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The Vazante Northern Extension is a continuation of the structurally controlled, hypogene nonsulfide zinc deposit from the Vazante Mine, Minas Gerais, Brazil. The deposit is hosted in Neoproterozoic carbonates of the Serra do Poço Verde Formation located in the Brasília Fold Belt along the western margin of the São Francisco Craton. The Northern Extension deposit is hosted within a shear zone that strikes 200 to 225 and dips 30º-70º NW and is associated with substantial folding that occurred in the same deformation (D2) event and later transcurrent faulting. The shear zone is composed of a tectonic-hydrothermal breccia that can be subdivided into four types: Type 1 Breccia– distally located from the willemite (Zn2SiO4) ore, weakly brecciated dolostone with some Fe-carbonate alteration; Type 2 Breccia–Strong Fe-carbonate alteration, intense brecciation; Type 3 Breccia–hematite replacement breccia, usually proximal to the Type 4 Breccia; Type 4 Breccia–willemite ore breccia, containing three generations of hypogene willemite (Zn2SiO4) as well as hematite (Fe2O3), and franklinite (ZnFe2O4). In the southern part of the deposit, late sulfide-rich veinlets are observed cutting the hypogene zinc silicate mineralization, and contain galena, sphalerite, native silver, covellite, and stromeyerite (Cu1-xAg1-xS). Geochemical studies conducted on the tectonic-hydrothermal breccia showed a strong regional signature enriched in Ag, Cd, Pb, and Zn. The presence of willemite as opposed to sphalerite and the ubiquity of hematite suggest that the zinc silicate mineralization has formed from the mixing between a low sulfur, acid, oxidizing metalliferous basinal brine similar to the fluids found in MVT deposits with a cooler, more oxidizing, meteoric fluid. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-02-29 16:45:36.41

Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1910. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed June 18, 2009)

Thesis (Ph. D.)--University of Canterbury, 2010. / Typescript (photocopy). "February 2010." Includes bibliographical references (p. 168-181). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Feb. 3, 2010). Additional advisors: Renato Camata, Derrick Dean, Chris M. Lawson, Andrei Stanishevsky, Sergey Vyazovkin. Includes bibliographical references (p. 133-140).

published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

The separation of oxidation-reduction reactions into individual half-cells with a resulting "mixed potential" is well known as a dissolution mechanism for metals; however, the mechanism by which non-conducting crystals lose ions to the solution has been studied only slightly.

In making this study it is important to search for ways to enhance and, if possible, make detection of MMO signals simpler in order that this technique for obtaining FS measurements may be extended to other materials. This attempt to improve measurement techniques has resulted in a significant discovery: the eddy-current techniques described in detail in a later section which should allow MMO to be observed and sensitively measured in many additional solids. The second major thrust of the study has been to use the newly discovered eddy-current technique in obtaining the first indisputable observation of MMO in zinc.

L’hydrogène est un vecteur énergétique qui peut être un atout pour nous aider à décarboner nos usages énergétiques. L’électrolyse de l’eau est un des moyens de production d’hydrogène qui présente un bon compromis pour obtenir un gaz en grande quantité tout en limitant le coût et l’impact environnemental. La compression est une des voies de stockage de l’hydrogène mais les électrolyseurs sont limités technologiquement pour atteindre des pressions de stockage satisfaisantes. Une des solutions pour pallier ce problème est l’électrolyse découplée. Il s’agit de séparer la production d’hydrogène et d’oxygène en deux étapes grâce à un intermédiaire oxydant/réducteur. La société Ergosup a développé le procédé ZHYNCELEC, un exemple de cette technologie qui utilise le zinc comme intermédiaire. La première étape est l’électrodéposition du zinc, ce qui acidifie la solution et permet la formation d’oxygène. Cette étape est inspirée de l’électrolyse industrielle du zinc. La deuxième étape est la réaction entre le dépôt et l’électrolyte produisant l’hydrogène et provoquant la dissolution du zinc en solution. Le sujet de cette étude est l’optimisation du procédé ZHYNCELEC.Ce travail peut être découpé en trois axes d’étude. Le premier axe concerne la sélection des différents matériaux d’électrode, choisi suivant leur performance électrochimique mais également suivant leur durabilité. Le deuxième axe a pour objectif d’optimiser la composition de l’électrolyte. Les éléments clés sont la concentration du zinc, la concentration de l’acide et la présence d’éventuels d’additifs en solution. Le troisième axe concerne l’aspect procédé et s’articule sur des conditions opératoires telles que la température, la densité de courant, la pression maximale en hydrogène ainsi que la géométrie du réacteur. Ces trois axes ne peuvent être étudiés séparément de par les interactions entre les différents paramètres, ce qui oblige à des compromis suivant l’application du procédé voulu. / Hydrogen is an energy carrier and a potential asset for helping to lower carbon levels of energetic uses. Water electrolysis is a way of production and a good compromise to generate a large quantity of cheap and low-environmental-impact hydrogen. Compression is used to store hydrogen but electrolysers are technologically limited to reach high pressures. One solution to overcome this problem is decoupling electrolysis. It aims at separating the hydrogen and oxygen production in two steps through mediation oxydizer/reducer. Ergosup company has developed ZHYNCELEC process, using different technologies such as zinc as mediator. The first step is zinc electrodeposition which increases the acidity of solution and lead to an oxygen formation. This step is inspired by industrial zinc electro winning. The second step is the reaction between the metallic deposition and electrolyte producing hydrogen and making the dissolution of zinc. The purpose of this study is the optimisation of ZHYNCELEC process.This work can be divided in three axes of study. First, the selection of the different electrode materials. They are chosen by electrochemical performances and durability. Secondly, electrolyte composition optimization. The key factors are zinc concentration, acid concentration and the possibility of additives presences. The final axe concerns the processing aspect and the operative conditions like temperature, current density, maximal hydrogen pressure and reactor geometry. These three axes cannot be studied separately because of the interaction between the different parameters, which forces at compromising following the aim of the application of the process.