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Статті в журналах з теми "Système métallogénique de l'or":
Grieve, Richard A. F. "Logan Medallist 4. Large-Scale Impact and Earth History." Geoscience Canada 44, no. 1 (April 20, 2017): 1. http://dx.doi.org/10.12789/geocanj.2017.44.113.
Carpantier, Jean-François. "Numéro 161 - mars 2021." Regards économiques, March 17, 2021. http://dx.doi.org/10.14428/regardseco/2021.03.16.01.
Дисертації з теми "Système métallogénique de l'or":
Perret, Julien. "Répartition spatio-temporelle du système métallogénique de l’or panafricain au sein du bouclier arabo-nubien : étude multiscalaire le long de la suture de Keraf (Soudan)." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0117.
The understanding of mechanisms leading to the transfer of gold transfer from the Earth’s mantle and core towards the crust requires the study of the geodynamical evolution of juvenile crust portions, i.e., crystallized from melt directly extracted from the mantle. The gold mineral system thus combines the deciphering of crustal fertilization geodynamical processes and subsequent transient tectono-metamorphic settings favorable for remobilization of this metal-enriched reservoir and formation of mineralized occurrences. This approach is applied to the Keraf and Atmur-Delgo sutures which are part of the Arabian-Nubian shield, the world-largest track of Neoproterozoic juvenile crust and one of the main Pan-African gold provinces, resulting from the assembly of Gondwana. We report the existence of two magmatic events with suprachondritic Hf and Nd signals, recording the build-up and maturation of island arcs along these suture zones between 840-810 Ma and 760-655 Ma. The ~185 Myr-long lifespan of the Keraf island arc and its predominant juvenile nature likely accounted for crustal gold fertilization at the regional scale. The earliest crustal growth stage, only recorded along the Keraf suture, is coeval to minor magmatic-hydrothermal gold event. Both the Keraf and Atmur-Delgo sutures keep record of the second island arc magmatic event. The matching between field and laboratory data exemplifies the district- to microscopic-scale spatial continuity of structural control on later gold-bearing structures. On one hand, a gold event occurred between 755-725 Ma, coeval with high-strain progressive deformation under lower amphibolite facies metamorphism related to tectonic accretion of the sedimentary wedge at the Atmur-Delgo intra-oceanic subduction site. At the microscopic scale, the ore formation involved the syn-metamorphic remobilization of the preexisting gold budget in sulfides. On another hand, several orogenic gold deposits display intrusion-hosted mineralized extension veins. The fault-valve mechanism induced the formation of mineralized veins, triggered by episodic and localized reactivation of crustal strike-slip shears within the Keraf suture zone until 550 Ma. These two gold events are the oldest and youngest vein-type gold episodes reported throughout the Arabian-Nubian shield to this day, respectively. The mineral system approach therefore enables district-scale ore targeting by translating magmatic processes and tectono-metamorphic settings into environments and geological features (e.g., relics of an island arc and/or an accretionary wedge, presence of late collisional strike-slip shears) favoring the formation of gold occurrences with very distinct structural, geochemical and timing characteristics in the western Arabian-Nubian shield. This alternative view of ore deposits contrasts sharply with the typological strategy which targets a single class of ore occurrence with an effectiveness limited to the deposit scale
Destremau, Blandine. "La République arabe du Yémen entre l'or vert et l'or noir : étude sur un système agraire." Amiens, 1989. http://www.theses.fr/1989AMIE0004.
Relatively isolated from the international economy for decades, the Yemen Arab Republic was quickly connected to it from the 1960's, in the context of the growing weight of the arabic oil rent and its redistribution. This opening led to considerable outflows of migrant labour force and inflows of remittances and imported goods, which submitted the old productive structures to an anhibiting and weakening competition. The dynamics which were established, whereby an increasing proportion of the economy became dependent on transfer incomes, were centered on distribution and bore a strong disicentive to production. The agrarian society, requiring an abundant labor force, endowed with relatively weak productive forces and production capacities handicapped by a rather difficult environment, was particularly affected. The dependency on food import grew correlatively. However, in the 1980's, the relative recession of the redistributive indirect rent economy set up the conditions for a recentering of the economy and better incentives for protected production activities, specifically in the agricultural sector. The future rests on a great part on the patterns of allocation of the country's new oil revenues, whether these revenues can be dedicated to the development of the country's productive capacity in order to satisfy in priority a strong demand for foodstuff, to secure the absorption of labour force and to reduce the dependency upon external sources of revenue, rather than restore rent allocation dynamics
Ducret, Philippe. "Le marché de l'or de 1971 à 1983 : étude statistique et évolution du rôle monétaire du métal précieux." Paris 10, 1987. http://www.theses.fr/1987PA100080.
