liters H₂O/liter of rock. The local presence of strained clinopyroxene microporphyroclasts and laminae of clinopyroxene-albite mylonite in the amphibolite layer suggest that hydration reactions did not go to completion. The presence of biotite in the amphibolite layer elsewhere at the outcrop suggests that fluid-rock ratios were not uniform during, or shortly after, deformation. Post deformational metamorphic re- actions in the amphibolite resulted in the formation of actinolitic rims on amphibole grains which continued to grow at the expense of adjacent, strained clinopyroxene microporphyroclasts. Textural relationships indicate that the actinolitic rims grew via diffusive processes in the presence of an intergranular fluid film. The ability of the zircon U-Pb system to yield useful geochronologic information on the timing of deformational events is a complex function of the degree of metamictization of the zircons, the chemistry and mineralogy of the enclosing rock, the P-T conditions of metamorphism and the presence and composition of metamorphic fluids. The possible effects of dynamic metamorphism on the isotopic ages obtained from zircons range from no apparent Pb loss to complete resetting of the isotopic "clock". The two examples presented here represent the two extremes: the mid-Paleozoic, greenschist-grade Rockfish Valley Fault Zone, and the PennsylvanianPermian amphibolite-grade Hope Valley Shear Zone. In the mylonites of the Rockfish Valley Fault Zone, zircons underwent brittle failure and were comminuted in the ductilely deforming matrix. Comparative U-Pb isotopic studies of zircons from the mylonites and from the Grenville-aged charnockitic protolith demonstrate that no appreciable Pb loss occurred as the result of intense mylonitization, despite the presence of aqueous fluids during deformation which affected the hydration of the mylonitic mineral assemblages. A detailed U-Pb isotopic study of a single outcrop of the late Precambrian Ponaganset gneiss was also undertaken. Amphibolite-grade mylonitization associated with movement along the Hope Valley Shear Zone caused some grain size reduction of the zircons in the mylonite zones. However, the primary cause of isotopic disturbance in these zircons is the extensive growth of U-rich metamorphic zircon during, or shortly after, metamorphism. Corrosion of pre-existing zircon also occurred during metamorphism/deformation, but it is difficult to quantify its effects on U-Pb systematics. The lower intercept ages of 289± 24 m.y. and 265± 62 m.y. from the pink gneiss and gray gneiss, respectively, both fall within the range of other published age estimates (e.g. Zartman et al. 1988) for Alleghanian deformation and metamorphism in southeastern New England. / Ph. D.

At present the Karoo Basin covers approximately 20 000 km2. It is a large intracratonic basin which, from Carboniferous to Jurassic times, was infilled with a succession of sediments ranging from glacial deposits to those deposited in warm, equable conditions. The Beaufort Group forms part of this succession, and was deposited in a terrestrial, river dominated environment. The dominant lithologies exposed in the Estcourt region in the KwaZulu-Natal Midlands belong to the lower and middle Beaufort divided by the PermoTriassic boundary. The Permo-Triassic palaeoenvironment in this region is reconstructed using sedimentary profiles combined with the study of the fossil remains discovered in the area, including plant, body, and trace fossils. The lower Beaufort sediments in this region belong to the Estcourt Formation, and the Middle Beaufort sediments to the Belmont Formation. The Estcourt Formation is dominated by a succession of alternating sandstones, siltstones and mudstones, which are interpreted as representing sediments deposited in a fluvial-floodplain environment, which can be divided into two sub-environments. The first is dominated by sediments that were deposited by meandering rivers on a semi-arid floodplain, and the second sub-environment is represented by those sediments deposited in lacustrine environments. Both of these subenvironments are closely linked and alternate in the rock record indicating many episodes of transgressive-regressive lacustrine episodes. The Estcourt Formation can be closely correlated with the lower Beaufort sediments mapped in other regions of the Karoo Basin, indicating similar climatic and environmental controls throughout the Karoo Basin of southern Africa. The Estcourt Formation also contains a wide variety of body and trace fossils. The PermoTriassic boundary can be traced along the western border of Estcourt by using the distribution pattern of the two mammal-like reptiles Dicynodon and Lystrosaurus. There is evidence of an overlap in the distribution between these to mammal-like reptiles, which together with palaeoflora evidence, indicates that Lystrosaurus evolved during the Late Permian and not Early Triassic as previously thought. The first Triassic sediments are represented in the Estcourt region by a series of maroon shales which can be correlated with the Palingkloof Member. / Thesis (M.Sc.)-University of Natal, 1997.

Call number: LD2668 .T4 1978 K623 / Master of Science