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Mantle xenoliths from the Abrahamskraal kimberlite : a craton-margin geotherm

  • Authors: Nowicki, Thomas Edward
  • Date: 1991
  • Subjects: Kimberlite , Kimberlite -- Inclusions
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4898 , http://hdl.handle.net/10962/d1001557
  • Description: The Abrahamskraal kimberlite pipe (group I) occurs approximately 5 km to the south-west of the geophysically defined margin of the Kaapvaal craton in the central Cape Province, and contains a variety of crustal and mantle xenoliths. This study focusses on xenoliths of deep-seated origin (mantle and lower-crustal), and in particular on garnet-orthopyroxene bearing assemblages which are amenable to thermobarometric techniques. Four major types of deep-seated xenolith have been identified, i.e. peridotites, dunites , eclogites, and garnet pyroxenites. The petrographic features and mineral compositions of these xenoliths are described . Pressures and temperatures of equilibration have been calculated primarily using the garnet-orthopyroxene thermometer of Harley (1984), and the Al-in-enstatite barometer of Nickel and Green (1985). The peridotites are coarse-textured (Harte, 1977), magnesium -rich rocks, and are typical examples of the common type I peridotites which generally dominate mantle xenolith suites in kimberlites. Garnet peridotite xenoliths define a geotherm which lies along a typical theoretical conductive geothermal gradient for shield areas (Pollack and Chapman, 1977), and which extends to a maximum pressure of 41 kb (~130 km). Comparison of the Abrahamskraal geotherm with that constructed for the northern Lesotho xenolith suite (calculated using the same thermobarometer couple), suggests that the lithosphere at the Namaqua /Kaapvaal boundary is not significantly thinner or hotter than that underlying the craton. Modelling of the craton boundary under the constraints provided by the Abrahamskraal geotherm, and by the distribution of diamond-bearing kimberlites in southern Africa, indicates that the Abrahamskraal kimberlite has sampled relatively thick, cool , Namaqua lithosphere. It is suggested that, in terms of diamond distribution, the age and magmatic history of the Namaqua lithosphere is of greater significance than its thickness. Two varieties of dunite occur at Abrahamskraal. Coarse-textured dunites with Mg-rich olivine compositions similar to those of the peridotitic olivines, probably originated by similar (but perhaps more extreme) processes to those which formed the peridotites. A finer-grained and relatively Fe-rich variety of dunite may represent ultramafic cumulates formed by fractionation of basic or ultrabasic magmas within the mantle. Two varieties of eclogite have been distinguished. Coarse-grained eclogites which yield relatively high temperature estimates, are believed to have originated from depths similar to those determined for the garnet peridotites, i.e. from the lower lithosphere. A distinctly finer grained variety of eclogite, yields significantly lower temperatures which may be based on frozen-in equilibria. A maximum depth of approximately 87 km (~ 27 kb) has been estimated for these xenoliths, but they may have originated from significantly shallower (possibly lower-crustal) levels. The garnet pyroxenite xenoliths are generally orthopyroxene-rich rocks which contain varying amounts of garnet (8 to 33 %) and clinopyroxene (0 to 64 %). Textural features indicate that the garnet and possibly some of the clinopyroxene has exsolved from an originally A l -rich orthopyroxene. The rocks are significantly more Fe-rich than the peridotite xenoliths, and their constituent minerals show a wide range of Mg/Mg+Fe ratios. The pressure-temperature array defined by the garnet pyroxenites is approximately isothermal, and spans a depth range from approximately 30 to 95 km. It deviates strongly (to higher temperatures) from the ambient geothermal gradient at the time of kimberlite emplacement, as inferred from the garnet peridotite xenoliths. The pressures and temperatures calculated for the garnet pyroxenites are based on mineral equilibria which are believed to have been frozen-in during cooling from an intial high­temperature (probably molten) state. Qualitative modelling of possible cooling paths in pressure-temperature-composition space, indicates that the apparent depth range displayed by the garnet pyroxenites, approximates the true depth range over which these rocks were emplaced. However, the apparent pressures calculated from core compositions are significantly lower than the true pressures at which the original rocks formed . The garnet pyroxenite xenoliths appear to represent a major, possibly Namaqua ­ age (~1000-1400 Ma), magmatic event involving the emplacement of large amounts of mafic magma over a significant depth range in the shallow upper mantle
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  • Date Issued: 1991

