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The eastern portion of the Namaqua-Natal Mobile Belt, the Natal Metamorphic Province is divided into four main tectonostratigraphic units. These units comprise two accreted island arcs: the Mzumbe and Margate Terranes; an imbricately thrust nappe zone consisting of four ophiolitic nappes in a hinterland-dipping duplex; and the highly deformed metavolcaniclastic/metagreywacke Mfongosi Group directly adjacent to the stable northern foreland of the Kaapvaal Craton. Theories of late-tectonic left-lateral movement in the southern island arcs are extrapolated northwards of the southern margin of the Kaapvaal Craton coincident with the Lilani-Matigulu Shear Zone. The relative timing and structural context of vein-hosted mineralization with respect to major recognized tectonic events is resolved in five separate areas, two in the Natal Nappe Zone and three in the Natal Thrust Front. The Madidima Nappe of the Natal Nappe Zone contains several north-northeast- to northeast-trending and northeast- to east-northeast trending quartzofeldspathic veined reefs considered to have formed in a late-tectonic left-lateral shear system (main shear and synthetic shear orientations, respectively). The northeast- to east-northeast-trending reef is duplicated due to infilling of normally-faulted steep structures in the semi-brittle, incremental normal faulting of the banded amphibolite component of the nappe. Later left-lateral movement has reactivated one of these steep structures along the southern margin of a regional F2-folded band of granite-gneiss in that a southwest extension of this structure may be responsible for sub-economic veining for a length of up to 9 km. The extensive flat-lying topography of the Mbongolwane Flats area, in which the reefs are situated, is accounted for by the accelerated weathering of rocks which underwent sustained late-tectonic metamorphism in the epidoteactinolite facies, accompanied by pervasive shearing and block rotation to the south of the southern limb of the regional F2 fold in the granite-gneiss. A large, kilometer-scale, open advective fluid system which provided fluid-mediated exchange between co-existing rocks existed at the time of vein formation. The fluid system was driven by early-tectonic intrusion of a granite gneiss and amphibole-rich granite. Two areas in the Mfongosi River valley, the northern and southern Mfongosi Valley areas, contain typical evidence of deformation at the leading edge of collision in a mobile belt. The southern Mfongosi Valley area, at the confluence of the Mfongosi and Tugela Rivers, contains veining which resulted from pressure solution of the host metavolcaniclastic/metagreywacke. Veining occupies predictable shear and tension fractures formed during the initial deformation of a foreland margin sequence, in addition to occupying those fractures formed by buckling on the layer-scale. The structural context of the northern Mfongosi Valley veining is defined by subsequent deformation and vein fragmentation such that the metavolcaniclastic/metagreywacke was reduced to a melange in which vein segments acted as competent clasts; a large-scale porphyroblast/matrix system. Formation of the Manyane Thrust to the south of the Mfongosi Group interrupted the normal retrograde metamorphism of the remainder of the Tugela Nappe and initiated a "hot iron effect" whereby a short-lived thermal pulse acted at the thrust plane, producing a reversed geothermal gradient in the underlying Mfongosi group. This reversed gradient would have been counteracted by a steepened normal geothermal gradient in the Mfongosi Group caused by overloading of the Natal Thrust Front by the Natal Nappe Zone. These geothermal gradients partly account for the concentration of veining in the areas of the Mfongosi Group which are directly adjacent to the Manyane Thrust, and directly adjacent to the Kaapvaal Craton, in the lower portions of the thrust front Stable isotope studies indicate fractionation between vein and wall rock under a short-lived, mainly rock-buffered, layer-scale fluid-movement system. Also forming part of the Mfongosi Group of the Natal Thrust Front, the Ngubevu area contains an apparently enigmatic distribution of veining accompanied by gold and base metal mineralization. The structural evolution of the Ngubevu area occurred during consistent left-lateral transpression into which has intruded early-tectonic veins, formed by pressure solution and having the same structural format as the early-tectonic veining in the southern Mfongosi Valley area. Subsequent deformation of the system was accompanied