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
Stratigraphy and sedimentology of the Cape and Karoo Sequences in the Eastern Cape Province
- Authors: Johnson, M R
- Date: 1976
- Subjects: Sediments (Geology) -- South Africa -- Eastern Cape Geology, Stratigraphic Sedimentology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5004 , http://hdl.handle.net/10962/d1005617
- Description: The Cape Supergroup (Sequence) comprises three groups, embracing a total of twenty-three formations, with a maximum combined thickness of approximately 8 km. The Table Mountain Group consists of medium-grained (occasionally fine- or coarse-grained), "clean", ultra-quartzose sandstone plus subordinate fine-grained, "dirty", subfeldspathic to feldspathic sandstone, mudrock, and rhythmitite. Average total thickness is about 3000 m. The Bokkeveld Group is composed of mudrock, rhythmitite and subordinate subfeldspathic to feldspathic sandstone (generally fine-grained and "dirty"), with a maximum total thickness of over 3000 m. The Witteberg Group comprises fine- to medium-grained ultra-quartzose sandstone, icaceous streaky rhythmitite, mudrock, and one thin diamictite unit; total thickness is about 1700 m. The strata belonging to the Cape Supergroup appear to have been largely deposited under marine conditions in environments ranging from outer shelf to beach. Deltaic deposits are,however, common in the upper part of the Bokkeveld Group and the Witteberg Group, while the main sandstone units in the upper third of the Table Mountain Group may have accumulated on a coastal alluvial plain. Deposition took place in a basin elongated in an east-west direction, with the palaeoslope inclined towards the south. Palaeocurrents were generally directed down the palaeoslope, but westerly 1 transport directions parallel to the palaeostrike and presumed shoreline are present in both the Table Mountain and Witteberg Groups. I The sedimentary rocks o~ the Karoo Sequence are subdivided into two groups (containing a total of eleven formations) and four ungrouped formations. Using the maximum thicknesses of the individual formations, a combined total thickness of about 12 km can be calculated. The sequence commences with the Dwyka Tillite, a 700-m-thick diamictite unit. The overlying Ecca Group consists of "varved" rhythmitite, dark, massive, fine- to very fine-grained ultra-lithofeldspathic sandstone and subordinate mudrock with a total thickness of 2000 - 3000 m. The Beaufort Group is composed of thick mudstone layers alternating with thinner fine-grained ultra-lithofeldspathic, lithofeldspathic and lithic sandstones, with the exception of the Katberg Formation which consists largely of sandstone. Fining-upward cycles are ubiquitous, while red mudstone is com~on, especially in the upper half of the group. A maximum thickness of about 6000 m was obtained in the East London area. The Molteno Formation Consists of up to 600 m of alternating fine- to coarse-grained sublithic sandstones (frequently pebbly) and grey mudstones, generally forming finingupward cycles. The Elliot Formation (up to 500 m thick) consists of red and grey mUdstones and subordinate fine-grained lithofeldspathic sandstones arranged in fining-upward cycles. The bulk of the Clarens Sandstone consists of very fine-grained massive (occasionally cross-bedded) sandstone, with a maximum thickness of 300 m. The Drakensberg Group, consisting of up to 1200 m of basalt with some pyroclastic intercalations near the base, caps the Karoo sedimentary succession. The deposition of the Dwyka Tillite by glacier action coincided with a major change from the generally shallow marine conditions which characterised the sedimentation of the Cape Supergroup (with the source area located on the craton to the north of the basin) to a deep linear trough receiving clastic sediments from a source area situated south and south-east of the basin. The Ecca Group,the lower half of which is characterised by the presence of "proximal" turbidite sandstones, records the gradual infilling of this basin, with deltaic conditions developing in the upper part of the group in the western half of the study area (i.e. in the Waterford Formation). The overlying strata were virtually all deposited under fluviatile conditions, the chief exceptions being a stratigraphic interval within the lower half of the Beaufort Group which appears to have formed in a large body of water, a~d the aeolian Clarens Sandstone. The fluviatile sediments were all deposite1 by rivers flowin~ towards the north and nort~-west, while the Clarens Sandstone was laid down by winds blowing from the west. The Ecca and Beaufort Group sandstones are characterised by a high rock fragment content with "felsit ic" gra ins being a prc;>minent constituent. This, together with the relative abundance of quartzfeldspar porphyry pebbles in the Katberg Sandstone unit (Beaufort Group) near East London, indicates that volcanic material probably formed a prominent part of the post-Dwyka Karoo provenance.
