Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-06-07T18:11:24Z No. of bitstreams: 1 Tese Rut Díaz.pdf: 2159528 bytes, checksum: 159d73b33fae80ff4ee36bea4366ea74 (MD5) / Made available in DSpace on 2017-06-07T18:11:24Z (GMT). No. of bitstreams: 1 Tese Rut Díaz.pdf: 2159528 bytes, checksum: 159d73b33fae80ff4ee36bea4366ea74 (MD5) / Fundação de Amparo a Pesquisa do Rio de Janeiro / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Petrobras/CENPES / Agência Nacional do Petróleo / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / O presente estudo utiliza a geoquímica inorgânica das espécies reduzidas do enxofre, operacionalmente definidas como acid - volatile sulfufide (AVS) e chromium -reducible sulfur (CRS),a composição isotópica ( δ 34 S) do sulfat o da água intersticial, do CRS, e das frações orgânicas (ácidos húmicos, ácid os fúlvicos e resíduo orgânico) para avaliar a diagênese do enxofre ao longo do Holoceno (últimos 12.000 anos cal AP) no Sistema de Ressurgência de Cabo Frio (SRCF) . Também foi usada a morfologia da pirita, considerando a distribuição de tamanho dos frambóides através de microscopia eletrônica de varredura (MEV), com o objetivo de inferir o estado de oxidação do ambiente de formação. Foram coletados quatro perfis sedimentares cur tos (b ox - cores ) e três longos ( kullembers ) em um gradiente “cross - shelf” na plataforma continental de Cabo Frio. A razão C/N e o a composição isotópica ( δ 13 C) da matéria orgânica reflete uma fonte marinha durante a diagênese recente. As diferentes caracter ísticas morfológicas, como as superfícies de oxidação nos microcristais, os processos de crescimento secundário e os poliframboides encontrados nas análises morfológicas da pirita, assim como também a variabilidade na distribuição dos diâmetros dos frambói des evidenciaram uma formação sob condição redox altamente dinâmica. A razão COT/CRS indica que o fator limitante para a formação da pirita é o enxofre , devido as condições de deposição do ambiente as quais favorecem a re - oxidação do sulfeto de hidrogênio. A composição isotópica do sulfato ao longo dos perfis apresenta um valor médio de +23‰, e não foi observado um fracionamento isotópico com respeito ao sulfato da água do mar (+ 21‰), indicando a diagênese do sulfato em um sistema aberto e baixas taxas de sulfato redução. No entanto, a composição isotópica do CRS apresentou sinais altamente empobrecidos em 34 S ( - 45‰ até - 25 ‰), indicando reações de re - oxidação no ciclo do enxofre. A composição isotópica das espécies orgânicas do enxofre apresenta um enrique cimento em 32 S quando comprados com o sulfato da água intersticial , e isotopicamente pesadas comparadas com a pirita. O incremento na razão S/C dos ácidos húmicos e o empobrecimento do sinal isotópico em 34 S com o avanço da profundidade indicam a captura d o enxofre de origem diagenético pela matéria orgânica. Um balanço de massa isotópico indica a predominância de uma fonte biossintética nos ácidos húmicos e diagenética nos ácidos fúlvicos, estes resultados guardam relação com a reatividade da matéria orgân ica em cada fração. No gradiente “cross - shelf” as frações orgânicas da plataforma média apresentam os menores conteúdo de enxofre biossíntetico, indicando a presença de matéria orgânica mais reativa. Estes resultados indicam que a sulfurização da matéria o rgânica e a cumulação de pirita em Cabo Frio foi favorecida pelo ciclo re - oxidativo do enxofre devido a intensas condições óxicas na coluna de água. O processo de diagênese do enxofre ao longo do Holoceno não guarda relação aparente com as mudanças oceanog ráficas registrada na área de estudo, assim sendo, adinâmica do enxofre esteve relacionada com a intensidade dos processos de diagênese / Four box-corer and tree kullemberg were collected in a cross - shelf gradient in the continental shelf of Cabo Frio. The box-corer were used to evaluated the sulfurization of the organic matter during the early diagenesis and also, study the pyrite morphology and size distribution of framboids by scanning electron microscopy (SEM) to infer the oxidation state of the environment during the early diagenesis. This study uses the inorganic geochemistry of reduced sulfur species operationally defined as acid-volatile sulfufide (AVS) and chromium - reducible sulfur (CRS), the isotopic composition ( δ 34 S) of pore water sulfate, CRS, and the isotopic