The morphology and biology of Anomala vetula Wied : an arthropod pest of turf in South Africa
- Authors: Bradford, B
- Date: 1946
- Subjects: Anomala
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5903 , http://hdl.handle.net/10962/d1013545
- Description: From Introduction: For the past eight years, the Zoology Department of Rhodes University College, in co-operation with African Explosives & Chemical Industries Ltd., has been studying certain entomological problems relating to turf on the golf course along the coastal belt of the Eastern Cape Province. The position is briefly as follows:- On the golf courses at Mossel Bay, Humewood (Port Elizabeth), Port Alfred and East London, vast damage has been done to the greens and fairways by "white grubs", the larval stages of Scarabaeidae. It would appear that these beetles had been present in the environs of the courses for many years, but it was only when large areas of the natural veld were converted into fairways, with a more or less uniform cover of grass, with Cynodon dactylon Pers. predominating, that conditions were inadvertently created which favoured the development of the beetles. It was not long after the establishment of these golf courses, that the beetles assumed the proportions of a pest, and the larvae began destroying the root system of the grasses covering the greens and fairways.
- Full Text:
- Date Issued: 1946
- Authors: Bradford, B
- Date: 1946
- Subjects: Anomala
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5903 , http://hdl.handle.net/10962/d1013545
- Description: From Introduction: For the past eight years, the Zoology Department of Rhodes University College, in co-operation with African Explosives & Chemical Industries Ltd., has been studying certain entomological problems relating to turf on the golf course along the coastal belt of the Eastern Cape Province. The position is briefly as follows:- On the golf courses at Mossel Bay, Humewood (Port Elizabeth), Port Alfred and East London, vast damage has been done to the greens and fairways by "white grubs", the larval stages of Scarabaeidae. It would appear that these beetles had been present in the environs of the courses for many years, but it was only when large areas of the natural veld were converted into fairways, with a more or less uniform cover of grass, with Cynodon dactylon Pers. predominating, that conditions were inadvertently created which favoured the development of the beetles. It was not long after the establishment of these golf courses, that the beetles assumed the proportions of a pest, and the larvae began destroying the root system of the grasses covering the greens and fairways.
- Full Text:
- Date Issued: 1946
Some comparative studies of the fauna in soils developed under natural forest, pine and bluegum
- Watts, John Christopher David
- Authors: Watts, John Christopher David
- Date: 1952
- Subjects: Soil science , Forest ecology , Soil animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5895 , http://hdl.handle.net/10962/d1013423
- Description: [From Introduction] It has been said that, "If a nation saves its trees, the trees will save the nation." The truth of this assertion is apparent in many parts of the world today. In South Africa, fires and demands in the past for timber have led to extensive depletion of the Natural Forests. In many cases, natural revegetation has been slow to develop and deterioration of the soil has resulted. The desire to replace the tree cover and at the same time to meet an increasing internal demand for timber, has led to widespread planting of Pine and Bluegum. It is probable that more trees have now been planted than were destroyed in the past. The silviculturist however, who develops a pure stand on land which previously supported the mixed stand, should anticipate a change in soil properties as a natural accompaniment of such an undertaking. The nature of this change is the primum mobile of the present comparative study. The forest soils studied were taken in the Cape Province in the following areas:- Grahamstown; Amatola Mountains, District Alice; Witte-els-Bosch, District Humansdorp, during the course of a year. The physical and chemical properties, and the faunal composition of the soil samples were examined in relation to the different tree covers. Because of the necessity of taking large numbers of samples and thorough examination of these to arrive at a definite conclusion, the work is necessarily incomplete. It is felt however that the results obtained justify a further study of this aspect of soil biology.
- Full Text:
- Date Issued: 1952
- Authors: Watts, John Christopher David
- Date: 1952
- Subjects: Soil science , Forest ecology , Soil animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5895 , http://hdl.handle.net/10962/d1013423
- Description: [From Introduction] It has been said that, "If a nation saves its trees, the trees will save the nation." The truth of this assertion is apparent in many parts of the world today. In South Africa, fires and demands in the past for timber have led to extensive depletion of the Natural Forests. In many cases, natural revegetation has been slow to develop and deterioration of the soil has resulted. The desire to replace the tree cover and at the same time to meet an increasing internal demand for timber, has led to widespread planting of Pine and Bluegum. It is probable that more trees have now been planted than were destroyed in the past. The silviculturist however, who develops a pure stand on land which previously supported the mixed stand, should anticipate a change in soil properties as a natural accompaniment of such an undertaking. The nature of this change is the primum mobile of the present comparative study. The forest soils studied were taken in the Cape Province in the following areas:- Grahamstown; Amatola Mountains, District Alice; Witte-els-Bosch, District Humansdorp, during the course of a year. The physical and chemical properties, and the faunal composition of the soil samples were examined in relation to the different tree covers. Because of the necessity of taking large numbers of samples and thorough examination of these to arrive at a definite conclusion, the work is necessarily incomplete. It is felt however that the results obtained justify a further study of this aspect of soil biology.
- Full Text:
- Date Issued: 1952
A preliminary investigation of the ecology of the Larger Kleinmond River Estuary, Bathurst District
- Brown, Alexander Claude, 1931-2005
- Authors: Brown, Alexander Claude, 1931-2005
- Date: 1953
- Subjects: Kleinemonde River Estuary (South Africa) , Estuaries -- South Africa , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5904 , http://hdl.handle.net/10962/d1014611
- Description: Introduction. On the coast of the Bathurst Division, Eastern Cape Province, some 42 miles south- east of Grahamstown, lie two estuaries opening within a few yards of one another. These are known as the Kleinemonde. This paper embodies the results of an ecological survey of the fauna of the Larger Kleinmond Estuary. The chief concern has been the aquatic fauna but animals living along the banks have also been dealt with as far as possible, as have the birds. This is the second of South Africa's blind estuaries to be studied, the Klein River, Hermanus, having been investigated in 1947-49 by workers from the University of Cape Town. Though common in South Africa, blind estuaries are rare in parts of the world such as Europe, and present an almost entirely new field of research for the ecologist. It is hoped, therefore, that the investigation of the Kleinmond Estuary and a comparison with the results obtained from the Klein River, Hermanus, will add to our knowledge of this subject and be of service to future investigators. The history of the Kleimnond River is worthy of mention, for the lagoon was not always blind and shallow. The early maps of the 1820 settlers show the river as a navigable stream; sailing vessels anchored out at sea and sent lighters up what was then known as the Lydendoch River to collect fresh meat. The area at the mouth of the river was called Port Jessie. In these early days the region abounded with game. Hippo and elephant were common. the former inhabiting deep pools in the upper reaches of the river; pools which have since completely silted up. Constant ploughing of the slopes adjoining the river has caused vast amounts of soil to be washed by rains into the stream, and today what was within living memory a deep, clear stream is a shallow, blind and muddy river, a reflection of man's destructive methods of farming. These changes must have had a far-reaching effect on the fauna of the estuary; an effect about which we can, alas, only speculate. It is perhaps significant that though rich in numbers, the fauna is poor in species, tunicates and echinoderms being apparently entirely absent. The work involved in this survey was undertaken between September 1952 and November 1953, under the direction of Professor J . Omer-Cooper of Rhodes University, frequent and regular visits being made to the estuary. The entire month of February, 1953, was spent on the shore of the lagoon, so that animals could be observed over a continuous period. The starting date of the survey was particularly fortunate, as on September 28th, 1952, the river came down in flood and broke through the sand-bar separating the lagoon from the sea. The work thus began at a definite point in the estuarine cycle, the importance of which it is hoped to show.