Masisebenzisane = Let us work together

Mdano

Mineralogy, petrology and geochemistry of the lower and lower critical zones, Northwestern Bushveld Complex

  • Authors: Teigler, Bernd
  • Date: 1991
  • Subjects: Mineralogy -- South Africa -- North-Western Transvaal Petrology -- South Africa -- North-Western Transvaal Geochemistry -- South Africa -- North-Western Transvaal
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4978 , http://hdl.handle.net/10962/d1005590
  • Description: This study of the lower part of the Rustenburg Layered Suite in the Western Bushveld Complex is based mainly on drill core samples from three localities, which are approximately 130 km apart. The NG-sequence, situated in the northwestern sector of the complex (Union Section, R.P.M.) extends from the floor of the complex to the base of the upper Critical Zone. The sequence is ca. 1800 m thick and it comprises mainly ultramafic cumulates, namely pyroxenites, olivine pyroxenites, harzburgites and dunites. Norites and anorthos ites are present only in minor proportion. Within the upper half of the NG-sequence ten prominent chromitite layers are correlated with the LGI MG4-interval. Correlation is also established between published sequences and the two other sequences studied, located 8 km and 55 km, respectively, east of Rustenburg. Whole-rock chemical data (major and trace elements), microprobe and Sr isotope data are presented. Petrographic studies provide modal analyses and measurements of grain size. All petrographic, mineralogical and other geochemical data point to an origin of the cumulates of the NG-sequence by crystallization from liquids of the U-type lineage and derivatives thereof. No evidence is found for the involvement of parental liquids with a distinctly different composition or crystallization order (A-liquids). However, subtle compositional variations of the parental liquids are evident in slight changes of the Cr content in orthopyroxene or in variations of Sr isotope ratio. The NG-sequence is characterized by intervals with reversed fractionation trends caused by repeated influxes of pristine magma (during periods of high magmatic activity) resulting in a high degree of rejuvenation. These intervals are overlain by others with a normal fractionation trend, interpreted as cumulates formed in periods with low or no magmatic activity, in which fractional crystallization controlled bulk composition of the evolving liquid. The Lower Zone in the NG-sequence is dominated by a progressive shift towards more primitive compositions, while in the Critical Zone fractionation was the major operating process in the magma chamber. However, during deposition of the pyroxenitic lower Critical Zone several replenishment events occurred, during which fresh Cr-rich magma was emplaced. Massive chromitite layers were deposited after mixing between the newly emplaced magma and the resident residual liquid shifted bulk compositions into the primary field of chrome-spinel. Cumulus plagioclase crystallized after bulk composition of the residual liquid was driven to the orthopyroxene plagioclase cotectic by continued fractional crystallization; this occurred once in the Lower Zone, yielding a single, thin norite layer, and again in the upper Critical Zone of the NG-sequence. A facies model is proposed based on the stratigraphic and compositional variations along strike in the Western Bushveld Complex. This model explains the variations by means of the position of the sequence with regard to a feeder system. The olivine- and orthopyroxene-rich, but plagioclase-poor NG-sequence represents the proximal facies, while the SF-sequence (poor in ferromagnesian phases, but plagioclase-rich) is developed as a distal facies, close to the Brits graben.
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  • Date Issued: 1991

Mtsitso

Mtsitso

Mtsitso in Holland 1991 used by a South African composer Hans Roosenschoon in his avante garde piece 'Timbila'

