Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study presents results of a detailed geological mapping and structural analysis of auriferous quartz-vein sets of the nine current open-pit operations, of the Siguiri Mining Complex in the northeastern parts of Guinea. The Siguiri Mining Complex is hosted by a low-grade metamorphic, turbiditic succession within the larger Siguiri Basin, which forms part of the Palaeoproterozoic Birimian Supergroup of the Boualé-Mossi domain on the West African Craton. The Siguiri Mining Complex is located in a deeply weathered saprolite profile developed over the monotonous succession of interlayered metapelites and -psammites. In fresh bedrock and core samples, the host succession is mainly made up of quartz-muscovite schists, muscovite-chlorite schists and metagreywackes, with isolated occurrences of intraformational breccias. The main deformation to have affected the metasedimentary succession of the Siguiri Mining Complex can be assigned to a D2 deformational event. D2 structures comprise of north-south trending strike-slip and reverse faults anastomosing around and enveloping open- to tightly folded domains exposed over an area of 12 by 3 km. The geometry, orientation and kinematics of faults and folds suggest that D2 structures formed during progressive deformation in an overall dextral transpressive brittle-ductile shear zone. Structures within the D2 corridor record east-northeast subhorizontal shortening and north-northwest subhorizontal extension. An omnipresent carbonate alteration in form of carbonate-alteration spots testifies to the pervasive, syn-D2 hydrothermal fluid-flow within the sediments. A structurally- and fracture-controlled fluid-flow is evidenced by the abundance of auriferous quartz veins throughout the Siguiri Mining Complex. These quartz veins host the bulk of the gold mineralization. One main and, at least, three minor sets of auriferous quartz veins can be distinguished. The main quartz-vein set shows very consistent easterly to northeasterly trends and steep southerly dips throughout the Siguiri Mining Complex. This orientation is consistent with the dextral transpressive kinematics and strain within the D2 host structure and illustrates the significance of D2 strains for the mineralization. The volumetrically minor vein sets can be shown to be related to different stages of F2 folding and fold amplification. Zones of economic-grade mineralization occur in areas where competent, psammitic units are developed in structural sites of increased dilatancy. Areas of dilatancy are represented by either dilational jog geometries within the overall transpressive structure or zones of pronounced shear-zone subparallel stretch. Jog geometries could be identified in the larger Bidini-Toubani-Sanu Tinti Complex having formed as a result of the anastomosing geometry of the bounding D2 shear zones. In the large Kami Complex, F2 axial culminations and depressions correspond to zones of increased stretch within the D2 transpression zone, delineated by closer vein spacing and the formation of D2 normal faults parallel to the main vein set and normal to F2 fold hinges. The size and extent of the Siguiri Mining Complex suggests that the host D2 transpressive corridor must be assumed to have a significantly larger along-strike continuation, being part of a larger shear zone system related to the accretionary history of Palaeoproterozoic basins and arcs onto the Archaean Man Shield in West Africa. / AFRIKAANSE OPSOMMING: Hierdie studie lewer die resultate voor van 'n gedetailleerde geologiese kartering en strukturele analise van die gouddraende kwarts-aar stelle in die huidige nege oop-groef operasies van die Siguiri Myn Kompleks, in die noordoostelike deel van Guinea. Die Siguiri Myn Kompleks is geherberg deur 'n lae metamorfiese graad turbidiet suksessie in die groter Siguiri Kom, wat deel form van die Paleo-Proterosoïkum Birimian Supergroep van die Boualé-Mossi streek op die Wes Afrika Kraton. Die Siguiri Myn Kompleks is geleë in die diep veweerde saproliet profiel, wat onwikkel het oor die eentonige suksessie van metapeliete en -psammiete. In vars bodemrots en kern monsters is die herberg-gesteente opgemaak uit kwarts-muskoviet skiste, muskoviet-chloriet skiste en metagrouwakte, as ook afgesonderde voorvalle van intraformasie breksies. Die hoof deformasie fase wat die metasedimentêre suksessie van die Siguiri Myn Kompleks geaffekteer het, kan toegeken word aan 'n D2 deformasie gebeurtenis. D2 strukture bestaan uit noord-suid neigende strekkingwaartse verskuiwings