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Thesis ( Ph.D.)--University of the Witwatersrand, Faculty of Science, 2001.

This thesis proposes some new valuation models and procedures for global and local ore reserve estimation. To obtain efficient grade and tonnage estimates for global borehole valuations of new gold mining properties, the appropriate spatial and distributional models for the mineralisation are absolutely essential. [Abbreviated Abstract. Open document to view full version] / GR 2016

A região de estudo localiza-se na porção da Bacia do Camaquã, sendo classicamente conhecida com “Janela Bom Jardim”. Esta área já foi intensamente estudada, principalmente em decorrência dos depósitos minerais amplamente distribuídos. Apesar disso ainda não existe um consenso com relação à evolução tectônica da região, desde processos formadores da bacia até eventos pósdeposicionais, como também com relação ao seu posicionamento estratigráfico dentro da sequência deposicional da Bacia do Camaquã. Dessa forma, este trabalho vem contribuir e acrescentar aos modelos anteriores com dados geocronológicos e termocronológicos, aplicados diretamente às rochas sedimentares da região, bem como, novos dados de estrutural. Para tanto, submetemos seis amostras de rochas sedimentares da região de Minas do Camaquã à análise pelo método U-Pb com LA-ICP-MS e SHRIMP, aplicado a zircões detríticos, no intuito de mapear possíveis áreas fonte dos sedimentos como também, propor uma idade máxima de deposição para a sequência. Estas mesmas amostras foram utilizadas para separação de apatitas para análise termocronológicas (traços de fissão em apatitas), com o objetivo de caracterizar eventos de soerguimento e denudação relacionados à tectônica que afetou a área. O estudo de proveniência possibilitou identificar uma grande contribuição de zircões de idade Brasiliana, principalmente do final do Neoproterozóico e secundariamente populações de zircões de idade Paleoproterozóica, principalmente relacionadas ao Ciclo Transamazônico. A população principal foi correlacionada às intrusões graníticas do Terreno Taquarembó, e possivelmente contribuições do Batólito Pelotas, como também, das sequências vulcano-sedimentares mais antigas da própria Bacia do Camaquã. As idades Paleoproterozóicas foram atribuídas á rochas do Complexo Granulítico Santa Maria Chico e Complexo Encantadas, como também, zircões retrabalhados das rochas metassedimentares do Complexo Metamórfico Porongos. Ainda foi possível estimarmos a idade máxima de deposição da sequência em 554 Ma a partir do grão de zircão mais jovem datado posicionando estas rochas dentro do intervalo deposicional do Grupo Santa Bárbara. A análise por traços de fissão em apatitas permitiu identificar quatro populações de idades principais. Estas populações foram atribuídas à influência de dois eventos orogênicos na margem sul – ocidental do Gondwana: Famatiniana e Gondwanides. O primeiro evento é bem documentado pelas populações de 407-362 Ma e o segundo pelas populações de 302 Ma e 242-211 Ma. A quarta população (133 Ma) foi registrada em uma única amostra indicando um evento térmico ocasionado por intrusões vulcânicas associadas ao vulcanismo Paraná-Etendeka (Cretáceo inferior). Por fim, dados estruturais permitiram identificar uma evolução tectônica complexa, marcada por processos relacionados formação da bacia até reativações pósdeposicionais. Os eventos D1 e D2 foram associados a esforços gerados durante os estágios finais do Ciclo Brasiliano, com campos de tensão S10E-N10W e SE-NW, respectivamente. Um evento D3 com campo de tensão W-L registra reativações causadas pela Orogenia Famatiniana. O evento D4 marcado por uma compressão NNE-SSW e uma extensão NE-SW são relacionados aos processos tectônicos Triássicos (Orogenia Gondwanides). Um último evento D5 extensional (L-W) foi correlacionado aos processos de separação do Gondwana. / The study area is located in the southern portion of the Camaquã Basin, being classically known as "Bom Jardim Window". This area has been intensely studied, mainly due to the ore deposits widely distributed. Yet there is still no consensus regarding the tectonic evolution of the region, since basin inception processes until postdepositional events, but also regarding its stratigraphic position within the depositional sequence Basin Camaquã. Thus, this work contributes to previous models with geochronological and thermochronological data, applied directly to the sedimentary rocks of the region, as well as new structural data. Therefore, we submitted six samples of sedimentary rocks from the Camaquã Mines region to U-Pb method with LA-ICP-MS e SHRIMP applied to detrital zircons in order to map possible source areas of the sediments, as well as, proposing a maximum depositional age for the sequence. These same samples were used for apatite separation for thermochronological analysis (apatite fission tracks), with the aim of characterizing uplift and denudation events related to tectonics process that affected the area. Provenance study enabled us to identify a large contribution of Brasiliano zircon ages, especially from Late-Neoproterozoic and secondarily, zircons populations of Paleoproterozoic age, mainly related to Trans-Amazonian Cycle. The main population was correlated with granitic intrusions from Taquarembó Terrene and possibly contributions from Pelotas Batholith, as well as, from older volcano-sedimentary sequences of the Camaquã Basin. Paleoproterozoic ages were assigned to rocks of Santa Maria Chico Granulitic Complex and Encantadas Complex, as well as, reworked zircons from metasedimentary rocks of Porongos Metamorphic Complex. Still it was possible to estimate the maximum deposition age of the sequence on 554 Ma from the youngest zircon grain dated. Previous isotopic data allow positioning these rocks within the depositional range of Santa Bárbara Group. Apatite fission track analysis identified four main ages populations. These populations were attributed to the influence of two orogenic events on the Southwestern margin of Gondwana: Famatinian and Gondwanides. The first event is well documented by the 407-362 Ma age populations and the second by the 302 Ma and 242-211 Ma. The fourth population (133 Ma) was recorded in only one sample indicating a thermal event caused by volcanic intrusions associated with volcanism Paraná-Etendeka (Lower Cretaceous). Finally, structural data allowed identifying a complex tectonic evolution, characterized by basin inception processes until post-depositional reactivations. The events D1 and D2 were associated with stresses generated during the final stages of the Brazilian Cycle with stress fields of S10E-SE-NW and SE-NW, respectively. A third event (D3) with W-L stress field records the reactivation Famatinian Orogeny. The D4 event marked by a NNE-SSW compression and a NE-SW extension related to Triassic tectonic processes (Gondwanides Orogeny). One last extensional (W-L) event (D5) was correlated to the processes of separation of Gondwana.