composition of difference organic fraction (humic acids, fulvic acids and organic residue to evaluated the sulfur diagenesis during the Holocene (last 12000 years cal AP) in the upwelling system of Cabo Frio. Carbon stable isotopes signatures and C/N ratios of total organic matter evidence a marine source during the early diagenesis. The observed increase in the atomic S/C ratios and t he 34 S depletion in humic acids with increasing depth evidence the diagenetic uptake of reduced sulfur species by organic matter during the early diagenesis. The different morphological characteristics observed, such as surface oxidation in the microcrysta ls, the processes of secondary growth and poliframboides found, as well as the variability in the framboids diameters distribution, show the formation under highly dyna mic redox condition. In the sedi m e nts from the Holocene the COT/CRS ratio indicates that the limiting factor for the pyrite formation is the sulfur. The isotopic composition of sulfate is around +23 ‰ , and without fractionation of sulfate with respect to sea water (21 + ‰) indicating a sulfur diagenesis in a open system and a low net sulfate r eductions. The isotopic composition of the CRS is highly depleted ( - 45 ‰ to - 35‰), indicating oxida tion reactions in the cycle of sulfur . The stable sulfur isotope composition of the organic fractions ( humic acids, fulvics acids and organic res idue ) was sub stantially enriched in 32 S when compared to bottom and pore water sulfate (δ 34 S SO4 2 - ~ +23‰), but isotopically heavier than the co - existing pyrite ( δ 34 S CRS = - 45‰ to - 35‰). The 34 S depletion in humic acids, fulvis acids and in the organic residue with increasing depth evidence the diagenetic uptake of reduced sulfur species by organic matter. A sulfur isotope mass balance indicated a predominance of biogenic sulfur in humic acids and in the organic residue, while the fulvic acids has a predominance of d iagenetic sulfur. In cross - shelf gradient, the organic fractions from the middle shlelf have the lower proportion on biosynthetic sulfur, indicating the presence of more reactive matter. The results evidenced that the sulfurization of organic matter and th e p yrite accumulation in the Cabo F rio sediments was favored by the sulfur re - oxidative cycling due to the intense oxic water conditions . The diageneses process in the sulfur cycle during the Holocene in sediments from the continental shelf don’t have rela tion with the changes in the oceanography conditions. The process of diagenesis of sulfur seem to be a continuous process

<p> The existence of significant and consistent fractionation of sulfur isotopes in natural coexisting sulfide mineral pairs is demonstrated. Such fractionations are shown to depend exclusively on the mineralogy of the assemblage and temperature of equilibration, consistent with a process of fractionation during equilibrium exchange of sulfur isotopes between the sulfide phases . The fractionation of sulfur isotopes between galena, sphalerite and pyrite has been determined experimentally over the temperature range 300-725°C . The fractionation for each mineral pair is shown to vary as T^(-2) so that three isotope geothermometer s have been calibrated. Experi mental results are applied to natural sulfide assemblages to determine the temperature of equilibration and extent to which isotopic equilibriurn has b een attained. </p> / Thesis / Doctor of Philosophy (PhD)

Les conditions oxydantes de la surface terrestre actuelle sont dues à la teneur élevée en dioxygène de l’atmosphère. Au début de l’histoire de la Terre il y a 4.54 milliards d'années (Ga), l’oxygène n’était pas stable dans l’atmosphère. Il a fallu deux épisodes d’augmentation brutale de ce gaz atmosphérique pour qu’il atteigne son niveau actuel : l’un vers 2.4 Ga, nommé le Grand Evènement Oxydant (GOE) qui fait l’objet de ce projet, l’autre 2 milliards d’années plus tard, nommé l’Evènement Oxydant Néo-protérozoïque (NOE). Le GOE est vraisemblablement le résultat de l’émersion généralisée de larges continents dont l’érosion libère le phosphate dans l’océan, un nutriment nécessaire à la production biologique, qui a donc permis l’explosion de la photosynthèse oxygénée. Ces deux hausses d’oxygène atmosphérique coïncident avec deux évolutions majeures dans l’histoire de la vie : (i) peu après le GOE, les eucaryotes sont apparus, alors que (ii) le NOE correspond à l’apparition des métazoaires et à l’explosion cambrienne. L’étude de ces phénomènes atmosphériques primitifs peut avoir d’importantes répercussions sur notre compréhension de l’origine et de l’évolution de la vie, qu’on estime principalement marine à cet âge. Les seules archives de ces temps primitifs sur Terre sont les roches sédimentaires. Pour savoir comment l’oxygénation de l’atmosphère a pu être reliée à cette vie marine, il faut tout d’abord comprendre comment l’océan a interagi avec l’atmosphère lors de cet évènement d’oxygénation. Cette question est au coeur de ce projet : comment le GOE a-t-il affecté les cycles biogéochimiques océaniques dont la vie est dépendante ? Nous nous sommes intéressés aux formations ferrifères litées ou BIFs (Banded Iron Formations). La chimie de ces roches marines fait écho à celle de l’océan contemporain à leur formation. Déterminer quantitativement la composition de l’océan à partir de celles des sédiments, même chimiques, est un défi quasiment impossible à relever y compris dans l’océan moderne. C’est pourquoi nous avons proposé de déterminer le temps de résidence d’éléments sensibles aux conditions redox de la surface, le soufre, le fer et le cuivre dans l’océan pré-GOE. Nous avons obtenu, par des séries temporelles, le spectre des fluctuations isotopiques de ces éléments enregistrées dans des carottes de formations ferrifères litées. La limite inférieure du spectre donne le temps de résidence de ces éléments dans l’eau de mer et fournit donc une indication solide sur la teneur de ces éléments dans l’océan à cette période. Nous avons analysé des échantillons protérozoïques proches de la limite Archéen-Protérozoïque du Transvaal (Afrique du Sud) et d’Hamersley (Australie). Des échantillons eoarchéens de Nuvvuagittuq (Canada) ont été récoltés mais n'ont pas pu être analysés faute de temps. / The present-day oxidizing conditions at Earth's surface are due to the high oxygen content of the atmosphere. However, oxygen was not always stable in the terrestrial atmosphere. Two distinct periods during which oxygen increased in a step-like manner were required to reach the current atmospheric oxygen level. The first, at about 2.4 Ga, is known as the Great Oxidation Event (GOE) and is at the core of this Ph.D. thesis. The other, occurring almost two billion years later, is called the Neo-Proterozoic Oxidation Event (NOE). The GOE likely is the result of the beginning widespread emergence of large continental expanses whose subsequent erosion gradually released phosphate into the ocean. Phosphate, a nutrient essential to organic production, in turn allowed the explosion of oxygenated photosynthesis. The GOE and NOE coincide with two major changes in the history of life. Shortly after the GOE, eukaryotes appeared, while the NOE corresponds to the appearance of metazoans and the Cambrian explosion. A better grasp of the GOE hence may have important implications for the understanding of the origin and evolution of life, which is thought to have been mainly marine at this stage in Earth history. The only records of the oxygen level during these ancient times are found in terrestrial sedimentary rocks. To understand how oxygenation of the atmosphere relates to marine life, we must first understand how the ocean was connected to the atmosphere during the GOE and how the GOE affected life-dependent ocean biogeochemical cycles. To this end we focused on banded iron formations (BIF). The chemistry of these sedimentary marine rocks directly reflects the chemistry of the contemporary ocean. Deriving quantitatively the composition of the ocean from a hydrogenous sediment is a challenge almost impossible to meet, even for the modern ocean. This is why we instead determined the residence time of redox-sensitive elements (in this case sulfur, iron, and copper) in the pre-GOE ocean. We specifically targeted the periods of isotopic fluctuations in these elements as recorded in BIF cores. The lower limit of the spectrum provides the residence time of these elements in seawater, hence giving a robust indication of their contents in the pre-GOE ocean. We sampled early Proterozoic BIF near the Archean-Proterozoic boundary in Transvaal (South Africa) and Hamersley (Australia), as well as Archean BIF from Nuvvuagittuq (Canada), though the latter were not analyzed during this thesis due to shortage of time.

