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.

Within the framework of this research, the complex geological history of the Pan African-Volta basin has been systematically reconstructed. Based on a broad review of literature and new data, 5 stages of geological-tectonic development have been identified. For the first time a systematic review of the mineral potential of the Pan-African Volta Basin was executed. Known and potentially existing mineralization have been related to the geotectonic history and metallogenetic conclusions have been drawn. Based on the findings of this research, the folded thrust belt located at the eastern rim of the Volta basin has been identified as the most prospective area for the ultramafic rocks with chromite, nickel mineralization and PGEs, hydrothermal gold and banded iron formation (BIF) but this will require further work.

Within the framework of this research, the complex geological history of the Pan African-Volta basin has been systematically reconstructed. Based on a broad review of literature and new data, 5 stages of geological-tectonic development have been identified. For the first time a systematic review of the mineral potential of the Pan-African Volta Basin was executed. Known and potentially existing mineralization have been related to the geotectonic history and metallogenetic conclusions have been drawn. Based on the findings of this research, the folded thrust belt located at the eastern rim of the Volta basin has been identified as the most prospective area for the ultramafic rocks with chromite, nickel mineralization and PGEs, hydrothermal gold and banded iron formation (BIF) but this will require further work.:Table of contents Table of contents iii List of tables v List of figures 1 Introduction 5 Summary of work done 6 Acknowledgements 6 1 In the Geology and regional geotectonic development of the West African Shield 7 1.1 Introduction 7 1.2 The basement of the Proterozoic sedimentary platform cover 9 1.3 Connection of West African Shield to Brazil 10 1.4 The Neoproterozoic sedimentary sequence and the extent of the Volta Basin 13 1.4.1 Introduction 13 1.4.2 The Neoproterozoic Sedimentary Sequence 15 1.5 The Pan-African Mobile Belt 23 1.5.1 The Buem Fold and thrust belt 23 1.5.2 New defined units 30 1.6 Interpretation of the deep structure of the Volta Basin 35 1.7 Metallic Minerals 37 1.7.1 Introduction 37 1.7.2 Iron (Fe) 39 1.7.3 Aluminium (Al) 46 1.7.4 Manganese (Mn) 50 1.7.5 Lead (Pb) 52 1.7.6 Copper (Cu) 55 1.7.7 Mineralisation related to ultramafic rocks 57 1.7.8 Gold (Au) 69 1.7.9 Tantalum (Ta) 72 1.7.10 Zirconium (Zr) 73 1.7.11 Heavy minerals in sands of Paleochannels 76 1.8 Non-metallic minerals 83 1.8.1 Introduction 83 1.8.2 Limestone (CaCO3) 84 1.8.3 Magnesite (MgCO3) 91 1.8.4 Barite (BaSO4) 93 1.8.5 Diamonds 97 1.8.6 Bitumen 100 1.9 Mineral Prediction with advangeo® Prediction Software 102 2 Minerogeny 109 2.1 Mineralisation controls and indicators 109 2.1.1 Geochemical Properties of selected stratigraphic units 109 2.1.2 Intrusive rocks 114 2.1.3 Volcanic rocks 118 2.1.4 Fault structural controls 119 2.1.5 Reactive Rocks 121 2.1.6 Other sedimentary controls: placers and paleoplacers 122 2.1.7 Laterites 122 2.1.8 Control of diamond occurrences 132 2.2 Key stages of metallogenic development 132 3 Discussion and recommendations 136 3.1 Recommendations 138 4 List of References 139 5 Appendices 144 5.1.1 Sample G113RK1 144 5.1.2 Sample G109RK1 145 5.1.3 Sample G116RK1 147 5.1.4 Sample G121RK1 149 5.1.5 Sample G121RK2 151 5.1.6 Sample G121RK3 152 5.1.7 Sample G131RK1 154 5.1.8 Sample G144RK2 155 5.1.9 Sample G145RK1 156 5.1.10 Sample G147RK1 157 5.2 Thin Sections 159 5.3 Deep drilling Data 174 5.4 Geophysical Datasets 176 5.5 Geochemical properties of volcanic rocks 181 5.6 Regional Geochemical Datasets (MSSP) 186 5.6.1 Methodology of data processing 188 5.7 Geochemical analysis – Electronic Dump 190 5.8 Geochemical properties of selected geo-tectonic units 190 5.8.1 Epicratonic basin 190 5.8.2 Foreland Basin 195 5.8.3 Thrusted continental margin 202