Appropriate integration of workers with physical limitations into a manual workplace – development of an assessment tool
- Authors: Pearson, Jessie T
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8209 , vital:21368
- Description: Background: People with physical limitations can contribute significantly to society and the economy, however, barriers to full and effective participation in the labour market often hinder decent employment. In light of this, placement decisions of impaired workers should be based on detailed information of the nature of the jobs available, as well as individual capabilities of the worker. An ergonomics approach to design attempts to achieve an appropriate balance between the capabilities of the worker and the requirements of the task and uses this balance to improve productivity and encourage physical and mental well-being, job satisfaction and safety. A specific analysis tool which can be applied to various workplaces and jobs, and provide information for decisions regarding placement of physically limited workers, will help to increase the percentage of correct placement in an appropriate workplace, resulting in optimum productivity and worker safety. Methods: An assessment tool which allows matching of job requirements and worker capabilities was developed based on a theoretical framework from Mattison and Goebel (2007), as well as principles defined by Almgren and Schaurig (2012) and Demura and Nakada (2010). The tool assesses range of motion, force and time components of the physical requirements of different tasks involved in the job, as well as movement capabilities and limitations of the worker. The tool was pilot tested in a case study with an above the knee amputee working at a research facility. Results: The tool successfully provided information regarding the matching of the work to the identified job. The output of the tool highlighted two tasks which would place the worker at risk due to physical requirements of the tasks being greater than movement capabilities of the worker. These tasks need to be further investigated to determine if accommodations can be made to assist the worker in safely performing the task, or if the job is not suitable for the worker. Conclusions: The tool developed was useful in providing information to inform appropriate placement of the physically limited worker. Further research needs to be done to validate and determine reliability of the tool.
- Full Text:
- Authors: Pearson, Jessie T
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/8209 , vital:21368
- Description: Background: People with physical limitations can contribute significantly to society and the economy, however, barriers to full and effective participation in the labour market often hinder decent employment. In light of this, placement decisions of impaired workers should be based on detailed information of the nature of the jobs available, as well as individual capabilities of the worker. An ergonomics approach to design attempts to achieve an appropriate balance between the capabilities of the worker and the requirements of the task and uses this balance to improve productivity and encourage physical and mental well-being, job satisfaction and safety. A specific analysis tool which can be applied to various workplaces and jobs, and provide information for decisions regarding placement of physically limited workers, will help to increase the percentage of correct placement in an appropriate workplace, resulting in optimum productivity and worker safety. Methods: An assessment tool which allows matching of job requirements and worker capabilities was developed based on a theoretical framework from Mattison and Goebel (2007), as well as principles defined by Almgren and Schaurig (2012) and Demura and Nakada (2010). The tool assesses range of motion, force and time components of the physical requirements of different tasks involved in the job, as well as movement capabilities and limitations of the worker. The tool was pilot tested in a case study with an above the knee amputee working at a research facility. Results: The tool successfully provided information regarding the matching of the work to the identified job. The output of the tool highlighted two tasks which would place the worker at risk due to physical requirements of the tasks being greater than movement capabilities of the worker. These tasks need to be further investigated to determine if accommodations can be made to assist the worker in safely performing the task, or if the job is not suitable for the worker. Conclusions: The tool developed was useful in providing information to inform appropriate placement of the physically limited worker. Further research needs to be done to validate and determine reliability of the tool.
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An investigation into the prevalence and growth of phishing attacks against South African financial targets
- Authors: Lala, Darshan Magan
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3157 , vital:20379
- Description: Phishing in the electronic communications medium is the act of sending unsolicited email messages with the intention of masquerading as a reputed business. The objective is to deceive the recipient into divulging personal and sensitive information such as bank account details, credit card numbers and passwords. Attacks against financial services are the most common types of targets for scammers. Phishing attacks in South Africa have cost businesses and consumers substantial amounts of financial loss. This research investigated existing literature to understand the basic concepts of email, phishing, spam and how these fit together. The research also looks into the increasing growth of phishing worldwide and in particular against South African targets. A quantitative study is performed and reported on; this involves the study and analysis of phishing statistics in a data set provided by the South African Anti-Phishing Working Group. The data set contains phishing URL information, country code where the site has been hosted, targeted company name, IP address information and timestamp of the phishing site. The data set contains 161 different phishing targets. The research primarily focuses on the trend in phishing attacks against six South African based financial institutions, but also correlates this with the overall global trend using statistical analysis. The results from the study of the data set are compared to existing statistics and literature regarding the prevalence and growth of phishing in South Africa. The question that this research answers is whether or not the prevalence and growth of phishing in South Africa correlates with the global trend in phishing attacks. The findings indicate that certain correlations exist between some of the South African phishing targets and global phishing trends.
