The influence of grade 3 teachers’ self-efficacy on the teaching of isixhosa home language reading-comprehension: recommendations for an indigenous mother-tongue based teaching framework
- Authors: Makeleni, Sive
- Date: 2019
- Subjects: Reading comprehension Xhosa language -- Study and teaching
- Language: English
- Type: Thesis , Doctoral , PhD (Education)
- Identifier: http://hdl.handle.net/10353/16632 , vital:40738
- Description: This thesis aimed to examine the extent to which Grade 3 teachers’ self-efficacy influence the teaching of IsiXhosa Home Language reading comprehension. The study was conducted in the Buffalo City Metro Education District, Eastern Cape, South Africa. Social Cognitive theory was adopted as a theoretical framework for this study. The study employed a mixed methods approach, wherein qualitative and quantitative data were collected. Concurrent triangulation was adopted as a research design. In the quantitative phase one hundred and twelve (112) Grade 3 teachers participated through filling in questionnaires. Whilst, in the qualitative phase six (6) teachers were interviewed. Quantitative data was analysed through using descriptive/inferential statistics for the appropriate variables of data, and QUAL analysis of data, using thematic analysis related to the relevant narrative data. The findings both quantitative and qualitative reveal that the teachers spend most of their time in teaching phonics, phonemic awareness and vocabulary and less time on teaching reading comprehension. The teachers feel that the prescribed Curriculum and Policy Statement that does not accommodate indigeneity and languageness of IsiXhosa Language suppresses their innovativeness and creativeness in teaching IsiXhosa Home Language reading comprehension. The teachers highlighted the orthographic uniqueness of IsiXhosa language as one of the gaps in the curriculum. The majority of the teachers believe that Curriculum and Assessment Policy Statement IsiXhosa Home Language Foundation Phase (CAPS), is back-translated from another language. Hence, the teachers feel unease to implement the curriculum as it is. Such conceptual gaps identified, negatively affected the teachers’ self-efficacy in teaching IsiXhosa Home Language reading comprehension. Also revealing in the findings are the teachers’ use of assessment as a mere compliance strategy. The findings also reveal that the teachers’ self-efficacy is affected by contextual factors. The study therefore recommends a decolonised IsiXhosa-sensitive Curriculum and Policy Statement that reflects the indigeneity and the languageness of IsiXhosa. The study further recommends an indigenous mother -tongue based framework of teaching IsiXhosa Home Language in the Foundation Phase
- Full Text:
- Date Issued: 2019
- Authors: Makeleni, Sive
- Date: 2019
- Subjects: Reading comprehension Xhosa language -- Study and teaching
- Language: English
- Type: Thesis , Doctoral , PhD (Education)
- Identifier: http://hdl.handle.net/10353/16632 , vital:40738
- Description: This thesis aimed to examine the extent to which Grade 3 teachers’ self-efficacy influence the teaching of IsiXhosa Home Language reading comprehension. The study was conducted in the Buffalo City Metro Education District, Eastern Cape, South Africa. Social Cognitive theory was adopted as a theoretical framework for this study. The study employed a mixed methods approach, wherein qualitative and quantitative data were collected. Concurrent triangulation was adopted as a research design. In the quantitative phase one hundred and twelve (112) Grade 3 teachers participated through filling in questionnaires. Whilst, in the qualitative phase six (6) teachers were interviewed. Quantitative data was analysed through using descriptive/inferential statistics for the appropriate variables of data, and QUAL analysis of data, using thematic analysis related to the relevant narrative data. The findings both quantitative and qualitative reveal that the teachers spend most of their time in teaching phonics, phonemic awareness and vocabulary and less time on teaching reading comprehension. The teachers feel that the prescribed Curriculum and Policy Statement that does not accommodate indigeneity and languageness of IsiXhosa Language suppresses their innovativeness and creativeness in teaching IsiXhosa Home Language reading comprehension. The teachers highlighted the orthographic uniqueness of IsiXhosa language as one of the gaps in the curriculum. The majority of the teachers believe that Curriculum and Assessment Policy Statement IsiXhosa Home Language Foundation Phase (CAPS), is back-translated from another language. Hence, the teachers feel unease to implement the curriculum as it is. Such conceptual gaps identified, negatively affected the teachers’ self-efficacy in teaching IsiXhosa Home Language reading comprehension. Also revealing in the findings are the teachers’ use of assessment as a mere compliance strategy. The findings also reveal that the teachers’ self-efficacy is affected by contextual factors. The study therefore recommends a decolonised IsiXhosa-sensitive Curriculum and Policy Statement that reflects the indigeneity and the languageness of IsiXhosa. The study further recommends an indigenous mother -tongue based framework of teaching IsiXhosa Home Language in the Foundation Phase