Mzeno

NUM Biennial report - 1991 Seventh national congress

  • Authors: NUM
  • Date: 1991
  • Subjects: NUM
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/149605 , vital:38868
  • Description: Over two years have passed since our last Congress and many developments have taken place in our industry and the country. Most significant of these developments was the release of our Honorory Life President Comrade Nelson Mandela and the other political prisoners together with the unbanning of the the African National Congress and other political parties. These developments are the fruits of our struggle, a struggle so many have sacrificed so much for. These developments are the culmination of our victory over the evil system of apartheid. These developments came about as a result of the sustained assault against the edifice of apartheid mounted by our people and the international community. It is true that the political and social landscape in the country has changed and that new challenges await mineworkers, our union and all the patriotic forces in the struggle to transform our country into a genuine democracy and a prosperous country. The edifice of Aparthied has been under constant siege forcing the government to sytematically dismantle discriminatory legislation. Whilst we have to fully acknowledge that this process is taking place, we will be naive to believe that the institutions, legacy and culture that was fostered over decades will vanish with the removal of apartheid laws. We need to be constantly vigilant against the introduction of neo-apartheid in the place of apartheid. It requires much more than the removal of laws to address the historical inequities of Apartheid and racism that remains deep in the fabric of our social, economic and political life. Through all the developments we are proud to state that mineworkers have not only made their contribution in bringing about the demise of the apartheid system but have made their mark as one of the most militant sectors of the struggling masses. Together with thousands of others we have been able to shift the balance of power near to our goal of a non racial democracy. Our assessment of these developments and what the implications are for the future will be assessed in this report to Congress. As these historic developments have been taking place our industry has been experiencing severe problems with increased job losses and a low gold price. The fight for job security and the restructuring of the mining industry requires immediate attention. Our endeavours over the last two years will be evaluated and some suggestions of a future strategy will be outlined for consideration. Progess and development is often accompanied with setbacks and diversions. It is important that we acknowleges these so that our union can strenghten where it is weak and consolidate where it must. This biennial report examines the socio-economic and socio-political developments in the country and the industry since our last Congress, and assesses the achievements and future possibilities and challenges for the union.
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  • Date Issued: 1991

Outpatient compliance with theophylline and phenytoin therapy:

  • Authors: Dowse, Roslind , Futter, William T
  • Date: 1991
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/157059 , vital:40083 , https://europepmc.org/article/med/1745939
  • Description: Poor compliance with prescribed medication is a significant problem in chronic disease states and is often responsible for the apparent failure of therapy. The determinants and extent of non-compliance are commonly incorrectly perceived by doctors. During routine therapeutic drug monitoring of epileptic and asthmatic outpatients at a local day hospital, non-compliance was identified as a significant problem. A compliance study was conducted on 80 epileptic and asthmatic patients to determine the nature and extent of this problem. Non-compliance was measured using four different methods, which were then compared using chi 2 tests.
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  • Date Issued: 1991

Peter Warlock: a study of the composer through the letters to Colin Taylor between 1911 and 1929

  • Authors: Smith, Barry, 1939-
  • Date: 1991
  • Subjects: Warlock, Peter, 1894-1930 -- Correspondence Taylor, Colin, 1881-1973 -- Correspondence Composers -- Great Britain -- Correspondence
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2657 , http://hdl.handle.net/10962/d1002323
  • Description: This thesis involves a comprehensive study of the letters written by Philip Heseltine (Peter Warlock) to Colin Taylor from 1911 to 1929. Warlock first came into contact with Taylor at Eton in 1908 when he studied the piano with him as a schoolboy. Through Taylor's imaginative teaching during the next four years Warlock's interest in and understanding of music, particularly modern music, grew and matured. At the same time a strong bond of friendship developed between the two men and continued until Warlock's early death in 1930. This is clearly illustrated in the surviving 87 letters. Warlock was a great letter writer and over a thousand of them have been preserved, mostly in the British Library. His letters to Taylor have a special significance in that they were written during the entire period of his adult life, most of them during the early formative and creative years. They cover a wide range of topics including the influential friendships with the composers Frederick Delius and Bernard van Dieren, contemporary British and foreign music and his own work as a composer, writer, and scholar. They also give us many important insights into his life and personality, written as they are with rare candour and humour. In this thesis each letter has been carefully and systematically studied and the resulting information used to augment and expand the existing knowledge of Warlock's life and personality, his friendship with Taylor, his music and writings. Because of the wide field which the life and works of Peter Warlock cover, this study has been limited to subjects arising out of the correspondence with Taylor. Where necessary, additional information has been interpolated from other sources, mainly to give a sense of continuity and to explain references which might otherwise seem obscure. For a detailed study of Warlock's music readers are referred to Ian Copley's book, The Music of Peter Warlock, (Dennis Dobson, London, 1979). A definitive biography has yet to be written.
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  • Date Issued: 1991

