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[English version]This PhD thesis focuses on the comprehensive chemical and isotopic characterization of various meteorite types, aiming to enhance our understanding of significant processes that shaped the early solar system and its current state. The study centers on the volatility-controlled evaporation and condensation of elements related to asteroid impacts, specifically investigating isotopes of the moderately volatile elements (MVE) zinc, gallium, copper, and iron. The first part of this project was dedicated to the development of a Ga purification technique for precise isotopes measurements. Once established, this method was applied to meteorite samples. Most meteorites are generally regarded as pristine objects, but this is not always the case. Some processes such as thermal metamorphism, aqueous alteration and or impact-shock can significantly alter the chemical and isotopic composition of a meteorite. To investigate this, we studied the bulk MVE isotopes compositions of metal-rich equilibrated ordinary chondrites (H6). We found that the isotope systems show a correlation between the absolute range of isotopes compositions and the 50 % condensation temperature, with the more volatile elements present a higher range of fractionation. Also the range of fractionation observed does not appear to be linked to the shock stages or weathering grades of the samples indicating other processes at play. Their compositions could be inherited from the early solar nebula and accretion processes of the ordinary chondrites parent bodies, with minor effects of thermal metamorphism. We then shifted to metal-rich carbonaceous chondrites (CB and CH) which are thought to have origins related to an impact-vapor plume. We investigated their bulk elemental compositions and their isotopes compositions in Zn, Ga, Cu, and Fe. The observed distinctions in isotopic levels, particularly in Ga, Cu, Fe, and Zn, suggest complex processes at play during their formation. We could confirm vari, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

L’étude de milieux analogues sur Terre est primordiale pour les missions d’exploration spatiale. Bien que l’Arctique canadien soit différent des terrains volcaniques sur Mars, il offre des conditions géologiques semblables. Les chapeaux de fer sont des formations géologiques clés pour l’étude de la surface martienne en raison de leurs processus de formation et de leur minéralogie unique, ainsi que de leur potentiel à conserver des biosignatures qui indiquent d’anciennes traces de vie. Ce projet vise à approfondir les connaissances sur la géologie et la télédétection des chapeaux de fer de l’Arctique canadien en tant qu’analogues martiens afin d’évaluer leur potentiel de détection par images satellitaires en utilisant une librairie spectrale basée sur des échantillons terrain. Au total, 42 échantillons ont été collectés à la surface de chapeaux de fer sur l’île Axel Heiberg, au Nunavut. L’analyse minéralogique par diffraction des rayons X de 12 échantillons représentatifs montre la présence de quartz dans tous les échantillons, de gypse dans la plupart, et de goethite, jarosite ou barytine dans moins de la moitié. L’analyse géochimique par fluorescence des rayons X confirme la prédominance de la silice, du calcium et du baryum, avec des quantités importantes de fer et de soufre. Le pH des échantillons en laboratoire varie de 1,85 à 7,51 et semble lié à leur minéralogie dominante. La signature spectrale VNIR-SWIR des échantillons a été utilisée avec plusieurs algorithmes de détection de cibles sur des images satellitaires PRISMA et WorldView, qui ont respectivement une haute résolution spectrale et spatiale. L’algorithme Spectral Feature Fitting s’est avéré le plus efficace dans la région d’étude pour détecter des chapeaux de fer étudiés sur le terrain ainsi que d’autres non vérifiés au sol. La combinaison des deux types d’images est optimale pour détecter les cibles avec celles-ci, éliminer les fausses cibles avec PRISMA, et affiner le contour des cibles avec WorldVi, The study of analogue environments on Earth is a critical element of space exploration missions. Although the Canadian Arctic is different than the volcanic terrain on Mars, it provides similar geological conditions. Gossans are key geological formations for Martian surface study due to their unique formation processes and mineralogy, and their potential to preserve biosignatures indicating ancient traces of life. This project aims to contribute new knowledge on the geology and remote sensing of gossans in the Canadian Arctic as Martian analogues to assess their potential for detection by satellite images using a field-based spectral library. In total, 42 samples were collected from the surface of gossans on Axel Heiberg Island, Nunavut. Mineralogical analysis of 12 representative samples by X-ray diffraction shows quartz in all samples, gypsum in most, and goethite, jarosite or barite in less than half. Geochemical analysis by X-ray fluorescence confirms the predominance of silica, calcium and barium, with significant quantities of iron and sulphur. The laboratory pH of the samples ranged from 1.85 to 7.51 and appears to be related to their dominant mineralogy. The VNIRSWIR spectral signatures of the samples were used with several target detection algorithms on PRISMA and WorldView satellite images, which have high spectral and spatial resolution, respectively. The Spectral Feature Fitting algorithm was the most effective in the study area to detect gossans that were investigated during fieldwork, and others that were not ground truthed. Combining the two types of images is optimal for detecting targets with these, eliminating false targets with PRISMA and refining target contours with WorldView. While one of the priorities of the scientific community is to document the geological history and processes that have shaped the surface of planetary bodies, this project represents a multi-scale analysis of Mars-like environment from outcrops to orbital sensors