by 1900 -trending tension gashes which were continually ptygmatically-folded, sheared and offset to form occasionally mineralized quartzofeldspathic "blows" and along-strike stringers in the epidote- actinolite schist. Where veining cross-cuts narrow calcite - graphite - sericite - quartz - albite - tourmaline ± chlorite schist layers, gold mineralization occurred. The late-tectonic tension gashes, antitaxially filled by quartz and amorphous calcite, cross-cut the entire range of lithologies. The fluid system during vein deposition varied: during infilling of early-tectonic fractures a short-lived fluid-flow system dominated, with the emplacement of re crystallized wallrock occurring in a closed, non-advective regime under the influence of diffusion caused by pressure solution. The fluid system changed to a more open, advective, greater than layer-scale rock-buffered one with a decreasing contribution of material from immediate host rocks. An internal fluid source is implied for the entire period of vein emplacement, derived from structural analyses which indicates negative dilation across the Mfongosi Group in this area and by comparison of vein:wallrock δ180 values which indicate a lack of igneous-derived fluids. The Phoenix Mine, in the central portion of the Tugela Nappe, and the Ayres Reef, hosted in Manyane amphibolite adjacent to the Manyane Thrust, are grouped together on the basis of their cross-cutting nature and timing with respect to metamorphism and deformation of the host rock, and also due to their similarity in isotopic plots. Both vein sets occur in approximately east-west to east-northeast-trending zones which show evidence of late-tectonic left-lateral movement. Phoenix Mine veining occurs in weakly-metamorphosed meta-gabbro/meta-norite of the Tugela Rand Complex. The Manyane amphibolite demonstrates the amphibolite facies of metamorphism due to the short-lived thermal pulse at the Manyane Thrust. Both sets of veining display slickenlines which are indicative of their emplacement prior to the late-tectonic left-lateral movement. The unusually thick quartz veins of both deposits are the results of late- to post-Tugela Rand Complex fluids or the tapping of late-tectonic metamorphic fluid reservoirs. This caused silica metasomatism and redeposition of material in post-thrusting collapse features. A highly channelized, single-pass fluid system is proposed in the absence of intrusion-derived fluids. Whole rock geochemical data allow a distinction to be made between the Natal Thrust Front and the Natal Nappe Zone: the Foremost nappe of the nappe zone consists primarily of N-type mid-ocean ridge basalts/ocean-floor to within-plate basalts which were intruded prior to nappe emplacement by metaluminous orogenic volcanic arc granitiods. The thrust front displays a lateral variation in metabasite/metasediment ratio, with the ratio increasing from east to west in this inlier. In the east, in the Nkandlha area, melanged metagreywackes dominate and there is a marked paucity of associated metabasites. In the central portions of the thrust front, in the vicinity of the Mfongosi area, active continental margin/continental arc magmatogenic greywackes and arkoses are interlayered with calk-alkaline volcanic arc basalts (volcaniclastics). The greywacke geochemistry indicates little to no mafic/ultramafic influences in sediment contribution and the source of sediment is inferred to be the southern portions of the Kaapvaal Craton. The Nkandlha and Mfongosi area Mfongosi Group segments are considered to be in-situ or para-autochthonous. The western-most Ngubevu area predominantly hosts metabasites. The geochemistry of the metabasites indicates that they are N-type mid-ocean ridge basalts/ocean floor basalts from a destructive plate margin setting. The metabasites are interbanded with metapelitic/metacalcsilicate layers produced in a shallow water oxic environment, here inferred as a spatially-restricted shallow, marginal basin. The metabasites in the Ngubevu area are notably similar to those of the Madidima Nappe, indicating a similar provenance and pre-collisional mode of formation. It is proposed that the variation in the Natal Thrust Front was due to a north-east/south-west distribution of lithological proportions or mixing, with greywackes dominating in the northeast (in proximity to the Kaapvaal Craton) and metabasites dominating in the southwest. Left-lateral transpressional movement within the Mfongosi Group of the Natal Thrust Front, and the Natal Nappe Zone, was continuous throughout plate collision and obduction. / Thesis (Ph.D.)-University of Natal, Durban, 2000.