- Full Text:
- Date Issued: 1976
The Late Cenozoic history and palaeoenvironments of the coastal margin of the south-western Cape Province, South Africa
- Authors: Tankard, Anthony James Tempest
- Date: 1976
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21068 , http://hdl.handle.net/10962/6257
- Description: This thesis examines the Late Cenozoic history and palaeoenvironments of the coastal margin between Elands Bay on the west coast and Die Kelders on the south coast. This study is introduced with a detailed discussion of eustatic sea level oscillation. The history of the existing ice sheets, sea floor spreading, isotopic composition changes of the oceans, and isostatic responses of the crust to varying loads are reviewed with regard to their bearing on sea level changes. A detailed account of the Neogene stratigraphy of the south-western Cape Province is presented. The Middle to early Late Miocene Saldanha Formation is characterised by shallow marine phosphatic sandstone and phosphorite. It is thought to have been deposited in a warm transgressive sea. The Pliocene Varswater Formation was deposited during a secondary transgression induced by.seaward tilting of the coastal margin during a time of worldwide regression. The Varswater Formation is characterised by pelletal phosphorites. It includes marine, estuarine, and fluvial facies. The estuarine sands and peats contain a rich fossil mammal fauna. Depositional environments of the Pelletal Phosphorite Member are examined by means of conventional grain size analysis to show that deposition took place on a shallow sublittoral platform dominated on the outer edge by a breaker-bar. Accretion of the breaker-bar to form a barrier-island allowed the development of an estuarine complex on the leeward side. Post-depositional diagenetic changes were examined by means of scanning electron microscopy. A detailed account of the petrology and geochemistry of the phosphorite and pelletal phosphorite is presented. The apatite mineral is a carbonate fluorapatite. It is concluded that the phosphorite is related to upwelling of phosphorus-rich waters.
- Full Text:
- Date Issued: 1976
Explanation of the geological map of the country east of Kariba
- Authors: Broderick, T J
- Date: 1977
- Subjects: Geology -- Kariba, Lake (Zambia and Zimbabwe) -- Maps , Geology -- Kariba, Lake (Zambia and Zimbabwe)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5075 , http://hdl.handle.net/10962/d1014650
- Description: The area covers part of the western end of the Zambezi Metamorphic Belt as it is known in Rhodesia. Most of the rocks are paragneisses of various ages that have suffered a long and complex history which has taken them into the highest facies of metamorphism and into the realm of granitization. Only the Karoo sediments of the Zambezi Valley are unaffected by these metamorphic events. From the scanty geochronological results obtainable from the north of Rhodesia, the history of this area started more than 2 500 million years ago. In the east and south-east of the mapped area are a group of highly migmatized granitic gneisses which represent a continuation westwards of similar rocks found in the area described in Bulletin 51 by Wiles (1961}. These Urungwe Paragneisses are regarded as forrning the basement on which all other rocks in the area lie, although their relationship with the Basement Complex is unknown. Climatically Kariba is hot and humid. Mean summer temperatures average 30°C (86°F), with temperatures in October that often exceed 40°C (100°F). Away from the Lake the humidity decreases and the increased altitudes above the Escarpment have a cooling effect. The township's mean annual rainfall is 665 millimetres (26,2 inches), most of which falls in the months between November and February. Basically. the area is well timbered but population pressures in the tribal areas, and depredation by elephants elsewhere, have made serious inroads upon the natural vegetation. The gneissic terrain above the Escarpment is characterized by mufuti trees (Brachystegia boehmiz). The baobab (Adansonia digitata) is common in the larger river valleys and in the low-lying area surrounding the lake shore where it occurs together with mopane (Colophospermum mopane) and thick jessie bush. In the river valleys, trees typical of the Zambezi Valley are common and include the tamarind (Tamarindus indica), mumvey (Kigelia africana) and Steculia species. Buffalo beans (Mucuma coriacea) are not uncommon in grassy river-beds. Physiographically, the area can be subdivided into three distinct regions, all of which have a marked geological control. They are- (1) The fault-lined Gwembe trough which has subsequently been inundated by the waters of Lake Kariba to an average altitude of 487 metres (1 600 feet) above sea level since the completion of the dam across the upstream entrance to the Kariba Gorge in 1960. The fiat land that now forms part of the lake shore is underlain by sediments of Karoo age and these, in the mapped area, occupy the Charara and Gachegache Basins, that lie to the north and south respectively of the Msango Range. These fiat-lying areas give way sharply to the gneissic terrain of the Zambezi Metamorphic Belt along the fault-lined Zambezi Escarpment. (2) The northern boundary of the area and the Msango Range are underlain by metasediments of the Makuti Group. The relief is strongly influenced by the regional geological structure of these complexly folded rocks with resistant meta-arkose and quartzite forming the sharp ridges and metapelites occupying the valleys. The ridges and valleys trend eastwards in the Msango Range, but along the northern boundary they trend north-westwards. (3) The linear topographic features of the Makuti Group terrain give way southwards to the older gneisses along an abrupt scarp edge, the base of which is marked by the Tsororo River. This terrain of gneisses is very rugged and highly dissected above the Zambezi Escarpment until it flattens out, at about 900 metres (2 950 feet) above sea level, into the Urungwe Tribal Trust Lands. In the rugged country above the Escarpment, granulites of the Piriwiri Group stand out above the gneisses as steep-sided conical bills. The country rises in a series of fault-lined steps to its highest point, at Nyamangwe trigonometrical beacon, which stands at 1 336 metres (4 382 feet) above sea level.
