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Zur Einschätzung der Goldführung von 26 ausgewählten Sand- und Kieslagerstätten in Sachsen wurden Proben auf ihre Goldgehalte untersucht. Die Mehrzahl der untersuchten Großproben wies Goldgehalte unterhalb der durchschnittlichen Zusammensetzung der Erdkruste auf. Eine mögliche Gewinnbarkeit des Goldes in Kies- und Sandlagerstätten hängt vom Goldgehalt im Rohkies und von der Anreicherung im Laufe der Aufbereitung im Tagebaubetrieb ab. Entscheidenden Einfluss auf die Gewinnung haben auch Korngröße und Kornform der Goldflitter. Die Broschüre fasst die Ergebnisse der Untersuchung zusammen und gibt Empfehlungen für das weitere Vorgehen.

The Palaeoproterozoic Birimian terrane of the West African Man Shield is a gold province of global importance. Gold mineralization at the Damang deposit, however, is unique amongst known gold deposits in Ghana. It comprises a stratigraphically controlled auriferous quartz-pebble conglomerate, which is overprinted by later orogenic gold contained in a sub-horizontal fault-fracture quartz vein array. Furthermore, this gold mineralization is hosted in sediments of the Tarkwaian System, rather than volcanics of the underlying Birimian Supergroup. This thesis integrates petrological, geochemical, thermodynamic and geochronological data to investigate the Damang deposit in the context of the regional tectonic and metallogenic framework. Staurolite-grade, amphibolite facies peak metamorphism at Damang occurred at around 595ºC and 5.5 kbar at 2005±26 Ma. This was immediately followed by a short period (~ 5 Ma) of rapid exhumation, at a rate of approximately 2.6 mm/yr. This decompression led to the formation of the fault-fracture mesh, which was enhanced by the silicification of host rocks during an earlier ‘Pink Haematite’ hydrothermal event that was associated with the intrusion of voluminous dolerite bodies. Orogenic gold mineralization occurred at the end of this exhumation period at conditions of 400–450ºC and 1–2 kbar. These conditions are in broad agreement with other Ghanaian deposits. A gold-bearing, CO₂-rich (X(CO₂) ~ 0.7), aqueous fluid generated through metamorphic devolatilization reactions close to peak metamorphism and during the subsequent exhumation fed the fault-fracture mesh. This fluid imparted a potassic–carbonation–sulphidation alteration overprint similar to that seen at orogenic gold deposits globally. This alteration signature is characterized and identified with portable infrared spectroscopic techniques. Exhumation rates following gold mineralization were less than 0.01 mm/yr, while ⁴⁰Ar/³⁹Ar dating of biotites give ages ranging between 1978.8±6.2 Ma and 1898±11 Ma, indicating extremely prolonged (~ 80 Ma) cooling through the interval 300–250ºC. Ultimately, this thesis demonstrates that the Damang deposit is part of the same regional metallogenic event that formed the other Ghanaian deposits. This implies that the Tarkwaian System elsewhere in Ghana may be prospective for orogenic gold mineralization.

Zur Einschätzung der Goldführung von 26 ausgewählten Sand- und Kieslagerstätten in Sachsen wurden Proben auf ihre Goldgehalte untersucht. Die Mehrzahl der untersuchten Großproben wies Goldgehalte unterhalb der durchschnittlichen Zusammensetzung der Erdkruste auf. Eine mögliche Gewinnbarkeit des Goldes in Kies- und Sandlagerstätten hängt vom Goldgehalt im Rohkies und von der Anreicherung im Laufe der Aufbereitung im Tagebaubetrieb ab. Entscheidenden Einfluss auf die Gewinnung haben auch Korngröße und Kornform der Goldflitter. Die Broschüre fasst die Ergebnisse der Untersuchung zusammen und gibt Empfehlungen für das weitere Vorgehen.

