Heavy mineral characterization and provenance interpretation of the Ecca Group of geological formations in Eastern Cape Province, South Africa
- Authors: Sinuka, Sikhulule
- Date: 2016
- Subjects: Minerals -- South Africa -- Eastern Cape -- Classification Geology -- South Africa -- Eastern Cape Formations (Geology) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2911 , vital:28125
- Description: The aim of the research focuses on characterizing heavy mineral assemblages and interpretation of the provenance of the Ecca Group of in the Eastern Cape Province, South Africa. In South Africa, the Ecca Group outcrops extensively in the Main Karoo Basin. Mudstone, siltstone, sandstone, minor conglomerate and coal are the major constituent lithologies within the group. For descriptive purposes, the Ecca is categorized into three different geographical areas: the southern area, the western and northwestern area and the northeastern area. Six of the sixteen geological formations, namely the Prince Albert, Whitehill, Collingham, Ripon, Fort Brown, Waterford and Koonap Formations are present in the study area and are best exposed in road cuttings. For purposes of comparison, the underlying Witteberg Group, the Dwyka (which has Formation status here), and the overlying Koonap Formation of the Beaufort Group, are included in the study. This study is motivated by the relatively little information that is available on the heavy minerals of the Ecca Group, and that research of this nature had not been undertaken in the study area before. Another contributing motivation was to determine whether heavy mineral assemblages could be used to identify formations of the Ecca Group and for correlating between different localities in accordance with studies done elsewhere. Additionally, diagnostic heavy mineral assemblages could aid with stratigraphic selection of future boreholes in the Ecca Group. Heavy minerals are natural provenance tracers because of their stable nature and hydrodynamic behaviour. They are both non-opaque and opaque, with apatite, epidote, garnet, rutile, staurolite, tourmaline and zircon being good examples of non-opaque grains while ilmenite and magnetite are the most common opaques. Heavies are either derived from stable minor accessory minerals or from abundant but unstable mafic components of the host rock. They are very useful in interpreting the provenance due to the fact that some minerals are diagnostic of certain source rocks. However, sediments are exposed to several factors (conditions) such as weathering, erosion, breakage due to abrasion, mixing and recycling during transportation from the source to the depositional area. This implies that there are parameters other than the parent lithology that determine their final composition.
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Stratigraphic interrelationships, sedimentology and post Karoo intrusions in the Katberg and Burgersdorp formations around the town of Whittlesea, Eastern Cape province, South Africa
- Authors: Mzana, Siphokazi Kwamnandi
- Date: 2016
- Subjects: Formations (Geology) -- South Africa -- Eastern Cape Sedimentology -- South Africa -- Eastern Cape Geology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15046 , vital:40157
- Description: Concentrating on the Katberg and Burgersdorp Formations, this research examined the sedimentary environments inter alia by conducting heavy mineral analysis, interpreting provenance and determining stratigraphic interrelationships of the two formations in the Tarkastad Subgroup (Beaufort Group, Karoo Supergroup) around the town of Whittlesea in the Eastern Cape Province of South Africa. It has been observed that the strata of the Katberg Formation are dominated by sandstones of a braided river system. On the other hand, the Burgersdorp Formation comprises mainly dark greyish-red mudstone, red shale with subordinate siltstone and red sandstone deposited on floodplains and channels of meandering rivers. The Katberg Formation becomes progressively less arenaceous to the north of the study area until it is virtually indistinguishable from the overlying Burgersdorp Formation. Dolerite dykes and sills that intruded the Karoo Supergroup disturbed and baked the sedimentary strata of the Tarkastad Subgroup as well as other Karoo successions. The Katberg formation is mostly found in elevated areas, commonly metamorphosed and capped by dolerite sills while the Burgersdorp is found in low lying areas and is less metamorphosed or not metamorphosed at all. Lithologies of the two formations and the Karoo dolerites have been geologically mapped and the interfingering relationship between the Burgersdorp and Katberg Formation is also shown on the map. Horizontal laminae, planar bedding and planar and trough cross-bedding characterise lithofacies in the two formations. The fossil hunt done during the course of the study did not yield any positive results in both formations. Initially, the pebbles from outcrops of the Katberg Formation in the East London area were described in hand specimen by Mountain (1939). This study took it further with petrographic- and modal analysis as well as grain size analysis for the sedimentary pebbles. Microscopic studies done on the rock samples collected in the study area revealed quartz and feldspar as the dominant constituents. Most of the feldspar is hazy as a result of dissolution and alteration to clays. Sparse sedimentary rock fragments and quartz overgrowths in some of the rocks and grains respectively, indicate phases of recycling from older sedimentary sources. Furthermore, the samples have a wide range of grain sizes, sorting, grain shapes and classification categories. Textural attributes of sediments such as mean grain size, sorting, skewness and kurtosis were used to characterise the nature of the transport processes and to reconstruct the depositional environment of the sediments. The sandstones of both the Katberg and Burgersdorp Formations are medium-grained and moderately sorted to moderately well sorted but the pebbles are very coarse- to coarse-grained. Deducing sediment provenance from the final product of a basin fill is anything but straight-forward because rocks break down and unstable minerals change during transportation along the pathways from source to basin and afterwards during diagenesis. Heavy mineral studies coupled with geochemical sandstone analysis were used to unravel the sources of sediments. Among the heavies found were opaque and non-opaque minerals which are highly resistant to weathering with zircon being the most dominant. The heavy mineral grains vary in shape from subround to angular-subround in shape. The integrated results of petrography, XRD, XRF and SEM/EDX were used to identify the source rock character and to evaluate the relative role of tectonics and climate in determining the geochemical composition of the Katberg and Burgersdorp sandstones. Sandstone composition was used to decipher the provenance and tectonic setting of source areas by standard triangular QtFL and QmFLt diagrams, tectonic setting discrimination diagrams and source rock composition diagrams to characterise the source rocks.