The contact metamorphic aureole of the Rustenburg Layered Suite of the Bushveld Complex extends to a depth of over 5 km into the underlying mainly argillaceous Pretoria Group. When compared to other parts of the metamorphic aureole, the Olifants River area is unique in that it is characterised by a high degree of syn-Bushveld Complex deformation and very coarse grained pelitic assemblages. This is believed to have resulted from a combination of greater magma thickness, a deeper emplacement depth and a high degree of subsidence related deformation that was focused along the Thabazimbi-Murchison Lineament. This area also contains a laterally extensive and deformed quartz-feldspar porphyry sill, the Roodekrans Complex that is shown to represent a hypabyssal equivalent of the volcanic Rooiberg Group. There are three main metamorphic zones. A wide andalusite zone dominated by staurolite, garnet and cordierite assemblages. This is followed by a narrow fibrolite zone without staurolite, and a wide inner aureole of migmatite. The migmatite zone is characterised by garnet-cordierite-aluminosilicate assemblages with corundum, spinel and orthopyroxene assemblages at the highest grades. Metamorphic pressure and temperature estimates indicate pressures of between 3 kb and 4 kb in the lower part of the andalusite zone at temperatures of approximately 550°C. Porphyroblast-matrix relationships reveal a close link between deformation and metamorphism resulting in a spectrum of textural relationships developed as a result of inhomogeneous strain. Porphyroblasts in low strain domains preserve textures of “static type" growth whereas syntectonic textures are found in foliated rocks. Pre-tectonic porphyroblasts in many foliated domains indicate that deformation outlasted porphyroblast growth and increased in intensity and extent with time. Retrograde porphyroblasts are post-tectonic. Evidence is presented for both rotation and non-rotation of porphyroblasts in relation to geographical coordinates during extensional top-to-south, down-dip shear in the floor. The unique structural setting in this area triggered the growth of large diapiric structures in the floor of the Rustenburg Layered Suite that are preserved as periclinal folds on the margin and within the northeastern Bushveld Complex. Extreme gravitational loading and heating of the floor by a thickness of up to 8 km of mafic magma resulted in the generation of evenly spaced, up to 7 km diameter wall-rock diapirs that penetrated the overlying magma chamber. Diapiric deformation is restricted to rocks above a decollement zone that is developed along competency contrasts and corresponds approximately with the 550 °C peak metamorphic isotherm. Strongly lineated, boudinaged and foliated rocks are developed in the interpericlinal domains between adjacent periclines. Migmatites in these domains are characterised by conjugate extensional ductile shears and associated asymmetrical boudinage suggesting bulk deformation by pure shear processes. The extension lineation was produced by lateral extension along flow lines directed toward dome culminations. Each of the four diapiric periclines is cut by a different erosional section enabling reconstruction of a typical diapir geometry. At the highest structural levels, periclines have bulbous shapes with overturned limb geometries forming overhangs. The surrounding layered igneous rocks are locally deformed into a series of outward verging folds that define a broad rim syncline. Deformation within the pericline cores is represented by constrictional deformation that produced radial curtain-type folds with steeply plunging lineations and concentrically orientated folds in the outer shell. Diapirism is closely linked to magma emplacement mechanisms. Floor folds in the country rocks were initiated in the interfinger areas of a fingered intrusion. With further magma additions and the coalescence of intrusion fingers into a single sheet, interfinger folds matured into large diapiric periclines which rose to the upper levels of the magma chamber. Strain rates estimated from strain analyses, pericline geometry and model cooling calculations are in the order of 10-14 S-1, corresponding to diapiric uplift rates of 0.6 cm/yr. Diapirism is broadly compatible with a N-S extension in the Olifants River area during emplacement of the Rustenburg Layered Suite. On a regional scale, this is indicated by existence of a major EW dyke swarm that coincides with the long axis of the Bushveld Complex. The accommodation of the Bushveld Complex into the Kaapvaal Craton was facilitated by a combination of craton-wide extension that accompanied plume related magmatic underplating, and loading of the Bushveld Complex. Isostatic adjustment in response to Bushveld Complex subsidence resulted in further development of large basement domes around the perimeter of the Bushveld Complex. / Thesis (Ph.D.)-University of Natal, Durban, 1998.

