Le Granite Passa Três est situé à l'Est de l'Etat du Paraná, au Sud du Brésil, et est allongé selon une direction NNE-SSW. Sa mise en place se fait au cœur des metapélites mesoprotérozoïques du Groupe Açungui (Province Mantiqueira). La minéralisation d’or du Granite Passa Três est composée par des veines de quartz contenant des quantités variables de fluorite, sulfures et carbonates. Les objectifs principaux de ce travail de thèse sont : de comprendre le modèle de formation du système de veines minéralisées en prenant en compte les relations entre magmatisme, hydrothermalisme, déformation et minéralogie à la fois dans l’espace et dans le temps ; la caractérisation de la nature, de la source et des conditions de dépôt des fluides ; et la caractérisation du modèle métallogénique de ce gisement singulier. Pour arriver à ces objectifs, les méthodes utilisées seront, en sus de la géologie structurale et de terrain : la pétrographie, la géochronologie U-Pb (LA-ICP-MS) sur zircon et 40Ar-39Ar sur muscovite, la microscopie électronique à balayage (MEB), la microsonde électronique, la fluorescence X (XFR), l’analyse isotopique du soufre (δ34S) et l’analyse microthermométrique et RAMAN des inclusions fluides. Les données structurales ont montré la coexistence de deux systèmes principaux de filons minéralisés, l’un N-S et l’autre E-W, avec des pendages de 60-75°W et 45-70°S, respectivement. Les deux systèmes sont interprétés comme contemporains et conjugués. Les corps minéralisés forment des géométries sigmoïdales qui résultent de l’ouverture en pull-aparts résultant de mouvements en faille normale le long de plans de glissement à faible pendage. Le fort pendage des structures minéralisées s’explique par l’enveloppe globale formée par la succession des pull-aparts. Quatre étapes minéralogiques sont à l’origine de la formation du système minéralisé : phase 1 [qtz 1 + fl], phase 2a [qtz 2 + py 2a ± or ± cpy ± aik ± fl ± sph ± musc], phase 2b [qtz 2 + py 2b + or + cpy + aik + ank ± sph ± fl ± musc] et phase 3 [qtz 3 + ank + calc + molyb ± aik ± musc ± fl]. L’or se trouve dans la forme d’or invisible et d’or natif dans des fractures qui affectent les pyrites des phases 2a et b, systématiquement associé avec la chalcopyrite et l’aikinite. L’altération associée à la minéralisation inclue des assemblages composés par muscovite/quartz/pyrite (altération du type greisen) et séricite/carbonate/clinochlore (altération phyllique). Les valeurs δ34S des pyrites (de -0.1‰ à 1.1‰) indiquant que le soufre du dépôt peut être d’origine magmatique. Cette hypothèse est en accord avec l’observation systématique, dans les parties supérieures du granite (sondage et niveaux supérieurs de la mine), de structures caractéristiques de transition magmatique-hydrothermale comme des systèmes aplo-pegmatitiques, des veines de quartz à bordure de K-feldspath, des concentrations de quartz de type stockscheider et des textures de solidification unilatérales (UST). Les résultats de géochronologie confirment cette hypothèse avec des âges U-Pb sur zircon (611.9±4.7 et 611.9±5.6 Ma pour le granite à grain moyen (GEM) et le microgranite (GEF) et 40Ar-39Ar sur muscovite (veines à bordure de K-feldspath : 612.9±2 à 608.8±2 Ma ; veines minéralisées : 611.7±2 à 608.8±2 Ma ; veines de quartz précoces : 608.4±2 Ma) très proches. Ces âges obtenus indiquent que la mise-en-place du granite, l’exsolution du fluide magmatique-hydrothermal et la formation des veines de quartz aurifères ont été réalisées pendant un écart de temps de 5 Ma, entre 613 et 608 Ma. La minéralisation (611 à 608 Ma) contemporaine de la cristallisation du granite (612 à 610 Ma), l’association de l’or avec des minéraux de bismuth (aikinite), la démonstration du contrôle structural sur la formation des veines et les évidences de transition magmatique-hydrothermale en domaine de coupole granitique montrent que le dépôt d’or du Granite Passa Três partage plusieurs similitudes avec les dépôts du type intrusion-related. / The Passa Três Granite is situated in southern Brazil (Paraná State) and presents a NNE-SSW elongated shape. This intrusion is emplaced within metapelites of the Mesoproterozoic Açungui Group (Ribeira Belt, Mantiqueira Province), between the N40E trending Morro Agudo and Lancinha faults. Gold mineralisation is composed of centimetric to metric quartz veins with fluorite, sulphides and carbonates. The main objectives of this work are i) to understand the model of formation of the mineralised veins systems taking into account the relationships between magmatism, hydrothermalism, deformation and mineralogy in space and time; ii) the characterization of the nature, source and emplacement conditions of the ore fluids; and iii) the characterization of a metallogenic model for this singular deposit. In order to reach these purposes, the methods to be applied include, beyond the structural geology and field works: petrography, U-Pb zircon (LA-ICP-MS) and 40Ar-39Ar muscovite