- Full Text:
- Date Issued: 2019
Energy services and energy poverty for sustainable development in Zimbabwe
- Authors: Mupindu, Chipo
- Date: 2017
- Subjects: Sustainable development -- Zimbabwe Zimbabwe -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/8408 , vital:32743
- Description: This study examines the effects of energy poverty on sustainable development in Zimbabwe. The principal objective of this study was to analyse Zimbabwe energy poverty as a contributing factor impacting on sustainable development. Access to energy was viewed as a human right in this study and attributes of ecological modernization and energy ladder theories were incorporated in the study so as to foster sustainable development. The study developed a symbiosis between energy poverty and human development in Zimbabwe. The power shortages have caused a lot of energy poverty and load shedding in the country and this has had adverse consequences on the transformation of the economy as well as the general human capacity development in the country. The supply shortage was as a result of many factors which include the lack of investment in the power sector by government for expanded generation capacity, ageing equipment, incorrect pricing, bad debts, droughts, internal conflicts, skills flight, and government energy sector regulation, vandalisation of equipment and under supply of coal to thermal power stations. The country needs to commit itself towards improving the current situation by revising the energy policy to include alternative sources, the integration of regional power systems and construction of more power stations, and by putting research monitoring and evaluation mechanisms in place so as to improve power generation capacity which meets the demand of the country. The evidence from the findings gathered in this study led to the conclusion that the Zimbabwe energy and power sector lacks the capacity to provide adequate reliable clean energy to the nation and this has affected the development of the country.
- Full Text:
- Date Issued: 2017
- Authors: Mupindu, Chipo
- Date: 2017
- Subjects: Sustainable development -- Zimbabwe Zimbabwe -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/8408 , vital:32743
- Description: This study examines the effects of energy poverty on sustainable development in Zimbabwe. The principal objective of this study was to analyse Zimbabwe energy poverty as a contributing factor impacting on sustainable development. Access to energy was viewed as a human right in this study and attributes of ecological modernization and energy ladder theories were incorporated in the study so as to foster sustainable development. The study developed a symbiosis between energy poverty and human development in Zimbabwe. The power shortages have caused a lot of energy poverty and load shedding in the country and this has had adverse consequences on the transformation of the economy as well as the general human capacity development in the country. The supply shortage was as a result of many factors which include the lack of investment in the power sector by government for expanded generation capacity, ageing equipment, incorrect pricing, bad debts, droughts, internal conflicts, skills flight, and government energy sector regulation, vandalisation of equipment and under supply of coal to thermal power stations. The country needs to commit itself towards improving the current situation by revising the energy policy to include alternative sources, the integration of regional power systems and construction of more power stations, and by putting research monitoring and evaluation mechanisms in place so as to improve power generation capacity which meets the demand of the country. The evidence from the findings gathered in this study led to the conclusion that the Zimbabwe energy and power sector lacks the capacity to provide adequate reliable clean energy to the nation and this has affected the development of the country.