en opskuiwings, wat anastomoserend oop- en steil geplooide gebiede omsluit en is oor 'n area van 12 by 3 km ontbloot. Die geometrie, oriëntasie en kinematika van verskuiwings en plooie stel voor dat D2 strukture gevorm het tydens progressiewe deformasie in 'n algemene regse transpressie skuifskeursone, onder brosheid-duktiliteit toestande. Strukture in die D2 gang wys 'n oos-noordoos subhorisontale verkorting en 'n noord-noordwes subhorisontale verlenging. Die alomteenwoordigheid van karbonaat alterasie, in die vorm van karbonaat-alterasie spikkels, getuig van die deurdringende, sin-D2 hidrotermiese vloeistof vloei in die sedimente. Die strukturele- en breuk-beheerde vloeistof vloei is ook duidelik, as gevolg van die oorvloed van gouddraende kwarts-are reg deur die Siguiri Myn Kompleks. Die kwarts-are bevat die grootmaat van die goud mineralisasie. Een hoof, en te minste drie minder belangrike stele van gouddraende kwarts-aar stelle kan uitgeken word. Die hoof kwarts-aar stel wys konstante oostelike to noordoostelike neigings en steil suidelike hellings, reg deur die Siguiri Myn Kompleks. Die oriëntasie is konstant met regse transpressie kinematika en vervorming in die D2 strukture en illustreer die belangrikheid van D2 vervorming vir mineralisasie. Die minder-belangrike aar stelle is verwant aan die verskillende staduims van F2 plooiing en plooi amplifikasie. Sones van ekonomiese graad mineralisasie kom voor in areas waar bevoegde eenhede van psammiete ontwikkel het in strukturele terreine van verhoogde dilatasie. Areas van dilatasie word verteenwoordig deur dilatasie uitwykings in die transpressie strukture of sones van skuifskeur subparalelle verlenging. Uitwykings geometrië kan geidentifiseer word in die groter Bidini-Toubani-Sanu Tinti Kompleks, waar dit gevorm het asgevolg van die anastomoserende geometrie van die D2 skuifskeur sones. In die groter Kami Kompleks kom F2 aksiale kulminerings en depressies voor in sones van verhoogde strekking binne-in die D2 transpressie sone en word uitgebeeld deur nader aar-spasiëring en die formasie van D2 afskuiwings, parallel aan die hoof kwarts-aar stel en normaal met betrekking tot die F2 plooi-skarniere. Die groote en omvang van die Siguiri Myn Kompleks stel voor dat die D2 transpressiewe gang nog n groter voorsetting het, en vorm deel van 'n groter skuifskeur sisteem en is verwant aan die anngroeings geskiedenis van die Paleo-Proterosoïese komme en boë aan die Argeïese Man Skild in Wes Afrika.

Gold exploration in the laterite terrains of the Siguiri basin (Guinea-West Africa) is discussed in this thesis. It seeks to propose and develop effective and reliable geochemical exploration techniques applied in such laterite terrains. The study is also intended to investigate and provide some geological clues as to why, in some target areas, the reconnaissance test drilling across the geochemical anomalies couldn’t intersect economic gold mineralisation. Targets were generated based on soil geochemical results, some of which were drilled without delivering economic discoveries even on areas with strong and consistent geochemical signatures. To find the failure and define the appropriate methods to be used is the core of the thesis. More importantly, the geological observation is aimed at sourcing and establishing the nature and validity of geochemical anomalies within the license area and their relationship with the underlying lithologies and structural networks. The geological field work conducted during this study is mostly based on regolith and surface geological mapping. The thick laterite cover, deep weathering, bedrock geology, gold geochemistry (the gold geochemical anomalous results are defined according to historical data before 2007), soil formations and variations in climate conditions are emphasized to illustrate the importance of mineral element mobility and dispersion in the weathering profiles. The knowledge and experience in regolith geochemistry and regolith mapping provide the advantage to exploration geologists. The depletion of ore resources and reserves in Siguiri and the continuous decline of the gold price in comparison to the complexity of exploring for gold are demanding more scientific-related thoughts and techniques to be integrated in the available geological, geochemical and geophysical information so as to reduce costs. The integration of good exploration strategy and technique may result in the possibility of making viable discoveries in this highly competitive geological environment where the mineral resources become depleted every day.

