Showing items 101 - 120 of 265

Your selections:

Exotic deposits derived from porphyry copper systems in Chile

  • Authors: Diaz Acevedo, Nelson Simon
  • Date: 1996
  • Subjects: Porphyry -- Chile , Copper mines and mining -- Chile , Copper ores -- Chile
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5050 , http://hdl.handle.net/10962/d1011149 , Porphyry -- Chile , Copper mines and mining -- Chile , Copper ores -- Chile
  • Description: The exotic orebodies related to cal-alkaline porphyry copper deposits. are sub-horizontal lenticular bodies of secondary copper minerals that impregnate Tertiary gravels and bedrock of different ages. They lie immediately downslope of the porphyry copper deposits, that is to say. they are related to the propylitic halo of the main deposits, and are considered to have originated with the deposition of copper minerals from solutions that overflowed during the secondary enrichment process. Supergene alteration took place between the late Oligocene and Miocene, by which time both orehodies (exotic and porphyry copper) were established. The paucity of tile denudation since the Miocene in the Andean segment from 21º to 26º latitude S. due to the dominance of a hyperarid climate explains the remarkable preservation of the shallow porphyry copper systems, supergene enriched blankets and associated deposits. This is reflected in the limonites, where the typical boxworks have been partially or totally destroyed on surface by the superleaching. As a result of the lateral migration of the copper-bearing solutions, the exotic deposits show a zonation. alteration and mineralization whose characteristics depend among other factors. on the reactivity of the bedrocks and the Cu/S ratio of the mother deposit. In these deposits three zones can be recognized: Proximal (0 to 2 km Intermediate (2 to 3) and Distal (3 to 8-14 km) with palaeodrainage control. The associations and mineralogical abundance are related to the climate (rain. temperature). In some deposits two important units are detected and they are the Cu-phosphates and Cu-lixiviable (to sulphuric acid) units. The size of tile Chilean exotic deposits varies between 100 and 3.500.000 tons of copper, with a total known resource of 8 M tons of copper. The large exotic deposits are comparable to the resources of a medium-sized porphyry copper- type deposit. The discovery of the exotic deposits is related to the exploration of porphyry copper deposits, where a mass balance of the leached column must be done. Moreover the lithology and alteration of the propylitic halo. permeability, structures, geophysics and geochemistry should be considered. The diorite model is not compatible with a supergene enrichment process, expressed by the absence of colour anomalies, exotic deposits and in the presence of secondary minerals like jarosite, which is coherent with the pyrite deficiency of the system. The projects are for exploitation of reserves by open pit methods. The projects plan to extract and to crush copper oxide ore which will he pre-treated with concentrated sulphuric acid prior to heap leaching, solvent extraction and electrowinning. The copper output varies between 10,000 and 50,000 ton per year of catilode copper. The total investment varies between 20 and 100 millions dollars. For project calculations, estimation of 65 % - 82 % copper recovery and 37 - 40 kg/ton net acid consumption can be used due to the nature of ore. The leaching time is estimated as 30 to 180 days for heaps of 4,5 to 30 metres high. As a result of this, the plant capacity is determined by an annual equivalent of 10,000 to 25,000 ton Cu per year. Pit planning has heen carried out using diverse software on the basis of 5 x 5 x 5 m and 10 x 10 x 10 m block models, evaluated using a kriging package built into the program, giving an overall waste/ore ratio (induding pre-stripping) of 0: I (in an outcrop) to 3: I. The location of the mine and plant sites are associated with the porphyry copper in production, for this the already installed facilities can be used. So there is no need to build a new mine camp or access. The environmental impact is summarized relating to the characterization of the physical, biological and socio-cuitural effects, using the framework of the Base Line study and the Impact evaluation derived from the construction and project operation phases. The conclusions and recommendations will diminish, mitigate and/or eliminate impact derived from the specific activities.
  • Full Text:
  • Date Issued: 1996

Fanelewe ukubetwa

Feeding, tentacle and gut morphology in five species of southern African intertidal holothuroids (Echinodermata)

  • Authors: Foster, Gregory G , Hodgson, Alan N
  • Date: 1996
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/447392 , vital:74621 , https://hdl.handle.net/10520/AJA00445096_757
  • Description: Compares the structure of the tentacles and digestive tracts of four species of intertidal dendrochirote, and one species of aspidochirote holothuroid by using light, scanning and transmission electron microscopy. Gut contents were sieved to determine the size of the particulate matter ingested. Concludes that there appears to be a relationship between tentacle morphology and the size and type of food ingested. Gut length, the thickness of the digestive epithelial layer and the number of vesicles present in the enterocyte cells of the digestive epithelium also differ in relation to the food ingested. Illustrates with several photographs.
  • Full Text:
  • Date Issued: 1996