- Full Text:
- Date Issued: 2017
Dryland conservation areas, indigenous people, livelihoods and natural resource values in South Africa: the case of Kgalagadi Transfrontier Park
- Authors: Thondhlana, Gladman
- Date: 2011
- Subjects: Human ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions biodiversity conservation -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions agriculture -- Kgalagadi Transfrontier Park (Botswana and South Africa) Indigenous peoples -- Ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources conservation areas -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Government policy -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Kgalagadi Transfrontier Park (Botswana and South Africa) -- Management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4777 , http://hdl.handle.net/10962/d1011732
- Description: Contemporary conservation and development understanding in both policy and academic circles espouses that natural resources have a significant contribution to the livelihoods of local people and that knowledge of this can better foster conservation policies that are consistent with livelihood and ecological needs. This thesis is based on research conducted in the southern Kalahari region, South Africa among the San and Mier communities bordering Kgalagadi Transfrontier Park. It looks at the importance of natural resources to the San and Mier community groups and ascertains the extent of resource use and its value within broader livelihood portfolios. It also focuses on the cultural values of natural resources and interactions among institutions and actors and how these shape natural resource governance and livelihood outcomes. Overall, natural resources represent an important livelihood source contributing up to 32 % and 9 % of the total income of the San and Mier respectively or up to 46 % and 23 % if livestock incomes are included. However, the dependence on, diversification patterns and distribution of natural resource income vary substantially between and within the two communities. With regards to the cultural values attached to natural resources by the San and Mier, the findings show that these arise from an incredibly diverse and sometimes conflicting array of values that punctuate the two communities’ way of life and they are inextricably linked to resource use. Lastly, governance of natural resources in the co-managed Park and communitymanaged resettlement farms is characterised by complex institutional arrangements, compounded by the existence of multiple actors that have multiple and sometimes conflicting objectives – as shaped by different meanings and interpretations of natural resources. Heightened inter- and intra-community conflicts are common, notably resource use conflicts between the San and Mier and between the San ‘modernist’ and ‘traditionalist’ groups. This demonstrates that the communities’ livelihood dynamics in general and the dependence on natural resources in particular, are closely linked with ecological, economic and social factors including history, culture and present livelihood needs. By exploring the social-environment interactions, the study highlights the complexities and diversity of resource use for livelihoods that should be taken into consideration for both conservation and development policy interventions and research. The main argument of the study is that the contribution of natural resources to local livelihood portfolios in co- and community-managed areas, can be better understood through a consideration of cultural dynamics and institutional arrangements since these condition natural resource access, value and use.
- Full Text:
- Date Issued: 2011
- Authors: Thondhlana, Gladman
- Date: 2011
- Subjects: Human ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions biodiversity conservation -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions agriculture -- Kgalagadi Transfrontier Park (Botswana and South Africa) Indigenous peoples -- Ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources conservation areas -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Government policy -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Kgalagadi Transfrontier Park (Botswana and South Africa) -- Management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4777 , http://hdl.handle.net/10962/d1011732
- Description: Contemporary conservation and development understanding in both policy and academic circles espouses that natural resources have a significant contribution to the livelihoods of local people and that knowledge of this can better foster conservation policies that are consistent with livelihood and ecological needs. This thesis is based on research conducted in the southern Kalahari region, South Africa among the San and Mier communities bordering Kgalagadi Transfrontier Park. It looks at the importance of natural resources to the San and Mier community groups and ascertains the extent of resource use and its value within broader livelihood portfolios. It also focuses on the cultural values of natural resources and interactions among institutions and actors and how these shape natural resource governance and livelihood outcomes. Overall, natural resources represent an important livelihood source contributing up to 32 % and 9 % of the total income of the San and Mier respectively or up to 46 % and 23 % if livestock incomes are included. However, the dependence on, diversification patterns and distribution of natural resource income vary substantially between and within the two communities. With regards to the cultural values attached to natural resources by the San and Mier, the findings show that these arise from an incredibly diverse and sometimes conflicting array of values that punctuate the two communities’ way of life and they are inextricably linked to resource use. Lastly, governance of natural resources in the co-managed Park and communitymanaged resettlement farms is characterised by complex institutional arrangements, compounded by the existence of multiple actors that have multiple and sometimes conflicting objectives – as shaped by different meanings and interpretations of natural resources. Heightened inter- and intra-community conflicts are common, notably resource use conflicts between the San and Mier and between the San ‘modernist’ and ‘traditionalist’ groups. This demonstrates that the communities’ livelihood dynamics in general and the dependence on natural resources in particular, are closely linked with ecological, economic and social factors including history, culture and present livelihood needs. By exploring the social-environment interactions, the study highlights the complexities and diversity of resource use for livelihoods that should be taken into consideration for both conservation and development policy interventions and research. The main argument of the study is that the contribution of natural resources to local livelihood portfolios in co- and community-managed areas, can be better understood through a consideration of cultural dynamics and institutional arrangements since these condition natural resource access, value and use.