This work deals with the place of gold in the International Monetary System during the years 1971 to 1983 and consists of two parts, one historical and the other one statistical. The historical side, which comes after a brief reminder of the gold linked events during a period starting at the date of Bretton-Woods agreements and ending in 1971, discusses essentially the evolution of the monetary role of the precious metal since the 15th of July 1971, date of the suspension of the dollar-gold convertibility. This study of the slow process of demonetarization of gold forms the body of the different marast readings of the events of the 1971-1983 periods. The second chapter of this first part is an attempt to explain, during the same period, the gold price’s historical evolution, according to the information given by the study of the running and the structure of the market. The statistical side is made of three chapters: the first one tries to give a microeconomic explanation of the formation of the price of the gold by studying the role and the behavior of the main operators on the market and among the other precious metals markets. The second chapter deals particularly with the impact of the different economic or monetary components of supply and demand upon the formation of the price and tries to determine the advantage of gold as an investment as part of the Modern Portfolio Theory. The last chapters devoted to the various models are reported as also several methods of graphic analysis. This study ends with a conclusion in the shape of an actualization of the available data concerning gold during the 1984-1986 periods and makes up on the role it could play as a part of a possible reform of the International Monetary System
Aubron, Claire. "Le lait des Andes vaut-il de l'or ? Logiques paysannes et insertion marchande de la production fromagère andine." Phd thesis, INAPG (AgroParisTech), 2006. http://tel.archives-ouvertes.fr/tel-00102383.
Dans un milieu montagnard sec et accidenté, la construction de systèmes d'irrigation permet aux propriétaires fonciers qui se succèdent à la tête de l'hacienda au cours du XXe siècle, de développer un élevage bovin laitier sur luzernières irriguées. Après la réforme agraire et suite à la destruction par le mouvement terroriste du Sentier Lumineux de la coopérative ayant remplacé l'hacienda, un nouveau système agraire voit le jour : les familles paysannes récupèrent les ressources accaparées jusque-là par l'hacienda et définissent les nouvelles modalités de leur contrôle, individuel ou collectif. Elles reprennent à leur compte l'orientation laitière sur luzernières irriguées instaurée par l'hacienda et alimentent avec le fromage qu'elles produisent un marché national des produits laitiers en expansion du fait d'une urbanisation croissante.
A partir de l'analyse des pratiques d'élevage – en particulier de gestion fourragère – rendue possible par le suivi mensuel de huit familles paysannes pendant un an, la thèse met en évidence l'existence d'une véritable logique laitière dans les systèmes de production andins : l'élevage laitier tel qu'il est mené est performant à bien des égards et garantit l'obtention d'un revenu à la fois régulier et sûr. De plus, il est compatible avec la mise en place d'activités non agricoles par les hommes, aujourd'hui nécessaires à la survie des populations paysannes andines.
La comparaison des systèmes de production laitiers andins met toutefois en évidence des écarts considérables du niveau de productivité du travail. Dans un contexte de libéralisation de l'économie, la concurrence entre les différents systèmes de production laitiers est pourtant amenée à se renforcer. En partie arbitrée par les industries laitières, la pression à la baisse qui s'exerce sur les prix risque d'affecter durement les producteurs de fromage fermier les moins compétitifs. Analysant cette fragilité économique du système agraire laitier, la thèse discute plusieurs propositions techniques et politiques susceptibles de renforcer sa durabilité.
Rallakis, Dimitrios. "Le système métallogénique et le piège redox dans le gisement d’uranium de type roll-front de Zoovch-Ovoo, Mongolie. Rôle des porteurs du carbone et du soufre." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0079.