Fifty years of ichthyology in Grahamstown

  • Authors: Skelton, Paul H
  • Date: 1996
  • Language: English
  • Type: text , Article
  • Identifier: vital:7138 , http://hdl.handle.net/10962/d1011816
  • Description: In July 1946, the fledgling Council for Scientific and Industrial Research (CSIR) awarded Dr J.L.B. (James Leonard Brierley) Smith of Rhodes University College a research fellowship of £800 to enable him to devote his energies to ichthyology. The university responded by providing accommodation, equipment and appointing Smith a research professor. These actions marked the beginning of what has become a major academic development in Grahamstown as represented by the J.L.B. Smith Institute of Ichthyology, the Department of Ichthyology and Fisheries Science (DIFS), and the Freshwater Fish Section at the Albany Museum. At present more than 40 people are employed in one way or other in these organizations, more than 20 of them professionals, in addition to whom there are 41 postgraduate students currently studying ichthyology or fisheries science through DIFS at Rhodes University. Altogether this represents a concentration of ichthyological expertise probably unmatched anywhere else in the world. It is opportune therefore to highlight a few of the more significant milestones in the history of ichthyology in Grahamstown and so illuminate some of the key factors behind this achievement.
  • Full Text:
  • Date Issued: 1996

Foster care as a form of substitute care in the black community : an exploratory-descriptive study

  • Authors: Sishuta, Happy Babalwa
  • Date: 1996
  • Subjects: Foster home care -- South Africa , Kinship care -- South Africa , Children, Black -- Services for -- South Africa , Black people -- Services for -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSocSc
  • Identifier: vital:3282 , http://hdl.handle.net/10962/d1006505 , Foster home care -- South Africa , Kinship care -- South Africa , Children, Black -- Services for -- South Africa , Black people -- Services for -- South Africa
  • Description: Kinship care is increasingly supplementing the more traditional forms of out-of-home care. Because related foster care has potential great value, the possibility of placement with relatives needs to be explored first. At its best it provides the child love and security with known people and possibly in a familiar environment. Yet, important as it is, this area of practice is seriously underdeveloped - few publications especially in South Africa exist on how children fare in this arrangement. This situation exists in spite of the fact that many children find themselves in both legal as well as privately arranged related foster care placements. Equally of course no comprehensive study has been undertaken to study the black family's perception of formal foster care and their adjustment to formal foster care practice which for many is a new encounter in their lives. More clarity on these issues pertaining to kinship care will not only improve our understanding but can lead to a better service. Socio-political influences have weakened the mutual aid system in African families. This has resulted in needs· and problems which the African family find it difficult to deal with. This has prompted families to make use of non-family support particularly services from specialized and other welfare agencies. Formal foster care is a foreign practice to the black community as a result of their tradition and custom. It offers a new method of coping with child care problems and indicates a shift from the conventional patterns among South African blacks. As a result there is often confusion and a lack of understanding, making the community not to make proper use of this service. This study is exploratory-descriptive. The sample comprised thirty foster parents. The main objective of this study was to investigate the nature and practice of formal foster care in the black community with specific emphasis on related foster care and its perception. The study has raised a number of issues for practice and policy consideration. Notable findings were: the need to (1) promote much more active involvement of foster parents, foster child and their families (2) educate the community about foster care (3) prepare, train, support and supervise foster parents. The study revealed that these placements have become indistinguishable from natural parenthood and the foster children have become absorbed into the foster family. A need exists for permanency planning in foster care. It is hoped that the research findings will contribute to the existing body of knowledge and that more studies will be undertaken in future.
  • Full Text:
  • Date Issued: 1996

Geochemical exploration in tropical terrains with special reference to base metals