- Full Text:
- Date Issued: 2011
Bacterial interaction in hide biodeterioration with special reference to selected Clostridium species
- Authors: Thompson, Gillian Ann
- Date: 1995
- Subjects: Hides and skins -- Preservation Aerobic bacteria Pseudomonas aeruginosa Clostridium Halobacterium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4041 , http://hdl.handle.net/10962/d1004102
- Description: Animal hides are the basic raw material of the leather industry and they undergo rapid putrefaction unless "cured". This study investigated the role and interactive effects of three selected bacteria, Pseudomonas aeruginosa. Clostridium histoly ticum and Clostridium sporogenes in in-situ cattle hide degradation using a model system set up for the purpose. The system consisted of 3cm diameter hide pieces contained in sealed jars and sterilised by ethylene oxide to remove resident microbes and inactivate autolytic tissue enzymes. The inocula were prepared either as individual cultures or as combinations of two inocula or all three inocula. Degradative changes during storage at 30°C were measured for up to 8 days using ten different parameters. Initial trials confirmed that the selected inocula were readily isolated from raw hides and could outcompete resident populations to produce putrefactive decomposition. Growth rates and enzyme profiles of the organisms and the effects of nutrients and reductants on their relative denaturative effects were used to standardise the system. Trials on the effects of ethylene oxide indicated the suitability of the method for hide and collagen sterilisation. The findings of in-situ trials with the selected inocula confirmed previous studies of protein putrefaction in that a bacterial succession was evident involving aerobic proteolytic bacteria, micro-aerophilic proteolytic bacteria and strictly anaerobic amino acid degrading bacteria. However, this study showed that the micro-aerophilic collagenase producing C. histolyticum degraded hides at a far greater rate when inoculated on its own than when in the presence of either or both of the other two inocula. It also demonstrated a bacterial antagonism between the two clostridia in which C. sporogenes prevented degradative changes occurring for up to 4-6 days possibly due to cysteine production by C. sporogenes. These findings have implications for hide preservation since maintenance of aerobic conditions and suppression of spore outgrowth could be used to delay growth of collagenase producing clostridia. The use of C. sporogenes as a biocontrol agent is also postulated. The model system was also used to examine salted hides during storage and these studies indicated that Halobacteriaceae do not produce collagenase but that inadequately salted hides could possibly be subject to degradation by delsulfovibrios.
- Full Text:
- Date Issued: 1995
- Authors: Thompson, Gillian Ann
- Date: 1995
- Subjects: Hides and skins -- Preservation Aerobic bacteria Pseudomonas aeruginosa Clostridium Halobacterium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4041 , http://hdl.handle.net/10962/d1004102
- Description: Animal hides are the basic raw material of the leather industry and they undergo rapid putrefaction unless "cured". This study investigated the role and interactive effects of three selected bacteria, Pseudomonas aeruginosa. Clostridium histoly ticum and Clostridium sporogenes in in-situ cattle hide degradation using a model system set up for the purpose. The system consisted of 3cm diameter hide pieces contained in sealed jars and sterilised by ethylene oxide to remove resident microbes and inactivate autolytic tissue enzymes. The inocula were prepared either as individual cultures or as combinations of two inocula or all three inocula. Degradative changes during storage at 30°C were measured for up to 8 days using ten different parameters. Initial trials confirmed that the selected inocula were readily isolated from raw hides and could outcompete resident populations to produce putrefactive decomposition. Growth rates and enzyme profiles of the organisms and the effects of nutrients and reductants on their relative denaturative effects were used to standardise the system. Trials on the effects of ethylene oxide indicated the suitability of the method for hide and collagen sterilisation. The findings of in-situ trials with the selected inocula confirmed previous studies of protein putrefaction in that a bacterial succession was evident involving aerobic proteolytic bacteria, micro-aerophilic proteolytic bacteria and strictly anaerobic amino acid degrading bacteria. However, this study showed that the micro-aerophilic collagenase producing C. histolyticum degraded hides at a far greater rate when inoculated on its own than when in the presence of either or both of the other two inocula. It also demonstrated a bacterial antagonism between the two clostridia in which C. sporogenes prevented degradative changes occurring for up to 4-6 days possibly due to cysteine production by C. sporogenes. These findings have implications for hide preservation since maintenance of aerobic conditions and suppression of spore outgrowth could be used to delay growth of collagenase producing clostridia. The use of C. sporogenes as a biocontrol agent is also postulated. The model system was also used to examine salted hides during storage and these studies indicated that Halobacteriaceae do not produce collagenase but that inadequately salted hides could possibly be subject to degradation by delsulfovibrios.
