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Njambaar

- Mbaye Ndiaye (lead vocal, riiti), Ibou Tine, Moustapha Dione, Fatou Talla Ndiaye, Arame Camara (chorus), Alioune Gueye (guitar), Elou Fall (keyboard, programming, drums), Pape Ndiaye (percussion), Jololi

No more lament

- Ajah Sy ( lead vocals, author, composer, chorus), Biram Ndeck Ndiaye, Aly Hachem (arrangement), Lamine Faye (guitar), El Hadji Niang, Aly Hachem, Ousmane Wade (keyboards), Moussa Traore (percussion), Jean Pierre Gomes (bass), Marie Codou Pouye, Ajah Sy, Abdourahmane Diallo,Missala man, Aly Hachem, Mame Gor Mboup (chorus), Studio 2000

Nouveau II

- Gnaore Djimi (vocals, creator), Gnaore Djimi The Best (album title), Showbiz

  • Authors: Gnaore Djimi (vocals, creator) , Gnaore Djimi The Best (album title) , Showbiz
  • Date: 2000
  • Subjects: Popular music , Popular music--Africa, West , Africa Cote d'Ivoire Abidjan f-iv
  • Language: French
  • Type: sound recordings , field recordings , sound recording-musical
  • Identifier: http://hdl.handle.net/10962/128992 , vital:36201 , International Library of African Music, Rhodes University, Grahamstown, South Africa , SDC17-07
  • Description: Ivorian popular song in the Polihet style that is based on the traditional sounds, gestures and heritage of Niamboua people who live in the southwest reagion of Cote d'Ivoire. Polihet is performed at funerals, baptisms,weddings with the themes of love, hate, death and peace
  • Full Text: false
  • Date Issued: 2000

Nyau masquerade performance : shifting the imperial gaze

- Guhrs, Tamara

  • Authors: Guhrs, Tamara
  • Date: 2000
  • Subjects: Masquerades -- Malawi , Masquerades -- Zambia , Malawi -- Religion , Zambia -- Religion , Masks, Chewa , Chewa (African people) -- Rites and ceremonies , Nyanja (African people) -- Rites and ceremonies , Secret societies -- Africa
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2140 , http://hdl.handle.net/10962/d1002372 , Masquerades -- Malawi , Masquerades -- Zambia , Malawi -- Religion , Zambia -- Religion , Masks, Chewa , Chewa (African people) -- Rites and ceremonies , Nyanja (African people) -- Rites and ceremonies , Secret societies -- Africa
  • Description: Nyau Masquerades have been studied by missionaries, anthropologists and religious specialists, but have seldom been documented by theatre and performance specialists. This dissertation argues for the acceptance of Ny au performance as a contemporary world theatre form rooted in tradition. Charting the uneasy relationship between the Nyau and those who have sought to record their performances, the author delineates a vivid dramaturgy of this art form. In doing so, the boundaries of what define theatre as it has traditionally been understood in dominant discourses are made more fluid. Nyau performances have been affected by Colonial processes in varied ways. They were banned by the former government of Northern Rhodesia and severely censored by Catholic Mission teachings in the former Nyasaland. Other forms of vilification have been more subtle. Information about performance in Africa has often been collected and arranged in ways which limit the understanding of these genres. Images of Africa which cluster around the notion of the 'Primitive Other' have enabled a representation of Ny au masking as a superstitious and outdated practice with no relevance for contemporary Africa. This work calls for a new examination of the Nyau, through the lens of local discourse as well as contemporary global understandings of performance. Chapter One examines the issue of primitivism and the ways in which Africa has historically been posited as the exotic Other to Europe. Chapter Two examines the Nyau ih terms of specific dramaturgical elements, adjusting previous misconceptions surrounding the theatr~ forms of Chewa and Nyanja people. Chapter Three is devoted to a discussion of space in ritual theatre and Nyau performance, while Chapter Four explores masking and questions of transformation and liminality. In conclusion, it is seen that the use of the mask is a metaphor for the suspension of rigid boundaries separating subject/object, self/other, ritual/theatre, a suspension which needs to take place before an enriched understanding of performance in Africa can be reached.
  • Full Text:
  • Date Issued: 2000

