Ultra deep mining presents many challenges to the mining engineer, one of which is the logistics to support mining operations quickly and efficiently. Typically, Witwatersrand gold mines operate at depths in excess of 2000 m with stoping taking place to 3500 m and investigations underway to mine to a depth of 5000 m. As mining progresses deeper and further from the shaft, the role of logistics becomes increasingly important if production targets are to be achieved. Access to the workings is often via sub vertical and even tertiary subvertical shaft systems with working faces as far as five kilometers from the shaft. It is inevitable therefore, that distance will negatively impact the working time available at the stope face, material transportation and distribution, as well as the removal of broken ore. Possible solutions to these logistical problems may be found in the use of different transportation systems or by applying sound design and operational principles to transportation systems, both in the horizontal and instope areas. This thesis investigates the challenges of logistics for ultra deep level gold mining in the Witwaterstrand basin for mining layouts planning to mine between 3000 m and 5000 m underground with typical horizontal distances of over 3000 m. The transportation needs analysis recognised that vertical transportation is a wellmanaged and organised system and is mainly the same for both shallow and deep level operations. As a result of this, the thesis only focuses on the logistical issues of the horizontal and in-stope processes. The literature review indicates that the majority of work previously conducted on transportation focused around the area of horizontal transportation with limited inputs to in-stope transportation systems. The review concludes that the traditional locomotive transportation system is the most applicable mode of horizontal transportation. Thus, special emphasis is given to trackbound transportation. An integrated approach is taken towards mine transportation advocating that underground logistics be considered as equally important as any other discipline, Le. rock engineering, ventilation, etc. In addition, the transportation process should consider each area equally important. All to often, the transportation of rock is considered of paramount importance over the transportation of personnel and material. Thus, the planning any transportation system should incorporate personnel, material and rock. To enable this, scheduling, communication and control are important with special attention required for transfer points in the transportation system. As each site has its own particular requirement, thus the final transportation systems must be drawn up based on the specific requirements of each mine. A guideline is proposed for the design of ultra deep level underground transport systems for personnel, material and rock transportation. Thus, providing mining engineers with sufficient information and data to select an appropriate transportation system to meet specific mine requirements. The thesis highlights areas requiring consideration by mine engineers when designing a transportation system from shaft to the working face. / Thesis (Ph.D.)-University of Natal, Durban, 2003.

Mining induced seismic activity and rockbursting are critical concerns for many underground operations. Seismic activity may arise from the crushing of highly stressed volumes of rock around mine openings or from shear motion on planes of weakness. Shear-slip on major planes of weakness such as faults, shear zones and weak contacts has long been recognized as a dominant mode of failure in underground mines. In certain circumstances, it can generate large seismic events and induce substantial damage to mine openings. The Big Bell Gold mine began experiencing major seismic activity and resultant damage in 1999. Several seismic events were recorded around the second graphitic shear between April 2000 and February 2002. It is likely that the seismic activity occurred as a result of the low strength of the shear structure combined with the high level of mining induced stresses. The stability of the second graphitic shear was examined in order to gain a better understanding of the causes and mechanisms of the seismic activity recorded in the vicinity of the shear structure as mining advanced. The data were derived from the observation of the structure exposures, numerical modelling and seismic monitoring. The numerical modelling predictions and the interpreted seismic monitoring data were subsequently compared in order to identify potential relationships between the two. This thesis proposes the Incremental Work Density (IWD) as a measure to evaluate the relative likelihood of shear-slip induced seismic activity upon major planes of weakness. IWD is readily evaluated using numerical modelling and is calculated as the product of the average driving shear stress and change in inelastic shear deformation