- Full Text:
- Date Issued: 1995
Gold fineness in hydrothermal ores : an investigation into the distribution of gold and silver in Southern Rhodesian gold ores
- Authors: Eales, Hugh V
- Date: 1961
- Subjects: Hydrothermal deposits -- Zimbabwe , Gold ores -- Zimbabwe , Silver ores -- Zimbabwe , Silver mines and mining -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5077 , http://hdl.handle.net/10962/d1014887
- Description: This investigation is concerned with primary variations in the silver content of gold which occurs in hydrothermal deposits, particularly those of hypothermal character which are found in Basement rocks in Southern Rhodesia. The nature of the gold produced by a number of different mines has been studied by reference to production data, and microscope techniques as well as gold and silver assays have been used to determine and to explain the variations in gold fineness. The literature does not contain a great deal of information which is relevant to this topic, but an attempt has been made here to summarize the more important contributions by different writers. From this it emerges that the interpretations given by different investigators are in conflict and that paradoxes may arise when efforts are made to explain observed variations in fineness in terms of certain generalizations which have become entrenched in the literaure. In particular, it is shown that falling temperature alone cannot account for the occurrence of silver-rich gold in certain deposits. The Gwanda district of Southern Rhodesia has been selected as a typical gold belt, and the variation in fineness in 150 producers is described. The deposits are hypothermal in character, and the average fineness of the gold is high but variable, but in a small proportion the fineness is low. It is shown that the nature of the host rock and the distance of a deposit from the granite contact appear to have no influence on the fineness of the gold and that there is no zonal arrangement of fineness values. There is a suggestion that diversity of mineral species in any particular area may be accompanied by rather wide fluctuations in the gold fineness. The variations of fineness in eight typical Southern Rhodesian deposits are studied in detail, by analysis of production data, by assaying specimens of the ore and by the examination of polished specimens of gold-bearing ore. Briefer reference is made to two other deposits in the territory, and to deposits in other countries which appear to bear out the conclusions reached in this section. It emerges that there are two factors which can commonly be correlated with variations in fineness. The first of these is the grade of the ore: high-grade ore generally contains purer gold than low-grade ore. Secondly, the textural evidence indicates that gold which separates relatively early in the paragenesis contains more silver than that which is deposited in the final stages of metallization. A general survey which draws on the literature as well as on the writer's examinations of deposits in the territory indicates that, in general, gold which is associated with late-stage minerals such as tellurides, antimony, bismuth and bismuthinite is silver-poor. Gold associated with galena may be either silver-rich or silver-poor, whereas gold which is of the same age as chalcopyrite or sphalerite is very frequently rich in silver. The difficulty which is encountered in establishing the age of gold which is intimately associated with pyrite and arsenopyrite renders uncertain the correlation between fineness and age of gold in these latter cases. There are, however, indications that gold which is truly contemporaneous with either pyrite or arsenopyrite is silver-rich. In the discussion, the objections to the common practice of singling out temperature as the most potent factor controlling gold fineness are listed. Chief amongst these objections is the fact that gold does not in all deposits increase in fineness with increasing depth: examples are quoted where fineness was found to decrease as deeper levels of the ore body were exploited. It is shown that there is no consistent relationship between the size of gold grains and their silver content. It is the writer's conclusion that in hydrothermal deposits in this territory the high fineness of the gold is due to increasing solubility of silver in the ore fluids in the late states, and that where hydrothermal deposits are characterized by gold with low average fineness, an unusually large proportion of the gold has been deposited early in the paragenotic sequence. In the majority of hypothermal deposits, however, the bulk of tho gold separates late in the sequence and the fineness is accordingly high. It is believed that the relationship which exists between fineness and tenor in many deposits is due to protracted crystallization of gold in those portions of the ore body which remained permeable to the latest stages. These portions of the ore body, which represent either valuable ore shoots or ore shoots in miniature, are likely to contain gold of variable character, but the average silver content will be low because a large proportion of the gold is "late" gold. The factors which might cause epithermal gold to have a lower fineness than mesothermal or hypothermal gold are briefly discussed. Some possible applications of this study are indicated in the final chapter. It is claimed that records of gold fineness might constitute a valuable addition to mill records. Tentative suggestions are made regarding a method whereby the approaching exhaustion of a deposit might in some cases be predicted. With regard to the origin of the gold in the Witwatersrand sediments, it is pointed out that the modified placer hypothesis is not fully equipped to explain certain of the variations in the composition of the gold.