Orientador: Francisco José Fonseca Ferreira / Dissertação(mestrado)- Universidade Federal do Paraná. Setor de Ciências da Terra. Curso de Pós-Graduação em Geologia / Inclui bibliografia / Resumo: A pesquisa realizada envolveu a integração de dados exploratórios de fontes diversas, com enfoque prospectivo para ouro, na região da Folha Botuverá-SC, escala 1:50.000, limitada pelas coordenadas 27°00' e 27°15' de latitude sul e 49°00' e 49°15' de longitude oeste. O contexto geológico desta região é marcado por rochas metamórficas do complexo Brusque intrudidas por corpos granitóides de natureza sin a tardi-tectônicos de quimismo dominantemente metaluminoso a peraluminoso, cálcio-alcalinos a alcalinos, conhecidos como Valsungana e Guabiruba. Esta área encerra as mais importantes ocorrências de ouro da região leste catarinense, com destaque aos filões de quartzo do Morro do Carneiro Branco - MCB, ao qual se deu mais ênfase, Ribeirão das Águas Cristalinas e Tigrano, cujo entendimento genético e metalogenético ainda carece de estudos, apesar da sugestiva relação com os corpos granitóides e um importante controle estrutural por zonas de cisalhamento. Os dados disponíveis, mapa geológico e carta metalogenética da Folha Botuverá, Projeto Aerogeofísico Serra do Mar Sul, incluindo magnetometria e gamaespectrometria, geoquímica de sedimentos de corrente, concentrados de bateia e de rocha do Projeto Brusque-Botuverá, além de dados geológicos e geoquímicos de projetos realizados por empresas de mineração que atuaram na região, formaram uma base de dados digital georreferenciada. Esta foi processada e integrada através de ferramentas disponíveis nos programas AutoCad 14, ArcView 3.0a, Er-Mapper 6.1 e Geosoft 4.5. Priorizando-se os dados gamaespectrométricos, os quais apresentaram os melhores resultados, foram determinadas as respostas aéreas de K, Th e U e suas relações (razões Th/K, U/Th e U/K, Parâmetro F=K*U/Th, além de potássio e urânio normalizados pelo tório), nas ocorrências conhecidas, onde foi possível caracterizar suas assinaturas radiométricas e sugerir novos alvos exploratórios. Na área do MCB foi realizado um levantamento gamaespectrométrico terrestre que permitiu determinar sua assinatura, revelada por elevados valores do parâmetro F e baixas razões Th/K. Análise de seções delgadas de amostras dos granitóides e milonitos da zona de cisalhamento que encerra os veios mineralizados do MCB, demostraram uma intensa sericitização e muscovitização, sugerindo uma alteração hidrotermal fílica, coerentes com as respostas geofísicas sobretudo a do potássio. Estes resultados, integrados em ambiente SIG aos demais dados geofísicos,geoquímicos e geológicos, possibilitaram propor três novos alvos exploratórios na Folha Botuverá. Uma caracterização estrutural preliminar efetuada através de lineamentos magnéticos, do satélite Landsat/TM5 e morfoestruturas derivadas do modelo digital de terreno, permitiu sugerir que as ocorrências do MCB, Braço da Cristalina, Tigrano, Três Barras e Russo, além dos novos alvos exploratórios, estão associadas à zonas de cisalhamento dextrais, contidas em uma megaestrutura sigmoidal, possivelmente associada à terceira fase de deformação regional. Palavras-chave: Integração de dados exploratórios; geoprocessamento, assinatura gamaespectrométrica, magnetometria, prospecção de ouro, Botuverá / Abstract: The research, which concerns gold exploratiori, involves integration of 1:50.000 data from several sources in the area of Botuvera SC (27°00'-27°15' S, 49o00'-49°15' W). The regional geological setting is marked by sin-late intrusion of the Valsungana/Guabiruba metaluminous to peraluminous and calc-alkaline to alkaline granitoids into the metamorphic rocks of the Brusque Complex. The studied area bears the most important occurrences of gold in Western Santa Catarina State, specially the filonean gold occurrences at Morro do Carneiro Branco - MCB, on which special emphasis is placed. Gold occurrences are also found in Ribeirao das Aguas Cristalinas (Aguas Cristalinas Creek) and Tigrano, the knowledge of whose genesis and metalogenesis is still limited despite their suggestive relation to the intruded granitoids and the important structural control by shear zones. Data from geological and metalogenetic mapping of the Botuvera region, from the Serra do Mar Sul airborne magnetometric and gammaspectrometric survey, from the Brusque- Botuvera stream sediment, pan concentrate and rock geochemical survey, and also from geological and geochemical work of mining companies form a georreferenced database that was processed and integrated using AutoCad R14, ArcView 3.0a, Er- Mapper 6.1 and Geosoft 4.5 software packages. With special emphasis being placed on the gammaspectrometric data, the airborne responses of K, Th and U and their relationships in (Th/K, U/Th and U/K, F=K*U/Th, and Th-normalized K and U), it was possible to determine new exploration targets from the radiometric signatures of known occurrences. In MCB, a terrestrial gammaspectrometric survey allowed signatures to be determined from high F values and low Th/K ratios. Analisys of thin sections of granitoid and myllonite from the shear zones suggests a phyllic hidrotermalism characterized by intense formation of sericite and muscovite cristais. From the integration geophyisical, geochemical and geological results achieved in a GIS environment, three new exploration targets are determined in Botuvera Region. Structural analysis of magnetic lineaments, Landsat/TM5 imagery and morphostructures derived from digital terrain modeling indicate that the occurrences in MCB, Braco da Cristalina and Tigrano are associated to dextral shearing zones in a sigmoidal megastructure possibly related to a third phase of regional deformation. Keywords: Exploratory integrated data, geoproccessing, gammaspectrometric signature, magnetometry, gold exploration, Botuvera.