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- Authors: Lala, Darshan Magan
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3157 , vital:20379
- Description: Phishing in the electronic communications medium is the act of sending unsolicited email messages with the intention of masquerading as a reputed business. The objective is to deceive the recipient into divulging personal and sensitive information such as bank account details, credit card numbers and passwords. Attacks against financial services are the most common types of targets for scammers. Phishing attacks in South Africa have cost businesses and consumers substantial amounts of financial loss. This research investigated existing literature to understand the basic concepts of email, phishing, spam and how these fit together. The research also looks into the increasing growth of phishing worldwide and in particular against South African targets. A quantitative study is performed and reported on; this involves the study and analysis of phishing statistics in a data set provided by the South African Anti-Phishing Working Group. The data set contains phishing URL information, country code where the site has been hosted, targeted company name, IP address information and timestamp of the phishing site. The data set contains 161 different phishing targets. The research primarily focuses on the trend in phishing attacks against six South African based financial institutions, but also correlates this with the overall global trend using statistical analysis. The results from the study of the data set are compared to existing statistics and literature regarding the prevalence and growth of phishing in South Africa. The question that this research answers is whether or not the prevalence and growth of phishing in South Africa correlates with the global trend in phishing attacks. The findings indicate that certain correlations exist between some of the South African phishing targets and global phishing trends.
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Bayesian accelerated life tests: exponential and Weibull models
- Authors: Izally, Sharkay Ruwade
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3003 , vital:20351
- Description: Reliability life testing is used for life data analysis in which samples are tested under normal conditions to obtain failure time data for reliability assessment. It can be costly and time consuming to obtain failure time data under normal operating conditions if the mean time to failure of a product is long. An alternative is to use failure time data from an accelerated life test (ALT) to extrapolate the reliability under normal conditions. In accelerated life testing, the units are placed under a higher than normal stress condition such as voltage, current, pressure, temperature, to make the items fail in a shorter period of time. The failure information is then transformed through an accelerated model commonly known as the time transformation function, to predict the reliability under normal operating conditions. The power law will be used as the time transformation function in this thesis. We will first consider a Bayesian inference model under the assumption that the underlying life distribution in the accelerated life test is exponentially distributed. The maximal data information (MDI) prior, the Ghosh Mergel and Liu (GML) prior and the Jeffreys prior will be derived for the exponential distribution. The propriety of the posterior distributions will be investigated. Results will be compared when using these non-informative priors in a simulation study by looking at the posterior variances. The Weibull distribution as the underlying life distribution in the accelerated life test will also be investigated. The maximal data information prior will be derived for the Weibull distribution using the power law. The uniform prior and a mixture of Gamma and uniform priors will be considered. The propriety of these posteriors will also be investigated. The predictive reliability at the use-stress will be computed for these models. The deviance information criterion will be used to compare these priors. As a result of using a time transformation function, Bayesian inference becomes analytically intractable and Markov Chain Monte Carlo (MCMC) methods will be used to alleviate this problem. The Metropolis-Hastings algorithm will be used to sample from the posteriors for the exponential model in the accelerated life test. The adaptive rejection sampling method will be used to sample from the posterior distributions when the Weibull model is considered.
