3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Metallogeny of the Boschhoek base metals occurrence and its geological context with respect to the polymetallic mineralization of the Stavoren Fragment of the Bushveld Complex, South Africa(2024) Chauke, RamesThe Boschhoek Prospect is an epigenetic mesothermal copper, lead, zinc and silver deposit within repeatedly fractured Nebo granite of the Lebowa Granite Suite. The Prospect is exposed as hilly gossanous bodies that grade vertically downwards into siderite-calcite-quartz veins system. Similar deposit occurred at Mutue Fides Tin deposit comprising predominantly of tin and fluorite within miarolitic Bobbejaankop granite. These deposits are associated with local scale structures and they are spatially separated by a regional sinistral strike-slip Wonderkop Fault. The study examines the spatial relationships and possible structural control the Wonderkop Fault bears on local scale structures. It investigates metallogeny of base metals and evaluates the petrological character of the Boschhoek Prospect in relation to the Mutue Fides deposits. Extensive fieldwork characterising tectonic structures and structural analysis in the study areas suggest strong link between the Wonderkop Fault and the local scale structures. In syn- and post-BIC intrusion period, the northeast-southwest striking Wonderkop Fault underwent a compressional event directed at northwest-southeast that resulted in splay morphologies on the Transvaal inliers and the felsic plutonic bodies along the fault. Several warping events and rheological failures in response to this reactivation created small-scale faults and veins adjacent to the fault that are associated with polymetallic deposits. The local scale structures mimic morphologically and geodynamically the regional scale Wonderkop Fault. Petrographic studies show pervasive sericitization of the Nebo granite is characteristic of mineralised zones. The varied nature of siderite-calcite-quartz-hematite veins suggest metalliferous fluids emanate from numerous sources including the LGS, the nearby inliers and the connate waters. Greisenization and albitization characterises the mineralised zones in the Bobbejaankop granite. The metals source emanate from magmatic-hydrothermal fluids concentrated in cupolas. Geochemistry results suggest that the Nebo and Bobbejaankop granite are cogenetic and possibly share the same continental source as ascertain by normalised La/Yb ratios. The Bobbejaankop granite experienced higher fractionation degrees accompanied by intensive magmatic-hydrothermal alterations as ascertain by TEDI (Ba x (Sr/Rb)), Zr/Hf versus Y/Ho, Yb/Nb ratios and normalised REE plots. Normalised iv REE plots and petrographic studies suggest that Bobbejaankop granite melt assimilated the Stavoren granophyre and gave rise to the granophyric and the hydrothermally unaltered variety of the Klipkloof granite.Item Structure of the fada-gourma shear zone Eastern Burkina Faso(2018) Sehloho, Pulane RelebohileThe Baoulé-Mossi Domain in eastern Burkina Faso is a greenstone belt-granitoid terrane, formed in a volcanic arc tectonic environment. Volcanism and magmatism were coeval at around 2239 Ma, and this formed the basement rocks of the Fada-Gourma Shear Zone (FGSZ) region. Crosscutting relations observed in the field, aided by zircon U-Pb age data reveal that pluton emplacement continued to post-2167±12 Ma. The youngest units are NW-trending dolerite dykes, dated at 1814±26 Ma in eastern Burkina Faso. The study area has five defined deformation events. D1 is responsible for the remnant NW-trending S1 foliation in some of the granite gneisses and the foliated and gneissic granodiorites outside of the shear zones. The σ1 principal compressive stress orientation was NE-SW. The metamorphic grade associated with D1 is amphibolite facies. D2 had a NW-SE oriented compressive stress direction, and this resulted in thrust faulting and the NE-trending dominant structural grain in the study area. The associated metamorphic grade for D2 is lower amphibolite facies. D3 involved a dextral-reverse slip along faults with a NE trend, with southeast-block-up displacement. The principal compressive stress axis was ENE-WSW to ESE-WNW directed. Metamorphic grade associated with D3 is greenschist facies to lower amphibolite facies. D4 caused the sinistral reactivation of the NE-trending D3 structures. The sinistral shear overprint the dextral displacement and a sigmoidal foliation related to D4 is discernible on the aeromagnetic imagery data. The principal compressive stress axis during D4 was NNE-SSW to N-S oriented. The metamorphic grade during D4 was greenschist facies. D5 is a late-stage brittle deformation that led the formation of NW-trending extensional fracture cleavage planes. The imagery data was integrated with field data to aid in establishing the orientation of foliations, and the kinematic and geometric information at map scale and at outcrop scale. Petrographic descriptions provided information at a micro-scale where available. The study area is host to gold mineralization, and there is a network of active artisanal mines in the northern domains of the study area. Tambiga Hill is one of the larger actively mined quartz stockwork vein deposits in the Gourma region. Gold mineralization is concomitant with quartz veins, and is hosted either adjacent to the quartz veins, or within the veins. Gold is either invisible, or occurs as nuggets. Pyrite, tourmaline, ankerite and minor malachite are also present as accessory minerals within the quartz veins. Gold mineralization is associated with the late stages of D2, and D3.