- Full Text:
- Date Issued: 1953
- Authors: Brown, Alexander Claude, 1931-2005
- Date: 1953
- Subjects: Kleinemonde River Estuary (South Africa) , Estuaries -- South Africa , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5904 , http://hdl.handle.net/10962/d1014611
- Description: Introduction. On the coast of the Bathurst Division, Eastern Cape Province, some 42 miles south- east of Grahamstown, lie two estuaries opening within a few yards of one another. These are known as the Kleinemonde. This paper embodies the results of an ecological survey of the fauna of the Larger Kleinmond Estuary. The chief concern has been the aquatic fauna but animals living along the banks have also been dealt with as far as possible, as have the birds. This is the second of South Africa's blind estuaries to be studied, the Klein River, Hermanus, having been investigated in 1947-49 by workers from the University of Cape Town. Though common in South Africa, blind estuaries are rare in parts of the world such as Europe, and present an almost entirely new field of research for the ecologist. It is hoped, therefore, that the investigation of the Kleinmond Estuary and a comparison with the results obtained from the Klein River, Hermanus, will add to our knowledge of this subject and be of service to future investigators. The history of the Kleimnond River is worthy of mention, for the lagoon was not always blind and shallow. The early maps of the 1820 settlers show the river as a navigable stream; sailing vessels anchored out at sea and sent lighters up what was then known as the Lydendoch River to collect fresh meat. The area at the mouth of the river was called Port Jessie. In these early days the region abounded with game. Hippo and elephant were common. the former inhabiting deep pools in the upper reaches of the river; pools which have since completely silted up. Constant ploughing of the slopes adjoining the river has caused vast amounts of soil to be washed by rains into the stream, and today what was within living memory a deep, clear stream is a shallow, blind and muddy river, a reflection of man's destructive methods of farming. These changes must have had a far-reaching effect on the fauna of the estuary; an effect about which we can, alas, only speculate. It is perhaps significant that though rich in numbers, the fauna is poor in species, tunicates and echinoderms being apparently entirely absent. The work involved in this survey was undertaken between September 1952 and November 1953, under the direction of Professor J . Omer-Cooper of Rhodes University, frequent and regular visits being made to the estuary. The entire month of February, 1953, was spent on the shore of the lagoon, so that animals could be observed over a continuous period. The starting date of the survey was particularly fortunate, as on September 28th, 1952, the river came down in flood and broke through the sand-bar separating the lagoon from the sea. The work thus began at a definite point in the estuarine cycle, the importance of which it is hoped to show.
- Full Text:
- Date Issued: 1953
A study of the biology of the Jameson reservoir near Grahamstown, Cape Province
- Authors: Darbyshire, John Frederick
- Date: 1959
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/6784 , vital:21179
- Description: 1. This thesis is an ecological study of a South African water storage reservoir and it’s tributary streams. 2. A brief description of the reservoir, the surrounding vegetation, superficial geological strata, soils and early history of the reservoir is given in Chapter I. 3. The surrounding vegetation is discussed in some detail in Chapter II. The zonation of the plants and the influence of water upon it are discussed. 4. The results of the regular investigations of the physicochemical environment are presented in Appendix 1 and the salient points noted in Chapter III. 5. The species of algae collected are listed in Appendix 2 and in Chapter IV are discussed in relation to habitat and abundance. 6. The animals are dealt with in a similar manner in Chapter V. Under 'Discussion and Conclusions' in Chapter VI an attempt is made to review the findings and discuss their significance.
- Full Text:
- Date Issued: 1959
- Authors: Darbyshire, John Frederick
- Date: 1959
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/6784 , vital:21179
- Description: 1. This thesis is an ecological study of a South African water storage reservoir and it’s tributary streams. 2. A brief description of the reservoir, the surrounding vegetation, superficial geological strata, soils and early history of the reservoir is given in Chapter I. 3. The surrounding vegetation is discussed in some detail in Chapter II. The zonation of the plants and the influence of water upon it are discussed. 4. The results of the regular investigations of the physicochemical environment are presented in Appendix 1 and the salient points noted in Chapter III. 5. The species of algae collected are listed in Appendix 2 and in Chapter IV are discussed in relation to habitat and abundance. 6. The animals are dealt with in a similar manner in Chapter V. Under 'Discussion and Conclusions' in Chapter VI an attempt is made to review the findings and discuss their significance.
- Full Text:
- Date Issued: 1959
Studies on the effects of microclimates on the distribution of larval ticks in the Eastern Cape Province
- Authors: Kraft, Mary Kay
- Date: 1962
- Subjects: Ticks -- South Africa -- Eastern Cape , Ticks -- Ecology -- South Africa -- Eastern Cape , Ticks -- South Africa -- Eastern Cape -- Geographical distribution , Ticks -- Control -- South Africa -- Eastern Cape , Ixodidae -- South Africa -- Eastern Cape , Microclimatology -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5898 , http://hdl.handle.net/10962/d1013469
- Description: 1. In studying the effects of micro-climates on the distribution of larval ticks in the Eastern Cape Province four species were considered, namely, Boophilus decoloratus (Koch), Rhipicephalus evertsi (Neu), Amblyomma hebraeum (Koch) and Ixodes pilosus (Koch). 2. Three types of investigation were made:- i) autumn and spring surveys of the distribution of larval clusters, which were assumed to be close to positions in which egg-masses had been laid. - (Four species); ii) observations on the survival and development of eggs and engorged female ticks in microclimatically distinct field plots. - (Four species); iii) observations on the behaviour of the larvae and of the engorged female ticks. - (B. decoloratus). 3. The survey and plot data suggest that in autumn larval clusters of I. pilosus were to be found only in well-shaded situations because more exposed places were micro-climatically unfavourable to the survival of earlier stages. 4. The surveys show that in spring 1957 larval clusters of I. pilosus were to be found in unshaded, as well as in shaded, situations. 5. The survey and plot data indicate that the winter of 1957 was not favourable to the development of larvae of B. decoloratus, and that in spring new larval clusters may be expected to appear first in the warmest situations and later in the generally cooler places. 6. The plot data show that during hot and dry periods exposed situations were unfavourable to tho engorged females and eggs of all four species considered, but that during such periods these stages could sometimes survive in well-shaded places. 7. The survey and plot data show that in autumn and in spring larval clusters of B. decoloratus and R. evertsi may be present in unshaded situations. 8. The plot investigations provide little information about the distribution of larval clusters of A. hebraeum, but the survey data suggest that it is not remarkably different from that of B. decaloratus and R. evertsi. 9. There is a discrepancy in the survey and plot data: the surveys show that larval clusters of R. evertsi, and B. decoloratus were rare or absent from well-shaded situations, whereas tho plot data suggest such situations were micro-climatically favourable to larval developmcnt during the months preceding Autumn. 10. The observations on the behaviour of larvae and engorged females of B. decoloratus provide information which suggests that the behaviour of those stages may account for the rarity of larval clusters in well-shaded places. 11. The relative density of larval clusters of B. decoloratus is evidently also affected by factors other than micro-climate . The dropping- off behaviour of engorged female ticks appears to be possibly important in this.
- Full Text:
- Date Issued: 1962
- Authors: Kraft, Mary Kay
- Date: 1962
- Subjects: Ticks -- South Africa -- Eastern Cape , Ticks -- Ecology -- South Africa -- Eastern Cape , Ticks -- South Africa -- Eastern Cape -- Geographical distribution , Ticks -- Control -- South Africa -- Eastern Cape , Ixodidae -- South Africa -- Eastern Cape , Microclimatology -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5898 , http://hdl.handle.net/10962/d1013469
- Description: 1. In studying the effects of micro-climates on the distribution of larval ticks in the Eastern Cape Province four species were considered, namely, Boophilus decoloratus (Koch), Rhipicephalus evertsi (Neu), Amblyomma hebraeum (Koch) and Ixodes pilosus (Koch). 2. Three types of investigation were made:- i) autumn and spring surveys of the distribution of larval clusters, which were assumed to be close to positions in which egg-masses had been laid. - (Four species); ii) observations on the survival and development of eggs and engorged female ticks in microclimatically distinct field plots. - (Four species); iii) observations on the behaviour of the larvae and of the engorged female ticks. - (B. decoloratus). 3. The survey and plot data suggest that in autumn larval clusters of I. pilosus were to be found only in well-shaded situations because more exposed places were micro-climatically unfavourable to the survival of earlier stages. 4. The surveys show that in spring 1957 larval clusters of I. pilosus were to be found in unshaded, as well as in shaded, situations. 5. The survey and plot data indicate that the winter of 1957 was not favourable to the development of larvae of B. decoloratus, and that in spring new larval clusters may be expected to appear first in the warmest situations and later in the generally cooler places. 6. The plot data show that during hot and dry periods exposed situations were unfavourable to tho engorged females and eggs of all four species considered, but that during such periods these stages could sometimes survive in well-shaded places. 7. The survey and plot data show that in autumn and in spring larval clusters of B. decoloratus and R. evertsi may be present in unshaded situations. 8. The plot investigations provide little information about the distribution of larval clusters of A. hebraeum, but the survey data suggest that it is not remarkably different from that of B. decaloratus and R. evertsi. 9. There is a discrepancy in the survey and plot data: the surveys show that larval clusters of R. evertsi, and B. decoloratus were rare or absent from well-shaded situations, whereas tho plot data suggest such situations were micro-climatically favourable to larval developmcnt during the months preceding Autumn. 10. The observations on the behaviour of larvae and engorged females of B. decoloratus provide information which suggests that the behaviour of those stages may account for the rarity of larval clusters in well-shaded places. 11. The relative density of larval clusters of B. decoloratus is evidently also affected by factors other than micro-climate . The dropping- off behaviour of engorged female ticks appears to be possibly important in this.