- 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
Geology of part of the central Damara belt around the Tumas River, South West Africa
- Authors: Bunting, F J L
- Date: 1978
- Subjects: Geology -- Namibia -- Damaraland , Geology, Stratigraphic -- Namibia , Geology -- Namibia -- Tumas River Watershed , Geology -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5049 , http://hdl.handle.net/10962/d1009957 , Geology -- Namibia -- Damaraland , Geology, Stratigraphic -- Namibia , Geology -- Namibia -- Tumas River Watershed , Geology -- Namibia
- Description: The investigation covering 1500 square kilometres within the central granite zone of the Damara belt, South West Africa, revealed Pre - Damara (Abbabis) basement unconformably overlain by metasediments of the Damara Supergroup. The term Leeukop member is proposed for basal metaconglomerates of the Nosib Group that immediately overlie the basement augen-gneisses. Augen-gneiss clasts are present within the Leeukop metaconglomerates. The Damara orogeny has only partly affected the Abbabis rocks of the Tumas River Inlier but further to the west the Husab suite of red granites and granite-gneisses, as field and geochemical evidence suggest, were derived syntectonically during the Damara orogeny by reactivation of the pre- Damara basement. Rõssing alaskitic granites represent late stage melts, that were also derived from Pre- Damara basement rocks during orogenesis, which accumulated post-tectonically in structural traps at the base of the Khomas Subgroup. Salem granitoids are present in synclinal structures associated with metasediments of the Khomas Subgroup and syntectonic derivation by anatexis during the Damara orogeny is suggested. In the east the differentiated Gawib granitoid stock was emplaced post- tectonically through basement rocks into the Damara metasediments. A deep seated origin is indicated by high crystallisation temperatures (>8500°) obtained from quarternary Qz-An-Ab-Or- H₂0 plots. The metamorphic grade increases westwards from medium grade to high grade. In the east, the metapelites contain andalusite, and coexisting muscovite and quartz. This indicates that temperatures of 6000° at 3,5- 4 kb pressure were attained. In the west, coexisting wollastonite and anorthite in the Khan gneisses indicate pressure- temperature conditions of 720° at 4,5-5 kb. Two tectonic events were responsible for the regional structure. An early F₁ episode produced east- west oriented overturned folds and was followed by an intense F₂ episode of isoclinal folding which is responsible for the dominant northeast - southwest regional fabric. The interference of these folds in the proximity of the underlying basement produced the complex dome and basin structures seen in the central and western parts of the area. An F₃ episode of minor importance was also recognized. The presence of continental basement rocks in this central part of the Damara belt is evidence for formation of the orogen by in-situ deformation rather than continental collision.
- Full Text:
- Date Issued: 1978
The geochemistry and petrology of Karroo basalts of the Barkly East area, north eastern Cape
- Authors: Pemberton, John
- Date: 1978 , 2013-10-17
- Subjects: Basalt -- South Africa -- Eastern Cape , Petrology -- South Africa -- Eastern Cape , Geochemistry -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5042 , http://hdl.handle.net/10962/d1007646 , Basalt -- South Africa -- Eastern Cape , Petrology -- South Africa -- Eastern Cape , Geochemistry -- South Africa -- Eastern Cape
- Description: Sixty one basalt samples from the Drakensberg Subgroup in the Barkly East area were analysed for major elements and fourteen trace elements viz. Sr, Rb, Zr, Y, Nb, Zn, Cu, Ni, Co, V, Cr, La, Ce and Nd . These data confirm the tholeiitic nature of the Drakensberg Subgroup. Geochemical differences in the major element compositions are small within the different units of the Drakensberg Subgroup. Small differences are also evident between these units. The trace element variation between the units and within the Lesotho Formation are more pronounced than the variation of the major elements. The Lesotho Formation samples show a minor vertical increase in value for the top half of the Naudes Nek section in Fe, Ti, P, Zr, Nb, Y, La, Ce and Nd . A decrease in value from the same position in Mg, Ni and Co was observed. These patterns of variation are interpreted as representing low-pressure fractionation of plagioclase, olivine and clinopyroxene. Differences between the units of the Drakensberg Subgroup are examined by using absolute trace element contents and interelement ratios. Ratios of incompatible elements differ for the different units leading to the suggestion that a heterogeneous mantle is the most likely explanation for these differences. A unique unit of flows designated the Omega Formation is examined. The basal massive unit displays an unusual pattern of variation with height which suggests an origin through two different differentiation mechanisms. The data from this thesis are compared with those of Cox and Hornung (1966) on the central Lesotho basalts, Bristow (1976) on the southern Lebombo basalts and Robey (1976) on the Karroo dolerites of the Eastern Cape. The geochemical comparison between the lavas of the Lesotho Formation in the Barkly East area, central Lesotho and the Karroo dolerites show no major differences. However the southern Lebombo basalts show an enrichment in Sr and depletion in Cr.