Le massif du Mayo Kebbi, situé au sud-ouest du Tchad entre le craton du Congo au Sud, le craton Ouest Africain à l’Ouest et le Métacraton du Sahara à l’Est, expose un segment de croûte juvenile néoprotérozoïque accrété dans la ceinture orogénique d’Afrique Centrale durant l’orogène Pan-Africaine. Il est constitué de deux ceintures de roches vertes (Zalbi et Goueygoudoum) séparées par le batholithe calco-alcalin du Mayo Kebbi et recoupées par des plutons à signature calco-alcaline hyperpotassique. Le tout est recouvert par des formations sédimentaires phanérozoïques. Les ceintures de roches vertes contiennent des zones minéralisées en sulfures encaissées par les roches métaplutoniques (granodiorites) et métavolcanosédimentaires (métabasaltes). La minéralisation est constituée d’un assemblage métallique à pyrite, pyrrhotite, arsénopyrite, chalcopyrite, pentlandite, pentlandite argentifère, pentlandite cobaltifère, sphalérite, de cobaltite. Les sulfures se trouvent à l’état disséminé ou sous forme de remplissage de fissures. Les roches vertes comprennent également des filons de quartz à calcite-chlorite et encaissant des minéralisations à pyrite, chalcopyrite, galène et or. L’analyse de l’or indique une association systématique avec l’argent. Le pluton calco-alcalin hyperpotassique de Zabili contient des indices de minéralisations en Uranium liés à la superposition de : (1) déformation ductile et altération métasomatique impliquant l'interaction entre les minéraux magmatiques avec un fluide riche en Na, d'origine magmatique, contemporain au dépôt d’oxydes d'uranium, (2) une déformation fragile et le dépôt de silicates hydratés d'uranium secondaires impliquant un fluide riche en Na-Ca. La minéralisation en uranium s’exprime sous forme d’uraninite, d’ekanite, de kasolite, de brannerite, et de silicates d’uranium tels que la coffinite. Un âge U-Th-Pb de 599 +/- 4 Ma a été obtenu sur des grains de monazite hydrothermales. Ces minéralisations d'uranium représentent l'expression extrême de la différenciation de la croûte, suite à la remobilisation de ce segment de croûte juvénile Néoprotérozoïque au cours de l’orogénèse Pan-Africaine / The Mayo Kebbi massiflocated in southwestern Chad between the Congo craton in the South, the West African craton in the west and the Sahara metacraton to the east exposes a segment of Neoproterozoic juvenile crust accreted in the Central African orogenic belt during the Pan African orogeny. It consists of two greenstone belts (Zalbi and Goueygoudoum) separated by the May Kebbi calc-alkaline batholith complexes and intruded by calc-alkaline high-K granitic plutons. The whole is covered by Phanerozoic sedimentary formations. The greenstone belts contain sulphide zones hosted mainly by metaplutonic rocks (granodiorites) and metabasalts and metavolcaniclastics. The mineralization comprises pyrite, pyrrhotite, arsenopyrite, chalcopyrite, pentlandite, pentlandite silver, pentlandite cobaltiferous, sphalerite, cobaltite. These sulphides are disseminated, aggregated in form of layers or are filling veins and cracks. The greenstones also contain quartz veins with calcite and chlorite comprising a mineralization made of pyrite, chalcopyrite, galena and gold. Gold is present both as native crystals and as electrum. The high-K calc-alkaline Zabili granitic pluton hosts uranium mineralization related to a superposition of: (1) ductile deformation and metasomatic alteration implying the interaction between magmatic minerals with a Na-rich fluid, of potential magmatic origin, coeval to the main deposition of uranium oxides, followed by (2) brittle deformation and deposition of secondary hydrated uranium silicates involving a Na-Ca-rich fluid. We propose that these uranium mineralizations represent the extreme expression of crustal differentiation as a result of Pan-African reworking of a Neoproterozoic juvenile crustal segment