- Full Text:
- Date Issued: 1962
The geology of the Vaal Reefs Gold Mine, Western Transvaal
- Authors: Jacob, Roger E
- Date: 1966
- Subjects: Vaal reefs gold mine , Gold ores -- Geology -- South Africa -- Transvaal. , Geology -- South Africa -- Transvaal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5078 , http://hdl.handle.net/10962/d1015171
- Description: Rocks forming part of the Main-Bird Series and the Kimberley-Elsburg Series of the Upper Division of the Witwatersrand System are found in the mine. The sequence studied starts with the Middle or MB 6 Zone of the Livingstone Stage followed by the Upper or MB 5 Zone. The Vaal Roof, forming the base of the Vaal Stage, rests disconformably on the older rocks. The Stage is subdivided into the Vaal Reef Zone, the Lower Vaal Zone, the Argillaceous Zone and the Upper Vaal Zone. The lower and upper contacts of the Argillaceous Zone are gradational. The Kimberley Stage follows unconformably and comprises the basal Gold Estates Conglomerate Zone, the Denny's Zone and the Gold Estates Zone. The overlying Elsburg Stage may be subdivided into the Bastard Zone and the Upper Elsburg Zone on lithological grounds. Most of the rocks are indurated quartz wackes with only a few orthoquartzite horizons such as the Denny's Zone and the immediate hangingwall of the Vaal Reef. Microscopically the rocks consist of detrital quartz and chert grains in a fine-grained sericitic to partly siliceous matrix which may constitute more than 50 per cent of the rock. Heavy minerals, such as zircon, chromite, rutile, leucoxone, pyrite, tourmaline, epidete, apetite and magnetite, occur in most of the zones. The Vaal Reef, the economic horizon, is of small-pebble, oligomictic conglomerate, often containing thucholite seams and granules, and varying in thickness from a mere parting to more than five feet. There appears to be a correlation between greater pebble size and higher ore grade but no correlation of sorting coefficients and gold value. The mineralogy of the Vaal Reef was studied by means of polished sections and heavy mineral concentrates. The minerals identified include gold, pyrite of several ages, pyrrhotite, chalcopyrite, uraninite, galena, brannerite, gersdorffite or cobaltite, skutterudite, linnacite, danaite, niccolite, pentlandite, magnotite, zircon, chromite, rutile, leucoxine, monazite, sphalerite, tourmaline, and fluorite. From a study of the silver content of gold in the Vaal Roof it is concluded that the variations in apparent fineness are a reflection of the composition of the gold in the original source rocks. There is a definite uranium-gold relationship in the Vaal Roof. With increase in grade the amount of U₃O₈ increases but the U₃O₈:AU ratio decreases. Use of these reations may indciate the payability in cases of incomplete core recovery.The intrusive rocks were studies in detail. Six types of intrusive rocks were found. From oldest to youngest those are quartz diabase (of three varieties), amygdaloidal diabase, ilmenite mela-microdiorite, mottled microdiorite, olivine lamprophyre and ankeritic beforsite, ranging in age from Lower Ventersdorp to post-Karroo. Most of the intrusives are highly altered due to the effects of regional metamorphism and deuteric alteration. Later formations, such as the Langgeleven and Allanridge Formations of the Ventersdorp System and the Black Roof and Dolomite Series of the Transvaal System, occur on the property. The various formations have been subjected to faulting and folding.
- Full Text:
- Date Issued: 1966
- Authors: Jacob, Roger E
- Date: 1966
- Subjects: Vaal reefs gold mine , Gold ores -- Geology -- South Africa -- Transvaal. , Geology -- South Africa -- Transvaal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5078 , http://hdl.handle.net/10962/d1015171
- Description: Rocks forming part of the Main-Bird Series and the Kimberley-Elsburg Series of the Upper Division of the Witwatersrand System are found in the mine. The sequence studied starts with the Middle or MB 6 Zone of the Livingstone Stage followed by the Upper or MB 5 Zone. The Vaal Roof, forming the base of the Vaal Stage, rests disconformably on the older rocks. The Stage is subdivided into the Vaal Reef Zone, the Lower Vaal Zone, the Argillaceous Zone and the Upper Vaal Zone. The lower and upper contacts of the Argillaceous Zone are gradational. The Kimberley Stage follows unconformably and comprises the basal Gold Estates Conglomerate Zone, the Denny's Zone and the Gold Estates Zone. The overlying Elsburg Stage may be subdivided into the Bastard Zone and the Upper Elsburg Zone on lithological grounds. Most of the rocks are indurated quartz wackes with only a few orthoquartzite horizons such as the Denny's Zone and the immediate hangingwall of the Vaal Reef. Microscopically the rocks consist of detrital quartz and chert grains in a fine-grained sericitic to partly siliceous matrix which may constitute more than 50 per cent of the rock. Heavy minerals, such as zircon, chromite, rutile, leucoxone, pyrite, tourmaline, epidete, apetite and magnetite, occur in most of the zones. The Vaal Reef, the economic horizon, is of small-pebble, oligomictic conglomerate, often containing thucholite seams and granules, and varying in thickness from a mere parting to more than five feet. There appears to be a correlation between greater pebble size and higher ore grade but no correlation of sorting coefficients and gold value. The mineralogy of the Vaal Reef was studied by means of polished sections and heavy mineral concentrates. The minerals identified include gold, pyrite of several ages, pyrrhotite, chalcopyrite, uraninite, galena, brannerite, gersdorffite or cobaltite, skutterudite, linnacite, danaite, niccolite, pentlandite, magnotite, zircon, chromite, rutile, leucoxine, monazite, sphalerite, tourmaline, and fluorite. From a study of the silver content of gold in the Vaal Roof it is concluded that the variations in apparent fineness are a reflection of the composition of the gold in the original source rocks. There is a definite uranium-gold relationship in the Vaal Roof. With increase in grade the amount of U₃O₈ increases but the U₃O₈:AU ratio decreases. Use of these reations may indciate the payability in cases of incomplete core recovery.The intrusive rocks were studies in detail. Six types of intrusive rocks were found. From oldest to youngest those are quartz diabase (of three varieties), amygdaloidal diabase, ilmenite mela-microdiorite, mottled microdiorite, olivine lamprophyre and ankeritic beforsite, ranging in age from Lower Ventersdorp to post-Karroo. Most of the intrusives are highly altered due to the effects of regional metamorphism and deuteric alteration. Later formations, such as the Langgeleven and Allanridge Formations of the Ventersdorp System and the Black Roof and Dolomite Series of the Transvaal System, occur on the property. The various formations have been subjected to faulting and folding.
- Full Text:
- Date Issued: 1966
Aspects of the ecology of piscivorous birds of Lake Kyle Rhodesia
- Authors: Junor, F J R
- Date: 1969
- Subjects: Bird populations -- Zimbabwe , Water birds -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5909 , http://hdl.handle.net/10962/d1015201
- Description: [From Introduction]. From an early period in the lake's history research was undataken to determine the potential of Kyle as a source of edible fish, In such a study, knowledge of the number and weight of fish consumed by piscivorous birds would seem to be an obvious consideration. Accordingly special investigation was undertaken into the food requirements of fish eating birds which live in the lake area. The method employed, on this occasion, to obtain the required information has differed radically from that more generally used by investigators working with similar objects in view. The common practise has been to examine the stomach contents of a considerable number of birds of the same species, which have been destroyed in order to make information available.
- Full Text:
- Date Issued: 1969
- Authors: Junor, F J R
- Date: 1969
- Subjects: Bird populations -- Zimbabwe , Water birds -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5909 , http://hdl.handle.net/10962/d1015201
- Description: [From Introduction]. From an early period in the lake's history research was undataken to determine the potential of Kyle as a source of edible fish, In such a study, knowledge of the number and weight of fish consumed by piscivorous birds would seem to be an obvious consideration. Accordingly special investigation was undertaken into the food requirements of fish eating birds which live in the lake area. The method employed, on this occasion, to obtain the required information has differed radically from that more generally used by investigators working with similar objects in view. The common practise has been to examine the stomach contents of a considerable number of birds of the same species, which have been destroyed in order to make information available.
- Full Text:
- Date Issued: 1969
Ecological studies on the non-parasitic larval stages of some tick species in the Eastern Cape Province of South Africa (Acarina : ixodidae)
- Londt, Jason G. H. (Jason Gilbert Hayden), 1943-
- Authors: Londt, Jason G. H. (Jason Gilbert Hayden), 1943-
- Date: 1971
- Subjects: Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5862 , http://hdl.handle.net/10962/d1012777 , Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Description: "Ticks have already been studied in our country and abroad. Progress in the field of taxonomy has probably been the most rapid and has culminated in a large number of papers and excellent monographs, but much more remains to be done. To produce an overall picture of the factors influencing the behaviour of the tick under natural conditions, studies have to be conducted on tick ecology and experimental physiology. We still have a lack of knowledge of host specificity, the selection of feeding sites on hosts and the nature of resistance to attacks by ticks. Because of the varied habits of different species of ticks, the first essential prerequisite is an adequate knowledge of their biology." (Jansen 1969). The above words sum up the position of research on ticks in southern Africa at the present time.