Observations of selective feeding of the aphid, Sitobion yakini (eastop) on leaf blades of barley (Hordeum vulgare L)

- Matsiliza, Babalwa

  • Authors: Matsiliza, Babalwa
  • Date: 2000
  • Subjects: Aphids , Phloem , Barley
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4212 , http://hdl.handle.net/10962/d1003781 , Aphids , Phloem , Barley
  • Description: Penetration of leaves of barley (Hordeum vulgare L.) plants grown under normal conditions and those exposed to physiological stress, by the aphid, Sitobion yakini was investigated using light and electron microscope techniques. This was carried out to determine if there was evidence of preferential feeding on either thin- or thick-walled sieve tubes in the barley leaf. Under both stress and non-stress conditions, preliminary results of an electron microscope investigation showed that penetration of the epidermis and mesophyll was largely intercellular, becoming partly intercellular and in part intracellular inside the vascular bundle. A total of 317 stylets and stylet tracks were encountered during the examination of 2000 serial sections. In non-stressed plant material, 293 (92%) terminated in thin-walled sieve tubes and only 24 (8%) in thick-walled sieve tubes. Investigation of 1000 serial sections using stressed plant material showed, that 84 of 89 (94%) stylets and stylet tracks encountered terminated in thin-walled sieve tubes. Furthermore, 90 of 94 (96%) stylets and stylet tracks encountered in 1000 serial sections from the second experiment of control non-stressed plant material (control) terminated in thin-walled sieve tubes. The thin-walled sieve tubes were significantly more visited (probed) by the aphid than the thick-walled sieve tubes. Under stress conditions, 50 of 89 (56%) stylets and stylet tracks which terminated in thin-walled sieve tubes were associated with the small longitudinal bundles. Under normal conditions, 65 of 94 (69%) stylets and stylet tracks which terminated in thin-walled sieve tubes were associated with the small longitudinal bundles. There were no significant differences on the number of probes of sieve elements between the two treatments. These data suggest that the aphid S. yakini feeds preferentially on the thin-walled sieve tubes of the small longitudinal vascular bundles in plants grown under normal conditions and those exposed to physiological stress, such as water stress. This further suggests that the thin-walled sieve tubes in barley leaf blades are more attractive to the aphid and are probably most functional in terms of phloem loading and transport.
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  • Date Issued: 2000

Oluwa Funmi

- Peter Gabriels Muonagor (written, arranged, produced and composed by), Tosia Alesh (arranged and produced by), Studio 2000

Omba

- Brighess (author, composer, lead singer, chorus, percussions), Turbo (chorus), Le Ziboua Stars (band), Cisky de Panza (chorus, guitar, arranger), Ras live I

On using AMOS, EQS, LISREL, Mx, RAMONA and SEPATH for structural equation modeling

