Extraction of metals from the seafloor has been considered for decades, beginning with manganese nodules in the 1970s. Today, the targets are massive sulphide deposits rich in copper, zinc, gold, and silver that are associated with hydrothermal vents or black smoker chimneys that occur at divergent and convergent plate margins such as mid-ocean ridges and volcanic island arcs respectively. A recent objective of the mining industry is to develop industry practices that coincide with concepts of sustainability or sustainable development. This objective, known by some as sustainable mining, has indeed become an essential part of the commissioning of any new project, regardless of geographical location. While there has been much work on sustainable mining practice for terrestrial mining, these frameworks are not directly applicable to seafloor projects. There are two problems facing the development of a seabed mining industry. First, there is a regulatory vacuum when considering the mining of seabed deposits, leading to important policy issues. Second, the economic, environmental, and social impacts of a seabed mining project are theoretical, and the real impacts are unknown. Thus, the identification, characterization, and analysis of the sustainability issues facing a seabed mining project are essential steps. To assist with performing these three steps, this thesis provides a process model based on the IDEF0 (Integration DEFinition) standard to assess seafloor massive sulphide mining projects from sustainable mining perspectives. This adaptation of IDEF0 provides a clear, visual representation of a hierarchical framework that can be used to identify “go no-go” sustainability criteria to assist decision makers interested in the potential development of an ore body. / Thesis (Master, Mining Engineering) -- Queen's University, 2011-12-12 12:54:28.436

Simulation technique has been used for a feasibility study of a deep exploration project for massive sulphides in an old mining district, the Skellefte field. The outcome under very different conditions has been studied. Under the specific conditions of the well known Skellefte field it is found to be possible to even calibrate the mathematical model.It is found that when the geology is not known in detail, an outcome of the order of 50 tons per meter drillhole is to be expected under a simple drilling strategy.When a certain knowledge about the general structures down to around 1 000 m is established, it is possible to improve the outcome by a factor of 2 through an optimization of the depth of investigation. The optimal depth of investigation is in the order of 500 m.On the other hand, when a minimum ore value is introduced as a function of depth, the expected outcome will again decrease with a factor of about 3.It must be underlined, that these results are average values in a mathematical model and do not say anything about the outcome in the single exploration case. However, in exploration campaigns of the order of 40 drillholes to a depth of 1000 m an analysis shows that at least one deep seated large body was found in 25% ot the exploration campaigns.Faced with the problem whether to go or not to go into a deep exploration phase, this technique can headlight the problem and it can give an estimate about the order of costs and benefits. / digitalisering@umu

L’objectif de cette thèse était d’utiliser les propriétés magnétiques des roches (paléomagnétisme, anisotropie de la susceptibilité magnétique (ASM) et différentes techniques d’analyse de la minéralogie magnétique), complété par d’autres méthodes classiques (microscopie pétrographique et électronique, goniométrie de texture, spectroscopie Raman, statistiques d’orientation préférentielle de forme et cathodoluminescence) pour aborder des thématiques récurrentes relatives à la formation des gisements métalliques. Cette approche a été appliquée à deux problèmes métallogéniques : (i) le traçage de la circulation du fluide ayant produit la métasomatose ferrifère des carbonates de La Florida (Cantabrie, Nord de l’Espagne) et la mise en place des minéralisations à Pb–Zn associées (MVT) ; et (ii) l’étude de la structuration des gossans et le décryptage de l’histoire de l'altération des amas sulfurés de la Ceinture Pyriteuse Sud Ibérique (CPSI, Andalousie, Sud de l’Espagne). Dans le premier cas, nous avons pu démontrer expérimentalement que la circulation des fluides produit une anisotropie de forme dont on peut retrouver l’empreinte dans le signal de l’ASM. Cette propriété nous a permis de définir une direction NE–SW de circulation du fluide métasomatique à La Florida. Dans le deuxième cas, le couplage entre l’ASM et le paléomagnétisme nous a permis de définir deux fabriques magnétiques dans les gossans primaires ; (i) une fabrique, d’âge ancien, de « compaction », caractéristique des parties supérieures des gossans, probablement associé au réchauffement de l’Oligocène supérieur et (ii) une fabrique de « mélange », plus récente, localisée dans les parties inférieures des gossans, formée probablement lors de l’événement messinien. La fabrique de « compaction » refléterait donc une altération plus mâture comparée à la fabrique de « mélange ». Par ailleurs, l’analyse de la minéralogie magnétique des gossans et des terrasses de la CPSI a révélé la présence « inhabituelle » de la pyrrhotite, une présence que nous avons attribué à l’activité de bactéries sulfato-réductrices dans des microdomaines réducteurs, disséminés dans un environnement globalement oxydant et très acide. / The purpose of this PhD thesis was to use the magnetic properties of rocks (paleomagnetism, anisotropy of the magnetic susceptibility (ASM) and various techniques of magnetic mineralogy analysis), supplemented by some traditional methods (petrographic and electronic microscopy, texture goniometry, Raman spectroscopy, shape preferential orientation statistics and cathodoluminescence) to study the formation of metal deposits. This approach was applied to two metallogenic studies: (i) the track of fluid circulation that produced the iron-bearing metasomatism of the carbonates of La Florida mining district (Cantabria, Northern Spain), and the Pb–Zn mineralization deposits (MVT); and (ii) the study of the internal structures of the gossans and the alteration history of the massive sulphides of the Iberian Pyrite Belt (IPB, Andalusia, Southern Spain). In the first case, we showed experimentally that the fluid circulation produces a shape anisotropy, recorded in the form of a magnetic anisotropy. This property enabled us to define a NE–SW direction of the circulation of the metasomatic fluid in the La Florida district mining. In the second case, the coupling of AMS and paleomagnetism enabled us to define two magnetic fabrics in the primary gossans; (i) a “compaction” fabric in the upper parts of the gossans, associated to an old age, and probably caused by the Late Oligocene Warming Event, and (ii) a “mixture” fabric, more recent, located in the lower parts of the gossans and probably formed during the Messinian Salinity Crisis. The “compaction” fabric would reflect an alteration stage more mature than the “mixture” fabric. In addition, the magnetic mineralogical analysis of the gossans and the associated terraces of the CPSI revealed the “curious” occurrence of the pyrrhotite, which was attributed to the sulfato-reducing bacteria activity in some reducing microdomains, disseminated in an environment globally oxidant and highly acid.