during a given mining increment or step. IWD is expected to correlate with shear-slip induced seismic activity in both space and time. In this thesis, IWD was applied to the case study of the second graphitic shear at the Big Bell mine. Exposures of the second graphitic shear yielded information about the physical characteristics of the structure and location within the mine. Numerical modelling was used to examine the influence of mining induced stresses on the overall behaviour of the shear structure. A multi-step model of the mine was created using the three- dimensional boundary element code of Map3D. The shear structure was physically incorporated into the model in order to simulate inelastic shear deformation. An elasto-plastic Mohr-Coulomb material model was used to describe the structure behaviour. The structure plane was divided into several elements in order to allow for the comparison of the numerical modelling predictions and the interpreted seismic data. Stress components, deformation components and IWD values were calculated for each element of the shear structure and each mining step. The seismic activity recorded in the vicinity of the second graphitic shear was back analysed. The seismic data were also gridded and smoothed. Gridding and smoothing of individual seismic moment and seismic energy values resulted in the definition of indicators of seismic activity for each element and mining step. The numerical model predicted inelastic shear deformation upon the second graphitic shear as mining advanced. The distribution of modelled IWD suggested that shear deformation was most likely seismic upon a zone below the stopes and most likely aseismic upon the upper zone of the shear structure. The distribution of seismic activity recorded in the vicinity of the shear structure verified the above predictions. The seismic events predominantly clustered upon the zone below the stopes. The results indicated that the seismic activity recorded in the vicinity of the second graphitic shear was most likely related to both the change in inelastic shear deformation and the level of driving shear stress during mechanical shearing. Time distribution of the seismic events also indicated that shear deformation and accompanying seismic activity were strongly influenced by mining and were time-dependant. Seismic activity in the vicinity of the second graphitic shear occurred as a result of the overall inelastic shear deformation of the shear structure under mining induced stresses. A satisfactory relationship was found between the spatial distribution of modelled IWD upon the shear structure and the spatial distribution of interpreted seismic activity (measured as either smoothed seismic moment or smoothed seismic energy). Seismic activity predominantly clustered around a zone of higher IWD upon the second graphitic shear as mining advanced. However, no significant statistical relationship was found between the modelled IWD and the interpreted seismic activity. The lack of statistical relationship between the modelled and seismic data may be attributed to several factors including the limitations of the techniques employed (e.g. Map3D modelling, seismic monitoring) and the complexity of the process involved.

Thesis (Ph.D.)--University of Melbourne, School of Anthropology, Geography and Environmental Studies, 2007. / Typescript. Includes bibliographical references (leaves 357-389).

Orientadores: Emilson Pereira Leite, Antônio João Paes de Barros / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-23T19:02:09Z (GMT). No. of bitstreams: 1 Agnoletto_Ethiane_M.pdf: 12212269 bytes, checksum: 5fb182951b423af2f6cff746f4bf074b (MD5) Previous issue date: 2013 / Resumo: A região garimpeira de Flor da Serra situa-se na porção Leste da Província Aurífera Alta Floresta, Norte do Mato Grosso, inserida no contexto geológico da porção Centro-Sul do Cráton Amazônico, constituída por suítes plutono-vulcânicas de idade paleoproterozóica e coberturas sedimentares associadas. Várias ocorrências de ouro estão dispostas em grandes zonas de descontinuidade crustal que delimitam terrenos geocronológicos e geológicos. O expressivo adensamento de corpos filoneanos e o histórico de produção destaca essa região de expressivo potencial exploratório. Neste contexto, o trabalho teve por objetivo a identificação de novos alvos exploratórios por meio da análise de dados geofísicos, descrição de testemunhos de sondagem e mapeamento de cavas garimpeiras. A integração desses dados contribuiu em especial à evolução do conhecimento geológico da região Flor da Serra, e também de maneira geral para o setor leste da PAAF. A área de estudo está inserida na Suíte Intrusiva Flor da Serra, que é constituída eminentemente por gabros, dioritos a monzogabros, entretanto com o mapeamento de cavas garimpeiras e descrição de furos de sondagem, verificou-se a existência de quatro unidades geológicas principais: (i) Granitóides do Embasamento de composição