- Full Text:
- Date Issued: 1971
- Authors: Londt, Jason G. H. (Jason Gilbert Hayden), 1943-
- Date: 1971
- Subjects: Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5862 , http://hdl.handle.net/10962/d1012777 , Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Description: "Ticks have already been studied in our country and abroad. Progress in the field of taxonomy has probably been the most rapid and has culminated in a large number of papers and excellent monographs, but much more remains to be done. To produce an overall picture of the factors influencing the behaviour of the tick under natural conditions, studies have to be conducted on tick ecology and experimental physiology. We still have a lack of knowledge of host specificity, the selection of feeding sites on hosts and the nature of resistance to attacks by ticks. Because of the varied habits of different species of ticks, the first essential prerequisite is an adequate knowledge of their biology." (Jansen 1969). The above words sum up the position of research on ticks in southern Africa at the present time.
- Full Text:
- Date Issued: 1971
The Birds' River dolerite complex
- Authors: Booth, P W K
- Date: 1971
- Subjects: Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5043 , http://hdl.handle.net/10962/d1007664 , Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Description: A plug-like intrusion of Karroo dolerite, near Dordrecht in the Eastern Cape of the Republic, is described. Field mapping with the, aid of aerial photographs has revealed that the contact of the intrusion, for the most part, dips very steeply outwards. In the south- eastern and eastern areas, however, sheet- or sill-like forms appear to be given off from the main intrusion. In plan view the intrusion is roughly oval shaped, its longer axis being aligned in a north-westerly direction. Its surface area measures approximately 60 square kilometres (24 square miles). A large number of xenoliths composed exclusively of Stormberg sediments, pyroclastic rocks and minor lavas, are to be found cropping out within the dolerite intrusion. These xenoliths, many of which occur in positions far above or below their normal stratigraphic elevation, are extremely variable in size - the largest having an area of approximately 15 square kilometres (6 square miles). The xenoliths represent fragments of the original "roof" of sediments and pyroclastics which have collapsed into and been engulfed by the dolerite magma. This type of dolerite intrusion is known as a "belljar" intrusion. A superficial classification of the dolerites, based chiefly on textural and certain mineralogical features, is presented. In the area surrounding the main intrusion are a number of dolerite dikes and sheets. The youngest phase of igneous activity is represented by the Dragon's Back dike, which cuts across the complex in a north-westerly direction. Several veining phenomena, as well as an interesting variety of metamorphic and metasomatic rocks, are associated with the main dolerite intrusion. Six diatremes are situated in the vicinity of the intrusion. Pyroclastic rocks are represented by a variety of types, and are to be found outside the area of the intrusion, and as xenoliths within it. A tentative interpretation of the mechanism of formation of the intrusion, which appears to be related to volcanic activity and cauldron subsidence, is presented.
- Full Text:
- Date Issued: 1971
- Authors: Booth, P W K
- Date: 1971
- Subjects: Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5043 , http://hdl.handle.net/10962/d1007664 , Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Description: A plug-like intrusion of Karroo dolerite, near Dordrecht in the Eastern Cape of the Republic, is described. Field mapping with the, aid of aerial photographs has revealed that the contact of the intrusion, for the most part, dips very steeply outwards. In the south- eastern and eastern areas, however, sheet- or sill-like forms appear to be given off from the main intrusion. In plan view the intrusion is roughly oval shaped, its longer axis being aligned in a north-westerly direction. Its surface area measures approximately 60 square kilometres (24 square miles). A large number of xenoliths composed exclusively of Stormberg sediments, pyroclastic rocks and minor lavas, are to be found cropping out within the dolerite intrusion. These xenoliths, many of which occur in positions far above or below their normal stratigraphic elevation, are extremely variable in size - the largest having an area of approximately 15 square kilometres (6 square miles). The xenoliths represent fragments of the original "roof" of sediments and pyroclastics which have collapsed into and been engulfed by the dolerite magma. This type of dolerite intrusion is known as a "belljar" intrusion. A superficial classification of the dolerites, based chiefly on textural and certain mineralogical features, is presented. In the area surrounding the main intrusion are a number of dolerite dikes and sheets. The youngest phase of igneous activity is represented by the Dragon's Back dike, which cuts across the complex in a north-westerly direction. Several veining phenomena, as well as an interesting variety of metamorphic and metasomatic rocks, are associated with the main dolerite intrusion. Six diatremes are situated in the vicinity of the intrusion. Pyroclastic rocks are represented by a variety of types, and are to be found outside the area of the intrusion, and as xenoliths within it. A tentative interpretation of the mechanism of formation of the intrusion, which appears to be related to volcanic activity and cauldron subsidence, is presented.
- Full Text:
- Date Issued: 1971
A contribution to the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa
- Authors: Bruton, Michael N
- Date: 1973
- Subjects: Cichlids , Tilapia , Mozambique tilapia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5839 , http://hdl.handle.net/10962/d1009950 , Cichlids , Tilapia , Mozambique tilapia
- Description: An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Previous work on Tilapia in Lake Sibaya is reviewed. Apart from brief gillnet surveys, which recorded the species' presence, no research on T. mossambica had been performed at Lake Sibaya before the two-year study of Minshull who collected data on food preferences, depth distribution of juveniles and breeding biology of adults. The main physiographical features of the lake are outlined. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1-7 m deep. Adult fishes (over 8 cm SL) are usually absent from water deeper than 12 m and shallower than 0.5 m, whereas juveniles may occur at all depths, and fry only in very shallow water. T. mossambica inhabits the littoral in the warm and transition periods (August to April) but moves into deep water in the cool season (May to July). Exposed and sheltered shallow areas are utilised for different purposes by adult fishes, the former for nesting, and the latter for feeding and mouth-brooding. Habitat selection by males was governed by nest site selection. Habitat Nests were most common in sheltered, sparsely vegetated littoral and sublittoral areas, but also present in well-vegetated sheltered areas. Breeding females preferred sheltered littoral areas but ventured onto the terrace to release the young. Juvenile and fry T. mossambica inhabited shallow exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour of T. mossambica is described, and integrated with data on T. mossambica from other systems. The breeding season spans seven months. Shoaling takes place in shallow water probably as a means of protection. T. mossambica is an omnivorous feeder relying largely on diatoms. The main predator is probably the barbel Clarias gariepinus, but avian predators may be more important. A method whereby the time of formation of rings on the scales of T. mossambica is described. The fishes were found to reach maturity after one year at a length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 14 cm (females) and 17 cm (males). The maximum final size was about 24 cm SL. An estimate of the standing crop for fishes in the littoral and subiittoral areas of the eastern and southern shores of the south basin is given. The data were derived from a mark and recapture The biology of T. mossambica in Lake Sibaya as revealed by the present study is discussed with reference to data on the same and similar species in other systems. The utilis ation of the available resources in the lake by T. mossambica is commented upon, and reference is made to the significance of stunting, and the import ance of the retention of generalised characters for the successful habitation of the cyclically-renewed habitat of the littoral. Precocious breeding in T. mossambica is regarded as a functional adaptation which increases the proportion of fishes small enough to utilise the rich food resources in shallow water.
- Full Text:
- Date Issued: 1973
- Authors: Bruton, Michael N
- Date: 1973
- Subjects: Cichlids , Tilapia , Mozambique tilapia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5839 , http://hdl.handle.net/10962/d1009950 , Cichlids , Tilapia , Mozambique tilapia
- Description: An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Previous work on Tilapia in Lake Sibaya is reviewed. Apart from brief gillnet surveys, which recorded the species' presence, no research on T. mossambica had been performed at Lake Sibaya before the two-year study of Minshull who collected data on food preferences, depth distribution of juveniles and breeding biology of adults. The main physiographical features of the lake are outlined. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1-7 m deep. Adult fishes (over 8 cm SL) are usually absent from water deeper than 12 m and shallower than 0.5 m, whereas juveniles may occur at all depths, and fry only in very shallow water. T. mossambica inhabits the littoral in the warm and transition periods (August to April) but moves into deep water in the cool season (May to July). Exposed and sheltered shallow areas are utilised for different purposes by adult fishes, the former for nesting, and the latter for feeding and mouth-brooding. Habitat selection by males was governed by nest site selection. Habitat Nests were most common in sheltered, sparsely vegetated littoral and sublittoral areas, but also present in well-vegetated sheltered areas. Breeding females preferred sheltered littoral areas but ventured onto the terrace to release the young. Juvenile and fry T. mossambica inhabited shallow exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour of T. mossambica is described, and integrated with data on T. mossambica from other systems. The breeding season spans seven months. Shoaling takes place in shallow water probably as a means of protection. T. mossambica is an omnivorous feeder relying largely on diatoms. The main predator is probably the barbel Clarias gariepinus, but avian predators may be more important. A method whereby the time of formation of rings on the scales of T. mossambica is described. The fishes were found to reach maturity after one year at a length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 14 cm (females) and 17 cm (males). The maximum final size was about 24 cm SL. An estimate of the standing crop for fishes in the littoral and subiittoral areas of the eastern and southern shores of the south basin is given. The data were derived from a mark and recapture The biology of T. mossambica in Lake Sibaya as revealed by the present study is discussed with reference to data on the same and similar species in other systems. The utilis ation of the available resources in the lake by T. mossambica is commented upon, and reference is made to the significance of stunting, and the import ance of the retention of generalised characters for the successful habitation of the cyclically-renewed habitat of the littoral. Precocious breeding in T. mossambica is regarded as a functional adaptation which increases the proportion of fishes small enough to utilise the rich food resources in shallow water.