The objective of the PhD thesis concerns the analysis of the processes governing the carbon-uranium-sulfide system in the aquifers of the roll-front type Zoovch Ovoo uranium-deposit (Mongolia). The Cenomanian Sainshand Formation hosting the ore deposit contains reservoirs made of silicoclastic sediments deposited in fluvio-lacustrine settings mostly characterized by unconsolidated silty clays and sands ranging from arenite to sub-arkose. Occasionally some decimetres thick sandstone beds are dolomite cemented. Four different dolomite fabrics are recognized and classified according to their crystal boundaries and geochemistry. Isotopic analysis indicates that they were formed from meteoric waters with the carbon source being probably the detrital material itself issued from basement rock erosion. Dolomites are genetically related to each other with possible recrystallization episodes that are indicated by gradual depletion in REE and Mn. The first dolomite type was depositionally controlled, while the next three parageneses are diagenetic. The third dolomite type is found only in samples that have experienced roll-front waters, whereas the fourth post-dates uranium formation. As a result the dolomite cements paragenetic evolution is used as reference to document the whole burial history of the deposit. Organic matter particles, pyrite and uranium are very intimately related. Organic matter present in clay, silt and sand is always represented by poorly preserved detrital elements of higher plant origin and is very immature (peat stage; vitrinite reflectance <0.4%). At the scale of the sedimentary particles, organic matter complexes U(VI). However, despite a systematic association to UO2, it cannot be considered as directly involved in the reduction mechanism of uranium because of the low burial temperatures (max 50°C) and hence very limited diagenesis. Nevertheless, the investigation reveals that organic matter is the most important element in the U trapping process. Indeed, it acts as a substrate sustaining and focusing bacterial activity into specific sedimentary layers. In turn the microbial communities catalyze the reduction of sulfur, iron and especially uranium leading to two major consequences: 1) the precipitation of UO2 onto organic matter particles and 2) the formation of pyrite which acts as an additional reducer for U(VI). It appears that the uranium ore deposit at Zoovch Ovoo is primarily controlled by the distribution of the detrital organic matter in the sedimentary system as well as by the permeability network allowing the input of S, U and micro-organisms. The rather shallow aquifers probably underwent a nearly continuous bacterial activity which is responsible of many chemical features and processes controlling the U and sulfide precipitation. However, main uranium deposition events occur since the beginning of exhumation when enhanced fluid movement sustains roll-front activity. The latter displaces and combines the ingredients of the biochemical trap, allowing progressive enrichment in uranium through time
Rallakis, Dimitrios. "Le système métallogénique et le piège redox dans le gisement d’uranium de type roll-front de Zoovch-Ovoo, Mongolie. Rôle des porteurs du carbone et du soufre." Electronic Thesis or Diss., Université de Lorraine, 2019. http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2019_0079_RALLAKIS.pdf.