tonalítica a granodiorítica com associação de magnetita + granada, intrudidos por rochas da (ii) Unidade Granodiorítica a Tonalítica de mesma composição. Essa unidade é truncada por (iii) Diques Máficos a Intermediários e localmente há presença de (iv) Rochas Cataclásticas a Miloníticas. Os litotipos foram variavelmente afetados por sete tipos de alteração hidrotermal (ordem temporal): (i) alteração potássica intensa, (ii) silicificação pervasiva, (iii) carbonatação, (iv) alteração com muscovita, (v) propilitização mais pontual, (vi) alteração Quartzo-Sericita-Pirita (QSP) com substituição total da rocha e, (vii) vênulas de calcita tardias. Foram realizados levantamentos geofísicos utilizando métodos geoelétricos (Polarização Induzida/Resistividade - IP/RES) e magnetometria em escala de depósito. Valores anômalos de cargabilidade e resistividade obtidos após aplicação de um algoritmo de inversão com vínculo de suavidade definiram zonas de intensa silicificação e de QSP. Essas zonas estão diretamente relacionadas a um minério do tipo disseminado, além de terem possibilitado a delimitação da interface saprólito-rocha sã (manto intempérico profundo de até 50 m). Para facilitar a interpretação geológica, foram gerados mapas do campo magnético anômalo reduzido ao equador magnético e da amplitude do sinal analítico. Esse último possibilitou a definição de um stock granítico intrusivo no embasamento heterogêneo. Para eliminar ruídos remanescentes nos mapas de anomalias magnéticas, foram aplicados os filtros cosseno direcional e continuação para cima, com geração de mapa que confirmou o padrão estrutural vigente no Sistema Flor da Serra. Essa estruturação está associada à diferentes níveis crustais, balizam os principais corpos filoneano da região e também estão associadas a alteração QSP. A integração dos principais lineamentos estruturais; bolsões de alta cargabilidade e resistividade; mapeamento detalhado de cavas desativadas e zona de borda da intrusão possibilitou a definição de pontos de interesse prospectivo metalogenético / Abstract: The gold mining area of Flor da Serra is located in the East portion of the Alta Floresta Gold Province (PAAF), North of the state of Mato Grosso, inserted into the geological context of the South-Central portion of the Amazon Craton, which comprises plutono-Paleoproterozoic volcanic suites and associated sedimentary cover. Several gold occurrences are arranged in large zones of crustal discontinuities demarcating land geochronological and geological. The significant densification of filoneano bodies and production history highlights the significant exploration potential of the area. In this context, this study aimed to identify new exploration targets through analysis of geophysical data, description of drill core samples and prospecting pits. The integrated analysis of these data contributed in particular to the development of the geological knowledge of Flor da Serra, and also generally for the eastern sector of the PAAF. The study area covers the Intrusive Suite Flor da Serra which consists essentially of gabbros, diorites to monzogabros, however mapping of prospecting pits and description of borehole samples confirmed the existence of at least four main geological units: (i) granitoids in Basement of tonalitic to granodioritic composition association with magnetite + garnet rocks intruded by (ii) granodioritic to tonalitic of the same composition. This unit is truncated by (iii) the Intermediate Mafic Dykes and locally by (iv) cataclastic to mylonitic rocks. Rocks of the Flor da Serra have been affected by the following hydrothermal alteration types (temporal sequence): (i) intense potassic alteration, (ii) pervasive silicification, (iii) carbonation, (iv) alteration with muscovite, (v) punctual propylitization, (vi) Quartz-Sericite-Pyrite (QSP) alteration with total replacement of the rock and (vii) late calcite veinlets. The geophysical survey consisted of the application of geoelectrical methods (Induced Polarization/Resistivity - IP/RES) and magnetometry at deposit scale. Anomalous values of chargeability and resistivity allowed defining zones of intense silicification and QSP closely related to a disseminated ore type, beyond the boundaries of the saprolite-bedrock interface (deep weathering mantle of up to 50 m). To facilitate geological interpretation, maps of the magnetic anomalous field reduced to the magnetic equador and the analytic signal amplitude were generated. The latter allowed the identification of granitic intrusive stock in heterogeneous basement. To improve the final product and eliminate remaining noise cosine directional filter and upward continuation to 100 m were applied, providing a map which confirmed the structural pattern prevailing in the Flor da Serra system. This structural system is associated with different crustal levels, controls the main filoneano bodies of the region and is attached to QSP alteration. The integration of the main structural lineaments; zones of high chargeability/resistivity; detailed mapping of deactivated pits; and boundary zone of the intrusion led to the definition of prospective metallogenic targets / Mestrado / Geologia e Recursos Naturais / Mestra em Geociências