  • Authors: Chiconela, Domingos Rubão
  • Date: 1996
  • Subjects: Geochemical prospecting -- Research -- Tropics , Geological mapping -- Research -- Tropics , Weathering -- Research -- Tropics , Geochemistry -- Research
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4953 , http://hdl.handle.net/10962/d1005565 , Geochemical prospecting -- Research -- Tropics , Geological mapping -- Research -- Tropics , Weathering -- Research -- Tropics , Geochemistry -- Research
  • Description: In tropical areas, the high rainfall induces severe-and pervasive weathering, producing a thick soil cover. The lithologies underneath may b~ recognised using geochemical mapping, which is based on certain elements that have the ability to differentiate between various lithologic units. Elements that are independent of the weathering process are normally selected for this purpose. The chemistry of mobility of base metals is an important factor to take into account when evaluating the mobility and distribution of these elements in a soil profile. Factors such as pH, Eh, organic material, clay minerals, Fe and Mn oxides are normally key aspects to be considered. When iron-rich rocks undergo deep weathering, lateritic profiles are developed. These are widespread in a belt bordering the equatorial zone, including the Brazilian shield, West and East Africa, parts of India and Northern Australia. In these profiles, the high rainfall promotes intense leaching of the different horizons. Where the pre-existing profiles are mostly preserved, the base metals are distributed throughout the profile: in the upper ferruginous horizon, goethite and hematite can adsorb large amounts of Mo, resulting in large dispersion halo. Other base metals such as Cu and Zn are less resistant in these freely-drained profiles and, therefore, they may be partly leached from the profile. In the lower horizons, Cu, ,zn, Ni and Co are retained, hosted in kaolinite and smectite, and thus, a high geochemical contrast will be identified in this horizon at the expense of a decline in the size of the dispersion haloes. The pre-existing profiles can be truncated, with a thin stone line developing at the contact between the lateritic profile and the recent soil. The conditions in these environments favour the retention of most of the pathfinder and target elements in all soil horizons, with the B horizon showing the highest contrast. If the primary rock is rich in AI, a bauxitic profile will be developed. The world distribution of bauxites closely resembles that of laterites. The behaviour of Co and Ni is very similar to that of iron during the bauxitization. Furthermore, the factors that induce residual enrichment of Al with removal of Fe in the soil profile will cause significant depletion of Co and Ni in these profiles. These metals are then concentrated at the base of the profile because of precipitation from downward percolating solutions. Many karst bauxite deposits in Southern Europe are enriched with Ni and Co in the basal horizon. Such horizon is mined as nickel ore in the bauxites of the Lokris region in Greece. Copper and molybdenum are strongly enriched.in bauxitic profiles. Concentration ratios are 8 and 3.2 for Cu and Mo respectively. Molybdenum is closely related to goethite and hematite, and therefore, the high concentration of Mo in a bauxitic profile will be consistent with the horizon where iron is concentrated. Copper concentrates at the base of the iron rich-horizon but also appears enriched in the saprolite together with Co. When sulphide bodies occur, in this environment, deep and penetrative weathering has resulted in considerable near-surface mobilization of iron and silica. The supergene alteration commonly obscures the identity of the primary sulphides at the surface. In this case, geochemical assessment of the resulting gossan has proved to be crucial in mineral exploration. A search in the secondary mineral assemblage, volatile and precious metals may lead to the information on the composition of the primary sulphide assemblage. The conclusion that will be reached is that if the geochemical properties (mobility, affinities with Fe or Mn oxides and/or clay minerals) of each of the base metals are understood, an appropriate sampling (optimum size-depth combination) will then be done. In such cases, a subdued, weak, but significant, geochemical response will be identified in the surface horizon.
  • Full Text:
  • Date Issued: 1996

Geochemical stratigraphy of the Mohale Dame-Katse Dam areas, Lesotho. Report on contract LHDA, Mohale Tunnel: Sampling and Testing of Cores. Lesotho Highlands Tunnel Partnership (Mohale)

  • Authors: Marsh, Julian S
  • Date: 1996
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/144857 , vital:38385
  • Description: In monotonous basalt sequences, such as the Karoo basalt sequence in Lesotho, geochemistry can be a useful adjunct to stratigraphic studies. The acceptance of geochemical criteria in defining stratigraphic units arises from work in the Columbia River Group in NW SA (Swanson et al., 1979) and is now widely employed. It has recently been successfully applied in the Karoo basalts (Marsh et al., in press). In the current investigation a stratigraphic framework for construction work related to the Katse-Mohale tunnel has been developed using the compositions of basalt samples collected from a number of borehole cores in relation to the geochemical stratigraphy of Marshet al. (in press).
  • Full Text:
  • Date Issued: 1996

Geology Field Trip Guide: Natural Sciences and Geography Educators visit

  • Authors: Marsh, Julian S
  • Date: 1996
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/144878 , vital:38387
  • Description: This is a brief guide to some of the interesting geological features in the immediate vicinity of Grahamstown. It summarises the geological history of the area, emphasizes that small-scale geological features are frequently part of much larger features, demonstrates how careful observation of rocks can lead to solving geological problems and reconstruction of ancient environments in which rocks formed, the importance to society, and how rocks in the Grahamstown area have contributed to a global scale understanding of the dynamic nature of planet Earth.
  • Full Text:
  • Date Issued: 1996