- Full Text:
- Date Issued: 1978
A mineralogical investigation of co-existing iron-titanium oxides from various igneous rocks with special reference to some South African titaniferous iron ores
- Authors: Reynolds, Ivan Melvin
- Date: 1979
- Subjects: Igneous rocks Mineralogy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4926 , http://hdl.handle.net/10962/d1004589
- Description: Part I consists of a detailied review of the available literature on the Fe- Ti oxides and their solid solution relationships. Particular attention is glven to the microstructures exhibited by these oxides and the hypotheses put forward to explain them. These data are synthesised and models are presented in which the microstructural developments in titaniferous magnetites amd ilmenites are explained in terms of current ideas on the influence of oxygen fugacity, exsolution mechanisms and crystal chemistry. These models have direct application to the microintergrowths observed in the naturally occurring Fe-Ti oxides from a wide range of igneous rocks. The available data on the minor and trace element chemistry of the Fe-Ti oxides are reviewed with particular reference to their variation in these minerals from different host rocks. The behaviour of the Fe-Ti oxides during secondary oxidation is discussed with particular reference to the oxidation of titaniferous magnetite and the weathering of ilmenite. The results of a mineralogical investigation into the co-existing Fe-Ti oxides from a range of igneous rocks including kimberlites, gabbros, dolerites, diabases, syenites, granophyres, granites and pegmatites are presented in Part 2 together with data on the ilmenites present in certain Eastern Cape beach sands. The kimberlite ilmenites are chemically distinct and can be readily distinguished on the basis of their relatively high MgO, Fe₂0₃ and Cr₂O₃ contents. They can also be distinguished from ilmenites from other igneous rocks on the basis of unit cell dimensions, d-spacings, reflectivities and micro-indentation hardness. The ilmenites from a wide range of basic to granitic igneous rocks exhibit a limited compositional range in which the MnO content appears to increase with increasing Si0₂ content. Relatively insensitive indirectly determined parameters such as unit cell dimensions, reflectivities and micro-indentation hardnesses cannot be used to distinguish between the ilmenites from the different rock types in these classes. The titaniferous magnetites exhibit progressively decreasing Ti0₂ contents from a maximum in the basic igneous rocks to a minimum in the granitic types. The titaniferous magnetite typically exhibits varying degrees of deuteric alteration, while the microstructures developed can be interpreted 1n terms of the models presented in Part 1. Part 3 represents an extension of Part 2 and deals with a mineralogical investigation of the titaniferous iron ores in five South African basic intrusions. The Bushveld and Kaffirskraal ores consist of multi-phase titaniferous magnetite grains containing crystallographically oriented ilmenite, ulvospinel and pleonaste microintergrowths. Minor coarser-grained ilmenite is also present. The Usushwana ores are texturally similar but contain abundant lamellar ilmenite in place of the ulvospinel. The primary features are well preserved in the unmetamorphosed Bushveld and Kaffirskraal ores. The Usushwana ores have been slightly metamorphosed resulting in the extensive replacement of the titaniferous magnetites by sphene and chlorite aggregates. The ores from these three complexes cannot be beneficiated by conventional ore-dressing techniques and require direct metallurgical treatment for the recovery of Fe, Ti0₂ and V₂O₅. The metamorphosed Mambula and Rooiwater ores have been recrystallised to a varying degrees and consist of multi-phase titaniferous magnetite grains containing modified ilmenite and pleonaste microintergrowths. These modified microstructures differ from those encountered in titaniferous magnetites from unmetnmorphosed basic rocks and their degree of modification can be related to the degree of met amorphism. Variable amounts of coarse granular ilmenite are also present and their development is related to the metamorphic grade and degree of recrystallisation. These ores can be partially beneficiated to yield ilmenite- and lower-Ti0₂ magnetite concentrates in which V₂O₅ contents of the magnetic fractions are higher than those of the original ores. The Trompsburg ores differ from those of the other complexes in that they are Mg-rich and are characterised by the presence of abundant olivine. The titaniferous magnetites typically exhibit well-defined ulvospinel cloth textures and are often surrounded by small amounts of graphite. They show evidence of a variety of extensive late-stage alteration features. The ores from the five investigated complexes are compared with similar ores from the Bushveld Complex. The ores from each complex can be readily distinguished on the basis of their chemical compositions and textural relationships. These features can be related to their crystallisation his tories and, in some cases, to post-crystallisation processes. The microstructural evolution of the ores from each complex is interpreted in terms of the models developed in Part I.