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Nature of occurrence and economic potential of granitic pegmatites of Mzimba district in Northern Malawi
- Authors: Salima, Jalf William Joseph
- Date: 2014
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: vital:11527 , http://hdl.handle.net/10353/d1016192
- Description: A swarm of granitic pegmatites occurs in Mzimba district from northern Kasungu to Kafukure near the western international border with Zambia. The granitic pegmatites are hosted by a mobile belt, within the Mozambiquan orogenic belt (c. 900 - 1800 Ma). They have been dated as 485 Ma. They intruded metasediments of high to medium grade metamorphic rocks of a Precambrian Basement Complex. The dominant trend of the pegmatites is NW - SE, exhibiting a cross-cutting relationship with the country rocks and their contacts with the latter are usually sharp. The six pegmatites investigated in this study are inhomogeneous, composed of a massive quartz core, an intermediate zone composed of a blocky pink K-feldspar rich sub-zone and muscovite rich sub-zone and a wall zone composed of quartz - pink K-feldspar - muscovite mineral assemblage. The Mzimba pegmatites are classified as lithium-caesium-tantalum (LCT) family of rare element granitic pegmatites as described by Černý and Ercit (2005). They belong to the beryl-columbite subtype and beryl-columbite-phosphate subtype of the rare element pegmatites. It is suggested that the pegmatites are the product of magmatic differentiation and that they form roofs of granite plutons lying deep below the current level of erosion. The six pegmatites were sampled and minerals analysed using standard analytical methods such as petrographic microscopy, X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis. Mineralogy of the granitic pegmatites indicates that they are predominantly composed of perthitic K-feldspar (perthite), Na-plagioclase (albite), quartz and muscovite as main mineral phases and accessory minerals including beryl, tantalite-columbite (ferrotantalite), iron-titanium oxides (ilmeno-rutile and ilmenite), tourmaline (schorl), garnet (almandine-spessartine) and triplite. Triplite is a very rare mineral found in a few pegmatites around the world, and this is the first reported account of this mineral in the Mzimba pegmatites and probably in Malawi. These minerals are being exploited by artisanal and small scale miners. Trace elements in K-feldspar and muscovite are significant indicators for the evaluation of economic potential of pegmatites as well as for the differentiation degree and origin of the magma. The K/Rb ratio for K-feldspars ranges between 12.72 and 109.38, while for muscovites it is between 16.66 and 82.36 indicating that the pegmatites are moderately evolved. The Ta versus Cs and the Ta versus K/Cs discrimination diagram indicates that all the investigated pegmatites plot above the 20 ppm threshold suggesting that the pegmatites have potential for Ta and Nb mineralization.
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Sedimentary environments and provenance of the Balfour Formation (Beaufort Group) in the area between Bedford and Adelaide, Eastern Cape Province, South Africa
- Authors: Oghenekome, Monica Enifome
- Date: 2012
- Subjects: Geology -- South Africa -- Balfour , Sedimentary basins -- South Africa -- Eastern Cape , Sediments (Geology) -- South Africa -- Eastern Cape , Sedimentation analysis , Beaufort Group (South Africa)
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: vital:11524 , http://hdl.handle.net/10353/d1004354 , Geology -- South Africa -- Balfour , Sedimentary basins -- South Africa -- Eastern Cape , Sediments (Geology) -- South Africa -- Eastern Cape , Sedimentation analysis , Beaufort Group (South Africa)
- Description: The research examines the sedimentary environments and provenance of the Balfour Formation of the Beaufort Group (Karoo Supergroup) in the Eastern Cape Province, South Africa. This Formation occurs in the southeastern part of the Karoo Basin. It consists of sedimentary rocks, which are an alternating siltstone, shale and mudstone succession with subordinate interbedded sandstone and subsequently intruded by Karoo dolerite in the form of sills and dykes. ithostratigraphically, the Balfour Formation is subdivided into five units namely, from the base to the top, the Oudeberg, Daggaboersnek, Barberskrans, Elandsberg and Palingkloof Members. The Balfour Formation is overlain by the Katberg Formation. This study involved field investigations in the vicinity of the towns of Bedford and Adelaide with integrated stratigraphical, sedimentological and petrological studies. A geological map was constructed after field investigations. Lithofacies of the Balfour Formation that were studied are characterised by sandstone facies (Sh, Sm, St, Sr, Sp) and fine-grained sediments (Fl or Fsm) which reflect point-bar, cut-bank, channel and floodplain deposits. Lithologically, the Oudeberg Member consists of sandstone of which some units are internally massive alternating with thin laminated siltstone and mudstone. The Daggaboersnek Member is characterised by regular, generally non-lenticular, overall stratification, in the Barberkrans Member consists of sandstone lithosomes, while the Elandsberg Member is an argillaceous unit, similar to the Daggaboersnek Member. The Palingkloof