Orientadores: Carlos Roberto de Souza Filho, Emilson Pereira Leite / Acompanhado de 1 mapa (folha solta dobrada) / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-20T13:02:06Z (GMT). No. of bitstreams: 1 Barbuena_Danilo_M.pdf: 27016795 bytes, checksum: 3180173cfc829018bd7f9a63e218afce (MD5) Previous issue date: 2012 / Resumo: A Provincia Aurifera de Alta Floresta (PAAF) situa-se na porcao centro-sul do craton Amazonico, entre os limites das Provincias Ventuari - Tapajos (1,95-1,8 Ga) e Rio Negro - Juruena (1,8-1,55 Ga). Em seu segmento leste, ocorrem mais de uma centena de depositos auriferos hospedados em rochas plutonicas e vulcanicas e concentrados ao longo do Cinturao Peru-Trairao, de direcao NW-SE. Inseridos neste cenario geologico, proximos ao municipio de Peixoto de Azevedo e a Vila Uniao do Norte, estao os depositos Pe Quente e Francisco, alvos deste trabalho. Em funcao de varios fatores como a dificuldade de acesso, a densa cobertura vegetal e o extenso manto de intemperismo, a extracao de informacoes geologicas na regiao amazonica e uma tarefa dificil e logisticamente onerosa. Nesse contexto, dados geofisicos e de sensoriamento remoto sao essenciais para a ampliacao do conhecimento geologico dessa regiao. Esse trabalho pretende, atraves do processamento e analise de dados geofisicos aereos, terrestres e de imagens ASTER: (i) refinar a cartografia geologica da porcao sudeste da PAAF, identificando estruturas impressas em diferentes niveis da crosta, (ii) individualizar possiveis corpos graniticos ainda nao cartografados, (iii) comparar as respostas geofisicas obtidas com dados terrestres e dados aerolevantados, (iv) determinar a relacao entre os realces gamaespectrometricos e magneticos terrestres de areas-tipo no sudeste da PAAF e, (v) relacionar assinaturas gamaespectrometricas a assinaturas espectrais da vegetacao, simultaneamente indicativas de padroes associados aos depositos auriferos. O processamento e interpretacao dos dados aeromagnetometricos e aerogamaespectrometricos do projeto Juruena-Teles Pires (Fase 1), adquiridos pelo Servico Geologico Brasileiro (CPRM), permitiram a geracao de um novo mapa geologico regional da porcao leste da PAAF. Levantamentos magnetometricos e gamaespectrometricos terrestres foram realizados nas areas dos depositos do Pe Quente e Francisco como parte dessa pesquisa. Sua comparacao com os dados aereos em linhas de aquisicao equivalentes espacialmente mostra que, apesar da diferenca consideravel de escala e de amostragem, os padroes sao mantidos em ambos os tipos de levantamento. Os dados terrestres proporcionaram ainda a producao de modelos prospectivos para depositos de Au baseados em tecnicas de Analise por Principais Componentes e Logica Fuzzy. As anomalias gamaespectrometricas extraidas dos dados geofisicos foram comparadas com as caracteristicas espectrais da vegetacao e de solos/rochas extraidas do processamento de dados ASTER. O estudo demonstrou que existe uma forte correlacao espacial entre zonas ricas em K e anomalias espectrais da vegetacao, indicando que assinaturas geofisicas e geobotanicas podem ser utilizadas de maneira complementar na vetorizacao de depositos de Au na PAAF / Abstract: The Alta Floresta Gold Province (AFGP) is located in the central-southern Amazon craton between the limits of the Ventuari-Tapajos (1.95-1.8 Ga) and Rio Negro-Juruena (1.8-1.55 Ga) provinces. In its eastern segment there are more than one hundred gold deposits hosted in volcanic and plutonic rocks and concentrated along the Peru-Trairao Belt in a NW-SE direction. Included in this geologic setting, near the Peixoto de Azevedo city and the Uniao do Norte village, are the Pe Quente and Francisco deposits which are the targets of this work. Due to several factors such as restricted access, the dense vegetation and extensive weathering, the extraction of geological information in the Amazon region is not trivial. In this context geophysical data and remote sensing are essential to expand the geological knowledge of this region. This study intends, through processing and analysis of airborne geophysical data, ground geophysical data and an ASTER image of the region, (i) refine the geological mapping of the southeastern portion of the AFGP, identifying structures in different levels of the crust, (ii) individualize granitic bodies that have not yet been mapped, (iii) compare the responses of airborne and field-based geophysical data, (iv) determine the relationship between ground gamma spectrometry and magnetic data sets in the southeast of AFGP and (v) relating gamma spectrometry signatures with spectral signatures of vegetation, both indicative of patterns associated with gold deposits. Processing