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- Date Issued: 1979
A review of landscape development and erosion cycles in southern Africa
- Authors: Corbett, Dudley Harold
- Date: 1979
- Subjects: Landscape changes -- Africa, Southern Erosion -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4899 , http://hdl.handle.net/10962/d1001558
- Description: The study of landforms has, to a large extent been neglected by exploration geologists. This is surprising because field geology is intimately related with landforms of one type or another. An understanding of the geomorphological history of a particular area will assist in the appreciation of the surficial environment, the processes of weathering, soil formation and duricrust (calcrete , ferricrete silcrete) formation. This has direct application in planning and interpreting geochemical sampling programmes. In order to understand the evolution of landforms it is necessary to study slope development in some detail. Agents of erosion and denudation constantly at work, remove detritus from hillcrests down to the drainage lines which form the local base level from whence material is transported down to the sea. The system is one of dynamic equilibrium, and the concept of grade is important in understanding hillslope evolution. Thus Section (1) of this discussion deals with past and present theories of hillslope evolution. Very little work has been done recently on the geomorphology of Southern Africa and the presently accepted classification of land surfaces is based on the work of Prof. L.C. King (numerous publications). However, through the more recent work of De Swardt and Bennet (1974) on the geomorphology of Natal, it is apparent that the present system of landform classification in Southern Africa requires widespread revision. The relationship of erosion cycles in Southern Africa to the late Jurassic-early Cretaceous break-up of Gondwanaland has received insufficient attention in the past. Erosion cycles bear an intimate relationship to offshore Cretaceous and Tertiary-Recent sedimentation. Valuable information on these sediments has only recently become available as a result of offshore exploration for oil. The findings of De Swardt and Bennet (1974) are summarized in Section (2) and the present land surface classification of Southern Africa is reviewed. Finally, some suggestions on a new interpretation of land surfaces in Southern Africa are given.
- Full Text:
- Date Issued: 1979
A review of the economic geology of tungsten
- Authors: Bowles, Michael
- Date: 1979
- Subjects: Tungsten Geology, Economic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4897 , http://hdl.handle.net/10962/d1001556
- Description: A description of the geochemistry of tungsten is given. The geochemical properties of tungsten have a strong influence on its mineralogy, distribution and abundance in crustal rocks and rock-forming minerals , and its migration/deposition within the ore-forming and supergene environments. The behaviour of tungsten during migration, from source to site of deposition, within the crust is discussed in some detail and environments considered favourable to the concentration of tungsten ore minerals are suggested. All major types of tungsten ore deposit are described with emphasis placed on those of greater economic importance. Characteristic features of each type of deposit are particularly emphasized in order to provide clear guidelines to exploration. Hydrothermal, pyrometasomatic and stratabound tungsten deposits present themselves, economically, as the most important exploration targets. The recently developed concept of syngenetic stratabound tungsten mineralisation is outlined. Exploration for deposits of this type should be aimed predominantly, but not exclusively, at volcano-sedimentary sequences of Lower Palaeozoic age, particularly within regions known to contain occurrences of Sb and Hg. Tungsten deposits commonly contain concentrations of one or more of the following metals: Sn, Sb, Bi, Mo, Au and Ag. The presence and possible extractive value of these metals, together with commonly associated metal impurities such as As, must always be taken into account in a feasibility study , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1979
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
Sedimentology of the Katberg sandstone in the Eastern Cape Province
- Authors: Stavrakis, Nicholas
- Date: 1979 , 2013-10-16
- Subjects: Sedimentology -- South Africa -- Eastern Cape , Geology, Stratigraphic -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5034 , http://hdl.handle.net/10962/d1007355 , Sedimentology -- South Africa -- Eastern Cape , Geology, Stratigraphic -- South Africa -- Eastern Cape
- Description: The Katberg Sandstone is an arenaceous formation occuring stratigraphically three querters of the way up in the Beaufort Group in the south-eastern part of the main Karoo basin. A sedimentological study was carried out on the Katberg Sandstone and adjacent formations, in a 2 000 km² area south of Queenstown. Stratigraphic sections were measured and lithofacies based on the style of Miall (1977) were established for the Katberg Sandstone, Balfour and Burgersdorp Formations. Stratigraphic relationships show that the Burgersdorp Formation in the study area, is the lateral (distal) equivalent of the Katberg Sandstone. The changeover from sandstone to predominantly shale lithology occurs roughly east-west between Cathcart and Whittlesea. Stream hydraulic theory is discussed and the sedimentary structures of the various lithofacies are explained in terms of this theory. An analysis was done of thirty-four palaeochannels, and their various