De par sa position, le Golfe du Lion est un site idéal pour l’investigation des changements paléo-environnementaux et des processus affectant le dépôt sédimentaire. Les travaux antérieurs ont permis de mettre en évidence les impacts de la variabilité climatique et glacioeustatique sur l’organisation stratigraphique de la marge, mais également sur les exports terrestres de matière organique.L’étude isotopique du carbone organique et de l’azote de la matière organique dans les sédiments du forage PRGL1-4 nous a permis de mettre en évidence de forts exports fluviaux lors des interstades survenus au cours des 200 000 derniers milles ans. La mise en regard de cette découverte avec les enregistrements paléo-climatologiques terrestre et marin disponibles dans la région indique que ces forts exports fluviaux résultent d’une augmentation des précipitations le long de la bordure Nord Méditerranéenne. Grâce à la position dePRGL1-4, nous proposons que ces pluies soient le résultat d’une augmentation du passage de dépressions Nord Atlantique dans le bassin Ouest Méditerranéen.Une caractérisation des isotopes du soufre préservés dans la pyrite sédimentaire a été réalisée. Les résultats obtenus ont permis de mettre en évidence une variation isotopique insoupçonnée, l’une des plus grandes observées de nos jours, dont la cyclicité semble indiquer un fort contrôle climatique. Nous proposons deux mécanismes influençant le fractionnement isotopique: une modulation de l’activité bactérienne par le climat, et/ou (ii) une modulation locale liée la nature des sédiments impliqués dans la formation des pyrites en lien avec les variations eustatiques. / By its position, the Gulf of Lion is an ideal location for investigation of past ecological changes and processes affecting the sedimentary deposition. Previous work has highlighted the impacts of climatic and glacio-eustatic changes on the GoL stratigraphic organization, but also on terrestrial exports of organic matter.This isotopic study based on the organic carbon and nitrogen preserved in PRGL1-4 sediments highlights important rivers runoff during warm periods of the last 200 000 years.Regional intercomparison with terrestrial and marine records indicates that these river exports resulting from an increase of precipitation over the North Mediterranean borderland.Using PRGL1-4 location, out of Mediterranean cyclogenetic area, we suggest that these pluvial events occurred in response to enhance passage of North Atlantic atmospheric perturbation into the Western Mediterranean basin.Pyrite sulfur isotopes investigations over the last 500 kyr have also been done. The stratigraphic variations (up to 76‰) in the isotopic data reported here are among the largest ever observed in pyrite, and are in phase with glacial-interglacial sea level. These results suggest that there exist important but previously overlooked depositional controls on sedimentary sulfur isotope records. Two different mechanisms influencing the isotopic fractionation can explain the observed dataset: a climatic modulation of the bacterial activity, and / or (ii) a local sedimentary modulation involve during early diagenetic formation of pyrite in relation with the eustatic variations.

The Río Blanco–Los Bronces (Chile) is one of the richest endowed porphyry copper-molybdenum districts worldwide, where about 20% of the known mineralization is hosted by tourmaline-cemented hydrothermal breccia. This work seeks: (1) to find a relationship between tourmaline chemical and/or isotopic composition and the degree of mineralization in the breccia, (2) to constrain the source of the mineralizing fluid in the breccia, and (3) to determine of the composition and age of intrusive units in three new exploration projects and correlate them with the known intrusive rocks of the mine areas. Tourmaline from mineralized and barren breccias has similar boron isotopic compositions but differences in Mg/(Mg+Fe) ratios, Al-contents and Al-Fe correlation, which may have exploration value. Boron and sulfur isotopes results are consistent with a magmatic source of hydrothermal fluids. Results of whole rock geochemistry and U-Pb and 40Ar/39Ar geochronology of intrusive units, breccia and late-stage veins are combined with previous U-Pb, Ar/Ar and Re-Os ages to