and interpretation of airborne gamma spectrometry and magnetic data of the Juruena-Teles Pires project (Phase 1), acquired by the Brazilian Geological Service (CPRM), allowed the generation of a new regional geological map of the eastern portion of the AFGP. Ground magnetometry and gamma spectrometry surveys were made in the areas of Pe Quente and Francisco deposits as part of this research and compared with airborne data and their response over the lines of flight, showing that even with a considerable difference of scale and sampling, these patterns are maintained in both survey types. These data resulted in the production of prospective models for Au-based deposits using Principal Component Analysis and Fuzzy Logic based techniques. Additionally, by processing an ASTER image, a correlation was found between the occurrence of gamma spectrometry anomalies with the spectral characteristics of vegetation and soil /rock, largely reflecting the strong spatial correlation between potassium-rich areas and spectral anomalies of vegetation, since this element is a essential macronutrient for the healthy development of several plants / Mestrado / Geologia e Recursos Naturais / Mestre em Geociências

Orientadores: Roberto Perez Xavier, Rúbia Ribeiro Viana / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-20T22:16:36Z (GMT). No. of bitstreams: 1 Rodrigues_RosanaMara_M.pdf: 7467149 bytes, checksum: 0b427a9b34399220f506b5a3a8d909f9 (MD5) Previous issue date: 2012 / Resumo: Depósitos auríferos na Província Aurífera de Alta Floresta (PAAF), localizada no centro-sul do Craton Amazônico, extremo norte do Estado de Mato Grosso, geralmente hospedam-se em suítes graníticas geradas em ambiente de arcos magmáticos que se desenvolveram e se agregaram progressivamente no decorrer do Paleoproterozóico (1,98 Ga - 1,87 Ga). A mineralização aurífera nesses depósitos está comumente associada a sulfetos (dominantemente pirita) que ocorrem tanto disseminados quanto em veios de quartzo. Em especial na sua porção leste, essa província contém mais de uma centena de depósitos e ocorrências auríferas que se concentram ao longo de um cinturão de direção NW-SE, denominado informalmente de Peru-Trairão, na região correspondente aos municípios de Nova Santa Helena, Peixoto de Azevedo, Matupá, Guarantã do Norte e Novo Mundo (MT). Neste contexto, o depósito X1 (alvo deste trabalho) representa um dos principais exemplos neste setor da PAAF de mineralização aurífera sulfetada e disseminada em rochas graníticas. Descrições de testemunhos de sondagem e estudos petrográficos no depósito X1 revelaram que o minério está hospedado em dois litotipos: (i) granodiorito fino a grosso e (ii) quartzo-feldspato pórfiro (QFP). Dados litogeoquímicos mostram que o granodiorito do depósito X1 representa um magmatismo cálcio-alcalino, de médio K, peraluminoso, magnesiano, moderado a fortemente oxidado e evoluído (granito tipo I). Entretanto, estudos geoquímicos no QFP não foram realizados em virtude da escassez de amostras sem ou com pouca alteração hidrotermal. Ambos litotipos mostram-se afetados por ampla alteração potássica com feldspato potássico que comumente baliza as zonas mineralizadas do depósito e alteração com muscovita + quartzo + sulfetos. De forma bastante restrita, ainda ocorrem alteração propilítica distal à mineralização, além de cloritização e carbonatação. Nesse cenário, as zonas mineralizadas encontram-se espacial e geneticamente relacionadas à intensa alteração com muscovita + quartzo que oblitera as zonas de alteração potássica. O minério é caracterizado por concentrações significativas de pirita disseminada, frequentemente acompanhada por calcopirita, rutilo e hematita, e mostra teores de ouro entre 0,5 e 10 ppm. De modo mais restrito, essa mesma associação paragenética também é encontrada em veios de quartzo sulfetados, porém com menores teores de ouro (~0,2 ppm). O ouro, frequentemente associado a minerais de Bi, Te e Ag, como tsumoita e hessita, além de galena, monazita, esfalerita e apatita, possui concentrações de Ag que variam de 20% a 30% e ocorre como inclusões de 20?m na pirita. Adicionalmente, as zonas mineralizadas do depósito X1 exibem assinatura geoquímica representada por Au + Ag + Bi ± Cu. Estudos de inclusões fluidas em amostras de veios de quartzo ± pirita ± calcopirita ± muscovita provenientes da zona mineralizada do depósito X1 revelam a existência de dois tipos de fluidos. O tipo I é representado por inclusões aquo-carbônicas trifásicas à temperatura ambiente. Essas inclusões mostram baixa salinidade (6 a 9% eq. NaCl) e temperaturas de homogeneização total entre 251,6 e 297,4ºC. Esses fluidos exibem variação no grau de preenchimento (40% - 95%) indicando aprisionamento heterogêneo, possivelmente por meio de imiscibilidade. O tipo II é representado por inclusões fluidas aquosas bifásicas à temperatura ambiente. São geralmente pobres em CO2, de salinidade baixa a elevada (0 a 25% eq. NaCl) e mostram temperaturas de