ancient flow characteristics were derived via multiple regression equations and a FORTRAN computer program. A statistical analysis of bedform structures, showed that flat-bedding of the upper flow regime is the dominant sedimentary structure of the Katberg Sandstone. Trough cross-bedding originating in aqueous dunes and planar cross-bedding of transverse bars, are fairly well represented while ripples are virtually absent. The opposite applies to the Balfour Formation where lower flow regime structures, viz., ripple cross-lamination and trough cross-bedding predominate. There is an even spread of (upper) flat-bedding, trough cross-bedding and ripple cross-lamination in the Burgersdorp Formation. Detailed measurement of typical short sequences from sections of the three formations, and transition matrix analyses, showed the facies assemblages to be of three stream types: (i) Katberg type: similar to Platte type of Miall (1977). Sediments were deposited by swiftly flowing, low sinuosity, braided, ephemeral streams with a predominantly sand bedload. Each flow started with preconsolidated silt and mud (flakes), and movement of exogenetic pebble lags. Channel avulsion and deposition of mud drapes in higher topographic levels of the stream were common phenomena. (ii) Balfour type: characterised by lateral accretion point bar type sequences of high sinuosity streams, and vertical accretion floodplain deposits. Lower flow regime dune and ripple bedform structures overlying (upper) flat-beds indicate a loss of stream power with channel migration. (iii) Burgersdorp type: similar to Katberg type for sandstone units, also crevasse-splays onto thick subaerially exposed floodplain aggradation reddish shales. Conventional microscopy and SEM studies showed tremendous diagenetic effects mostly in the form of secondary quartz growth in the sandstones of the three formations. Electron microprobe analyses were done on titanomagnetite grains from heavy mineral layers of the Katberg Sandstone, so that thermometric predictions could be made on provenance rocks. Palaeocurrents of the Katberg Sandstone are mostly Rank 4 and 5 types (Miall, 1974), i.e., they were generated within bars with not much change in stream orientation. Burgersdorp and Balfour formation palaeocurrents are Rank 1 - 3 types. In the case of the former this is owing to directional changes in channels as a result of frequent crevasse-splays, and in the case of the latter owing to differences in orientation between entire tracts of highly sinuous palaeostreams. Palaeocurrent directions in the Katberg Sandstone indicate a southeasterly provenance which accords with the findings of other Beaufort Group workers. Bed relief index calculations (Smith, 1970), made on Katberg rocks, considered together with the abundance of planar cross-bedding (of transverse bars) and apparent absence of longitudinal bars, testify to the deposition of the Katberg Sandstone in the distal parts of the braided stream environment. The Beaufort sediments of the study area have the sedimentological characteristics of a molasse sequence, but a different implied tectonogenesis. During Balfour sedimentation the equilibrium base was being raised very slowly at the source and complete fluvial sequences were deposited under a humid temperate climate, on a slowly subsiding plain. During Katberg/Burgersdorp times, source area tectonism was pronounced but interrupted and incomplete sequences were deposited under an arid climate. Provenance rocks for the formations studied included biotite mesoperthitic granite, granulite, charnockite, granite porphyry, granophyre, metaquartzite, greenschist and possibly diorite, epidosit e and alkaline volcanic rocks. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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- Date Issued: 1979
The behaviour of the elements Ni, Co, Cu, Pb, Zn, Au, Ag, Mo, Sn, W and U in the magmatic, hydrothermal, sedimentary and weathering environments
- Authors: Anderson, J R
- Date: 1979
- Subjects: Elements , Environment , Ore deposits , Classification , Geochemistry , Crystal chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4896 , http://hdl.handle.net/10962/d1001555
- Description: In the last two decades much has been published on the behaviour of certain elements in the magmatic , hydrothermal, sedimentary and weathering environments , but the information is scattered throughout the literature . This situation prompted the present study on the elements Ni, Co, Cu, Pb , Zn , Au, Ag , Mo , Sn, W and U. The behaviour of the elements Ni, Cu, Pb , ZN, Au, Sn , W and U has been studied experimentally in some depth. Ag has been moderately studied, but there is very little information about Co and Mo. Studies on the complexes formed by the elements within the hydrothermal and aqueous environment are often inconclusive and controversial , but conclusions are drawn as to the more likely complexes formed . A genetic classification of ore deposits is used as a framework for the discussion . The source of the elements is regarded as being the mantle, and therefore discussion on other possible sources is beyond the scope of this dissertation. The crystal chemistry and geochemistry of the elements are presented and the essay concludes with a discussion on the elements within their depositional environments
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- Date Issued: 1979
The geochemistry and petrology of the Karoo andesites and associated basalts of the north-eastern Cape Province
- Authors: Rumble, Keith Christopher
- Date: 1979 , 2013-02-11
- Subjects: Basalt , South Africa , Cape of Good Hope , Geochemistry , Petrology , Andesite