geochronology, scanning electron microscopy (SEM), electron-microprobe analyses (EPMA), X-ray fluorescence (XRF), isotopic analysis of sulphur (δ34S), and microthermometric and Raman analysis of fluid inclusions. Structural data showed the coexistence of two major normal mineralised vein systems, one N-S and the other one E-W, with dips of 60-75ºW and 45-70ºS, respectively. Both systems are interpreted to be contemporaneous and conjugated. Orebodies form sigmoidal geometries that resulted of the opening of pull-aparts as a consequence of the normal movements along low-angle fault planes. High-angle dip of the global mineralised structures is explained by the succession of the pull-aparts. Four mineralogical stages resulted in the formation of the mineralised system: phase 1 [quartz 1 + fluorite], phase 2a [quartz 2 + pyrite 2a ± gold ± chalcopyrite ± aikinite ± fluorite ± sphalerite ± muscovite], phase 2b [quartz 2 + pyrite 2b + gold + chalcopyrite + aikinite + ankerite ± sphalerite ± fluorite ± muscovite] and phase 3 [quartz 3 + ankerite + calcite + molybdenite ± aikinite ± muscovite ± fluorite]. Gold occurs as invisible gold and as native grains within fractures that affect pyrite 2a and 2b, commonly associated with chalcopyrite and aikinite. Alteration related to the mineralisation includes muscovite/quartz/pyrite (greisen type alteration) and sericite/carbonato/clinochlore (phyllic alteration) assemblages. The δ34S values of pyrite crystals (from -0.1‰ to 1.1‰) indicate that the sulphur in this deposit may have a magmatic origin. This hypothesis agrees with the systematic observation, within the upper part of the granite (drill holes and superior levels of the mine), of structures typical of magmatic-hydrothermal transition such as aplite-pegmatite systems, quartz veins with K-feldspar border, quartz concentration of stockscheider type and unilateral solidification textures (UST). Geochronological data confirm this hypothesis with U-Pb zircon ages (611.9±4.7 and 611.9±5.6 Ma for medium grained granite facies (GEM) and microgranite (GEF), respectively) and 40Ar-39Ar muscovite dating (veins with K-feldspar border: 612.9±2 to 608.8±2 Ma; mineralised veins: 611.7±2 to 608.8±2 Ma; barren vein: 608.4±2 Ma), that are very close. These ages indicate that the granite emplacement, the magmatic-hydrothermal fluid release and the formation of gold-bearing quartz veins occur during a time lapse of approximately 5 Ma, between 613 and 608 Ma. The mineralisation (611 to 608 Ma) coeval to granite crystallization (612 to 610 Ma), the association of gold with Bi minerals (aikinite), the strong structural control for veins and magmatic-hydrothermal transition features at the roof of a small granitic intrusion suggest that the Passa Três gold deposit shares several similarities with intrusion-related gold deposits.

Sixteen samples from 8 locations within and surrounding the Björkdal mine area in northern Sweden were chosen in order to reevaluate and characterize previous interpretations of the lithology and hydrothermal alteration. Geochemical analysis by ICP-MS was made in order to chemically classify the lithology of the area and petrological studies were made by study of thin sections and core logging. Three different sets of major alteration types with similar protolith were noted where two dominated: a) a silicified, sericitic, deformed unit; b) a felspathic altered unit with various intensity of epidote; c) amphibole and a so called green banded unit that has undergone Ca-Mg-metasomatism. The main host rock lithology could be identified as a coarse grained, equigranular, plagioclase and (Na-K)-feldspar dominated rock with slightly elongated, stubby grains that have an interlocked, igneous texture. Apatite is a reoccurring accessory mineral in all samples and remains relatively undamaged. Fragmental quartz occur in the samples and is primary to later forming alteration minerals.Amphiboleis also considered to be primary, but can also been formed during regional metamorphism. Two lithologies could be identified in addition to the main protolith. Two samples were located above the marble horizon and was classified as basaltic unit with Ca-plagioclase, biotite and amphibole. One sample mainly consisted of aligned amphibole and biotite and is considered to be an amphibolite xenolith or a dyke intruding the main protolith rock. An increase in the alteration minerals albite, amphibole, epidote and allanite, with peak intensity found north-east of the mine site. This is confirmed by the geochemistry of major elements Fe2O3, MgO, CaO and the ratio between Na2O and K2O. The zonation is explained by a suggested increase in temperaturecondition during metamorphosis. This could be explained by either an underlying intrusion or bystructurally controlled variation in metamorphism by e.g. major faults running through the area.Comparisons with previous work in Björkdal favors an intrusion-related origin for the gold deposit.