- Full Text:
- Date Issued: 1973
The agricultural development of the 1820 settlement down to 1846
- Authors: Webb, Arthur (Arthur C M)
- Date: 1975
- Subjects: Agriculture -- South Africa -- Eastern Cape -- History Agricultural colonies -- South Africa -- Eastern Cape British settlers of 1820 (South Africa) Cape of Good Hope (South Africa) -- History -- 1795-1872
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1060 , http://hdl.handle.net/10962/d1007519
- Description: Preface: The arrival of the 1820 Settlers in South Africa and their impact on the political and social life of the Cape Colony has been well covered by historical research. This work is an attempt to illuminate yet another area in which their impact was felt. The failure of the settlement scheme under which these people were introduced into the colony has tended to detract from the importance which agriculture played in the early years of their residence in South Africa. The failure of the first crops may well have ended the attempts by many to establish themselves on the land but for others it was the beginning of a process of adaptation to the agricultural conditions of a new country. In this they were remarkably successful and within a decade the English farming community of the eastern frontier was prospering. The theme of this work traces the progress of these farmers through the initial period of crop failures, which condemned the settlement in the eyes of many, and through the ensuing years and later misfortune, the Sixth Frontier war of 1834-35. Both these setbacks were very significant in moulding the development of agriculture as practised by these farmers. In the past, historians have tended to over-estimate the reverse suffered by these farmers during this frontier war. The seemingly paradoxical questions raised by the rapid recovery of this community after the war have been left largely unanswered. Some attempt is made in the pages which follow to shed new light on this issue. In the first three chapters of this work the letters written by Thomas Philipps to his family in Britain form the chief source of information. Much of this correspondence has already found wider publication in a volume edited by Arthur Keppel-Jones, but there are significant omissions, particularly with regard to Philipps' commentary on agricultural matters. Unfortunately, this series of letters ends in 1830, and the chief sources for the latter period of this work are the various entries made) on agricultural matters, in the Graham's Town Journal, together with the farm diary of James Collett, another frontier farmer. From these, and various other works, it has been possible to trace the major developments of this farming community.
- Full Text:
- Date Issued: 1975
- Authors: Webb, Arthur (Arthur C M)
- Date: 1975
- Subjects: Agriculture -- South Africa -- Eastern Cape -- History Agricultural colonies -- South Africa -- Eastern Cape British settlers of 1820 (South Africa) Cape of Good Hope (South Africa) -- History -- 1795-1872
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1060 , http://hdl.handle.net/10962/d1007519
- Description: Preface: The arrival of the 1820 Settlers in South Africa and their impact on the political and social life of the Cape Colony has been well covered by historical research. This work is an attempt to illuminate yet another area in which their impact was felt. The failure of the settlement scheme under which these people were introduced into the colony has tended to detract from the importance which agriculture played in the early years of their residence in South Africa. The failure of the first crops may well have ended the attempts by many to establish themselves on the land but for others it was the beginning of a process of adaptation to the agricultural conditions of a new country. In this they were remarkably successful and within a decade the English farming community of the eastern frontier was prospering. The theme of this work traces the progress of these farmers through the initial period of crop failures, which condemned the settlement in the eyes of many, and through the ensuing years and later misfortune, the Sixth Frontier war of 1834-35. Both these setbacks were very significant in moulding the development of agriculture as practised by these farmers. In the past, historians have tended to over-estimate the reverse suffered by these farmers during this frontier war. The seemingly paradoxical questions raised by the rapid recovery of this community after the war have been left largely unanswered. Some attempt is made in the pages which follow to shed new light on this issue. In the first three chapters of this work the letters written by Thomas Philipps to his family in Britain form the chief source of information. Much of this correspondence has already found wider publication in a volume edited by Arthur Keppel-Jones, but there are significant omissions, particularly with regard to Philipps' commentary on agricultural matters. Unfortunately, this series of letters ends in 1830, and the chief sources for the latter period of this work are the various entries made) on agricultural matters, in the Graham's Town Journal, together with the farm diary of James Collett, another frontier farmer. From these, and various other works, it has been possible to trace the major developments of this farming community.
- Full Text:
- Date Issued: 1975
Aspects of the geochemistry of the Karroo dolerites and basalts of the north-eastern Cape
- Authors: Robey, Julian van Aardt
- Date: 1976
- Subjects: Diabase -- South Africa -- Cape of Good Hope , Basalt -- South Africa -- Cape of Good Hope , Geochemistry -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5060 , http://hdl.handle.net/10962/d1013070
- Description: The Birds River Gabbro Complex is intruded into sediments of the Karroo Stormberg Group in the area SW of Dordrecht in the northeastern Cape. A geochemical investigation, restricted to the igneous rock suite, gabbro-ferrogabbro-ferrotholeiite, presents new major-element data as well as data for twelve trace elements - Ba, Sr, Rb, Zr, Y, Nb , Zn, Cu, Ni, Co, V and Cr. The strong degree of differentiation of Kokstad-type tholeiitic magma in the Birds River intrusion, as noted by previous investigators, is revealed in variation diagrams in which data are plotted against a simple index of fractionation. Later differentiates are strongly enriched in Si, Ti, Fe, Na, K, P, Ba, Rb, Zr, Y, Nb, Zn and Cu but depleted in Mg, Ca, AI, Ni, Co and Cr. Extreme differentiation resulted in a strong depletion of Ti, Fe, P, Cu and V in the most highly evolved ferrotholeiites. Field evidence suggests the initial emplacement of strongly fractionated magmatic residua derived from fractional crystallization processes in a magma chamber at depth during cauldron subsidence of a mass of sediments within an annular fracture. These porphyritic, in part glassy, ferrotholeiites are enriched in Si, Na, K, Ba, Zr, Rb, Y, Nb and Zn and were engulfed by a later episode of renewed hypabyssal intrusive activity from the original source area. The younger gabbro was emplaced in a series of closely-spaced heaves or pulses of relatively undifferentiated Kokstad-type magma. The gabbro differentiated in place to form ferrogabbros which chemically closely approximate ferrotholeiite compositions. toidal facies. Residual liquids crystallized as a pegmatoidal facies. A simple fractional crystallization path, modelled on the assumption that the gabbro and ferrotholeiite form a continuous series, indicates that the least evolved ferrotholeiite can be derived from the initial gabbro composition by the fractionation of major amounts of plagioclase and pyroxene but lesser amounts of olivine. Crystallization and removal of magnetite and other Fe-oxides were relatively more important during the later stages of differentiation. The variation of major- and trace-elements in tholeiitic Karroo magma under conditions of strong differentiation at Birds River serves as a framework for the regional study of the geochemistry of other Karroo dolerites and volcanics of the north-eastern Cape. New geochemical data are presented for a sample of thirty chilled and coarse-grained Karroo dolerites collected throughout the north eastern Cape. For the most part, the chilled dolerites are relatively undifferentiated and the average composition differs only slightly from that determined by Walker and Poldervaart (1949). Variation diagrams reveal the steady increase in Si, Al, Ca, Na, K and P and the residual trace elements Ba, Zr, Rb, Y, Nb and Zn with increasing differentiation of the dolerites from more basic types. The concentrations of K, Ba and Rb are highly variable in some Karroo dolerites while new data suggest that Nb levels in the dolerites are low, being generally less than 10 ppm. The strong variation of the K-related elements (K, Ba and Rb) as well as the large ranges determined for certain inter-element ratios, such as K/Rb, Zr/Nb and K/Zr in the chilled Karroo dolerites, suggest that factors other than fractional crystallization processes need to be considered to account for individual variations. Little correlation exists between petrographic type as defined by Walker and Poldervaart (1949) and geochemical character. New geochemical data are also presented for ten Karroo basaltic lavas from the lowermost horizons of the lava sequence exposed in the Barkly East area. Major- and trace-element data indicate that these earliest Karroo extrusives are on average enriched in Si and Rb but depleted in Co and Ni when compared with the averaged chilled Karroo dolerite. Compared with basalts from Lesotho, the Barkly East basalts are enriched in Si but depleted in Ni and possibly Nb, Cu and V. The andesite is markedly enriched in Si, Na, K, Ba, Sr, Rb, Zr and Nb but depleted in Mg, Ca, V, Ni , Cu, Co and Cr. The subdued rate of Ni depletion and the absence of olivine as a major phenocryst phase in the series basalt to andesite, in the Barkly East area, suggests that differentiation trends may be controlled by the fractional crystallization of orthopyroxene and plagioclase, the two common phenocrysts present in these volcanics. The strong depletion of V and Cu in the andesite may indicate some magnetite removal during fractional crystallization.