- Full Text:
- Date Issued: 1961
- Authors: Eales, Hugh V
- Date: 1961
- Subjects: Hydrothermal deposits -- Zimbabwe , Gold ores -- Zimbabwe , Silver ores -- Zimbabwe , Silver mines and mining -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5077 , http://hdl.handle.net/10962/d1014887
- Description: This investigation is concerned with primary variations in the silver content of gold which occurs in hydrothermal deposits, particularly those of hypothermal character which are found in Basement rocks in Southern Rhodesia. The nature of the gold produced by a number of different mines has been studied by reference to production data, and microscope techniques as well as gold and silver assays have been used to determine and to explain the variations in gold fineness. The literature does not contain a great deal of information which is relevant to this topic, but an attempt has been made here to summarize the more important contributions by different writers. From this it emerges that the interpretations given by different investigators are in conflict and that paradoxes may arise when efforts are made to explain observed variations in fineness in terms of certain generalizations which have become entrenched in the literaure. In particular, it is shown that falling temperature alone cannot account for the occurrence of silver-rich gold in certain deposits. The Gwanda district of Southern Rhodesia has been selected as a typical gold belt, and the variation in fineness in 150 producers is described. The deposits are hypothermal in character, and the average fineness of the gold is high but variable, but in a small proportion the fineness is low. It is shown that the nature of the host rock and the distance of a deposit from the granite contact appear to have no influence on the fineness of the gold and that there is no zonal arrangement of fineness values. There is a suggestion that diversity of mineral species in any particular area may be accompanied by rather wide fluctuations in the gold fineness. The variations of fineness in eight typical Southern Rhodesian deposits are studied in detail, by analysis of production data, by assaying specimens of the ore and by the examination of polished specimens of gold-bearing ore. Briefer reference is made to two other deposits in the territory, and to deposits in other countries which appear to bear out the conclusions reached in this section. It emerges that there are two factors which can commonly be correlated with variations in fineness. The first of these is the grade of the ore: high-grade ore generally contains purer gold than low-grade ore. Secondly, the textural evidence indicates that gold which separates relatively early in the paragenesis contains more silver than that which is deposited in the final stages of metallization. A general survey which draws on the literature as well as on the writer's examinations of deposits in the territory indicates that, in general, gold which is associated with late-stage minerals such as tellurides, antimony, bismuth and bismuthinite is silver-poor. Gold associated with galena may be either silver-rich or silver-poor, whereas gold which is of the same age as chalcopyrite or sphalerite is very frequently rich in silver. The difficulty which is encountered in establishing the age of gold which is intimately associated with pyrite and arsenopyrite renders uncertain the correlation between fineness and age of gold in these latter cases. There are, however, indications that gold which is truly contemporaneous with either pyrite or arsenopyrite is silver-rich. In the discussion, the objections to the common practice of singling out temperature as the most potent factor controlling gold fineness are listed. Chief amongst these objections is the fact that gold does not in all deposits increase in fineness with increasing depth: examples are quoted where fineness was found to decrease as deeper levels of the ore body were exploited. It is shown that there is no consistent relationship between the size of gold grains and their silver content. It is the writer's conclusion that in hydrothermal deposits in this territory the high fineness of the gold is due to increasing solubility of silver in the ore fluids in the late states, and that where hydrothermal deposits are characterized by gold with low average fineness, an unusually large proportion of the gold has been deposited early in the paragenotic sequence. In the majority of hypothermal deposits, however, the bulk of tho gold separates late in the sequence and the fineness is accordingly high. It is believed that the relationship which exists between fineness and tenor in many deposits is due to protracted crystallization of gold in those portions of the ore body which remained permeable to the latest stages. These portions of the ore body, which represent either valuable ore shoots or ore shoots in miniature, are likely to contain gold of variable character, but the average silver content will be low because a large proportion of the gold is "late" gold. The factors which might cause epithermal gold to have a lower fineness than mesothermal or hypothermal gold are briefly discussed. Some possible applications of this study are indicated in the final chapter. It is claimed that records of gold fineness might constitute a valuable addition to mill records. Tentative suggestions are made regarding a method whereby the approaching exhaustion of a deposit might in some cases be predicted. With regard to the origin of the gold in the Witwatersrand sediments, it is pointed out that the modified placer hypothesis is not fully equipped to explain certain of the variations in the composition of the gold.
- Full Text:
- Date Issued: 1961
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