Planning for a new South Africa

  • Authors: COSATU
  • Date: 1991
  • Subjects: COSATU
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/135328 , vital:37258
  • Description: COSATU has adopted the Freedom Charter. But if we look carefully at the Freedom Charter, nowhere does it say how everyone will share in the country’s wealth. This Is because a Chartrr is a statement of beliefs and a guide to policy. It is not a detailed programme.
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  • Date Issued: 1991

Preliminary geochemical data for dolerite dykes and sills of the southern part of the Etendeka Igneous Province

  • Authors: Marsh, Julian S , Erlank, Anthony J , Duncan, Andrew R
  • Date: 1991
  • Language: English
  • Type: text , report
  • Identifier: http://hdl.handle.net/10962/132133 , vital:36803
  • Description: Over the last 15 years systematic geochemical and petrological investigation of the igneous rocks of the Early Cretaceous - Late Jurassic Etendeka Igneous Province of northwestern Namibia have focused on the tholeiitic basaltic lavas and interbedded silicic volcanic rocks and the large central subvolcanic complexes of Brandberg, Erongo, Oken­yenya, Messum, Doros and Cape Cross. Previously these rocks were grouped into the Karoo Volcanic Province of South Africa, but in view of the distinct age difference between the igneous rocks of the Etendeka region and Karoo rocks occurring elsewhere in southern Africa , we propose to regard them as constituting a separate Etendeka Igneous Province which exhibits a close lithological, geochemical and temporal correlation with the Parana Flood Basalt Province of South America.
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  • Date Issued: 1991

Racial segregation in East London, 1836-1948

  • Authors: Nel, Etienne L
  • Date: 1991
  • Language: English
  • Type: Article
  • Identifier: vital:6717 , http://hdl.handle.net/10962/d1006790
  • Description: Urban racial segregation in East London has a distinctive heritage, making the city one of South Africa's most segregated in the pre-Union era. Segregation was initiated by the British military in the then colony of British Kaffraria, and was later enhanced by successive municipal councils. Municipal ordinances ensured exceptionally high levels of segregation in the city during the 19th century. The enforcement of Asian segregation in this era is noteworthy. Urban planning in the 20th century resulted as much from local as national considerations and legislation. Segregation was a reality in East London prior to the passage of the Group Areas Act. The deteriorating social circumstances in the long-segregated African areas in particular receive special mention, as do government attempts to rectify the situation through the institution of state commissions.
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  • Date Issued: 1991

Rates of return to education of blacks in South Africa

  • Authors: Serumaga-Zake, Philip A
  • Date: 1991
  • Subjects: Black people -- Education -- South Africa -- Statistics Black people -- Employment -- South Africa -- Statistics Black people -- South Africa -- Economic conditions -- Statistics
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5565 , http://hdl.handle.net/10962/d1002084
  • Description: The principal objectives of this empirical study were to test the hypothesis that eduction is a major determinant of people's earnings differentials and to calculate private and social rates of return to education of blacks in South Africa excluding Transkei, Bophuthatswana, Venda and Ciskei. Basically, the data for working men and women used in the study were extracted from the 1985 current Population survey files comprising a sample representative of the black population. Lifetime earnings profiles are constructed from these data for five educational levels, namely, no schooling up to standard 1, standards 2 to 4, standards 5 to 7, standards 8 to 9 and standard 10. Schooling is assumed to account for 60% of the income differentials between these profiles, after adjustment for the differing probabilities of finding work of persons in specific age-education groups. Imputed average household outlays on schooling are taken as the private direct cost of education supplemented by estimates of per pupil spending by the various government departments responsible for black schooling for calculation of the social costs per year of primary and secondary schooling. Indirect cost in the form of imputed foregone earnings are included from standard 5 (age 15) onwards. The resulting private internal rates of return to education of males are about 16% at primary level and 24% for secondary schooling. Corresponding social rates of return are about 6% for primary and 15% for secondary education. The estimates for females indicate that between no schooling and standards 2 to 4 level, the private and social rates of return are -1% and -4% respectively, from standards 2 to 4 to standards 5 to 7 level, private returns of 12% and social returns of 4% are reported and for the remaining secondary school phases private returns of 32% and social returns of 15% are estimated. It is implied that black education is receiving minimal government financial assistance compared to those of the other population groups. The evidence of the results of the study indicates that; besides education, marital status, locational, regional and occupational variables also influence earnings differentials, the governments responsible for black education should emphasize human capital investment in relation to physical capital investment, on average more educated persons are better off than the less educated ones and with the exception of female early primary schooling, generally, it is worthwhile for an individual to undertake a certain educational programme investment
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  • Date Issued: 1991