- Language: English
- Type: Thesis , Masters , M.Sc
- Identifier: vital:4902 , http://hdl.handle.net/10962/d1001562
- Description: New geochemical data consisting of major and 15 trace element analyses are presented for 41 rocks from three andesitic and associated basaltic rock occurrences in the North Eastern Cape Province. These include the Pronksberg, Belmore and Roodehoek localities. Field evidence suggests that the three andesites were emplaced during the early stages of Karoo volcanicity. Geochemical variations within the Pronksberg and Roodehoek andesite are small, manifesting the undifferentiated nature of the magmas. Variations within the Belmore andesite are interpreted as representing fractionation of orthopyroxene, accompanied by only minor plagioclase fractionation. Differences in trace element concentrations and inter-element ratios between the andesites and associated basalts of the Pronksberg and Belmore volcanic suites precludes the possibility of the two rock types being genetically related. Geochemical differences constrain the possibility of the three andesites being cogenetic. Magmatic processes resulting in their formation are, however, thought to be similar. The differences in chemistry between the Pronksberg Basalt (High K Type) and Pronksberg Basalt (Drumbo Type) are interpreted as representing the combined influence of weathering, the presence of amygdales and the within-flow variations of alkali elements on the Pronksberg Basalt (High K Type). Similarities in petrography and chemistry justifies a correlation of the Pronksberg Basalt (Drumbo Type) with the Drumbo Basalt Member in the Barkly East area. Data for the Drumbo Basalt (This study) in the Barkly East area confirms and complements previously presented data. Normative chemistry and strontium isotope data indicate a process involving crustal assimilation or melting of crustal rocks as being the most likely explanation for the genesis of the Karoo andesites , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1979
A review of mineral exploration drilling with particular reference to Southern Africa
- Authors: Bertram, N G E
- Date: 1980
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4931 , http://hdl.handle.net/10962/d1004930
- Description: The field of mineral exploration drilling is reviewed with particular reference to examples, and techniques practised, in southern Africa. Drilling is the most· definitive process in exploration and the most cost intensive. It is, therefore, imperative to insure that the maximum geological information available is obtained from a borehole to warrant the cost of drilling it. Methods and techniques of obtaining this information, at little additional expense, are described and reviewed. Non-core percussion and rotary drilled boreholes cost significantly less than diamond drill holes and, as a result, many more holes can be drilled for the money available. While the logging of cuttings is notoriously neglected in most exploration programmes; a great deal of information is available to the conscientious evaluator. Down-the-hole logging and sampling techniques improve the reliability of the borehole samples and provide rapid and inexpensive analyses and lithological data. Cored, or diamond drill boreholes, are the most versatile of the drilling methods available and provide the most reliable lithological and grade information. The handling, logging, sampling and storage of core and core data is discussed. For little additional expense, comprehensive and accurate borehole surveys can be conducted and oriented cores obtained from the borehole. The natural tendency of a borehole to deviate can be used to advantage with controlled drilling techniques. Multiple ore intersections are possible through controlled deflections from a master hole. Mathematical, statistical and simulation models are available to optimise borehole siting, spacing and grid dimensions .
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- Date Issued: 1980
A review of unconformity-type uranium deposits
- Authors: Dabrowski, F A
- Date: 1980 , 2013-04-02
- Subjects: Uranium ores , Mineralogy , Geochemistry , Unconformities (Geology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4917 , http://hdl.handle.net/10962/d1003289 , Uranium ores , Mineralogy , Geochemistry , Unconformities (Geology)
- Description: Intense interest in uranium in the past decade has led to the discovery of new kinds of deposits of which the so-called unconformity-type are economically the most important. Presently known occurrences are restricted to Australia and Canada where they are characterized chiefly by their spatial relationship to Lower-Middle Proterozoic unconformities. Other common features include similar host-rock assemblages, structural controls, alteration, mineralogy, age relationships and fluid-inclusion data. Similar characteristics in other vein-type deposits, including those of the Beaverlodge district in Canada, deposits in France and Portugal, and the Schwartzwalder mine in the United States, suggest that they may also be of the unconformity-type. Various interpretations of the geological relationships of unconformity-type deposits have resulted in a number of genetic hypotheses, which require different exploration philosophies. Nearsurface supergene processes are considered to be most important although other mechanisms may have played contributing roles in the concentration of uranium. There is considerable potential for further discoveries of unconformity-type uranium deposits throughout the world. No such deposits are yet known in southern Africa although several favourable Precambrian unconformities are present.