homogeneização total entre 68,4ºC e 126,5. A forte relação da alteração hidrotermal e mineralização aurífera associada com dois pulsos magmáticos (granodiorito e QFP) sugerem que o depósito X1 tenha se originado a partir de um sistema magmático-hidrotermal. A presença de estruturas (e.g. lineamentos NW e NE observados na área do depósito X1) podem ter promovido ou auxiliado uma maior circulação de fluidos provenientes da cristalização magmática e/ou permitido o acesso de fluidos externos (e.g. meteóricos?). A mineralização aurífera pode estar relacionada tanto à imiscibilidade de fluidos como à interação de fluidos magmáticos quentes, aquo-carbônicos, provenientes da cristalização do sistema magmático local, com fluidos externos, mais frios e oxidantes. Esse mecanismo teria causado o resfriamento do sistema, intensificação da zona de muscovita e quartzo através da substituição progressiva do feldspato potássico e aumento da ¿O2 (hematita estável) causando a precipitação do ouro. Neste contexto, a íntima associação espacial com plútons graníticos oxidados, do tipo I, alojados em ambiente de arcos vulcânicos, os tipos e padrões da alteração hidrotermal assim como a associação paragenética do minério, sugerem que o depósito X1 possa estar geneticamente relacionado a sistemas magmáticos-hidrotermais similares aos sistemas do tipo ouro pórfiro, ricos em ouro, porém, pobres em cobre, similar aos depósitos de Maricunga (Chile) e La Colosa (Colômbia). O depósito X1 também poderia ser enquadrado no modelo IRGS (intrusion-related gold systems), pela forte associação do Au com minerais de Bi e Te, contudo, a natureza oxidada das hospedeiras graníticas e dos fluidos mineralizantes, presença de hematita no minério, assim como o extenso e zonado padrão da alteração hidrotermal, não se mostram coerentes com essa classe de depósitos auríferos / Abstract: The Alta Floresta Gold Province (PAAF) is located in the southern sector of the Amazon Craton, northern sector of Mato Grosso state, and contains a series of gold deposits hosted by granitic suites generated in continental arc settings during the Paleoproterozoic (1.98 Ga - 1.87 Ga). Gold mineralization in these deposits is commonly associated with sulfides (dominantly pyrite) that occur disseminated in the host rocks, as well in quartz veins. Particularly in the eastern portion of this province, in the Nova Santa Helena, Peixoto de Azevedo, Matupá, Guarantã do Norte and Novo Mundo (MT) region, the great majority of these gold occurrences and deposits concentrate along a NW-SE-striking belt informally named Peru-Trairão. In this context, the X1 deposit (case study of this work) represents a prime example in this sector of the PAAF of disseminated gold - sulfide mineralization in granitic rocks. Descriptions of drill core samples and petrographic investigations reveal that the gold mineralization at the X1 deposit is hosted by two granitic rock types: (i) fine to coarse-grained granodiorite and (ii) quartz-feldspar porphyry (QFP). Lithogeochemical data show that the granodiorite represents a calc-alkaline, medium K, peraluminous, magnesium, moderate to strongly oxidized and I-type magmatism. No geochemical data could be obtained for the QFP due to the lack of samples without or with little hydrothermal alteration. Both rocks have been affected by pervasive potassic alteration with K-feldspar, which usually envelope the main orebodies and by muscovite + quartz + sulfide alteration. Propylitic alteration, generally distal to the mineralized zones, chloritization and carbonation, are very restricted alteration types. In this scenario, the mineralized zones are spatially and genetically related to intense muscovite + quartz alteration that overprints the potassic alteration. The mineralization is marked by significant concentrations of disseminated pyrite, often accompanied by chalcopyrite, rutile and hematite, with gold grades ranging from 0.5 to 10 ppm. More subordinately, the same paragenetic association is also found in quartz veins, but with lower gold grades (~ 0.2 ppm). Gold is frequently found as inclusions of up to 20 ?m in pyrite, often in association with Bi, Te and Ag-bearing minerals, such as tsumoite (Bi = 60% + Te = 40%), Bi + Mo, hessita (Ag = 63% + Te = 37%), as well as galena, monazite, sphalerite and apatite. Gold also contains Ag concentrations in the 20% - 30% range. As a consequence, the X1 deposit exhibits a geochemical signature represented by Au + Ag + Bi ± Pb ± Cu. Fluid inclusion studies in quartz ± pyrite ± chalcopyrite ± muscovite veins from the mineralized zones reveal the existence of two types of fluids. The type I is represented by three-phase inclusions with aqueous-carbonic fluids of low salinity (6-9% eq. NaCl) and total homogenization varying from 251,6 to 297.4ºC. These aqueous-carbonic fluids exhibit variation in the degree of fill (40% - 95%) which indicates heterogeneous entrapment, possibly by means of immiscibility. The type II