elucidate the magmatic and hydrothermal history of the district.:1 Introduction 1.1 Motivation of the study and statement of research questions 1.2 Scope of the study 2 Porphyry copper deposits (PCDs) 2.1 Introduction 2.1.1 Global copper inventory 2.1.2 Definition and classification of PCDs 2.2 Regional scale characteristics of PCDs 2.2.1 Tectonic setting 2.2.2 Space and time distribution 2.2.3 Porphyry stocks and their pluton and volcanic connections 2.2.4 Wall-rock Influence 2.3 Deposit-scale characteristics 2.3.1 Porphyry stocks and dikes 2.3.2 Hydrothermal breccia 2.3.3 Alteration-mineralization zoning 2.4 Processes of PCD formation 2.4.1 Arc magmatism 2.4.2 Magmatic volatiles 2.4.3 Genetic models 3 Regional setting of the study area 3.1 Tectono-magmatic setting 3.2 Metallogenic belts 4 Río Blanco – Los Bronces mining district 4.1 Mining history 4.2 District geology 4.2.1 Stratified rocks 4.2.2 Plutonic and hypabyssal intrusions 4.2.3 Structures 4.2.4 Alteration and mineralization 4.2.1 Geochronology database 5 Results 5.1 Plutonic units 5.1.1 Petrography 5.1.2 Whole rock (WR) geochemistry 5.1.3 Geochronology 5.2 Mineralization 5.2.1 Petrography 5.2.2 Tourmaline occurrence and composition 5.2.3 Sulfides and sulfates 6 Discussion 6.1 Time-space relationships of intrusion, brecciation and hydrothermal alteration 6.2 Stable isotope constraints on fluid source and evolution 6.2.1 Oxygen, hydrogen and sulfur isotopes 6.2.2 Boron isotopes 6.3 Tourmaline as a redox indicator and significance for exploration 7 Summary and conclusions 8 References Digital supplement Appendix (Methods) 9 Appendix Methods 9.1 Optical microscopy (OM) 9.2 Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) 9.3 Whole rock chemical analysis 9.4 Electron microprobe analyses (EMPA) 9.5 Boron isotopes 9.6 Sulfur isotopes 9.7 40Ar/39Ar dating 9.8 Zircon separation and characterization 9.9 U-Pb zircon LA-ICP-MS dating 9.10 U-Pb zircon CA-ID-TIMS dating 9.11 Single zircon evaporation as screening method

Groundwater chemistry on the Niagara Peninsula has been identified as highly mineralized in comparison to groundwaters collected from the same bedrock formations elsewhere in southern Ontario. Three geochemical zones were discerned using hierarchical cluster analysis and other geochemical and isotopic methods. The Escarpment Zone, located along the Niagara and Onondaga Escarpments, is characterized by unconfined aquifer conditions, parameters reflective of surficial contaminants, including road salt, and elevated HCO3, DOC, NO3-, coliform bacteria and tritium. In contrast, in the Salina Zone thick, low-permeability sediments and gypsiferous bedrock results in highly mineralized groundwaters with Ca-SO4 geochemical facies and elevated S2-, Ca2+, Mg2+, K+, Na+, SO42-, Cl-, Br-, Sr2+, NH4+ and CH4. The Guelph Zone contains the lowest electrical conductivity of the three zones and elevated F-. Outliers exist with groundwater geochemistry that differs from the local geochemical zone and the host aquifer. These sites have elevated SO42- (>1000 to 5200 mg/L) with depleted δ34SSO4 (-2.2 to 14.3‰ VCDT) signatures that differs starkly from Devonian and Silurian evaporites (~20 to 32 ‰) in the host formations. This exogenic SO4 was identified in a cross-formational northeast – southwest linear trend crossing three major groundwater flow systems. The lack of down-stream impact in these systems and tritium groundwater ages that are typically only decades old indicate a young, non-geological origin and implicate anthropogenic activities. Additionally, nine samples were identified with elevated methane concentrations and δ13CCH4 signatures within the thermogenic range. As thermogenic methane is not produced within shallow aquifers and would be short-lived in the presence of the ubiquitous sulfate, these samples imply recent upward migration of methane from depth through vertical conduits. Taken together, the evidence supports large-scale upward movement of fluids in the centre of the Niagara geochemical anomaly and more sporadic upward transport of gases over a wider area of the peninsula. The most likely vector is through corroded and leaking casings or boreholes of abandoned (century) gas wells that are common across the peninsula. / Thesis / Master of Science (MSc)