Intrusion-related, carbonate rock–hosted replacement deposits are an important source of global base metal production that includes: Cu-Zn skarn, Zn-Pb-Ag carbonate replacement and Ag-base metal deposits. These deposits are located in multiple geological settings and are commonly associated with low-grade Cu-Mo calc-alkaline porphyry districts. Visible alteration halos to these deposits range from ten to hundreds of metres around high temperature skarn deposits, being small to imperceptible around the distal relatively low temperature members of this clan. Patterns of visible and cryptic alteration are described and constrained in this study particularly around paleo-fluid flow zones at different distances and elevations from the ore centre. This was done in order to identify the large-scale zonation, mechanisms, and effects of fluid infiltration especially into the distal portions of these deposits. The main alteration tracers employed included mineralogy, major and trace element geochemistry, oxygen and carbon isotopes, and the fluorescent signature of calcite veins associated with the fluids conduits. Two areas were selected for this study: the large Cu-Zn Antamina skarn and the Ag-base metal Uchucchacua vein deposits in the Peruvian Central Andes as these deposits represent the end-members of the polymetallic carbonate rock-hosted deposits and hence, provide an excellent opportunity to examine the margins and upper sections of these hydrothermal systems. Geochronological analyses of intrusive dikes were used to establish the magmatic and hydrothermal evolution associated with mineralization, as well as the genetic linkage between proximal and distal portions of the mineralizing system at Antamina. Oxygen, carbon and strontium isotope data of vein minerals is also used to constrain the temperature of the fluids proximal and distal to the magmatic centre. Chemical data of fluorescent and non-fluorescent veins were used to determine the main activators of fluorescence and to constrain its relationship with mineralizing fluids. In summary, results of this research identify a large-scale zonation of visible and cryptic alteration around paleo-fluid flow zones demonstrating the linkage between Ag-base metal veins, replacement and skarn deposits. Anomalous halos determined throughout Antamina and Uchucchacua deposits may contribute to the development of a more systematic exploration methodology for these types of deposits.

Intrusion-related, carbonate rock–hosted replacement deposits are an important source of global base metal production that includes: Cu-Zn skarn, Zn-Pb-Ag carbonate replacement and Ag-base metal deposits. These deposits are located in multiple geological settings and are commonly associated with low-grade Cu-Mo calc-alkaline porphyry districts. Visible alteration halos to these deposits range from ten to hundreds of metres around high temperature skarn deposits, being small to imperceptible around the distal relatively low temperature members of this clan. Patterns of visible and cryptic alteration are described and constrained in this study particularly around paleo-fluid flow zones at different distances and elevations from the ore centre. This was done in order to identify the large-scale zonation, mechanisms, and effects of fluid infiltration especially into the distal portions of these deposits. The main alteration tracers employed included mineralogy, major and trace element geochemistry, oxygen and carbon isotopes, and the fluorescent signature of calcite veins associated with the fluids conduits. Two areas were selected for this study: the large Cu-Zn Antamina skarn and the Ag-base metal Uchucchacua vein deposits in the Peruvian Central Andes as these deposits represent the end-members of the polymetallic carbonate rock-hosted deposits and hence, provide an excellent opportunity to examine the margins and upper sections of these hydrothermal systems. Geochronological analyses of intrusive dikes were used to establish the magmatic and hydrothermal evolution associated with mineralization, as well as the genetic linkage between proximal and distal portions of the mineralizing system at Antamina. Oxygen, carbon and strontium isotope data of vein minerals is also used to constrain the temperature of the fluids proximal and distal to the magmatic centre. Chemical data of fluorescent and non-fluorescent veins were used to determine the main activators of fluorescence and to constrain its relationship with mineralizing fluids. In summary, results of this research identify a large-scale zonation of visible and cryptic alteration around paleo-fluid flow zones demonstrating the linkage between Ag-base metal veins, replacement and skarn deposits. Anomalous halos determined throughout Antamina and Uchucchacua deposits may contribute to the development of a more systematic exploration methodology for these types of deposits.