is represented by two-phase CO2-poor aqueous fluids of low to high salinity (0-25% eq. NaCl) and total homogenization between 68.4 ° C to 126.5. The strong spatial relationship between the hydrothermal alteration types and the gold mineralization with two magmatic pulses (granodiorite and QFP) suggest that the deposit X1 may have developed from a magmatic-hydrothermal system. The presence of structures, such as the NW and NE lineaments observed in the X1 deposit area may have promoted a higher flow rate of magmatic fluids and/or allowed access of external fluids (e.g. meteoric?). The gold mineralization may be related both to fluid immiscibility and the interaction of magmatic fluids with colder and oxidizing fluids. This mechanism likely caused the development of the muscovite - quartz zone with the progressive cooling of the system, as well as increase in ¿O2 (hematite stable) which may have caused the gold precipitation. Collectively, the close spatial relationship with relatively oxidized (magnetite-bearing) I-type granitic plutons emplaced in a volcanic arc setting, the types and distribution of the hydrothermal alteration and the ore mineral association, suggest that the X1 deposit may be genetically linked to magmatic-hydrothermal systems similar to gold-only, Cu-poor porphyry systems, as those from the Maricunga belt (Chile) and La Colosa (Colombia). Despite containing some features also encountered in intrusion-related gold deposit class, such as the correlation of Au with Bi and Te, the oxidized nature of the granitic host rocks and the conspicuous occurrence of hematite in the gold ore, seem not to be consistent with this gold mineral system / Mestrado / Metalogenese / Mestre em Geociências

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 Masumbi Au-Cu deposit in the Ndori Greenstone Belt of western Kenya is hosted in dacitic volcanics of the Nyanzian Group (2710 ± 340 Ma) and dioritic to granodioritic felsic intrusives (2504 ± 48 Ma). The deposit is characterised by gold and copper mineralisation that is associated with quartz-sulphide veins and veinlets. The copper mineralisation typically occurs as chalcopyrite. Gold is closely associated with pyrite in mineralogy and its pathfinder elements silver, bismuth, tellurium and selenium in geochemistry. The gold occurs in two forms that may indicate two generations of precipitation: the equant and the elongate forms. Based on Au/Ag ratios, the equant gold grains can be classified as native gold as their gold content is greater than 90 wt%. The elongate gold grains can be classified as electrums as their silver content is greater than 38 wt%. While there is a strong Au-Ag association within individual gold grains supporting an orogenic model for the gold mineralisation, mineralisation at the Masumbi Prospect appears atypical of Archaean orogenic gold deposits because of the abundance of copper (up to 0.43%). The enrichment of silver, copper, bismuth and tellurium in ore assemblages is common in porphyry, VMS and epithermal systems, but their presence at Masumbi does not preclude the formation as an orogenic deposit. Assay results from three Masumbi diamond drill-holes show an apparent correlation between gold and copper. However, petrography and electron probe microanalyses results from this study indicate that chalcopyrite is an earlier phase than pyrite as it occasionally occurs as inclusions in pyrite. This petrogenetic relationship between pyrite and chalcopyrite suggests that there is no temporal relationship between gold and copper mineralisation. Statistical analysis of the assays shows no linear correlation between gold and copper thereby supporting the above findings. The gold and copper mineralisation have been interpreted as forming as two separate events with copper forming first followed by gold. These events are both related to the intrusion of the felsic rocks that are associated with the Aruan metamorphic event that has been responsible for the bulk of the gold mineralisation on the Tanzanian Craton. The common alteration assemblage in the Masumbi rocks comprises chlorite and epidote. This alteration assemblage is typical of regional greenschist metamorphic facies grading into amphibolite metamorphic facies in the Nyanzian Group of Kenya. However, these alteration minerals could possibly be products of propylitic alteration in the rock groundmass. Other alteration mineral assemblages, possibly of hydrothermal origin, comprise muscovite, sericite, quartz, carbonate, associated with the sulphides pyrite and chalcopyrite. Although the occurrence of gold appears to be controlled by the presence of pyrite, it is also associated with silicification. Exploration methods have been proposed to target undiscovered gold deposits in the Ndori Greenstone Belt that are similar to the Masumbi deposit. These methods could probably be applied to vein-type gold deposits in other granite-greenstone terranes in the Lake Victoria Goldfields.