Member is composed predominantly of red mudstone that can be used to distinguish the Balfour Formation from the overlying Katberg Formation, which consists predominantly of sandstone. The stratigraphic sequence displays two fining upward megacycles of sedimentary deposits with change in the sediment supply pattern from low-sinuosity to high-sinuosity river systems which reflect both braid and meandering deposits, respectively. Sedimentary structures in the sandstone units and the provenance of the Balfour Formation indicate that these deposits were produced by rivers flowing from the southeast with minor drift towards the northwest. According to the composition of the sediments and their sequence of deposition the Formation represents a fluvial environment. Mineralogical and grain size data from the sandstones of the various members of the Balfour Formation indicate the same source area of granitic, metamorphic and older sedimentary rocks and show no significant petrographic differences. The petrographic and geochemical investigations confirmed the sandstone to be feldspathic litharenite and ultralithofeldspathic sandstone. The palaeocurrent investigation indicates the main provenance to have been situated to the southeast of the Karoo basin. Heavy-mineral concentrations within the sandstones also give an indication that the source had a transitional arc plate tectonic setting.
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Lithostratigraphy sedimentology and provenance of the Balfour Formation Beaufort Group in the Fort Beaufort Alice area Eastern Cape Province South Africa
- Authors: Katemaunzanga, David
- Date: 2009
- Subjects: Sedimentary structures -- South Africa -- Eastern Cape , Formations (Geology) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: vital:11521 , http://hdl.handle.net/10353/274 , Sedimentary structures -- South Africa -- Eastern Cape , Formations (Geology) -- South Africa -- Eastern Cape
- Description: A traverse through the Balfour Formation was chosen in the area around the towns of Fort Beaufort and Alice in the Eastern Cape Province. The main objectives of the study were to map the lithological variations within the Balfour Formation and to distinguish it from the underlying Middleton Formation and the overlying Katberg Formation. A combined desktop, field and laboratory approach was used in this study. Aerial photographs, satellite images and digital topographical maps formed the basis of the desktop work. After desktop mapping, a number of field traverses were measured through the study area. Sedimentary structures were observed, photomosaics were done, stratigraphic sections were measured and samples were collected for thin sectioning, heavy mineral separation and major, trace and REE analysis. Sedimentological development of the Balfour Formation has been outlined in relation to its provenance during the Late Permian. Lithological variation of the Balfour Formation is characterised by alternating sandstone-dominated and mudstone-dominated members. Arenaceous Oudeberg and Barberskrans Members are contain facies ranging from intraformational conglomerates (Gmm), massive sandstones (Sm & Ss), horizontally laminated sandstones (Sh), planar and trough cross-bedded sandstones (Sp, Sl & St), trough cross-laminated sandstones (Sr) and fine-grained sediments (Fm & Fl), whereas the mudstone dominated members are characterised by the facies Fm and Fl. Lithofacies together with bedforms observed in the Balfour Formation were used in architecturalelement analysis. Sandstone–rich members are dominated by channel fill elements such as LS, DA, SB, LA and CH, whereas the fine-grained component consists of mainly, FF iii element. The mudstone-dominated members contain FF, CS and LV elements, with LA, SB and CH in the subordinate sandstones. Petrography, geochemistry and palaeocurrent analysis indicated that the source of the Balfour Formation was to the south-east and the rocks had a transitional/dissected magmatic arc signature. This led to the postulation of the Karoo Basin to have developed in a retro-arc foreland basin where there was supralithospheric loading in the Cape Fold Belt due to a compressional regime initiated by the subduction of Palaeo-Pacific plate underneath the Gondwana plate. The tectonic loading was episodic with eight major paroxysms affecting the Karoo Supergroup. The Balfour Formation coincides with the fourth paroxysm, this paroxysm in turn consists of two third-order paroxysm that initiated the deposition of the Oudeberg and Barberskrans Members in low sinuosity streams. Each paroxysm was followed by a period of quiescence and these resulted in the deposition of the Daggaboersnek, Elandsberg and Palingkloof Members in meandering streams. Depositional environments were determined mainly from the sedimentary structures and 3D architecture of the rock types. Sandstone rich members were formed by seasonal and ephemeral high energy low sinuous streams whereas the fine-grained rich members were formed by ephemeral meandering streams. Palaeoclimates have been equated to the present temperate climates; they were semi-arid becoming arid towards the top of the Balfour Formation. This has been determined geochemistry (CIA), sedimentary structures and other rock properties like colour.
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