- Peprah, Syvester

  • Authors: Peprah, Syvester
  • Date: 2000
  • Subjects: Latent variables , Multivariate analysis , Mathematical statistics -- computer programs
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:11082 , http://hdl.handle.net/10948/279 , Latent variables , Multivariate analysis , Mathematical statistics -- computer programs
  • Description: Structural Equation Modeling is a common name for the statistical analysis of Structural Equation Models. Structural Equation Models are models that specify relationships between a set of variables and can be specified by means of path diagrams. A number of Structural Equation Modeling programs have been developed. These include, amongst others, AMOS, EQS, LISREL, Mx, RAMONA and SEPATH. A number of studies have been published on the use of some of the applications mentioned above. They include, amongst others, Brown (1986), Waller (1993) and Kano (1997). Structural Equation Models are increasingly being used in the social, economic and behavioral sciences. More and more people are therefore making use of one or more of the Structural Equation Modeling applications on the market. This study is performed with the aim of using each of the Structural Equation Modeling applications AMOS, EQS, LISREL, Mx, RAMONA and SEPATH for the first time and document the experience, joy and the difficulties encountered while using them. This treatise is different from the comparisons already published in that it is based on the use of AMOS, EQS, LISREL, Mx, RAMONA and SEPATH to fit a Structural Equation Model for peer influences on ambition, which is specified for data obtained by Duncan, Haller and Portes (1971), by myself as a first time user of each of the programs mentioned. The impressive features as well as the difficulties encountered are listed for each application. Recommendations for possible improvements to the various applications are also proposed. Finally, recommendations for future studies on the use of Structural Equation Modeling programs are made.
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  • Date Issued: 2000

Onow Nee Jik Weel

- Mbaye Ndiaye (lead vocal, riiti), Ibou Tine, Moustapha Dione, Fatou Talla Ndiaye, Arame Camara (chorus), Alioune Gueye (guitar), Elou Fall (keyboard, programming, drums), Pape Ndiaye (percussion), Jololi

Organisational leaders' perceptions of the challenges and constraints of the leadership development of Blacks in South African private organisations

- Nyamuda, Paul Andrew

  • Authors: Nyamuda, Paul Andrew
  • Date: 2000
  • Subjects: Leadership , Black people -- South Africa , Black people -- Employment -- South Africa
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:3033 , http://hdl.handle.net/10962/d1002542 , Leadership , Black people -- South Africa , Black people -- Employment -- South Africa
  • Description: In recent years, it has become clear that a lot of corporate collapse can be traced down to poor leadership. As more and more black executives are climbing the corporate ladder, it is becoming all the more necessary to explore how their effective leadership development can occur with private organisations in South Africa. There are many challenges and constraints associated with the leadership development of these executives. This can be expected as they are entering an environment which has been largely white-dominated. As a result they find themselves facing the challenges of succeeding amidst negative perceptions they have experienced from their superiors and subtle pressures from subordinates. Therefore, it can only be expected that if organisations are to maintain a competitive advantage they need to understand how to effectively develop this new breed of leaders. Hence, the researcher has used a qualitative approach to investigate the complexities of the experiences of black executives in private organisations. In terms of the theoretical framework, the research focuses on some of the new approaches to leadership. It was discovered that leadership development is essentially a process that goes beyond mere training sessions, and largely involves the relationships one has within the organisation. This involves relationships with superiors, peers, and subordinates. The research indicates that if these relationships are managed effectively, leadership development is enhanced. Whilst the role of formal training programs appeared somewhat downplayed, it was clear that these programs had a strong role in terms of their psychological impact on participants. They certainly affected their perception of the organisation and their own self-efficacy. The research, therefore illustrates how there are a variety of individual and organisational attributes that form a basis for effective leadership development of blacks in private organisations. The researcher argues that if these are implemented, organisational well-being is enhanced.
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  • Date Issued: 2000

Osipope

- Priscilia Ngando (lead vocal), Mevio-Mayo, Dany Mouanga, Mouasso (rhythm guitars), Aubin Sandjo, Scorpionkabambay, Mouche Bass (bass guitar), Dany Mouanga, Eric Sefu (solo guitar), Aubin Sandjo, Paul Balong (keyboard), Abel Massock, Fabo Claude, Nono (chorus), Moussa Haissam, Danger Ngando Konne (composers), Aubin Sandjo (drum, percussion, keyboard), Alhadji Mallam Issa (talking drum), Moussa Haissam

Ostrich calpastatin purification and partial characterization of the liver inhibitor