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- Authors: Izally, Sharkay Ruwade
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3003 , vital:20351
- Description: Reliability life testing is used for life data analysis in which samples are tested under normal conditions to obtain failure time data for reliability assessment. It can be costly and time consuming to obtain failure time data under normal operating conditions if the mean time to failure of a product is long. An alternative is to use failure time data from an accelerated life test (ALT) to extrapolate the reliability under normal conditions. In accelerated life testing, the units are placed under a higher than normal stress condition such as voltage, current, pressure, temperature, to make the items fail in a shorter period of time. The failure information is then transformed through an accelerated model commonly known as the time transformation function, to predict the reliability under normal operating conditions. The power law will be used as the time transformation function in this thesis. We will first consider a Bayesian inference model under the assumption that the underlying life distribution in the accelerated life test is exponentially distributed. The maximal data information (MDI) prior, the Ghosh Mergel and Liu (GML) prior and the Jeffreys prior will be derived for the exponential distribution. The propriety of the posterior distributions will be investigated. Results will be compared when using these non-informative priors in a simulation study by looking at the posterior variances. The Weibull distribution as the underlying life distribution in the accelerated life test will also be investigated. The maximal data information prior will be derived for the Weibull distribution using the power law. The uniform prior and a mixture of Gamma and uniform priors will be considered. The propriety of these posteriors will also be investigated. The predictive reliability at the use-stress will be computed for these models. The deviance information criterion will be used to compare these priors. As a result of using a time transformation function, Bayesian inference becomes analytically intractable and Markov Chain Monte Carlo (MCMC) methods will be used to alleviate this problem. The Metropolis-Hastings algorithm will be used to sample from the posteriors for the exponential model in the accelerated life test. The adaptive rejection sampling method will be used to sample from the posterior distributions when the Weibull model is considered.
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Geochemical exploration for copper - cobalt in the Democratic Republic of Congo, Central African Copperbelt: a case study on PR851
- Authors: Katombe-Kisumbule, Paul
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3035 , vital:20354
- Description: The PR851 licence area is located at about 80 km west from the town of Likasi in the district of Haut-Katanga and 175 km north-west of Lubumbashi, the capital city of Katanga Province in the Democratic Republic of Congo. The exploration licence was granted by the government of the Democratic Republic of Congo to First Quantum Minerals Ltd through its Congolese subsidiary Compagnie Minière de Sakania Sprl (CoMiSa Sprl) under certificate N˚ CAMI/CR/70/2003 on the 10th of October 2003 for a period of 5 years with a possibility of renewal for 3 years in respect to the new Congolese mining code. The PR851 area lies on fragments of Mines Subgroup rocks of the Roan Group in the Congolese Copperbelt where most of the Cu-Co and stratiform-stratabound deposits such as Kipushi, Ruashi-Etoile, Kinsevere, Kipoi, Luishya, Luswishi, Shituru, Kamoya, Kambove, Tenke- Fungurume, Shinkolobwe, Swambo, Mindingi and Kamoto among others are found. During the 20th century, the Union Minière du Haut Katanga (U.M.H.K.) undertook mineral exploration in the Congolese Copperbelt and numerous copper- and cobalt-occurrences were identified (for instance Kibamba copper occurrence in PR851 area). From 2003, the Compagnie Minière de Sakania Sprl initiated a grassroots exploration program in PR851 area and geochemical exploration survey as one of the mineral exploration tools was implemented to aim at detecting copper and cobalt concentration in soil. The B horizon of the thick tropical soil in the area was sampled and soil samples were sent to Genalysis laboratories in Johannesburg, Republic of South Africa for main chemical analysis of Cu and Co only, whereas 10% of analyzed samples were dispatched to Perth, Western Australia for quality control analysis. Thresholds for anomalies of copper and cobalt were defined by literature comparison, standard deviations and spatial analysis. The anomalies were tested at a later stage by reverse circulation / diamond drilling during the year of 2005 to 2008 and the Cu-Co resources were estimated by Digital Mining Services of Harare, Zimbabwe in the year of 2008. Geological logging of chips from reverse circulation and diamond drill cores revealed that copper mineralization is represented by malachite, chrysocolla, chalcopyrite and bornite whereas cobalt mineralization appeared in form of heterogenite. The source of supergene mineralization remains unknown. Recommendations have been made to undertake more geological exploration work in order to fully investigate the geological setting and structural architecture of the region, which may result in a better understanding of the Cu-Co mineralization system and ore genesis. The latter has been no consensus up-to-date and different theories have been proposed to discuss the ore genesis, including syn- and dia- genetic, synorogenic and sulphide remobilization to late-to-post- orogenic Cu-Zn-Pb Kipushi-type deposit. However, geological observations favored that the diagenetic and syngenetic models are applicable to numerous deposits in the Central African Copperbelt.
