Masters Degrees (Earth Sciences)

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Browsing Masters Degrees (Earth Sciences) by Author "Carelse, Candice"

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    Mineralogy and provenance of the Namakwa Sands heavy mineral satellite deposits
    (Stellenbosch : Stellenbosch University, 2012-12) Carelse, Candice; Rozendaal, Abraham; Stellenbosch University. Faculty of Science. Dept. of Earth Sciences.
    ENGLISH ABSTRACT: Five areas proximal to the world class Namakwa Sands heavy mineral deposit have been studied and include the farms Houtkraal Remainder Portion 2, Houtkraal Remainder, Geelwal Karoo, Graauwduinen and Rietfontein. These are locally referred to as the satellite deposits and are sub-economic occurrences. The primary objective of the study was to quantify the mineralogy and mineral chemistry, determine the provenance of the heavy mineral suite and draw a comparison between the satellite deposits and the Namakwa Sands deposit from an exploratory point of view. Methodology used to achieve the above objectives included optical microscopy, Scanning Electron Microscope (SEM), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN), X- Ray Fluorescence (XRF) and Zr-geothermometry of rutile. The five satellite areas contain the same heavy mineral suite but mineral proportions differ. The total heavy mineral population (THM) are diverse and consist of ilmenite and its alteration products (hydrated ilmenite, pseudorutile and leucoxene), magnetite, hematite, spinel, rutile, tourmaline, pyroxene, amphibole, garnet, aluminosilicates, staurolite, corundum, epidote, zircon, monazite and sphene. Ilmenite and garnet are the two most dominant heavy minerals present. The valuable heavy minerals (VHM) suite consists of ilmenite, zircon, rutile and leucoxene. The mineralogy of the satellite areas and chemistry of the ore minerals (rutile, zircon, ilmenite and leucoxene) are similar to the Namakwa Sands deposit. The whole spectrum of ilmenite alteration products (hydrated ilmenite, pseudorutile, and leucoxene) is present and allowed the quantitative use of the alteration index. The indices is low (22-24%) and indicates that the surficial deposits have formed under arid to semi-arid climatological conditions which preserved the pristine character of most of the minerals. This allowed reliable provenance studies using the characteristics of most of the heavy mineral suite, which showed that the minerals were derived from a diversity of source rocks. These included mainly medium to high-grade metamorphites and felsic intrusives of the underlying Mesoproterozoic Namaqualand Metamorphic Complex and a minor contribution from the Neoproterozoic Gariep Supergroup. This relationship indicates a limited transport distance from source to depositional basin. Mineral ratios in particular the THM-VHM relationship showed that the deposits located close to the shoreline such as Geelwal Karoo, Graauwduinen and Rietfontein have a relatively low proportion of valuable heavy minerals whereas those more inland such as Houtkraal Remainder Portion 2 and Houtkraal Remainder are close to unity. Heavy mineral concentration as such is low in the satellite areas and the mechanism to increase the concentration is clearly not only a function of distance from the present shoreline but is also topographically controlled. Steep sided linear depressions channelled the unconsolidated sediments and heavy minerals were upgraded into economic concentrations by aeolian processes. The quality of the valuable heavy minerals in the satellite areas however is similar to those of the adjacent Namakwa Sands deposit. This study has demonstrated that Houtkraal Remainder is the northeasterly continuation of the red aeolian sand (RAS) associated East Mine orebody and offers the best exploration potential.