- Roman, Henry James

  • Authors: Roman, Henry James
  • Date: 2000
  • Subjects: Calpastatin , Protease inhibitors , Ion exchange chromatography , Ostriches
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:11090 , http://hdl.handle.net/10948/d1015522
  • Description: The isolation and purification of calpastatin from ostrich liver is presented, along with its physicochemical and kinetic properties. By using extraction from liver, ion-exchange chromatography on DEAE-Toyopearl, heating to 90 °C for 10 min and rechromatography on Toyopearl Super-Q 650 S, ostrich calpastatin was isolated and purified from ostrich liver. The purified intact calpastatin showed homogeneity on SDS-PAGE (Mr of 105.6 K). Amino acid analysis showed that ostrich calpastatin resembled that of rabbit liver and human erythrocyte calpastatin. An N-terminal sequence could not be obtained because the N-terminus was found to be blocked by an as yet unknown amino acid residue. The Mr values of degradative forms of ostrich liver calpastatin were determined to be 56 K and 90 K. By using PAG-IEF the pI of the intact form was determined to be 5.1. Ostrich liver calpastatin behaved characteristically like other calpastatins during kinetic analysis. Calpastatin inhibited calpain from pH 6 to 9 and was found to be unaffected by temperatures as high as 100 °C. Calpastatin also inhibited calpain activity at Ca2+ concentrations ranging from 1 to 10 mM. The inhibitor was shown to be phosphorylated because after incubation with alkaline phosphatase there was a decrease in inhibitory activity. No inhibitory effects were detected against other proteases such as chymotrypsin and trypsin, with both proteases inactivating calpastatin completely. Ostrich liver calpain was shown to have a pH optimum of 7.5 and a temperature optimum of 30 °C. In terms of its thermodynamic properties it resembled that of other ostrich proteases; DH, DS and DG being 47.07 kJ/mol, -91.1 J/mol/K and 74.237 kJ/mol, respectively. Ostrich liver calpain showed a Km of 0.14 % (w/v). The enzyme was active at both milli- and micro-molar concentrations of Ca2+. Ostrich liver calpastatin showed many physical, chemical and kinetic properties similar to those of other known calpastatins.
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  • Date Issued: 2000

Outsourcing for competitive advantage : an evaluation of an owner driver proposition in a South African removals company

- Coleman, Belinda

  • Authors: Coleman, Belinda
  • Date: 2000
  • Subjects: Contracting out -- South Africa , Storage and removal trade -- Subcontracting -- South Africa , Trucking -- South Africa , Benchmarking (Management) -- South Africa
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:11002 , http://hdl.handle.net/10948/d1015540
  • Description: The aim of the research was to assess what competitive advantage a Removals company could expect to gain by outsourcing its driver function to owner drivers. An extensive literature review identified key outsourcing issues. The literature was related to a case study of Stuttaford Van Lines (SVL), a company that is experiencing problems with its current independent contractor driver arrangements and that needs to review its outsourcing decision. In order to learn from best practice in the field of outsourcing to owner drivers, a benchmarking exercise was undertaken at South African Breweries (SAB). The benchmarking exercise identified six key issues that contributed to the success of the SAB owner driver scheme. These points, together with others identified from the literature, were integrated into a recommended outsourcing implementation process for SVL. The research found that it is possible for SVL to outsource the driver function to owner drivers and that such a scheme can be expected to improve customer service levels. The success of the scheme will depend on the selection of the drivers and how effectively it is managed. It was found that it would not be profitable for SVL to outsource to owner drivers using the compensation model proposed. Cost reduction is however only one of the factors to consider in an outsourcing decision.
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  • Date Issued: 2000

Palynology and palaeo-environment of Pleistocene hyaena coprolites from an open-air site at Oyster Bay, Eastern Cape coast, South Africa