Elinor Ostrom (2005: 238) assumes that in understanding the make up and behaviour of institutional systems governing natural resources: “Resource users are explicitly thought of as rational egoists who plunder local resources so as to maximise their own short-term benefits. Government officials are implicitly depicted, on the other hand, as seeking, the more general public interest, having the relevant information at hand and the capability of designing optimal policies.” This thesis examines the validity of this assumption through an historical analysis of the deep-level gold mining industry of the Witwatersrand, South Africa. The main focus of the assessment is on the institutions of ownership – that is, the development of mining rights and title legislation between 1886 and 2008. The study looks at the legislations’ transformation and implementation from the perspective of the gold mining industry – made up of the mining finance houses and the Chamber of Mines of South Africa – and that of the state. The transformation of the mining industry’s institutional framework was both a choice by government as well as that of the firms in the mining industry. The theoretical framework is constructed from four areas of economic thought. These include: the neoclassical and Keynesian schools of macroeconomic thought; industrial organisation and its relevance to the relationship between firms and the market; institutional and new institutional economics; and finally property rights. The determinants of policy design and the impact of such design on firms and industry is examined. The development, implementation and use of the aforementioned legislation is examined from two perspectives, namely, that of preserver or exploiter. Throughout the history of this prominent South African industry, the motivation for action from the industry or government has oscillated between the two extremes of preserver or exploiter over the time period examined. The conclusion is drawn on an overall and broad focus of actions – with a strong focus on the most recent developments in mining legislation – post-1992.

This project examines arsenic in plants growing near closed or reclaimed gold mines located in the traditional territories of two Yukon First Nations. A total of 238 soil and plant samples (comprising 9 different species) were collected from Mt. Nansen, Arctic Gold and Silver, and Venus Mine tailing properties. At each property, samples were collected near the suspected point source of contamination, approximately 1 -3 km away, and from background sites. Species were chosen for their ethnobotanical significance to the Little Salmon/Carmacks and the Carcross/Tagish First Nations, based on interviews with Elders and other knowledgeable people. Total and inorganic arsenic concentrations were determined using ICP-MS and AAS instrumentation, and organic arsenic concentrations were calculated from the difference. Uptake of arsenic by plants was low compared to soil arsenic concentrations. In both plants and soil, the arsenic form was predominantly inorganic. Concentrations in berries at all three sites were low or undetectable, and are therefore considered safe to eat under Health Canada tolerable daily intake guidelines for inorganic arsenic. At Mt. Nansen, the lichen "caribou moss" (Cetraria/Cladina spp.), Bolete mushrooms (Leccinum spp.), and the medicinal shrubs willow (Salix spp.) and Labrador tea (Ledum groenlandicum/L. decumbens spp.) had high mean arsenic concentrations around point sources or at sites up to 1.5 km away. These localized high concentrations will not likely affect foraging animals, given their constant movement. However, Carmacks residents could avoid gathering all species with elevated arsenic around the Mt. Nansen mining property until reclamation is complete. / Arts, Faculty of / Geography, Department of / Graduate