- Full Text:
- Authors: Katombe-Kisumbule, Paul
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3035 , vital:20354
- Description: The PR851 licence area is located at about 80 km west from the town of Likasi in the district of Haut-Katanga and 175 km north-west of Lubumbashi, the capital city of Katanga Province in the Democratic Republic of Congo. The exploration licence was granted by the government of the Democratic Republic of Congo to First Quantum Minerals Ltd through its Congolese subsidiary Compagnie Minière de Sakania Sprl (CoMiSa Sprl) under certificate N˚ CAMI/CR/70/2003 on the 10th of October 2003 for a period of 5 years with a possibility of renewal for 3 years in respect to the new Congolese mining code. The PR851 area lies on fragments of Mines Subgroup rocks of the Roan Group in the Congolese Copperbelt where most of the Cu-Co and stratiform-stratabound deposits such as Kipushi, Ruashi-Etoile, Kinsevere, Kipoi, Luishya, Luswishi, Shituru, Kamoya, Kambove, Tenke- Fungurume, Shinkolobwe, Swambo, Mindingi and Kamoto among others are found. During the 20th century, the Union Minière du Haut Katanga (U.M.H.K.) undertook mineral exploration in the Congolese Copperbelt and numerous copper- and cobalt-occurrences were identified (for instance Kibamba copper occurrence in PR851 area). From 2003, the Compagnie Minière de Sakania Sprl initiated a grassroots exploration program in PR851 area and geochemical exploration survey as one of the mineral exploration tools was implemented to aim at detecting copper and cobalt concentration in soil. The B horizon of the thick tropical soil in the area was sampled and soil samples were sent to Genalysis laboratories in Johannesburg, Republic of South Africa for main chemical analysis of Cu and Co only, whereas 10% of analyzed samples were dispatched to Perth, Western Australia for quality control analysis. Thresholds for anomalies of copper and cobalt were defined by literature comparison, standard deviations and spatial analysis. The anomalies were tested at a later stage by reverse circulation / diamond drilling during the year of 2005 to 2008 and the Cu-Co resources were estimated by Digital Mining Services of Harare, Zimbabwe in the year of 2008. Geological logging of chips from reverse circulation and diamond drill cores revealed that copper mineralization is represented by malachite, chrysocolla, chalcopyrite and bornite whereas cobalt mineralization appeared in form of heterogenite. The source of supergene mineralization remains unknown. Recommendations have been made to undertake more geological exploration work in order to fully investigate the geological setting and structural architecture of the region, which may result in a better understanding of the Cu-Co mineralization system and ore genesis. The latter has been no consensus up-to-date and different theories have been proposed to discuss the ore genesis, including syn- and dia- genetic, synorogenic and sulphide remobilization to late-to-post- orogenic Cu-Zn-Pb Kipushi-type deposit. However, geological observations favored that the diagenetic and syngenetic models are applicable to numerous deposits in the Central African Copperbelt.
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Characterisation of a plasmodium falciparum type II Hsp40 chaperone exported to the cytosol of infected erythrocytes
- Maphumulo, Philile Nompumelelo
- Authors: Maphumulo, Philile Nompumelelo
- Date: 2013
- Subjects: Erythrocytes , Heat shock proteins , Plasmodium falciparum , Molecular chaperones , Malaria -- Prevention -- Research , Protein folding , Proteins -- Analysis , Malaria -- Immunological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4128 , http://hdl.handle.net/10962/d1015681
- Description: Heat Shock 40 kDa proteins (Hsp40s) partner with heat shock 70 kDa proteins (Hsp70s) in facilitating, among other chaperone activities; correct protein transport, productive protein folding and assembly within the cells; under both normal and stressful conditions. Hsp40 proteins regulate the ATPase activity of Hsp70 through interaction with the J-domain. Plasmodium falciparum Hsp70s (PfHsp70s) do not contain a Plasmodium export element (PEXEL) sequence although PfHsp70-1 and PfHsp70-3 have been located outside of the parasitophorous vacuole. Studies reveal that a type I P. falciparum (PfHsp40) chaperone (PF14_0359) stimulates the rate of ATP hydrolysis of the cytosolic PfHsp70 (PfHsp70-1) and that of human Hsp70A1A. PFE0055c is a PEXEL-bearing type II Hsp40 that is exported into the cytosol of P. falciparum-infected erythrocytes; where it potentially interacts with human Hsp70. Studies reveal that PFE0055c associates with structures found in the erythrocyte cytosol termed “J-dots” which are believed to be involved in trafficking parasite-encoded proteins through the erythrocyte cytosol. If P. falciparum exports PFE0055c into the host cytosol, it may be proposed that it interacts with human Hsp70, making it a possible drug target. The effect of PFE0055c on the ATPase activity of human Hsp70A1A has not been previously characterised. Central to this study was bioinformatic analysis and biochemical characterisation PFE0055c using an in vitro (ATPase assay) approach. Structural domains that classify PFE0055c as a type II Hsp40 were identified with similarity to two other exported type II PfHsp40s. Plasmids encoding the hexahistidine-tagged versions of PFE0055c and human Hsp70A1A were used for the expression and purification of these proteins from Escherichia coli. Purification was achieved using nickel affinity chromatography. The urea-denaturing method was used to obtain the purified PFE0055c whilst human Hsp70A1A was purified using the native method. PFE0055c could stimulate the ATPase activity of alfalfa Hsp70, although such was not the case for human Hsp70A1A in vitro.