Intrusion-related, carbonate rock–hosted replacement deposits are an important source of global base metal production that includes: Cu-Zn skarn, Zn-Pb-Ag carbonate replacement and Ag-base metal deposits. These deposits are located in multiple geological settings and are commonly associated with low-grade Cu-Mo calc-alkaline porphyry districts. Visible alteration halos to these deposits range from ten to hundreds of metres around high temperature skarn deposits, being small to imperceptible around the distal relatively low temperature members of this clan. Patterns of visible and cryptic alteration are described and constrained in this study particularly around paleo-fluid flow zones at different distances and elevations from the ore centre. This was done in order to identify the large-scale zonation, mechanisms, and effects of fluid infiltration especially into the distal portions of these deposits. The main alteration tracers employed included mineralogy, major and trace element geochemistry, oxygen and carbon isotopes, and the fluorescent signature of calcite veins associated with the fluids conduits. Two areas were selected for this study: the large Cu-Zn Antamina skarn and the Ag-base metal Uchucchacua vein deposits in the Peruvian Central Andes as these deposits represent the end-members of the polymetallic carbonate rock-hosted deposits and hence, provide an excellent opportunity to examine the margins and upper sections of these hydrothermal systems. Geochronological analyses of intrusive dikes were used to establish the magmatic and hydrothermal evolution associated with mineralization, as well as the genetic linkage between proximal and distal portions of the mineralizing system at Antamina. Oxygen, carbon and strontium isotope data of vein minerals is also used to constrain the temperature of the fluids proximal and distal to the magmatic centre. Chemical data of fluorescent and non-fluorescent veins were used to determine the main activators of fluorescence and to constrain its relationship with mineralizing fluids. In summary, results of this research identify a large-scale zonation of visible and cryptic alteration around paleo-fluid flow zones demonstrating the linkage between Ag-base metal veins, replacement and skarn deposits. Anomalous halos determined throughout Antamina and Uchucchacua deposits may contribute to the development of a more systematic exploration methodology for these types of deposits. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

[Truncated abstract] The Tintina Gold Province (TGP) comprises numerous (<15) gold belts and districts throughout interior Alaska and Yukon that are associated with Cretaceous plutonic rocks. With a gold endowment of ∼70Moz, most districts are defined by their placer gold contributions, which comprise greater than 30 Moz, but four districts have experience significant increases in gold exploration with notable discoveries at Fort Knox (5.4 Moz), Donlin Creek (12.3 Moz), Pogo (5.8 Moz), True North (0.79 Moz), and Brewery Creek (0.85 Moz). All significant TGP gold deposits are spatially and temporally related to reduced (ilmenite-series) and radiogenic Cretaceous intrusive rocks that intrude (meta-) sedimentary strata. The similar characteristics that these deposits share are the foundation for the development of a reduced intrusion-related gold deposit model. Associated gold deposits have a wide variety of geological and geochemical features and are categorized as intrusion-centered (includes intrusion-hosted, skarns and replacements), shear-related, and epizonal. The TGP is characterized by vast, remote under-explored areas, unglaciated regions with variable oxidation depths and discontinuous permafrost, which, in combination with a still-evolving geological model, create significant exploration challenges. Twenty-five Early and mid-Cretaceous (145-90 Ma) plutonic suites and belts are defined across Alaska and Yukon on the basis of lithological, geochemical, isotopic, and geochronometric similarities. These features, when combined with aeromagnetic characteristics, magnetic susceptibility measurements, and whole-rock ferric:ferrous ratios define the distribution of magnetite- and ilmenite-series plutonic belts. Magnetite-series plutonic belts are dominantly associated with the older parts of the plutonic episode and comprise subduction-generated metaluminous plutons that are distributed preferentially in the more seaward localities dominated by primitive tectonic elements. Ilmenite-series plutonic belts comprise slightly-younger, slightly-peraluminous plutons in more landward localities in pericratonic to continental margin settings. They were likely initiated in response to crustal thickening following terrane collision. The youngest plutonic belt forms a small, but significant, magnetite-series belt in the farthest inboard position, associated with alkalic plutons that were emplaced during weak extension. Intrusion-related metallogenic provinces with distinctive metal associations are distributed, largely in accord with classical redox-sensitive granite-series. Copper, Au and Fe mineralisation are associated with magnetite-series plutons and tungsten mineralisation associated with ilmenite-series plutons. However, there are some notable deviations from expected associations, as intrusion-related Ag-Pb-Zn deposits are few, and significant tin mineralisation is rare. Most significantly, many gold deposits and occurrences are associated with ilmenite-series plutons which form the basis for the reduced intrusion-related gold deposit model