- Carrion, J S, Brink, J S, Scott, Lucy E P, Binneman, J N F

  • Authors: Carrion, J S , Brink, J S , Scott, Lucy E P , Binneman, J N F
  • Date: 2000
  • Language: English
  • Type: Article
  • Identifier: vital:7000 , http://hdl.handle.net/10962/d1008357
  • Description: Hyaena coprolites in a soil horizon at Oyster Bay, Eastern Cape coast, South Africa, were found associated with abundant, early Last Glacial vertebrate faunal remains that were apparently accumulated by brown hyaenas and prehistoric humans. Artefacts of the Howieson's Poort sub-stage of the Middle Stone Age occur in the same soil. Although direct association between the different finds cannot be demonstrated, there is evidence to suggest that they are broadly contemporaneous. Pollen assemblages in the coprolites were dominated by Myrica and, to a lesser extent, Stoebe-Elytropappus type and Poaceae. Comparison with the modern pollen spectrum suggests that the past environment differed markedly from the current. The presence of Stoebe-Elytropappus, in particular, is considered to indicate a displacement of vegetation zones to lower altitudes. Both fossil pollen and fauna suggest a landscape with a complex mosaic of vegetation indicative of overall cooler, more inland conditions than today.
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  • Date Issued: 2000

Patterns of belief in Bushman creation tales: an interpretive study relating to /Xam, Maluti, and Zu/'oasi sources

- Howard, Nadine B

  • Authors: Howard, Nadine B
  • Date: 2000
  • Subjects: South Africa , Creation -- Mythology , Spirituality -- Africa , San (African people) -- Religion , San (African people) -- Folklore
  • Language: English
  • Type: Text
  • Identifier: vital:549 , http://hdl.handle.net/10962/d1019978 , Donated by Geoffrey Howard, 2010.
  • Description: “Patterns of Belief in Bushman Creation Tales” regard /Xam, Maluti, and Zu/’oasi mythology. The study divides into three sections. The Early Period of Conceptual Unity concerns creation of the eland, a symbolic antelope. All beings are animal-persons of the early race. The /Xam deity /Kaggen creates and secretly cares for an eland to whom he feeds honey. The family, missing honey, sends Mongoose to spy on /Kaggen. He sees the eland and informs his father who kills it without Kaggen’s knowledge. Kaggen weeps bitterly. Elsewhere, when Cagn’s away Maluti sons hunt and discover an unknown creature. They try repeatedly to stab it as it breaks away, but returns to lay down. Finally Gewi kills it. They take meat and blood home, but later see Cagn’s snares and feel afraid. The Transition Period of Conceptual Separation and Restoration follows. Separation of animals and people takes place through re-creation and naming. The former animal-person world passes away. Maluti elands are re-created as Gewi tries to undo his “mischief”. Churning the eland’s blood, it scatters, becoming snakes, then hartebeests. Cagn and his wife help: spinning blood, adding fat from the heart. They produce multitudes of untamed elands. Gewi who “spoilt” them must hunt and kill one, but he fails. Cagn then teaches both sons to hunt. However, his elands are swift, and he will now dwell in their bones. “That day game were given to men to eat,” and the transition to knowing is made. Zu/’oasi animal-persons journey to the fire of creation; there to be beautifully marked or otherwise distinguished. /Xam antelope await their naming through the eating or drinking of liquid honeys which colour their hides. The Third Section offers an overview of concepts the thesis presents. It also bears the key to unlock a very old mystery. , Intended as a Masters of Arts thesis for the University of Natal, the author was unable to complete the final chapter before her death, and the thesis was never submitted for examination. It was the wish of her husband that her careful study should be brought to light and be made available to other students of this field.
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  • Date Issued: 2000

PBS 2000

- Didier Sourou Awadi aka DJ Awadi (performer, author), Amadou Barry aka Doug E. Tee, Duggy Tee (performer, author), Palm Tree Enter/Africa with P.B.S. Production

Peer group supervision as an adjunct to individual supervision: an investigation of models of learning