Detailed studies, both chemical and physical, have been performed on various dolomites and vug-filling carbonates, to determine the pathways and extent of the mineralizing fluids associated with the Pering Zn-Pb deposit within the Griqualand West sub-basin. Three carbonate phases were identified within the vugs using cathodoluminescence microscopy. The first phase formed a reaction rim on the host dolomites during the deposition of sphalerite and oscillatory zoned carbonate. Finally calcite was deposited, which is associated with post-mineralizing fluids. The vug-filling carbonates have very radiogenic 87Sr/86Sr values (0.72-0.76) compared with the host dolomites (0.70-0.73). The gangue carbonate minerals deposited within the vugs have similar radiogenic 87Sr/86Sr values to the gangue minerals of the main Pering orebody, indicating that the vugs formed part of the aquifer system through which the mineralizing fluids migrated. Radiogenic 87Sr was not acquired from the surrounding host dolomite. The mineralizing fluids may have picked up radiogenic 87Sr when migrating through porous rocks such as the Makwassie Quartz Porphyry of the Ventersdorp Supergroup or felsic rocks forming the Kaapvaal Craton. In addition, radiogenic Sr may have been acquired from dewatering of the Lokammona shales within the area, or expelled from amphibolite and granulite rocks involved in the Kheis or Namaqua Tectonic events. Two models are proposed to explain the genesis of the main Pering deposit and the occurrence of sphalerite in the vug-filling carbonates surrounding the deposit: 1) Mixing Model; and 2) Single Fluid Model. The Single Fluid Model is preferred which involves a single fluid migration and interaction with the carbonate host rock and/or pore fluid. The metals were probably transported as chloride complexes together with reduced sulphur at temperatures greater than 2000 C. Deposition of the ore minerals resulted from either a dilution of the fluid, a pH increase or a temperature decrease. Both dolomites and vug-filling carbonates have a model Pb age between 2.0 and 2.7. Secondary 1Ga model ages indicate a minor Namaqua tectonic influence. Carbon and oxygen isotopes indicate that the fluids originated in a deep burial environment. Future exploration work using cathodoluminescence microscopy and staining techniques will be both useful and cost-effective. Isotopic work should concentrate on the Rb-Sr system as radiogenic 87Sr/86Sr values are the best indicators of the path of the mineralizing fluid, and the proximity to ore concentrations. / Thesis (M.Sc.)-University of Natal, 1992.

Copies of author's previously published articles inserted. / Includes bibliographical references (6 leaves) / xi, 131, [71] leaves : ill., maps ; 30 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 Geophysics, 1999

Typescript (photocopy) / xiv, 220 leaves, [11] leaves of plates : ill., charts, maps ; 30 cm. + 2 fold. col. maps in end pocket / 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, 1982

Four folded ill. in v. 1 pocket / Four microfiches in v. 2 pocket / Lacks abstract. / Includes bibliography / 2 v. : ill. (some col.), maps ; 30 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, 1987

The stratigraphy of the late Precarnbrian upper Brachina Subgroup has been studied in detail throughout the southern and central Flinders Ranges of South Australia. Ten stratigraphically significant facies associations are readily recognisable within which 18 separate and distinct lithotypes have been defined and described. The complex regional strati - graphic arrangement has been simplified by using a Markov Chain technique of analysis. The resultant lithotype stratigraphy is used as the base upon which the palaeogeographic history of the upper Brachina Subgroup is reconstructed. A detailed sedimentologic analysis of each lithotype was undertaken in order to ascertain their individual palaeoenvironments of deposition. This involved a petrologic analysis of the arenaceous component of each lithotype, the analysis of the suite of sedimentary structures contained within each lithotype, and the analysis of all directional structures for palaeocurrent directions. For this latter analysis a new computer technique was developed whereby up to 3 individual populations can be separately analysed from any one distribution. Deposition of the upper Brachina Subgroup succession was due to a phase of uplift tectonism and minor accompanying basic volcanism. Within this succession two distinct depositional episodes are readily discernable. During the first episode a massive sand influx flowed from a westerly source region ( the Gawler Craton ) into a shallow submerged, though possibly tidally influenced mudflat as a prograding deltaic succession ( the " Alligator River Delta " ). This initial delta developed in the western region of the Adelaide ' Geosyncline ' as a fluvial and tide modified, wave dominated system which was fed by stable outlet channels, protected by barrier - bars and surrounded by a low intertidal aerobic mudflat. Preserved wi - bhin this mudflat deposit are the probable body fossils of primitive cup - shaped coelenterates ( ? ), which were possibly the