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- Date Issued: 1980
Geochemical and mineralogical aspects of the Molteno Formation, South Africa
- Authors: Reynolds, Adrian J
- Date: 1980
- Subjects: Sediments (Geology) -- South Africa , Mineralogy -- South Africa , Petrology -- South Africa , Geochemistry -- South Africa , Molteno Formation (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4901 , http://hdl.handle.net/10962/d1001561
- Description: The Triassic Molteno Formation is a clastic sedimentary sequence consisting of a series of cycles, dominated lithologically by coarse grained sandstones. Aspects of the petrography have been examined using the conventional petrographic microscope as well as the scanning electron microscope. Both solution and overgrowth features are present not only on the quartz grains but also on certain of the heavy mineral species present. Intrastratal solution of garnet would appear to be a significant feature in the Molteno Formation. Mineralogical examination of the laterally persistent Indwe Sandstone Member indicates no significant variation in heavy mineral content. Evidence from a study of zircon elongation ratios shows the presence of two distinct zircon populations indicating two provenance areas. X-ray diffraction and electron microprobe analysis has identified mineral species characteristic of granites, pegmatitic granite and metamorphic rocks, especially amphibolites. Palaeocurrent data indicates that this source area lay to the south-east; to the south the source area consisted mainly of the Cape Supergroup sediments. Analysis for Nb, Zr, Y, Sr, Rb, Zn, Mn, Ba, Cu, Ni, Co, Cr, V and Ti for 22 samples from the Molteno Formation, indicates, as expected for a highly arenaceous sequence, a substantial depletion in these trace elements. No consistent variation of trace element concentration occurs with height in the sequence so trace element content may not be used for purposes of stratigraphic correlation. There are indications of trace element variation with geographical position, no doubt a reflection of the contribution of 2 source areas of different compositions. Factor analysis of the interelement correlations has identified 3 factors which influence the trace element content of the Molteno Formation these are a "heavy mineral" factor, a "pH-Eh" factor and a "clay mineral" factor. These trace factors are ultimately an expression of the source rock composition, the prevailing climate and a combination of the two. Comparison with the more argillaceous overlying Elliot Formation, indicates that factors influencing geochemical variation in this sequence were far more complex than for the Molteno Formation
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- Date Issued: 1980
Geological and economic factors affecting ore reserve estimation and grade control in porphyry type deposits
- Authors: Reichhard-Barends, E O
- Date: 1980
- Subjects: Porphyry , Geology, Economic , Ore deposits , Copper mines and mining
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4921 , http://hdl.handle.net/10962/d1004466
- Description: From introduction: The mining of porphyry type deposits accounts for about 50% of the world's present copper (Figs.I,2) and molybdenum production and resources. Mining organizations therefore invest substantial amounts of time, money and skills in the location and delineation of these types of deposit. The optimization of this investment effort is based on complex inter-relationships between geological, economic and political factors. The object of this dissertation is to review the geological and some of the economic aspects involved in the exploration and evaluation of porphyry deposits . These may hopefully provide some practical guidelines for decision making during the exploration and evaluation of such deposits. For the purpose of this dissertation, the exploration-evaluation of porphyry deposits, has been divided into three main stages:- Stage 1 : Geological mapping, interpretation of exploration drilling results and other geological factors which may help in understanding the shape and nature of the deposit. A knowledge of existing geological models for porphyry deposits will be essential in understanding the geological factors affecting tonnage and grade of these deposits Stage 2 Stage 3 (see Part I). Determination of grade-tonnage relationships. This is important in order to establish the different tonnage-grade alternatives for the deposit. Based on this, reserve estimations are calculated for different possible scales of mining. Drilling and sampling techniques, as well as statistical and preliminary economic evaluation methods are applied during this stage (see Part 2). Mine development and feasibility studies involve factors that influence type and scale of mining, and factors affecting mineral processing and extraction in relation to tonnage- grade alternatives. These factors are reviewed in Part 3.
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- Date Issued: 1980
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
Interpretation of mineralogical, chemical and morphological features of duricrusts and its application to mineral exploration
- Authors: Friggens, Peter John
- Date: 1980 , 2013-04-02
- Subjects: Duricrusts , Mineralogy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5021 , http://hdl.handle.net/10962/d1006345 , Duricrusts , Mineralogy
- Description: Introduction: The object of mineral exploration is to locate economic deposits with minimum expenditure in time and money . In order to achieve this goal it is essential to select the most favourable environment and to design the search procedures for the environment in question. Duricrusts are a striking feature of tropical and subtropical landscapes where they occur as extensive, resistant horizons which form a surface or near-surface caprock and are best seen in incised landscapes. Since they cover many potentially rich mineral , provinces of the world, it is important to question what effect they have on mineral exploration. Duricrusts are defined as specific soil types formed by near-surface processes associated with weathering . In spite of the sheer aerial extent of soils over the landsurfaces of the earth, Levinson (1974) expressed surprise at how little exploration geologists know about this surficial environment . Weathering and pedogenetic processes therefore, require discussion in this text. However, in order to adhere to the scope of this dissertation only a brief description of the factors and characteristics of soil formation are given in the first chapter. In the second part, duricrusts are differentiated on the basis of composition into laterite, silcrete and calcrete. Beginning with a concise description of both natural and experimental investigations concerned with mineral decomposition and neomineralisation during weathering, the morphological, physical and chemical characters of each type are described. Environmental factors are then discussed in an attempt to identify specific duricrust types in terms of climate, geographic location, age and formation process . Once duricrust structure and texture are related to topography, specific types may be used to assess the significance of suspected markers in the landscape and permit identification of individual weathering surfaces on which mineralisation may give rise to gossans of widely different physical and chemical characteristics. The interpretation of photogeological, geochemical and geophysical data acquired during mineral exploration in duricrust terrains is problematical and some of the limitations to these search procedures are discussed in the final .chapter
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- Date Issued: 1980