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In recent years, advancements in machine learning based interpolation methods have enabled the production of high-resolution maps of sea surface partial pressure of CO2 (pCO2) derived from observations extracted from databases such as the Surface Ocean CO2 Atlas (SOCAT). These pCO2-products now allow quantifying the oceanic air-sea CO2 exchange based on observations. However, most of them do not yet explicitly include the coastal ocean. Instead, they simply extend the open ocean values onto the nearshore shallow waters, or their spatial resolution is simply so coarse that they do not accurately capture the highly heterogeneous spatiotemporal pCO2 dynamics of coastal zones. Until today, only one global pCO2-product was specifically designed for the coastal ocean (Laruelle et al. 2017). This product however has shortcomings because it only provides a climatology covering a relatively short period (1998–2015), thus hindering its application to the evaluation of the interannual variability and the long-term trends of the coastal air-sea CO2 exchange, a temporal evolution that is still poorly understood and highly debated. Here we aim at closing this knowledge gap and update the coastal product of Laruelle et al. (2017) to investigate the longest global monthly time series available for the coastal ocean from 1982 to 2020. The method remains based on a 2-step Self Organizing Maps and Feed Forward Network method adapted for coastal regions, but we include additional environmental predictors and use a larger pool of training and validation data with ~ 18 million direct observations extracted from the latest release of the SOCAT database. Our study reveals that the coastal ocean has been acting as an atmospheric CO2 sink of -0.4 Pg C yr-1 (-0.2 Pg C yr-1 with a narrower coastal domain) on average since 1982, and the intensity of this sink has increased at a rate of 0.1 Pg C yr-1 decade-1 (0.03 Pg C yr-1 decade-1 with a narrower coastal domain) over time. Our results also sh, info:eu-repo/semantics/published

Coastal ecosystems release or absorb carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), but the net effects of these ecosystems on the radiative balance remain unknown. We compiled a dataset of observations from 738 sites from studies published between 1975 and 2020 to quantify CO2, CH4 and N2O fluxes in estuaries and coastal vegetation in ten global regions. We show that the CO2-equivalent (CO2e) uptake by coastal vegetation is decreased by 23–27% due to estuarine CO2e outgassing, resulting in a global median net sink of 391 or 444 TgCO2e yr−1 using the 20- or 100-year global warming potentials, respectively. Globally, total coastal CH4 and N2O emissions decrease the coastal CO2 sink by 9–20%. Southeast Asia, North America and Africa are critical regional hotspots of GHG sinks. Understanding these hotspots can guide our efforts to strengthen coastal CO2 uptake while effectively reducing CH4 and N2O emissions., SCOPUS: ar.j, info:eu-repo/semantics/published