- Full Text:
- Date Issued: 1976
- Authors: Robey, Julian van Aardt
- Date: 1976
- Subjects: Diabase -- South Africa -- Cape of Good Hope , Basalt -- South Africa -- Cape of Good Hope , Geochemistry -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5060 , http://hdl.handle.net/10962/d1013070
- Description: The Birds River Gabbro Complex is intruded into sediments of the Karroo Stormberg Group in the area SW of Dordrecht in the northeastern Cape. A geochemical investigation, restricted to the igneous rock suite, gabbro-ferrogabbro-ferrotholeiite, presents new major-element data as well as data for twelve trace elements - Ba, Sr, Rb, Zr, Y, Nb , Zn, Cu, Ni, Co, V and Cr. The strong degree of differentiation of Kokstad-type tholeiitic magma in the Birds River intrusion, as noted by previous investigators, is revealed in variation diagrams in which data are plotted against a simple index of fractionation. Later differentiates are strongly enriched in Si, Ti, Fe, Na, K, P, Ba, Rb, Zr, Y, Nb, Zn and Cu but depleted in Mg, Ca, AI, Ni, Co and Cr. Extreme differentiation resulted in a strong depletion of Ti, Fe, P, Cu and V in the most highly evolved ferrotholeiites. Field evidence suggests the initial emplacement of strongly fractionated magmatic residua derived from fractional crystallization processes in a magma chamber at depth during cauldron subsidence of a mass of sediments within an annular fracture. These porphyritic, in part glassy, ferrotholeiites are enriched in Si, Na, K, Ba, Zr, Rb, Y, Nb and Zn and were engulfed by a later episode of renewed hypabyssal intrusive activity from the original source area. The younger gabbro was emplaced in a series of closely-spaced heaves or pulses of relatively undifferentiated Kokstad-type magma. The gabbro differentiated in place to form ferrogabbros which chemically closely approximate ferrotholeiite compositions. toidal facies. Residual liquids crystallized as a pegmatoidal facies. A simple fractional crystallization path, modelled on the assumption that the gabbro and ferrotholeiite form a continuous series, indicates that the least evolved ferrotholeiite can be derived from the initial gabbro composition by the fractionation of major amounts of plagioclase and pyroxene but lesser amounts of olivine. Crystallization and removal of magnetite and other Fe-oxides were relatively more important during the later stages of differentiation. The variation of major- and trace-elements in tholeiitic Karroo magma under conditions of strong differentiation at Birds River serves as a framework for the regional study of the geochemistry of other Karroo dolerites and volcanics of the north-eastern Cape. New geochemical data are presented for a sample of thirty chilled and coarse-grained Karroo dolerites collected throughout the north eastern Cape. For the most part, the chilled dolerites are relatively undifferentiated and the average composition differs only slightly from that determined by Walker and Poldervaart (1949). Variation diagrams reveal the steady increase in Si, Al, Ca, Na, K and P and the residual trace elements Ba, Zr, Rb, Y, Nb and Zn with increasing differentiation of the dolerites from more basic types. The concentrations of K, Ba and Rb are highly variable in some Karroo dolerites while new data suggest that Nb levels in the dolerites are low, being generally less than 10 ppm. The strong variation of the K-related elements (K, Ba and Rb) as well as the large ranges determined for certain inter-element ratios, such as K/Rb, Zr/Nb and K/Zr in the chilled Karroo dolerites, suggest that factors other than fractional crystallization processes need to be considered to account for individual variations. Little correlation exists between petrographic type as defined by Walker and Poldervaart (1949) and geochemical character. New geochemical data are also presented for ten Karroo basaltic lavas from the lowermost horizons of the lava sequence exposed in the Barkly East area. Major- and trace-element data indicate that these earliest Karroo extrusives are on average enriched in Si and Rb but depleted in Co and Ni when compared with the averaged chilled Karroo dolerite. Compared with basalts from Lesotho, the Barkly East basalts are enriched in Si but depleted in Ni and possibly Nb, Cu and V. The andesite is markedly enriched in Si, Na, K, Ba, Sr, Rb, Zr and Nb but depleted in Mg, Ca, V, Ni , Cu, Co and Cr. The subdued rate of Ni depletion and the absence of olivine as a major phenocryst phase in the series basalt to andesite, in the Barkly East area, suggests that differentiation trends may be controlled by the fractional crystallization of orthopyroxene and plagioclase, the two common phenocrysts present in these volcanics. The strong depletion of V and Cu in the andesite may indicate some magnetite removal during fractional crystallization.
- Full Text:
- Date Issued: 1976
Reaction phenomena between Karroo Dolerite and cave sandstone xenoliths in the Bird's River complex
- Authors: Kenyon, A K
- Date: 1976
- Subjects: Volcanic ash, tuff, etc , Igneous rocks -- Inclusions , Sandstone
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4996 , http://hdl.handle.net/10962/d1005608
- Description: Mapping of the north-eastern portion of the Bird1s River Complex revealed that two large xenoliths composed of pyroclastic rocks and sandstone of the Cave Sandstone Stage have reacted with the dolerite. All the reaction phenomena normally associated with Karroo Dolerite are encountered. These are: (a) Metasomatism during the stage of iron enrichment of the dolerite with the production of a pyroxene-plagioclase metasomatic granophyre (b) Metasomatism during the stage of alkali enrichment of the dolerite with the production of a potassium feldspar adinole C c) Assimilation 'vi th the production of contaminated doleri tes Cd) Fusion 'vi th the production of glassy rocks including buchi tes (e) The production of rheomorphic veins
- Full Text:
- Date Issued: 1976
- Authors: Kenyon, A K
- Date: 1976
- Subjects: Volcanic ash, tuff, etc , Igneous rocks -- Inclusions , Sandstone
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4996 , http://hdl.handle.net/10962/d1005608
- Description: Mapping of the north-eastern portion of the Bird1s River Complex revealed that two large xenoliths composed of pyroclastic rocks and sandstone of the Cave Sandstone Stage have reacted with the dolerite. All the reaction phenomena normally associated with Karroo Dolerite are encountered. These are: (a) Metasomatism during the stage of iron enrichment of the dolerite with the production of a pyroxene-plagioclase metasomatic granophyre (b) Metasomatism during the stage of alkali enrichment of the dolerite with the production of a potassium feldspar adinole C c) Assimilation 'vi th the production of contaminated doleri tes Cd) Fusion 'vi th the production of glassy rocks including buchi tes (e) The production of rheomorphic veins
- Full Text:
- Date Issued: 1976
An investigation of plant-derived cardiac glycosides as a possible basis for aposematism in the aphidophagous hoverfly Ischiodon aegryptius (Wiedemann) (Diptera: Syrphidae)
- Authors: Malcolm, Stephen Baillie
- Date: 1977
- Subjects: Diptera , Syrphidae , Aphidophagous insects , Predatory animals , Insect-plant relationships , Insect pests -- Biological control , Insects as carriers of disease
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5864 , http://hdl.handle.net/10962/d1012798 , Diptera , Syrphidae , Aphidophagous insects , Predatory animals , Insect-plant relationships , Insect pests -- Biological control , Insects as carriers of disease
- Description: The chemical defences of insects against predators are either passive or aggressive. Passive defence is achieved through crypsis, and aggressive defence is maintained by a conspicuous or 'aposematic' (Poulton, 1890) appearance that advertises some noxious quality of the insect harmful to a predator. Aposematism is mutually beneficial to both the bearer and its predator, whereas crypsis only benefits the prey species. It is therefore not surprising that the fascinating array of chemical defences in insects is both diverse and widespread (Roth and Eisner, 1962). Intro. p. 1.
- Full Text:
- Date Issued: 1977
- Authors: Malcolm, Stephen Baillie
- Date: 1977
- Subjects: Diptera , Syrphidae , Aphidophagous insects , Predatory animals , Insect-plant relationships , Insect pests -- Biological control , Insects as carriers of disease
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5864 , http://hdl.handle.net/10962/d1012798 , Diptera , Syrphidae , Aphidophagous insects , Predatory animals , Insect-plant relationships , Insect pests -- Biological control , Insects as carriers of disease
- Description: The chemical defences of insects against predators are either passive or aggressive. Passive defence is achieved through crypsis, and aggressive defence is maintained by a conspicuous or 'aposematic' (Poulton, 1890) appearance that advertises some noxious quality of the insect harmful to a predator. Aposematism is mutually beneficial to both the bearer and its predator, whereas crypsis only benefits the prey species. It is therefore not surprising that the fascinating array of chemical defences in insects is both diverse and widespread (Roth and Eisner, 1962). Intro. p. 1.