George Webb Hardy's the Black Peril and the social meaning of ‘Black Peril’ in early twentieth-century South Africa

  • Authors: Cornwell, Gareth D N
  • Date: 1996
  • Language: English
  • Type: text , article
  • Identifier: vital:6116 , http://hdl.handle.net/10962/d1004240 , https://doi.org/10.1080/03057079608708504
  • Description: preprint , The 'Black Peril' — the threatened rape of white women by black men — was an important factor in the moral economy underpinning colonial debate about the 'Native Question' in early twentieth-century South Africa. This essay gives sympathetic consideration to studies which have attempted to link the recurrence of Black Peril panics with specific disturbances in the economy or body politic, before offering symptomatic readings of two pieces of writing by George Webb Hardy, the article 'The Black Peril' (1904) and the novel The Black Peril (1912). These readings suggest that the rape threat was essentially a rationalization of white men's fear of sexual competition from black men. The imagery of purity and contagion, in terms of which the 'endogamous imperative' is typically represented in such texts, suggests that the idea of caste may usefully be invoked in attempts to explain the seemingly irrational public hysteria surrounding the Black Peril phenomenon.
  • Full Text:
  • Date Issued: 1996

Glycerol production by Dunaliella species in saline waste water treatment

  • Authors: Emmett, Robyn Angela
  • Date: 1996
  • Subjects: Dunaliella -- Growth , Glycine
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4019 , http://hdl.handle.net/10962/d1004079 , Dunaliella -- Growth , Glycine
  • Description: In recent years, much research has focused on Algal High Rate Oxidation Ponds as both an economic means for wastewater treatment and as a system for the mass production of algae. With the advent of these systems for the treatment of saline organic effluents, the extreme halophile, Dunaliella salina was considered. In this study, the growth and productivity of a number of Dunaliella species (and strains thereof) was evaluated in hide soak liquor tannery effluent. Hide soak liquor, diluted to 20% with water, proved to be highly suitable as a growth medium for the majority of the Dunaliella species under study and in some instances, resulted in enhanced growth rates and higher biomass yields compared to those obtained in defined inorganic medium. A few Dunaliella species failed to grow in this effluent. A correlation was observed between the lack of growth displayed by these species in this organio-rich medium and their failure to utilise organic compounds. Glycine, a major component of this effluent, possibly stimulates the growth of Dunaliella. Studies on the mechanism of growth stimulation by glycine revealed that an algal-bacterial relationship existed whereby the bacteria mineralised the amino acid, releasing ammonia which was then utilised by the alga. Results of this work revealed significant variations in the intracellular glycerol content amongst the Dunaliella species under study. Large differences were also observed between the glycerol contents of effluent-grown and control Dunaliella cells, where the effluent-grown cells were characterised by greatly reduced intracellular glycerol content. These reduced glycerol levels are assumed to have arisen from the glycine-induced stimulation of glycerol release which was observed in this study, where the high glycine content of the hide soak liquor is proposed to have induced glycerol release. This enhanced glycerol release in tatmery effluent could play a central role in the fimction of Dunaliella-based High Rate Oxidation Ponding systems, by stimulating bacterial activity. Observed glycerol productivities were therefore proposed to be a fimction of the type and concentration of the organic constituents of the medium. A similar medium-induced phenomenon was observed in the starch content of Dunaliella cells.
  • Full Text:
  • Date Issued: 1996

Gold exploration in tropical and sub-tropical terrains with special emphasis on Central and Western Africa

