Petrography and geochemistry of the Masoke Iron Formation and its associated ferruginous counterparts, kanye basin Botswana
- Authors: Nkabelane, Ndifelani Oriel
- Date: 2019
- Subjects: Petrology -- South Africa , Geochemistry -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/115221 , vital:34101
- Description: A sequence of Transvaal Supergroup sediments extends into southern Botswana beneath Kalahari cover as the Kanye basin, these are known to host billions of tons @ 60>Fe. Masoke Iron Formation (Kanye Basin) which is stratigraphic correlative of The Ghaap Group and Chuniespoort Group of the Griqualand West basin and Transvaal basin, respectively. The Palaeoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa hosts high grade (>60% Fe) hematitic and specularitic iron and manganese mineralisation. It is therefore important to study and record the petrographic, mineralogy and geochemistry of Masoke Iron Formation, compare the results to the much known Kuruman and Griquatown Iron Formations. This study systematically investigate and record the petrography, mineralogy and geochemistry of all Masoke Iron Formation of Taupone Group in the Kanye Basin, which is stratigraphic correlative of The Ghaap Group and Chuniespoort Group of the Griqualand West basin and Transvaal basin, respectively. The further objective is to compare Masoke Iron Formation to the equivalent units in the Transvaal basin and Griqualand basin. In contrast to both Transvaal and Griqualand West Basin the Masoke iron Formation (Kanye Basin) has not been the subject of systematic scientific investigations. The study covers three main areas in the Kanye Basin: Keng Pan Area, Ukwi/Moretlwa hill and Janeng Hill Area. The mineralogy and geochemistry of these areas are presented in this study. Kanye Basin has a potential to host a large iron ore deposit, the geological setting in this area incorporates many of the elements necessary for iron ore formation. These include: banded iron formation (BIF), major unconformities with prolonged periods of weathering, carbonate sequences etc. In addition, several large deposits and mines are known from this area. This area can potentially have both hypogene and supergene enrichment of BIF. In this model, prospectively for new deposits is a function of the following: presence of iron formation units, proximity of mapped Asbestos Hills and Voëlwater BIF, thrust faulting (as indicated by the aero-magnetic interpretation), duplication of the ore horizon by folding, intersection of the BIF by major extensional fault, proximity of Olifantshoek/Waterberg outcrop, Gamagara unconformity, presence of carbonates (dolomites) and thin Kalahari sand cover. Major BIF units in the area of study include: the Masoke Iron Formation, equivalent to Kuruman Formation of the Asbestos Hills Subgroup, the Rooinekke iron formation of the Koegas Subgroup and the Hotazel Formation of the Voëlwater Subgroup. Supergene enrichment of these BIFs may occur wherever they are overlain by a major regional unconformity. The base of the Waterberg and the OlifantshoekSupergroups represent major unconformities in this regional target area. Potential for hypogene deposits is indicated by faulting (preferably extensional) proximal to BIF.
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- Date Issued: 2019
Petrography, geochemistry and origin of atypical sedimentary-igneous contact relationships at the base of the Hotazel Formation around Middelplaats, Northern Cape Province, RSA
- Authors: Terracin, Matthew Theodore
- Date: 2014
- Subjects: Petrology -- South Africa , Geochemistry -- South Africa , Igneous rocks -- South Africa , Manganese ores -- South Africa , Manganese ores -- Geology -- South Africa , Metasomatism (Mineralogy) , Potassium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5059 , http://hdl.handle.net/10962/d1012985
- Description: In the Middelplaats mine area of the Kalahari manganese field, two drill holes (MP53 and MP54) intersected anomalously high-grade manganese ore sitting stratigraphically just above an igneous body (likely a dike or sill). Manganese ore located within approximate 5 meters of the contact with the underlying igneous rocks has been substantially metasomatically upgraded from 25 percent manganese, to over 40 percent whilst the dominant manganese species within the ore has been altered to hausmannite. This report demonstrates the metasomatic alteration is related to devolatilization (removal and/or remobilization of H₂O, CO₂ and CaO) due to contact metamorphism caused by the underlying igneous rocks. The Middelplaats mine is situated in the southwest corner of the Kalahari manganese field where the paleo basin shallows out and ends. Within the mine area, several stratigraphic units pinch out or are truncated by the side of the basin. This pinching out of lithological formations has led to the underlying Ongeluk Formation being in contact with the much younger units of the Hotazel Formation. Therefore, geochemical investigation into the nature and source of the igneous rocks was also undertaken to see if the rocks from the two drill holes were related to one another and/or the underlying Ongeluk Formation. Results of these geochemical studies have demonstrated that the Middelplaats igneous rocks (dolerites) from the two drill holes (MP53 and MP54) share a co-genetic source region. There is also reasonable geochemical evidence that the source region of the Middelplaats igneous rocks was substantially similar to the source region of the Ongeluk Formation. This may indicate that the source region of the Ongeluk Formation was reactivated at some later stage resulting in the emplacement of doleritic dikes or sills in the Middelplaats mine area. The Middelplaats igneous rocks were also found to have undergone a slight but pervasive potassic alteration; with most of the original plagioclase feldspar showing some level of replacement by a potassium enriched feldspar. Although no source for this potassic fluid was found, the devolatilization reaction within the manganese ore appears to have released some potassium into the surrounding rocks. This additional potassium may be responsible for some localized potassic alteration.
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- Date Issued: 2014
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