- Full Text:
- Date Issued: 1977
A contribution to the petrology of kimberlites
- Authors: Kruger, Floris Johan
- Date: 1978 , 2013-10-17
- Subjects: Kimberlite -- Africa, Southern , Petrology , Igneous rocks -- Inclusions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5024 , http://hdl.handle.net/10962/d1006886 , Kimberlite -- Africa, Southern , Petrology , Igneous rocks -- Inclusions
- Description: The petrogenetic relationships of the different varieties of kimberlite in the De Beers Mine and Letseng-Ia-terai composite diatremes have been investigated using petrographic and chemical methods. Kimberlites in the Letseng-Ia-terai diatreme were found to be strongly contaminated by crustal material, mainly basalt. A method to correct for the effects of the contamination has been developed and applied to these kimberlites. Using the corrected data, the four kimberlite types in each group appear to be related to each other by crystal/liquid fractionation models. However the two groups cannot be related to each other. The De Beer Mine has two varieties of kimberlite, a monticellite apatite and calcite rich variety which intruded first, and a phlogopite rich type forming a discrete cylindrical body within the earlier kimberlite. These two kimberlites do not appear to be related by any of the fractionation models discussed. An examination of the data from this work and published sources, suggests that kimberlites are derived from below the low velocity zone by small degrees of partial melting involving garnet lherzolite with subordinate phlogopite and carbonate. Diamonds are probably incorporated as xenocrysts in the magma. Upward movement and emplacement of kimberlite appears to have been very rapid. The diatremes were probably eroded and shaped by gas, derived from the kimberlite magma, escaping to surface along weak zones in the earth's crust. Xenoliths of crustal material incorporated in the kimberlite on intrusion have also been studied and various features due to alteration by the magma are described, including the formation of natrolite and cebollite. The latter is a rare mineral that has not been described from kimberlite before. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1978
- Authors: Kruger, Floris Johan
- Date: 1978 , 2013-10-17
- Subjects: Kimberlite -- Africa, Southern , Petrology , Igneous rocks -- Inclusions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5024 , http://hdl.handle.net/10962/d1006886 , Kimberlite -- Africa, Southern , Petrology , Igneous rocks -- Inclusions
- Description: The petrogenetic relationships of the different varieties of kimberlite in the De Beers Mine and Letseng-Ia-terai composite diatremes have been investigated using petrographic and chemical methods. Kimberlites in the Letseng-Ia-terai diatreme were found to be strongly contaminated by crustal material, mainly basalt. A method to correct for the effects of the contamination has been developed and applied to these kimberlites. Using the corrected data, the four kimberlite types in each group appear to be related to each other by crystal/liquid fractionation models. However the two groups cannot be related to each other. The De Beer Mine has two varieties of kimberlite, a monticellite apatite and calcite rich variety which intruded first, and a phlogopite rich type forming a discrete cylindrical body within the earlier kimberlite. These two kimberlites do not appear to be related by any of the fractionation models discussed. An examination of the data from this work and published sources, suggests that kimberlites are derived from below the low velocity zone by small degrees of partial melting involving garnet lherzolite with subordinate phlogopite and carbonate. Diamonds are probably incorporated as xenocrysts in the magma. Upward movement and emplacement of kimberlite appears to have been very rapid. The diatremes were probably eroded and shaped by gas, derived from the kimberlite magma, escaping to surface along weak zones in the earth's crust. Xenoliths of crustal material incorporated in the kimberlite on intrusion have also been studied and various features due to alteration by the magma are described, including the formation of natrolite and cebollite. The latter is a rare mineral that has not been described from kimberlite before. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1978
Gold mineralization in archaean cherts and iron-formations a review of the economic geology
- Authors: Bellamy, R E S
- Date: 1979
- Subjects: Gold ores -- Geology -- South Africa , Gold mines and mining -- South Africa , Greenstone belts -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4968 , http://hdl.handle.net/10962/d1005580 , Gold ores -- Geology -- South Africa , Gold mines and mining -- South Africa , Greenstone belts -- South Africa
- Description: The distribution of gold in igneous rocks and minerals is described and discussed. Not all the gold in igneous rocks is contained within early formed crystal lattices. Evidence that gold can be associated with late stage crystallizing phases is described. It is concluded that some of the gold in hydrothermal and volcanogenic deposits may have come from a primary magmatic source rather than having been leached from solid country rock. Gold is probably transported as chloride complexes at temperatures greater than about 300°C. At lower temperatures it is probably transported with other metals as sulphide and thio-sulphide complexes. The precipitation of gold from the transporting medium is brought about by changes in the physico-chemical conditions within that medium. Decrease in pressure is probably not a major cause of precipitation in volcanogenic environments. The geology of volcanogenic iron-formations is described and discussed, relative to the development of greenstone belts. Oxide facies iron-formations were formed in shallow oxidizing environments. They are associated with volcanogenic and clastic sediments. Sulphide facies iron-formations were precipitated in the deeper parts of geosynclinal structures. They are associated with mafic and ultramafic rocks similar to modern oceanic volcanic assemblages. Carbonate facies iron-formations were deposited in the regions between oxide facies and sulphide facies. Other banded iron-formations are found associated with base metal massive sulphide deposits related to arctype volcanic centres. These deposits are found in the regions where carbonate facies iron-formations were formed. Exploration for and exploitation of gold deposits in Archaean iron-formations are discussed. Geochemical exploration programmes are aided by the association of gold with trace amounts of base metals. Geophysical exploration methods that can be employed include magnetometer, I.P. and E.M. surveys. The metallurgical treatment of the ores should include "roasting" because a large proportion of the gold occurs as submicroscopic grains within sulphide mineral crystals.
- Full Text:
- Date Issued: 1979
- Authors: Bellamy, R E S
- Date: 1979
- Subjects: Gold ores -- Geology -- South Africa , Gold mines and mining -- South Africa , Greenstone belts -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4968 , http://hdl.handle.net/10962/d1005580 , Gold ores -- Geology -- South Africa , Gold mines and mining -- South Africa , Greenstone belts -- South Africa
- Description: The distribution of gold in igneous rocks and minerals is described and discussed. Not all the gold in igneous rocks is contained within early formed crystal lattices. Evidence that gold can be associated with late stage crystallizing phases is described. It is concluded that some of the gold in hydrothermal and volcanogenic deposits may have come from a primary magmatic source rather than having been leached from solid country rock. Gold is probably transported as chloride complexes at temperatures greater than about 300°C. At lower temperatures it is probably transported with other metals as sulphide and thio-sulphide complexes. The precipitation of gold from the transporting medium is brought about by changes in the physico-chemical conditions within that medium. Decrease in pressure is probably not a major cause of precipitation in volcanogenic environments. The geology of volcanogenic iron-formations is described and discussed, relative to the development of greenstone belts. Oxide facies iron-formations were formed in shallow oxidizing environments. They are associated with volcanogenic and clastic sediments. Sulphide facies iron-formations were precipitated in the deeper parts of geosynclinal structures. They are associated with mafic and ultramafic rocks similar to modern oceanic volcanic assemblages. Carbonate facies iron-formations were deposited in the regions between oxide facies and sulphide facies. Other banded iron-formations are found associated with base metal massive sulphide deposits related to arctype volcanic centres. These deposits are found in the regions where carbonate facies iron-formations were formed. Exploration for and exploitation of gold deposits in Archaean iron-formations are discussed. Geochemical exploration programmes are aided by the association of gold with trace amounts of base metals. Geophysical exploration methods that can be employed include magnetometer, I.P. and E.M. surveys. The metallurgical treatment of the ores should include "roasting" because a large proportion of the gold occurs as submicroscopic grains within sulphide mineral crystals.
- Full Text:
- Date Issued: 1979
Geological factors in the evaluation of vein deposits
- Authors: Neuhoff, Larry E.
- Date: 1980 , 2013-04-02
- Subjects: Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5029 , http://hdl.handle.net/10962/d1006911 , Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
- Description: From introduction: Vein-type mineralization, particularly gold, copper, tin and tungsten has provided a source of metal to man for over 2000 years. These deposits are usually small but in some cases are of very high grade. Prior to 1940 veins were extremely important sources of metals because of their relatively high-grades. However, with improved mining, smelting and concentrating methods, much lower grade material became economic, hence these smaller deposits could no longer hold their dominance. Recently the energy crisis and escalating costs of capital for large projects has made smaller deposits attractive once more (Temblay and Descarreaux, 1978) . At the present time gold, tin and tungsten command high prices on world markets. It is for these reasons that a study of the evaluation techniques pertaining to these deposits has been undertaken. In this review the geological factors which influence the evaluation are stressed. In particular, emphasis is placed on the emplacement of vein deposits, and the subsequent chemical and structural modifications of these deposits. The latter part of the review concentrates on the limitations of the sampling and ore reserve techniques that can be applied to the evaluation of mineralized veins. In the conclusion those techniques that are most applicable are stressed, and an evaluation model is outlined.