- Full Text:
- Authors: Maphumulo, Philile Nompumelelo
- Date: 2013
- Subjects: Erythrocytes , Heat shock proteins , Plasmodium falciparum , Molecular chaperones , Malaria -- Prevention -- Research , Protein folding , Proteins -- Analysis , Malaria -- Immunological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4128 , http://hdl.handle.net/10962/d1015681
- Description: Heat Shock 40 kDa proteins (Hsp40s) partner with heat shock 70 kDa proteins (Hsp70s) in facilitating, among other chaperone activities; correct protein transport, productive protein folding and assembly within the cells; under both normal and stressful conditions. Hsp40 proteins regulate the ATPase activity of Hsp70 through interaction with the J-domain. Plasmodium falciparum Hsp70s (PfHsp70s) do not contain a Plasmodium export element (PEXEL) sequence although PfHsp70-1 and PfHsp70-3 have been located outside of the parasitophorous vacuole. Studies reveal that a type I P. falciparum (PfHsp40) chaperone (PF14_0359) stimulates the rate of ATP hydrolysis of the cytosolic PfHsp70 (PfHsp70-1) and that of human Hsp70A1A. PFE0055c is a PEXEL-bearing type II Hsp40 that is exported into the cytosol of P. falciparum-infected erythrocytes; where it potentially interacts with human Hsp70. Studies reveal that PFE0055c associates with structures found in the erythrocyte cytosol termed “J-dots” which are believed to be involved in trafficking parasite-encoded proteins through the erythrocyte cytosol. If P. falciparum exports PFE0055c into the host cytosol, it may be proposed that it interacts with human Hsp70, making it a possible drug target. The effect of PFE0055c on the ATPase activity of human Hsp70A1A has not been previously characterised. Central to this study was bioinformatic analysis and biochemical characterisation PFE0055c using an in vitro (ATPase assay) approach. Structural domains that classify PFE0055c as a type II Hsp40 were identified with similarity to two other exported type II PfHsp40s. Plasmids encoding the hexahistidine-tagged versions of PFE0055c and human Hsp70A1A were used for the expression and purification of these proteins from Escherichia coli. Purification was achieved using nickel affinity chromatography. The urea-denaturing method was used to obtain the purified PFE0055c whilst human Hsp70A1A was purified using the native method. PFE0055c could stimulate the ATPase activity of alfalfa Hsp70, although such was not the case for human Hsp70A1A in vitro.