Gedemsa caldera is a peralkaline volcanic depression located in the Central sector of the Main Ethiopian Rift. An integrated volcanological study of stratigraphic sections was carried out in order to constrain the eruptive history of Gedemsa caldera volcano (GCV), Ethiopia. Textural analyses on plagioclase crystals together with field observations shed light on magma chamber processes feeding the volcanic complex. A multi-vent eruption is ascribed to the pre-caldera volcanic products, as can be seen from the varying caldera wall sequences comprising lavas and pyroclastic deposits. At least three major caldera-forming eruptions are identified producing: 1) a lower ignimbrite, 2) extensive pumice fall and pyroclastic density current deposits, and 3) an upper ignimbrite exposed in different areas of the caldera, indicating a sector collapse. We identified 20 individual pyroclastic deposits found outside and within the caldera that erupted after the climactic caldera collapse. The most recent volcanic activity at Gedemsa is characterized by rhyolitic lava domes and pyroclastic deposits from eruptions through numerous vents aligned with WNW-ESE pre-existing cross-cutting structures. Macrocryst disequilibrium textures such as fine-scale oscillatory zoning (FOZ), sieve textures, glomerocryst, and synneusis indicate that magma reservoir is characterized by repeated magma injection, convection flows, and mixing., SCOPUS: ar.j, info:eu-repo/semantics/published

Search for life in the Universe is one of the main reasons for space exploration and has been blooming since the 1960’s, as being one of the most fundamental questions for Humankind: “are we alone in the universe?”. For now, extraterrestrial life has not been detected anywhere in the Universe. Nevertheless, the notion of habitability, i.e. the capacity of an environment to sustain life as we know it, has emerged, with the nearest planetary bodies we have access to being the best candidates, particularly Mars due to its many similarities with Earth, including proficient liquid water activity at some point in its history. Liquid water is the main parameter when considering extraterrestrial life since it is a universal solvent and requires temperatures adequate for biological reactions. One way to investigate extraterrestrial life is to look for molecules that are produced by biological activity. As such, an important component has been detected in the martian atmosphere: methane (CH4). On Earth, it is mainly a product of microorganism activity, thus making it a main element for life consideration on Mars. Methane can be a biological product, but it can also be produced by abiotic reactions, with rock-gas-water interactions without life intervention. On Earth, hydrothermal systems such as the ones observed in the abyss sustain ecosystems based on favorable temperature-pressure-pH conditions, and on local production of dihydrogen (H2) and CH4, both used as an energy source by microorganisms. On Earth, these hydrothermal systems are based on serpentinization, a redox reaction oxidizing Fe2+ in mafic minerals (olivine and pyroxene), and which can form serpentine (reaction’s characteristic mineral product), clays, talc, (hydr)oxides, … and H2. In addition to being a potential energy source for microorganisms, this H2 is a fuel for Fischer-Tropsch-Type (FTT) reactions: abiotic gas-rock reactions using a metallic catalyst present in rocks to sustain H2 interaction with a car, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

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Les compagnies minières doivent mettre en priorité la vision du développement durable afin de diminuer leur emprunte environnementale tout en optimisant leurs opérations. Une saine gestion de l’eau est primordiale afin de respecter les normes environnementales telles la Directive 019 au Québec et le Règlement sur les effluents de mines de métaux et diamant au Canada ainsi que pour maintenir leur image face aux investisseurs et communautés environnantes. La présence de contaminants d’intérêt émergeant (CEC) pose son lot de défi quant à la caractérisation et au traitement des différents effluents seuls et en mélanges sur les sites miniers, dépendamment de la méthode de gestion de l’eau. Les CEC dans les effluents miniers, lesquelles ont vu leur intérêt augmenter suite au resserrement de la règlementation dans l’industrie minière, peuvent être classifiés dans les quatre groupes suivants : 1) les nouveaux contaminants d’intérêt (Mn, Se, xanthates, éléments de terres rares); 2) les contaminants communs ayant des concentrations cibles de traitement faibles en environnement sensible (As, Cu, Zn); 3) les contaminants difficiles à traiter (thiosels, salinité) et 4) les composés azotés (N-NH3, NO2-, NO3-, CNO-, SCN-). Des méthodes de traitements conventionnelles augmentant la salinité résiduelle comportent des limites au niveau de l’efficacité de traitement. Ces dernières sont aussi souvent affectées par la température de l’eau pouvant être limitées en climat froid. Cette problématique peut être adressée par l’utilisation de méthodes de traitement par oxydation avancée ou de filtration membranaire. La prédiction de la qualité de l’eau à l’aide de la modélisation numérique est aussi très importante afin d’aider les opérateurs miniers à minimiser les risques environnementaux. L’objectif principal de cette étude était de prédire la spéciation des CEC à l’aide du modèle PHREEQC ainsi que d’évaluer l’effet sur la toxicité aquatique sur le crustacé Daphnia magna avant et après trai