  • Authors: Breedt, Machiel Christoffel
  • Date: 1996
  • Subjects: Geochemical prospecting -- Tropics , Geochemical prospecting -- Africa , Gold ores -- Geology -- Tropics , Gold ores -- Geology -- Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4966 , http://hdl.handle.net/10962/d1005578 , Geochemical prospecting -- Tropics , Geochemical prospecting -- Africa , Gold ores -- Geology -- Tropics , Gold ores -- Geology -- Africa
  • Description: The aim of this dissertation is an attempt to' provide a general guide for future gold exploration in tropical and sub-tropical terrains. The dissertation includes a brief discussion of the various exploration techniques used in regional and local exploration. This provide the necessary background knowledge to discriminate between the constraints and applications and to be able to select the techniques which are more suitable for gold exploration in tropical and sub-tropical terrains. Weathering, gold geochemistry and soil formation, fields often neglected, are emphasized to illustrate the importance of the mobility and dispersion of gold in the weathering of the lateritic soil profile. A sound knowledge and experience in regolith mapping is to the advantage of the explorationist. Case studies with special emphasis on Central- and Western Africa are included to illustrate the effectiveness of some of the gold exploration techniques in tropical and sub-tropical terrains. Gold exploration is a highly complex and demanding science and to be successfull involves the full intergration of all geological, geochemical and geophysical information available. An intergrated exploration method and strategy would enhance the possibility of making viable discoveries in this highly competative environment where our mineral resources become more depleted every day. Where applicable, the reader is refered to various recommended literature sources to provide the necessary background knowledge which form an integral part of gold exploration.
  • Full Text:
  • Date Issued: 1996

Hillslopes of the Suurberg, a few km north of the pass & hotel, northern Alexandria district

Hillslopes of the Suurberg, a few km north of the pass & hotel, northern Alexandria district

Hillslopes of the Suurberg, a few km north of the pass & hotel, northern Alexandria district

Hiyole

I have gone with the crow

Inhibitors to change: a case study of teacher change in a rural African context

  • Authors: Stiles, Kathy Greaves
  • Date: 1996
  • Subjects: Education, Elementary -- Zimbabwe Educational change -- Zimbabwe Environmental education -- Study and teaching (Elementary) -- Zimbabwe Teachers -- Training of -- Zimbabwe
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1578 , http://hdl.handle.net/10962/d1003460
  • Description: Environmental education is taught as part of the Primary School Environmental and Agricultural Science (EAS) curriculum in Zimbabwe. An attempt to improve the quality of learning in EAS resulted in a research project at the University of Zimbabwe that aimed to transpose innovative constructivist pedagogy from a western context to a rural African one. This writer has used a definition of teacher change as social change and a belief that sustainable pedagogical change involves a transformative process. The research backs up previous findings that failure to recognise and deal with how people actually experience the change process, accounts for much failure of social change. This qualitative research has attempted to provide some understanding of the complex interrelationships of factors that affected expected change in teaching style. By focusing on the process of teacher change within innovation, this researcher was able to identify inhibitors to change that were subsequently critically reflected on by the tea~hers themselves. The disappointing resistance to change first noted within the project has become a source of unexpected but potentially important illuminative understanding of teacher education and development in a non-western environment.
  • Full Text:
  • Date Issued: 1996

Introducing a multi-cultural dimension into the study of literature at secondary school level

  • Authors: Vogel, Sonja
  • Date: 1996
  • Subjects: English literature -- Study and teaching (Secondary) -- South Africa Multicultural education -- South Africa Culture in literature Ethnicity in literature
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1584 , http://hdl.handle.net/10962/d1003466
  • Description: The first aim of teaching English literature has always been for the student to gain enjoyment from, and acquire skill in, reading. Further goals point to the affective development of pupils involving such qualities as critical thinking and expressing views, empathetic understanding of other people, moral awareness and increased self-knowledge and self-understanding. These are indeed laudable aims, but examiners have always had difficulties in examining them adequately to satisfy the critics. Teachers often doubt that they achieve such lofty aims. These very aims have the sceptics sneering at the discipline because such qualities cannot be measured and the pupil's worth for the workplace cannot be satisfactorily assessed. This has resulted in the merit of the study of literature being questioned and usually found wanting. Therefore, on the one hand, this research looks for a method of studying literature which will ensure that the study will be neccesary and desirable today and into the foreseeable future. On the other hand, the socio-political changes in South Africa, particularly since 1992, have offered a possible area of research to complement the first. During the past few years, South Africans have been forced to recognise the fact that a multitude of different races and people live and work together more closely in this country and yet they know nothing, or very little, of one another. Thus this research also investigates the addition of a cultural component to literature study to help young people gain empathetic understanding of different cultures and of their own cultures as well, to be able to live together in harmony. With this approach, pupils may conceivably be educated through literature, to become well-adjusted, critical, effective adults so that they may play their role as citizens and shapers of their increasingly complex, multi-cultural society. Because of the context of literature study, in which this personal growth takes place, the aims identified above may be measured and assessed to suit both the sceptics and the devotees of literature study.
  • Full Text:
  • Date Issued: 1996

isiZukulwane

Just below Perseverance, Port Elizabeth

  • Disclaimer
  • Privacy
  • Copyright
  • Contact