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Evolution of the UG2 unit, Bushveld Complex, South Africa : mineral composition and petrological evidence
- Authors: Everitt, Simon James
- Date: 2013
- Subjects: Textures -- South Africa -- Bushveld Complex Petrology -- South Africa -- Bushveld Complex Chromite -- South Africa -- Bushveld Complex Mineralogy -- South Africa -- Bushveld Complex
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4913 , http://hdl.handle.net/10962/d1001573
- Description: Several disequilibrium textures are found to occur within the hanging wall and footwall of the UG2 chromitite layer of the Bushveld Complex, South Africa. These textures include plagioclase chadacrysts found included within orthopyroxene and clinopyroxene as well as the orthopyroxenes exhibiting round crystal boundaries that appear to be resorbed. Textures found within the UG2 stratigraphy such as linear boundaries and 120° triple junctions at interfaces of adjacent plagioclase or pyroxene grains also suggest that recrystallization has taken place. The presence of both disequilibrium textures and recrystallization textures would suggest that a complex emplacement history has occurred. Ideally, this would be expected to be manifested by minerals of the same type but which are texturally distinct showing different composition. However this has been found not to be the case; minerals that suggest disequilibrium textures show similar compositions to the minerals which appear to have formed in equilibrium. This is also the same for recrystallized crystals which show the same compositions as crystals that have not been recrystallized. For example tabular clinopyroxene, which has a compositional range of En 44.6 to En 50.5, is indistinguishable from clinopyroxene occuring as discontinuous rims, En 44.3-48.2, and as intergranular necking connecting primocrysts of orthopyroxene ( En 44.3-50.4). Similarly, plagioclase occurring as inclusions with An 66.3-76.0 is indistinguishable from plagioclase occurring as zoned or recrystallized interstitial grains ( An 69.0- An 77.4). Compositional variation has however, been found to be controlled to an extent by stratigraphy in that minerals show different compositions within one layer to the same minerals within another layer, consistent with an evolving magma composition. It is concluded therefore that while composition is not texturally controlled it is to an extent stratigraphy controlled and that the evidence collected within the study supports two models for the formation of chromite within the Bushveld complex. The evidence is consistent with a combination of the magma mixing model and magma injection model to account for the textures and compositional variations found within the study. The evidence may also show support for models involving late modification of minerals by magmatic fluids but not as prominently as for the models mentioned above , Microsoft� Word 2010 , Adobe Acrobat 9.53 Paper Capture Plug-in
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- Authors: Everitt, Simon James
- Date: 2013
- Subjects: Textures -- South Africa -- Bushveld Complex Petrology -- South Africa -- Bushveld Complex Chromite -- South Africa -- Bushveld Complex Mineralogy -- South Africa -- Bushveld Complex
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4913 , http://hdl.handle.net/10962/d1001573
- Description: Several disequilibrium textures are found to occur within the hanging wall and footwall of the UG2 chromitite layer of the Bushveld Complex, South Africa. These textures include plagioclase chadacrysts found included within orthopyroxene and clinopyroxene as well as the orthopyroxenes exhibiting round crystal boundaries that appear to be resorbed. Textures found within the UG2 stratigraphy such as linear boundaries and 120° triple junctions at interfaces of adjacent plagioclase or pyroxene grains also suggest that recrystallization has taken place. The presence of both disequilibrium textures and recrystallization textures would suggest that a complex emplacement history has occurred. Ideally, this would be expected to be manifested by minerals of the same type but which are texturally distinct showing different composition. However this has been found not to be the case; minerals that suggest disequilibrium textures show similar compositions to the minerals which appear to have formed in equilibrium. This is also the same for recrystallized crystals which show the same compositions as crystals that have not been recrystallized. For example tabular clinopyroxene, which has a compositional range of En 44.6 to En 50.5, is indistinguishable from clinopyroxene occuring as discontinuous rims, En 44.3-48.2, and as intergranular necking connecting primocrysts of orthopyroxene ( En 44.3-50.4). Similarly, plagioclase occurring as inclusions with An 66.3-76.0 is indistinguishable from plagioclase occurring as zoned or recrystallized interstitial grains ( An 69.0- An 77.4). Compositional variation has however, been found to be controlled to an extent by stratigraphy in that minerals show different compositions within one layer to the same minerals within another layer, consistent with an evolving magma composition. It is concluded therefore that while composition is not texturally controlled it is to an extent stratigraphy controlled and that the evidence collected within the study supports two models for the formation of chromite within the Bushveld complex. The evidence is consistent with a combination of the magma mixing model and magma injection model to account for the textures and compositional variations found within the study. The evidence may also show support for models involving late modification of minerals by magmatic fluids but not as prominently as for the models mentioned above , Microsoft� Word 2010 , Adobe Acrobat 9.53 Paper Capture Plug-in
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