- Akhurst, Jacqueline Elizabeth

  • Authors: Akhurst, Jacqueline Elizabeth
  • Date: 2000
  • Subjects: Peer-group tutoring of students Psychotherapy -- Study and teaching -- Supervision Psychology -- Supervision of
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2922 , http://hdl.handle.net/10962/d1002431
  • Description: Supervision of practice makes an important contribution to the development of psychotherapeutic skills in the training of psychologists (Bernard and Goodyear, 1998). Much research has, until recently, focussed on dyadic, hierarchical models of supervision, even though other forms of supervision have been developed. Peer group supervision has had little attention in the literature, although it is a common form of supervision utilised by psychologists in practice (Lewis, Greenburg and Hatch, 1988). A review of the literature considers the purposes of supervision; elements of dyadic supervision; various forms of group, peer and peer group supervision; and the leaming process in supervision. The development and implementation of a peer supervision group (pSG) of intern psychologists within the training setting of a University is described in this study. The PSG model was developed from the model proposed by Wilbur, Roberts-Wilbur, Morris, Betz and Hart (1991). Transcripts from nine audio-taped PSG sessions were analysed, and a comparison with four audio-taped dyadic supervision sessions was then undertaken. Grounded Theory methodology was employed in the design of the study and analysis of the data. The form and content of the two models of supervision were examined, with particular attention to the perspective of the trainees' learning experiences. The relative merits of both forms of supervision were assessed, and this analysis clearly demonstrates that peer group supervision has the potential to complement dyadic supervision by contributing differing learning experiences. A model of key influences upon, and effects of, participation in the two forms of supervision has been developed. Suggestions are made of ways in which dyadic supervision may be optimised, and recommendations for further development of the PSG emerge. The results were then considered from a neo-Vygotskian perspective. This enabled the findings to be linked to a comprehensive theory of learning, pointing to the key role of speech in thinking, and the contributions of the various forms of dialogue to deepened understandings. The discussion includes: consideration of techniques which enable trainees to obtain assistance from both more experienced practitioners as well as from their peers; an exploration of aspects of subjectivity and intersubjectivity; and contextual influences which have bearing on the study. This study identifies the need for further consideration of the supervision process in South Africa, and makes recommendations for the training of supervisors. The neo-Vygotskian model offers great promise both as a framework for understanding the leaming process in. supervision, and for developing guidelines for enhancing supervisory practice.
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  • Date Issued: 2000

Perspectives on inter-professional collaboration : mediation

- Tatchell, Dolores

  • Authors: Tatchell, Dolores
  • Date: 2000
  • Subjects: Divorce mediation -- South Africa , Custody of children-- South Africa
  • Language: English
  • Type: Thesis , Masters , MSocSc
  • Identifier: vital:707 , http://hdl.handle.net/10962/d1006519 , Divorce mediation -- South Africa , Custody of children-- South Africa
  • Description: This research is based on the continuous search for alternatives in dealing with custody and access of minor children in divorcing families. In spite of the Mediation in Certain Divorce Matters Act, 1987, providing for mediation, it did not lead to the widespread implementation of mediation as an alternative form of dispute resolution in divorce matters. The family advocate as provided for in the Act, serves to protect the interest of minor children in disputes. However, custody evaluation is still used to determine the custody of minor children. Custody evaluation comprises an in depth study and assessment of the structure and functioning of the family made by a social worker and written up in the form of an evaluative report which is then submitted to the family advocate. It occurred to the researcher that there had to be better ways of dealing with custody disputes and consequently the damage done by the parents who fight over their children without any regard for the children’s feelings. It was considered an option to find out from the professionals directly involved with divorce and custody disputes why they have not considered alternatives, such as mediation, to resolve the disputes arising out of a divorce. Semi-structured interviews were conducted with five social workers and five attorneys to gain their perspectives on mediation, how the two professions could cooperate to assist divorcing couples and how inter-professional collaboration could be used to promote the use of mediation in East London. The family advocate was identified as a key role player. The possibility of mandatory mediation was raised with recommendations that it be considered. The co-mediation model was raised to enhance inter-professional collaboration. Social workers see their role as mediating custody issues where the attorneys see their role as mediating division of property and assets. Both professions recognize that they have their own unique contribution to make. Both social workers and attorneys have been found to be willing to collaborate with each other to make a mediation service available to divorcing couples
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  • Date Issued: 2000