The objective of the PhD thesis concerns the analysis of the processes governing the carbon-uranium-sulfide system in the aquifers of the roll-front type Zoovch Ovoo uranium-deposit (Mongolia). The Cenomanian Sainshand Formation hosting the ore deposit contains reservoirs made of silicoclastic sediments deposited in fluvio-lacustrine settings mostly characterized by unconsolidated silty clays and sands ranging from arenite to sub-arkose. Occasionally some decimetres thick sandstone beds are dolomite cemented. Four different dolomite fabrics are recognized and classified according to their crystal boundaries and geochemistry. Isotopic analysis indicates that they were formed from meteoric waters with the carbon source being probably the detrital material itself issued from basement rock erosion. Dolomites are genetically related to each other with possible recrystallization episodes that are indicated by gradual depletion in REE and Mn. The first dolomite type was depositionally controlled, while the next three parageneses are diagenetic. The third dolomite type is found only in samples that have experienced roll-front waters, whereas the fourth post-dates uranium formation. As a result the dolomite cements paragenetic evolution is used as reference to document the whole burial history of the deposit. Organic matter particles, pyrite and uranium are very intimately related. Organic matter present in clay, silt and sand is always represented by poorly preserved detrital elements of higher plant origin and is very immature (peat stage; vitrinite reflectance <0.4%). At the scale of the sedimentary particles, organic matter complexes U(VI). However, despite a systematic association to UO2, it cannot be considered as directly involved in the reduction mechanism of uranium because of the low burial temperatures (max 50°C) and hence very limited diagenesis. Nevertheless, the investigation reveals that organic matter is the most important element in the U trapping process. Indeed, it acts as a substrate sustaining and focusing bacterial activity into specific sedimentary layers. In turn the microbial communities catalyze the reduction of sulfur, iron and especially uranium leading to two major consequences: 1) the precipitation of UO2 onto organic matter particles and 2) the formation of pyrite which acts as an additional reducer for U(VI). It appears that the uranium ore deposit at Zoovch Ovoo is primarily controlled by the distribution of the detrital organic matter in the sedimentary system as well as by the permeability network allowing the input of S, U and micro-organisms. The rather shallow aquifers probably underwent a nearly continuous bacterial activity which is responsible of many chemical features and processes controlling the U and sulfide precipitation. However, main uranium deposition events occur since the beginning of exhumation when enhanced fluid movement sustains roll-front activity. The latter displaces and combines the ingredients of the biochemical trap, allowing progressive enrichment in uranium through time
Mamane, Mamadou Marah. "Le système métallogénique des gisements d’uranium associés à la faille d’Arlit (Bassin de Tim Mersoï, Niger) : diagenèse, circulations des fluides et mécanismes d’enrichissement en métaux (U, Cu, V)." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0231/document.
The main U-deposits of Niger (Arlit, Akouta, and Imouraren) are all located in the Tim Mersoï Basin, east of the Arlit Fault. The deposits of Arlit and Akouta are hosted in Carboniferous formations and have a substantially reduced uranium mineralization, while the Imouraren deposit is contained in a Jurassic formation in the form of predominantly oxidized uranium mineralization with some pockets of reduced mineralization. New ore bodies discoveries west of the Arlit Fault in the regions of Arlit and Akouta and the differences between the U-deposits in the Carboniferous and Jurassic, have encouraged a reevaluation of the previous metallogenic models. The objective is to determine whether the uranium mineralizations of Tim Mersoï Basin were formed during the same diagenetic/hydrothermal event in relation with a major geotectonic event, or if they are polyphase over time, in order to propose a general metallogenic model. A multi-technique approach involving a detailed study of diagenesis, fluid circulations, mineralization, geochronology and geothermometry was applied to trace the burial history of the basin and constrain the P-T conditions of uranium deposition. Two main phases of uranium mineralization are distinguished: (i) A diagenetic/hydrothermal episode between 100 and 135 Ma in which primary uranium and copper minerals precipitate in reduced environment under conditions close to maximum burial (P : 80-120 bars, T : 115-150 °C), in relation with Atlantic rift periods during Cretaceous. (ii) A serie of remobilizations of primary uranium minerals in oxidizing environment to form secondary uranium, vanadium and copper minerals under supergene conditions related to uplift since 50 Ma, during the major events of oxidation in western Africa
Dressel, Bárbara. "Analyse structurale, pétrologique et métallogénique de la minéralisation aurifère néoprotérozoïque du Granite de Passa Três, Campo Largo – PR, Sud du Brésil : implications sur les relations granite/minéralisation." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG023.
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
Книги з теми "Système métallogénique de l'or":
Frendelvel, José. L'or des étoiles - nouveau regard sur le système solaire. FRENDELVEL, 2005.
Pengam, Franck. Géopolitique de L'or: Le Métal Jaune Au Coeur du Système International. Independently Published, 2020.
Частини книг з теми "Système métallogénique de l'or":
LEDRU, Patrick, Antonio BENEDICTO, Guoxiang CHI, Charles KHAIRALLAH, Julien MERCADIER, Jonathan POH, and John ROBBINS. "Le système métallogénique à la discordance du bassin de l’Athabasca (Canada)." In Ressources métalliques 2, 135–85. ISTE Group, 2022. http://dx.doi.org/10.51926/iste.9136.ch3.