REE fractionation and Ce anomalies in weathered Karoo dolerite

  • Authors: Marsh, Julian S
  • Date: 1991
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/145819 , vital:38469 , https://doi.org/10.1016/0009-2541(91)90099-D
  • Description: Analyses of samples from a weathering profile on Karoo dolerite allow elements to be divided into three groups depending on their behaviour. Si, K, Na, Mg, Ca, Sr, Ba and V are mobilized and removed from weathered products. Fe, Al. Ti, Zr, Hf, Zn, Cu, Sc, Co and Ni are immobile. REE, Y, and to a lesser extent Cr, are mobile and redistributed within the profile without a net loss of these elements from the profile. Large positive Ce anomalies are developed in oxidized weathered products by preferential leaching of the other REE's. Negative Ce anomalies and REE enrichment is a feature of less altered dolerite.
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  • Date Issued: 1991

Rhodes University Annual Report 1991

Rhodes University Graduation Ceremony 1991

  • Authors: Rhodes University
  • Date: 1991
  • Subjects: Relly, Gavin Walter Hamilton
  • Language: English
  • Type: text
  • Identifier: vital:8125 , http://hdl.handle.net/10962/d1006750 , Relly, Gavin Walter Hamilton
  • Description: Rhodes University Graduation Ceremonies Friday, 12 April 1991 at 8 p.m. [and] Saturday, 13 April 1991 at 10 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday, 18 May 1991 at 10.00 a.m. in the Guild Theatre. , The Installation of Gavin Walter Hamilton Relly as Chancellor of Rhodes University to be followed by a Graduation Ceremony Friday, 12 April 1991 at 10 a.m. in the 1820 Settlers National Monument.
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  • Date Issued: 1991

Rites of passage: Substance dependence and the negotiation of development tasks - a case study

  • Authors: Roux, Catharina
  • Date: 1991
  • Subjects: Uncatalogued
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10962/193242 , vital:45313
  • Description: This thesis is an attempt to provide an understanding of drug addiction in its relation to the tasks and arrests which take place during the developmental process. Current theories of drug addiction are situated within the parameters of developmental theory; Object Relations Theory, Lacanian Structuralism and Freud’s concept of the Oedipus Complex are drawn on. The dual regressive and progressive function of drugs as it relates to developmental tasks and arrests is illustrated, the argument being that a very specific relationship exists between the compulsive use of drugs and the developmental tasks which need to be avoided as well as those which need to be negotiated. The case study research method is made use of in the attempt to illustrate the links between drug addiction and specific developmental tasks. I present an in-depth analysis of the developmental history of Rafiq Jaffer, an inpatient at the drug unit at Lentegeur Psychiatric Hospital, drawing on the material which was collected during nine months of individual therapy. As Borderline Personality Disorder is the primary diagnosis in the case of Rafiq Jaffer, the emphasis is by necessity put on borderline pathology. The primary aim of the thesis is, however, to highlight the need to understand the compulsive use of drugs within the context of the developmental process, thereby developing a conceptualisation against which further cases may be tested. , Thesis (MA) -- Faculty of Humanities, Psychology, 1991
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  • Date Issued: 1991

Sinclair Beiles. A South African Abroad. Venice California The Lapis Press, 1991

  • Authors: Doherty, Christo
  • Date: 1991
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/460565 , vital:75948 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_140
  • Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
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  • Date Issued: 1991
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