- Full Text:
- Date Issued: 1980
- Authors: Neuhoff, Larry E.
- Date: 1980 , 2013-04-02
- Subjects: Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5029 , http://hdl.handle.net/10962/d1006911 , Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
- Description: From introduction: Vein-type mineralization, particularly gold, copper, tin and tungsten has provided a source of metal to man for over 2000 years. These deposits are usually small but in some cases are of very high grade. Prior to 1940 veins were extremely important sources of metals because of their relatively high-grades. However, with improved mining, smelting and concentrating methods, much lower grade material became economic, hence these smaller deposits could no longer hold their dominance. Recently the energy crisis and escalating costs of capital for large projects has made smaller deposits attractive once more (Temblay and Descarreaux, 1978) . At the present time gold, tin and tungsten command high prices on world markets. It is for these reasons that a study of the evaluation techniques pertaining to these deposits has been undertaken. In this review the geological factors which influence the evaluation are stressed. In particular, emphasis is placed on the emplacement of vein deposits, and the subsequent chemical and structural modifications of these deposits. The latter part of the review concentrates on the limitations of the sampling and ore reserve techniques that can be applied to the evaluation of mineralized veins. In the conclusion those techniques that are most applicable are stressed, and an evaluation model is outlined.
- Full Text:
- Date Issued: 1980
The evaluation of melatonin as a possible antidepressive
- Authors: Skene, Debra Jean
- Date: 1980
- Subjects: Melatonin , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3728 , http://hdl.handle.net/10962/d1001465
- Description: Melatonin, a hormone of the pineal gland, was evaluated in a variety of animal models of depression. Measurements of the frog righting reflex and rat locomotor activity showed that low doses of melatonin have a serotonin-like potentiating effect following monoamine oxidase inhibition. High doses of melatonin caused a reduction in the duration of rat immobility in the Porsolt model of depression and exerted a chlorpromazine-like effect on conditioned avoidance behaviour. In view of the indoleamine hypothesis of depressive disorders, the possibility of melatonin being a potential antidepressive is discussed and it is concluded that melatonin might be useful in the treatment of "agitated" depressions
- Full Text:
- Date Issued: 1980
- Authors: Skene, Debra Jean
- Date: 1980
- Subjects: Melatonin , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3728 , http://hdl.handle.net/10962/d1001465
- Description: Melatonin, a hormone of the pineal gland, was evaluated in a variety of animal models of depression. Measurements of the frog righting reflex and rat locomotor activity showed that low doses of melatonin have a serotonin-like potentiating effect following monoamine oxidase inhibition. High doses of melatonin caused a reduction in the duration of rat immobility in the Porsolt model of depression and exerted a chlorpromazine-like effect on conditioned avoidance behaviour. In view of the indoleamine hypothesis of depressive disorders, the possibility of melatonin being a potential antidepressive is discussed and it is concluded that melatonin might be useful in the treatment of "agitated" depressions
- Full Text:
- Date Issued: 1980
The extrusive and intrusive basaltic rocks of the Molteno-Jamestown area
- Authors: Mitchell, Andrew Alexander
- Date: 1980
- Subjects: Basalt -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4900 , http://hdl.handle.net/10962/d1001559
- Description: The Karoo basalt outliers between Molteno and Jamestown in the north-eastern Cape Province are associated with two central volcanic vent complexes, referred to in the text as the Brosterlea and the Modderfontein complexes. The basalts, particularly those associated with the Brosterlea complex, show geochemical variations throughout the sequence, a factor which has facilitated the subdivision of the Brosterlea basalts into a series of discrete units, each having its own chemical characteristics. Most of the basalt units at Brosterlea can be correlated with units identified in the Barkly East basalt suite. As is the case around Barkly East, the Brosterlea basalt units cannot be related to one another by any simple crystal fractionation or partial melting process, and the most feasible alternative explanation lies in the existence of inhomogeneities in the upper mantle at the time of generation of the magmas. New electron microprobe data are presented for the silicate phases in the Karoo basalts. Analyses of augites from a limited number of slides indicate that pyroxenes from different basalt units define different trends on the Ca - Mg - Fe triangular diagram. The plagioclases in the Brosterlea basalts are fairly Ca-rich (average 70% An), and the K-content of the plagioclases is shown to vary with the K-content of the parent basalt. A comparison of the Karoo Central Province with the younger Columbia River and Deccan Trap Provinces shows many similarities in the evolutionary history of the three provinces. The Karoo Province, however, is distinct from the other two provinces in some aspects of the geochemistry. Broadly speaking, the Karoo basalts are depleted in the incompatible elements relative to the Columbia River and Deccan basalts, and often enriched in the transition metals, most specifically Cr
- Full Text:
- Date Issued: 1980
- Authors: Mitchell, Andrew Alexander
- Date: 1980
- Subjects: Basalt -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4900 , http://hdl.handle.net/10962/d1001559
- Description: The Karoo basalt outliers between Molteno and Jamestown in the north-eastern Cape Province are associated with two central volcanic vent complexes, referred to in the text as the Brosterlea and the Modderfontein complexes. The basalts, particularly those associated with the Brosterlea complex, show geochemical variations throughout the sequence, a factor which has facilitated the subdivision of the Brosterlea basalts into a series of discrete units, each having its own chemical characteristics. Most of the basalt units at Brosterlea can be correlated with units identified in the Barkly East basalt suite. As is the case around Barkly East, the Brosterlea basalt units cannot be related to one another by any simple crystal fractionation or partial melting process, and the most feasible alternative explanation lies in the existence of inhomogeneities in the upper mantle at the time of generation of the magmas. New electron microprobe data are presented for the silicate phases in the Karoo basalts. Analyses of augites from a limited number of slides indicate that pyroxenes from different basalt units define different trends on the Ca - Mg - Fe triangular diagram. The plagioclases in the Brosterlea basalts are fairly Ca-rich (average 70% An), and the K-content of the plagioclases is shown to vary with the K-content of the parent basalt. A comparison of the Karoo Central Province with the younger Columbia River and Deccan Trap Provinces shows many similarities in the evolutionary history of the three provinces. The Karoo Province, however, is distinct from the other two provinces in some aspects of the geochemistry. Broadly speaking, the Karoo basalts are depleted in the incompatible elements relative to the Columbia River and Deccan basalts, and often enriched in the transition metals, most specifically Cr
- Full Text:
- Date Issued: 1980
A review of the use of geophysics in base- and precious-metal exploration
- Authors: Furnell, R G
- Date: 1981
- Subjects: Geophysics , Geological surveys , Precious metals , Mining geology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5015 , http://hdl.handle.net/10962/d1006144
- Description: The object of geophysical surveys in mineral exploration has traditionally been to detect subsurface geological features, which may reflect the presence of mineralization in depth and, if possible, to measure the dimensions of the causative body. Geophysical methods may also be used to locate extensions to known mineralization and for determining the size, depth and internal characteristics of an orebody. Marked improvements in geological concepts of ore genesis have led to a better appreciation, amongst geologists, of mineralized environments, and this has had an effect on the use of geophysics in recent years. Geophysical surveys are being increasingly used as an aid in environmental reconstructions and the results of regional surveys may be used to provide an indirect guide to ore. One of the main applications of geophysics lies in areas where the orebodies and associated structures are not exposed, as most geophysical measurements are more expensive than surface geological or geochemical surveys.
- Full Text:
- Date Issued: 1981
- Authors: Furnell, R G
- Date: 1981
- Subjects: Geophysics , Geological surveys , Precious metals , Mining geology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5015 , http://hdl.handle.net/10962/d1006144
- Description: The object of geophysical surveys in mineral exploration has traditionally been to detect subsurface geological features, which may reflect the presence of mineralization in depth and, if possible, to measure the dimensions of the causative body. Geophysical methods may also be used to locate extensions to known mineralization and for determining the size, depth and internal characteristics of an orebody. Marked improvements in geological concepts of ore genesis have led to a better appreciation, amongst geologists, of mineralized environments, and this has had an effect on the use of geophysics in recent years. Geophysical surveys are being increasingly used as an aid in environmental reconstructions and the results of regional surveys may be used to provide an indirect guide to ore. One of the main applications of geophysics lies in areas where the orebodies and associated structures are not exposed, as most geophysical measurements are more expensive than surface geological or geochemical surveys.
- Full Text:
- Date Issued: 1981