The Coeur d'Alene district in northern Idaho is a world class Pb-Ag mesothermal vein system that has produced about 360 million ounces of silver, lead, and zinc since the 1880s. Despite the long history of exploration and production, the district does not have a predictive model for exploration based on a sound understanding of structural controls on the silver ore deposits; this is certainly the case for the Sunshine Mine and surrounding area. Fault kinematic history in the district shows a regional scale fault system reactivated over time with dextral, sinistral, and dip-slip displacement. The fault system is superimposed on regional deformation fabrics that were examined for this study in the Sunshine Mine area. Cleavage sets observed in the Sunshine mine area, distinguished by orientation and superposition relationships, are consistent with the findings of Smith (2004) which defined cleavage sets referred to as S1, S2, and S3. Two additional deformation fabrics that appear spatially tied to fault zones formed between development of cleavages S2 and S3. The multiple cleavages, fault zones, and their intersections are interpreted to act as pathways for hydrothermal fluids associated with vein formation and silver ore deposition. Thin section kinematic analysis of vein and shear zone samples defined a dip-slip sense of shear associated with the Sterling vein. Electron Backscatter Diffraction (EBSD) analysis of vein and shear zone samples failed to define a lattice preferred crystallographic orientation that defined shear sense. Similarly, cathodoluminescence (CL) analysis of thin section textures failed to define a dominant shear sense and fault kinematics. Nevertheless, additional study using these techniques is warranted. Both field observation and thin section analysis demonstrate a direct relationship between shear zones, veins, and mineralization potential, clarifying the need for detailed fault maps for the Sunshine Mine area and Coeur d'Alene district.

ABSTRACT PRODUCTION OF HEAVY-MEDIA-QUALITY MAGNETITE CONCENTRATE FROM KESiKK&Ouml / PR&Uuml / IRON ORE TAILINGS G&uuml / ng&ouml / r, Kazim M. Sc. Department of Mining Engineering Supervisor: Prof. Dr. M. &Uuml / mit Atalay May 2010, 91 pages The aim of this research was to investigate the possibility of the production of a magnetite concentrate which is suitable for preparation of heavy media from iron ore tailings of G&uuml / ncem Mining Company magnetic separation facility. During the study, three different tailings named as low grade, medium grade and high grade with 5.91 % Fe3O4, 19.06 % Fe3O4 and 37.06 % Fe3O4, respectively, were used. Mineralogical analyses of test samples showed that magnetite and hematite were the major ore minerals while pyrite and chalcopyrite were found in trace amounts. Actimolite, tremolite, epidote, chlorite, quartz, calcite, and dolomite were the gangue minerals. The effects of feed particle size and applied magnetic field intensity on the Fe3O4 grade and recovery of concentrate were examined throughout magnetic concentration tests. The highest grade magnetite concentrate with 79.98% Fe3O4 content was obtained with 65.42% recovery from 100% -75 micron size feed at 1000 Gauss magnetic field intensity from high grade tailing.

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