Petrographic and geochemical constraints on the origin and post-depositional history of the Hotazel iron-manganese deposits, Kalahari Manganese Field, South Africa

- Tsikos, Harilaos

  • Authors: Tsikos, Harilaos
  • Date: 2000
  • Subjects: Manganese ores -- South Africa Manganese ores -- Geology -- South Africa Iron ores -- Geology -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4987 , http://hdl.handle.net/10962/d1005599
  • Description: The giant Palaeoproterozoic manganese deposits of the Kalahari manganese field (KMF), Northern Cape Province, South Mrica, have been a world renowned resource of manganese ore for many decades. In recent years, the mineralogical composition, geochemistry and genesis of these deposits have been the objects of many geological investigations, yet their origin remains contentious up to the present day. A characteristic feature of the Kalahari deposits is the intimate association of manganese ore and iron-formation of the Superior-type, in the form of three discrete sedimentary cycles constituting the Hotazel Formation. This striking lithological association is an almost unique feature on a global scale. From that point of view, the present study is effectively the first attempt to shed light on the origin and post-depositional history of the Hotazel succession, using as prime focus the petrographic and geochemical characteristics ofthe host iron-formation. Petrographic and whole-rock geochemical information of iron-formation from the southern parts of the KMF, suggests that the Hotazel iron-formation is almost identical to other iron-formations of the world of similar age and petrological character. The rock exhibits essentially no high-grade metamorphic or low-temperature alteration effects. Mineralogically, it contains abundant chert, magnetite, subordinate amounts of silicate minerals (greenalite, minnesotaite, stilpnomelane) and appreciable concentrations of carbonate constituents in the form of coexisting calcite and ankerite. Such mineralogical composition is indicative of processes occurring in a diagenetic" to burial (up to very low-greenschist facies) metamorphic environment. Bulk-rock geochemical data point towards a simple composition with Si02, total Fe-oxide and CaO being the chief major oxide components. Whole-rock rare-earth element data suggest that the iron-formation precipitated from a water column with chemical signatures comparable to modern, shallow oceanic seawater. The virtual absence of positive Eu anomalies is a feature that compares well with similar data from Neoproterozoic, glaciogenic iron-formations of the Rapitan type, and suggests but only a dilute hydrothermal signal, poten!ially derived from distal submarine volcanic activity. Carbon and oxygen isotope data from iron-formation and Mn-bearing carbonates as well as overlying ferriferous limestone of the Mooidraai Formation, compare well with the literature. The former exhibit variable depletion relative to seawater in terms of both BC and 180, while the latter have signatures comparable to normal marine bicarbonate. Isotopic variations appear to be related to fluctuations in the amount of co-precipitated marine carbonate, in conjunction with processes of coupled organic matter oxidation - FelMn reduction in the diagenetic environment. Oxygen isotope data from quartz-magnetite-calcite triplets suggest that crystallisation took place under open-system conditions, with magnetite being the most susceptible phase in terms of fluid-rock isotopic exchange. Data also suggest that the calcite-magnetite pair may constitute a more reliable geothermometer than the quartz-magnetite one, mainly due to the interlinked diagenetic histories between calcite and magnetite. Iron-formation from the northern parts of the KMF can by categorised into three main classes, namely pristine, altered and oxidised. Pristine iron-formation is identical to the one seen in the southernmost parts of the field. Altered iron-formation corresponds to a carbonate-free derivative of intense oxidation and leaching processes at the expense ofpristine iron-formation, and contains almost exclusively binary quartz-hematite mixtures. The rock appears to have lost essentially its entire pre-existing carbonate-related components (i.e., Ca, Mg, Sr, most Mn and Ba) and displays residual enrichments in elements such as Cr, Th, V, Ni and Pb, which would have behaved as immobile constituents during low-temperature alteration. The low temperature origin of altered iron-formation is supported by oxygen isotope data from quartz-hematite pairs which indicate that isotopically light hematite would have derived from oxidation of magneftte and other ferroussilicate compounds in the presence of a low-temperature meteoric fluid, while quartz would have remained isotopically unchanged. Occasional occurrences of acmite-hematite assemblages suggest localised metasomatic processes related to the action ofNaCI-rich fluids at the expense of altered iron-formation. The conditions of acmite genesis are very poorly constrained due to the very broad stability limits of the mineral in environments ranging from magmatic to surface-related. Oxidised iron-formation constitutes a distinct rock-type and shares common attributes with both the pristine and the altered iron-formation. The rock contains hematite as an important constituent while the amount of magnetite is substantially reduced. With regard to carbonate nlinerals, calcite contents are clearly very low or absent, having being replaced in most instances by a single, Mgenriched, dolomite/ankerite:type species. Oxidised iron-formation contains somewhat higher amounts of iron and reduced amounts of Sr and Ba relative to pristine iron-formation, whereas enrichments in elements such as Ni, Th, Pb, Cr, and V are seen, similar to altered iron-formation. Oxidised iron-formation appears to have originated from processes of dissolution-mobilisationreprecipitation of solutes derived primarily from leaching that produced altered iron-formation. It is proposed that the Hotazel iron-formation and associated manganese deposits were formed as a result of episodic sea-level fluctuations in a stratified depositional environment that gradually evolved into a shallow carbonate platform. A critical parameter in the development of manganese sediment may include regional climatic patterns related to a glacial event (Makganyene diamictite) prior to deposition of the Hotazel strata. This suggestion draws parallels with processes that are believed to have led to the formation of worldwide iron-formations and associated manganese deposits subsequent to Neoproterozoic episodes of glaciation. Submarine volcanism related to the underlying Ongeluk lavas appears to have had very little (if any) metallogenic significance, while evidence for a sudden rise in the oxygen contents of the atmosphere and ambient waters is lacking. With regard to later alteration processes, combination of geological and geochemical data point towards the potential influence of surface weathering prior to deposition of rocks of the unconformably overlying Olifantshoek Supergroup, possibly coupled with fault- and/or thrustcontrolled fluid-flow and leaching of the Hotazel succession during post-Olifantshoek times.
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  • Date Issued: 2000