ancestral organisms of the Ediacara assemblage. With, continued sediment influx and basin shallowing, this initial delta system evolved to an unbarred fluvial modified, tide - dominated delta which was fed by migrating channels and surrounded by an intertidal mudflat. This mudflat was anaerobic, possibly due to the activity of abundant microscopic organisms. The second depositional episode of the upper Brachina Subgroup developed when tectonic instability affected a portion of the basin's western margin ( Uplift I ). As a result, part of the previously deposited deltaic succession was eroded and reworked into a vast, thin intertidal sandflat which extended through the central region, and into the northern region of the Adelaide ' Geosyncline '. A second phase of tectonic instability ( Uplift II ) caused renewed activity along the basin ' s western margin, and also induced the emergence of at least two islands within the basin. Around these islands a thin, dominantly fluvial deposit was generated. The final phase of tectonic instability ( Uplift III ) affected only the western margin of the basin, and produced a narrow sand deposit of probable beach origin. Meanwhile, within the basin gradual subsidence induced the development of a shallow, possibly tidal aerobic mudflat and marked the end of the upper Brachina Subgroup phase of sedimentation. / Thesis (Ph.D.)--Department of Geology and Mineralogy, 1978.

During deposition of the mixed carbonate - clastic sequence of the Mundallio Subgroup, the " Adelaide Geosyncline " was a very shallow, elongate sedimentary basin, flanked to the west and east by older Precambrian basement. In much of the southern and northern Flinders Ranges, clastic deposition predominated in the lower Mundallio Subgroup. In the north, alternating development of shallow mudflats and sandflats ( Nankabunyana Formation ) depended on the interplay between the sediment supply and winnowing processes, while dolomite mudstones were locally deposited in the shallowest areas. In the eastern half of the Willouran Ranges, massive shales were deposited as the environment remained persistently below wave base ( Camel Flat Shale ), but a renewed sand influx led to deposition of the Tilterana Sandstone. In the southern Flinders Ranges, terrigenous clay and silt were deposited on submergent mudflats which shallowed into intermittently exposed dolomite mudflats ( Nathaltee Formation ). Dolomite mudflats were a more persistent feature in areas more distal from the terrigenous source, and sometimes contained isolated, ephemeral lakes which were sites of magnesite deposition ( Yadlamalka Formation ). Dolomite and magnesite mudstone deposition of the Yadlamalka Formation became wide spread in the northern and southern Flinders Ranges in the upper Mundallio Subgroup, as shallowing and retreat of the basin margin led to the formation of semi - isolated lakes, separated and enclosed by exposed carbonate mudflats. The elastics deposited in association with these carbonate mudstones consisted largely of sand sized detritus, probably derived from the reworking of aeolian deposits. In the eastern Willouran Ranges, the greater influx of sand and the slightly deeper, largely submergent environments, led to the deposition of the sandstones, dolomites and siltstones of the Mirra Formation. Because of little clastic influx into the northern Mt. Lofty Ranges, shallow to occasionally exposed environments were largely sites of dolomite deposition ( Skillogalee Dolomite ). To the south, shales were deposited in slightly deeper environments ( Woolshed Flat Shale ), although local dolomite deposition occurred in the Adelaide region ( Castambul Formation, Montacute Dolomite ). In the uppermost part of the subgroup, the area of shale deposition extended northward, encroaching over the dolomite mudflats of the upper Skillogalee Dolomite. Dolomite, occurring largely as mudstones, is the major carbonate mineral present in the Mundallio Subgroup, but magnesite is also widespread. Limestones are not present. The carbonates experienced minor replacement by early diagenetic chert, initially precipitated as both crystalline and amorphous phases. Within the upper Mundallio Subgroup, the preservation of fine details of the detrital texture of dolomite mudstones and peloidal dolomites, and the high Sr contents of dolomites ( largely in the range of 400 - 650 ppm ), suggest that these sediments consisted of Ca - Mg carbonates ( protodolomite, Mg - calcite ) at the time of deposition. Slightly greater recrystallisation of dolomites in the lower Mundallio Subgroup resulted in their lower Sr and higher Mn and Fe contents. Magnesite mudstones may have initially precipitated as hydrated Mg - carbonates. Lithification of surface sediments as a result of subaerial exposure, led to the formation of micritic magnesite. Much of this magnesite was subsequently reworked into intraclastic beds. The carbonate mineralogy of this sequence, and the evidence of only rare sulphates, indicate that the carbonates were precipitated from alkaline, Mg - Ca - C03 waters, with a higher carbonate and lower sulphate content than seawater. / Thesis (Ph.D.)--Department of Geology and Mineralogy, 1980.

