M.Sc. (Geography) / Hailstorms are well-known phenomena in the summer rainfall region of southern Africa where they cause extensive damage - especially in the agricultural sector. This thesis examines the geography and climatology of hail in the Transvaal. It deals with three main issues, namely a) the spatial and temporal characteristics of hail days (HDs); b) rainfall and atmospheric conditions prevailing during hail events; and c) the geography of hail damage as it pertains to maize. In the Transvaal, hail day frequency (HDF) increases with altitude and latitude in a non-linear (exponential) manner. Variations in altitude, as reflected in the diverse physiography of the area, account for most of the spatial and temporal variations in hail occurrence. Seven hail regions can be distinguished which differ from one another in terms of the onset times of hail, its seasonal occurrence and annual HDF patterns. In general, most hailstorms occur during November with the peak onset time varying between 16:00 and 20:00. The most notable finding concerning rain - hail interrelationships, is that rainfall and HDF appear to be inversely related, years/months with high hail incidence being dry and vice versa. Daily and seasonal precipitation characteristics also differ between 'high hail years' (HHYs; dry) and 'low hail years' (LHYs; wet). For instance, during HHYs, the peak hail season is delayed while the rain season peaks earlier. Moreover, while the frequency of convective systems remains nearly the same during HHYs as in 'normal' years, the average precipitation area and the volumetric production decreases significantly. These anomalies appear to be the result of changes in the large-scale circulation patterns (as reflected by the transition from baroclinic to quasi-barotropic conditions) which influence the precipitation from mesoscale convective systems. It is likely that the Southern Oscillation plays a role in these changes, particularly during November and December. However, although these Southern Oscillation Index (SOl) - HDF associations are weak, they are appreciably stronger than those between the SOl and rainfall. Rainfall characteristics on HDs differ from those of non-hail rain days in that, on HDs, more rain falls and the rain-bearing systems are more extensive. In general, atmospheric conditions are less stable, and the humidity level is higher, on HDs than on other days. Furthermore, HDs are characterized by warm north easterly winds near the surface but cold, dry south westerlies at the 600 hPa level. Above this the south westerlies become progressively stronger

The 2.9 Ga old Usushwana Complex in the Piet Retief-Amsterdam area (south-eastern Transvaal) represents an exposed segment of a layered intrusion. It has the form of a dyke-like body elongated in a northwesterly direction, and extends to an estimated depth of 3000 -5500 m. Lithologically, the Complex consists of a cumulate succession of mafic rocks capped by granitoids and has intruded along the contact between the basement and the supracrustal sequences of the Kaapvaal Craton. Differentiation of an already contaminated gabbroic magma resulted in an ordered stratigraphic sequence comprising progressively more evolved lithotypes, with at least two imperfect cyclic units developed over a stratigraphic thickness of about 700 metres (Hlelo River Section). Meso- to orthocumulate textured gabbros and quartz gabbros grade upwards into magnetite- and apatite-bearing quartz gabbros, interlayered with discontinuous magnetitite horizons. The gabbros in turn grade into hornblende-rich, granophyric granodiorites. The differentiation process is regarded as having been considerably enhanced by the assimilation of acidic material, derived by partial melting of the felsic country rocks at the roof of the magma chamber. Recrystallisation of these rocks gave rise to the microgranites that locally overlie the granodiorites. Mineralogical, textural and geochemical features indicate a relatively advanced fractionation stage, suggesting that the exposed sequence of the Usushwana Complex in the study area represents the upper portion of the intrusion. No significant mineralised occurrences were identified. However, on the basis of similarities between the Usushwana Complex and other mafic layered intrusions which host significant ore deposits, it is suggested that economic concentrations of base metal(Cu-Ni) sulphides, PGE and chromitites are likely to be developed at lower stratigraphic levels.

The aim of ·this study is to present a picture of the circumstances and the manner in which the mission was undertaken. With this in mind reference has been made to individual men and their particular importance and also to the decislons of the Church Assembly as they affected Mission. In part, the thesis is fuller for the earlier years, for the writer holds that these were the most formative as they established the pattern. Furthormore the writer wishes to make clear that the Mission become the work of black men with the white Mission Secretary of the 1950's filling an administrative role. This does not mean he was unimportant but for the nature of this study and its desire to ·emphasise the role of the black man, the work of these individual administrators has been largely omitted. In the concluding chapters the writer has shown the effects of political changes and African Nationalism on the Mission with a further chapter on the Mission's educational work. / KMBT_363 / Adobe Acrobat 9.53 Paper Capture Plug-in

A number of ilmenite-rich heavy mineral deposits occur along the northern margin of the intracratonic Karoo basin, and are hosted by the fluvio-deltaic Middle Ecca Group. Coastal reworking of delta front sands within a regressive, microtidal shoreline may be considered as a depositional model for the development of the heavy mineral deposits. An economic analysis of titanium suggests long term positive demand, and sustained high prices for this commodity. An evaluation of the Dwarsfontein ilmenite-rich heavy mineral deposit, using available data, indicates how important it is for deposits of this type to be situated close to an upgrading plant or export harbour.

M.Sc. (Zoology) / Please refer to full text to view abstract

Bibliography: pages 100-109. / The Kaap Valley Tonalite (KVT) was a homogenous hornblende+ biotite tonalite that had been subjected to overail propylitic and potassic alteration. Petrographic studies reveal that carbonate alteration and increased proportions of hydrous minerals occur along the KVT and Barberton greenstone belt contact zone, and along major shear zones within the KVT.

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M.Sc. (Geology) / Please refer to full text to view abstract

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Thesis (Ph.D.)--University of the Witwatersrand, Science Faculty (Geophysics), 1980 / The physical processes at the source of mine tremors at the East Rand Proprietary Mines (E.R.P.M.) near Johannesburg were investigated. [Abbreviated Abstract. Open document to view full version] / AC2017