Phloem loading in the sucrose-export-defective (SXD-1) mutant maize is limited by callose deposition at plasmodesmata in bundle sheath-vascular parenchyma interface

- Botha, Christiaan E J, Cross, Robin H M, Van Bel, A J E, Peter, Craig I

  • Authors: Botha, Christiaan E J , Cross, Robin H M , Van Bel, A J E , Peter, Craig I
  • Date: 2000
  • Language: English
  • Type: Article
  • Identifier: vital:6503 , http://hdl.handle.net/10962/d1005926
  • Description: Using Lucifer Yellow we have demonstrated that the phloem-loading pathway from the mesophyll to the bundle sheath-vascular parenchyma interface in Zea mays source leaves follows a symplasmic route in small and intermediate vascular bundles in control as well as in the green sections of mutant sucrose-export-defective (SXD-1) plants. In the anthocyanin-rich mutant leaf sections, Lucifer Yellow transport was prohibited along the same path, at the bundle sheath-vascular parenchyma interface in particular. Plasmodesmata at the latter interface in SXD-1 anthocyanin-rich leaf sections appear to be structurally altered through callose deposition at the plasmodesmal orifices. We suggest that a transport bottleneck at the bundle sheath-vascular parenchyma interface is thus orchestrated and regulated through callose formation, preventing symplasmic transport across this important loading interface.
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  • Date Issued: 2000
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