M.Sc. / The evolution of oxygen in the Earth's atmosphere during the early Precambrian has been a subject of debate for many years. Two fundamental models oppose another. The one by Cloud, Holland and co-workers suggests that the atmosphere was essentially anoxic until about 2.2Ga and then became highly oxygenated due to a sudden rise in oxygen levels. The, other advocated by Dimroth, Kimberley and Ohmoto suggests that the atmosphere was oxygenated as early as 3.5Ga. The most crucial assumption for the Cloud-Holland model for the evolution of atmospheric oxygen is that the 2.2-2.3Ga Hekpoort paleosol formed under reducing atmospheric conditions. However, regional field, drill core, petrographic and geochemical investigations of the Hekpoort paleosol during this study clearly show that the Hekpoort paleosol in fact represents an oxidised lateritic weathering profile. In addition, the Hekpoort paleosol correlates well to the oxidised saprolites below the Gamagara/Mapedi erosion surface in the Northern Cape Province. The basis for theassumption by Holland and co-workers that a dramatic rise in atmospheric oxygen levels took place at 2.2Ga thus falls away. During this study extensive red beds, belonging to the Dwaal Heuvel Formation were discovered directly above the Hekpoort paleosol in the Pretoria Group in Botswana and the western Transvaal area. The red beds show two stages of development, firstly fluvial and then deltaic. The red beds are correlated with the Gamagara/Mapedi red beds in Griqualand West. Apart from this evidence for highly oxygenated conditions immediately above the Hekpoort/Ongeluk lavas, hematitic ferricrete, pisolitic mudclast conglomerate and hematitic oolitic ironstones were also found in the Timeball Hill Formation underlying the Hekpoort lava. Oolitic ironstones are developed over an area of more than 100 000 km2. Several different types of oolites are developed within the oolitic ironstone which contains up to 73wt% Fe203. The ferricrete and hematitic pisolitic mudclast conglomerate contain oncolites. These ferricretes, pisolitic mudclast conglomerate and oolitic ironstones suggest that the atmosphere was already highly oxidising between 2.4 and 2.45Ga, prior to deposition of the Hekpoort lava. Pretoria Group rocks that were deposited in close contact with the atmosphere show no evidence for an anoxic atmosphere. It is suggested that atmospheric oxygen levels may have fluctuated through time but at the same time increased in a steplike manner during deposition of the Transvaal Supergroup. However, at this moment in time we do not have enough information available to develop a quantitative model for the evolution of atmospheric oxygen. New age data available on the Hekpoort/Ongeluk lava unit indicate that it may be 2.395Ga old i.e. some 200Ma older than thought earlier. Thus, the atmosphere could have been highly oxygenated in very early Paleoproterozoic times. Uraninite, pyrite and siderite present in older Archean sedimentary rocks do, however, argue for more reducing atmospheric conditions at that time. Both the Cloud-Holland and Dimroth-Ohmoto models of atmospheric oxygen development are therefore in need of revision.