The present study provides the results of detailed mapping and analysis of structures encountered in Seguelen pit of Siguiri gold mine, Guinea, where the Siguiri mine is geo-tectonically located in the Baoulé-Mossi domain of Man Shield in West African craton. The gold deposit is hosted in low-grade metamorphic sediments of turbidites sequences which form part of the Lower Proterozoic of Birimian Super group. Three rock formations of Balato, Fatoya and Kintinian underlay the overall pits. The Siguiri gold mine is characterized by the deep weathering profile, developed over the rocks reaching 200 m below the surface in some areas and often capped by the lateritic gravel or duricrust. The rock formations at Seguelen area are characterised by strong bedding monotonously dipping towards SW and trending NW-SE. The lithology of the host rocks has strong control on the disseminated mineralisation throughout the deposit. Two domains of rock formations are clearly distinguished at Seguelen:  Fatoya Formation(Ffm) domain ; and  Kintinian Formation (Kfm) domain. The two domains are separated by a contact zone of 1.7 m wide parallel to bedding and characterised by the presence of quartz fragments as well as thinly sheeted shale and black shale. This contact zone is identified as disconformity. The major tectonic deformation which has affected the region is known as D2 corresponding to the Eburnean orogeny. The major D2 related structures is the regional thrust striking N-S over an area of 12 km long and 3 km wide and within which corridors all Siguiri gold Mine open pits are located. In the N-S trending structures, there is east-northeast shortening and north-northwest extension. There is pervasive hydrothermal alteration (carbonatization and sideritization) and supergene alteration in the all pits. The hydrothermal alteration attests the intensity of hydrothermal fluid-flow over the host rocks. The hydrothermal fluids flowed along the fractures and within the wall rocks through bedding plans to form numerous auriferous quartz veins bearing disseminated sulphides through chemical reaction between fluids and wall rocks, which are remarkable at Seguelen pit. Three quartz vein sets are distinguished at Seguelen:  NNE-SSW quartz vein set  NE-SW quartz vein set  NW-SE quartz vein set The NE-SW and NNE-SSW quartz veins are often lenticular and associated with the bulk mineralisation.

The Koulekoun Gold project is the most important prospect of Avocet Mining plc. It is one of the projects within the TriK-block in Guinea (West Africa) for which an exploration permit has been granted. The Koulekoun deposit is located within the Siguiri basin of Birimian age in the Eastern Guinea region; where most Guinea’s gold mines are situated. The present study involves the investigation of structural elements (S₀, S₁, S₂, intrusive contacts, faults and veins) from selected drill cores from drill sections that intersect the Koulekoun orebody in four parts of the deposit; characterizes the principal orientations of measured structures and determines their relationships using stereonet; in order to predict important intersections to focus on in exploration programs within the TriK-block and suggests a possible structural model of the Koulekoun deposit. Raw data used for the present research was collected from half-core samples due to the absence of surface outcrop from which direct measurements could have been made. Measured data were interpreted using stereographic projection. Often no preferred orientations of structural elements exist in the area, suggesting a complex structural situation, particularly with regard to hydrothermal vein attitudes. Thus, it has been illustrated from structural data analysis and S₀ data 3d interpolation of the four sub-structural domains (North-East, North-West, Central and South) that NE-SW structures (S₂, intrusive contact, fault and vein) have controlled the occurrency of gold mineralization in the Koulekoun deposit area. Geometrical relationships between structure main cluster orientation from stereonet analysis show the majority of S₀ moderately E-dipping; intrusive contacts dip at moderate angle to the SE in all zones, except in the North-East zone where they are sub-vertical and SE-dipping. Fault planes show variable orientation of NE-SW, NW-SE and E-W, and steeply SE-dipping. Vein planes correspond to fault systems and show high variability in their orientation with numerous orders of vein direction in each domain. The cross-cutting relationships suggest two principal generations of faults: the NE-SW fault (F1) and the NW-SE fault (F2). These two fault systems and their associated vein intersection areas preferably define the ore shoot zones within the Koulekoun deposit. The proposed structural model of the Koulekoun deposit suggests the intersection and interference of major NW-SE and minor NE-SW structures. The interference of folds formed basin-dome structures with oval shape geometries striking NW-SE and that dominantly occur in North-East, North-West and Central zones. The South Zone is characterized by NE-SW gently plunging and moderately inclined folds with NW-SE striking axial surface. Gold mineralization occurs at the edges of basin-dome structures in North-East, North-West and Central zones. Mineralized porphyry intrusions are likely located within the axial surface of the South zone folds and extend toward the Central zone. The proposed model is compliant with the earlier model of the Koulekoun deposit presented by Tenova (2013); Fahey et al. (2013) describing the Koulekoun deposit as an auriferous NE-SW trending fault zone, intersecting a major NW-striking and steeply E-dipping porphyry units. The model also fits within the regional structural context suggested by Lahondere et al. (1999a) related to the E-W vein structures attributed to NW-SE fractures and to the conjugated fault of NE-SW direction. Comparatively to the three industrial gold deposits (Siguiri, Lero, Kiniero) being currently mined in the Siguiri Basin, and defined as mesothermal vein and lode mineralization hosted in Birimian meta-sedimentary rocks (Lalande, 2005), the Koulekoun gold deposit appears to be a porphyry hosted orogenic disseminated style mineralization system (Fahey et al., 2013). Although, similarities between the Koulekoun gold deposit and these three industrial deposits (Siguiri, Lero, Kiniero) constitute of the intensive extends of the weathering profile and at some stages, by the existence of numerous ring-shaped and curved lineaments enhanced by drag folding (Lero deposit for instance). It is therefore recommended that targets selection around the Koulekoun deposit and within the TriK-block for further exploration programs be concentrated along NW-SE structures, in objective to determine possible intersection zones with NE-SW structures.