L’être humain a altéré ou remplacé 75% des systèmes terrestres planétaires, avec un rythme croissant de façon exponentielle depuis le début de la mondialisation. Ces modifications, couplées aux changements climatiques globaux, obligent tous les organismes à des adaptations extrêmement rapides à l’échelle de leur évolution, qu’elles soient physiologiques ou écologiques. Les plantes, à travers leur mode de vie fixe, sont particulièrement vulnérables aux menaces que représente les activités anthropiques et les changements globaux car elles sont forcées de s’adapter ou de s’éteindre. Ce n’est qu’à travers la dispersion de leurs propagules que les plantes peuvent migrer, lorsqu’un habitat propice est accessible pour leur établissement. Le système boréal ne fait d’ailleurs pas exception aux menaces anthropiques car, malgré une faible densité de population, c’est par exemple 23% du domaine du domaine boréal canadien qui a déjà été altéré par les activités humaines. Les changements climatiques sont de surcroît accélérés dans les régions les plus froides, comme le montrent les récents pics de chaleurs aux pôles ou les canicules récurrentes des régions boréales. Le domaine boréal a longtemps été perçu comme une zone du globe hébergeant une biodiversité de façon homogène à l’échelle régionale. Cependant, des études de plus en plus nombreuses tendent à prouver le contraire. Des habitats rares à l’échelle régionale ont par exemple été décrits dans le domaine boréal. Ces habitats peuvent résulter de la structure forestière, d’une géologie particulière ou bien encore de l’histoire de la zone en question. Dans un contexte d’anthropisation grandissante, ces habitats sont d’autant plus menacés qu’ils ne se retrouvent pas en grande quantité sur le territoire : cela signifiant que leur disparition peut signifier une extinction locale des espèces en étant dépendante pour se développer. C’est dans ce contexte que prend place la présente thèse, dans la région de l’Abitibi, à l’ouest du Qu

Antarctic ice cores are invaluable, direct and high-resolution archives of the past atmosphere and the evolution of Earth’s climate. These unique deposits have revealed tight interplays between dust and climate in Southern Hemisphere. We developed an algorithm (complemented with Monte Carlo simulations) using a large database of REE patterns measured in sediments/soils from well-known dust Potential Source Areas (PSAs) located in the Southern Hemisphere to determine respective contributions of these sources that best fit REE patterns measured in ice cores. We applied this methodology to Epica Dome C (EDC)[1] ice core and provide the first continuous, high-resolution record of dust provenance in Antarctica through the Last Glacial-Interglacial Transition (LGIT-2.9 to 33.7kyr BP). Our reconstructed provenance record is consistent with (i) reported isotopic signature of Antarctic dust and (ii) the climatic evolution of the various PSAs contributing to Antarctic depositions. More importantly, our results compare well with our provenance record in Epica Dronning Maud Land (EDML)[2]. Both cores show a major shift in sources between 14 and 15kyr BP when the contribution of Patagonia (main supplier of dust) fell from ̴55% and ̴70% to 35% and ̴50% in EDC and EDML, respectively. After 14kyr BP, dust from Southern Africa (and to a less extent Australia and New Zealand) became more prevalent from ̴20% and ̴8% to ̴35% and ̴23% in EDC and EDML, respectively. Intriguingly, this compositional shift occurs later than the decline in total dust flux observed between 16-18kyr BP in EDC and EDML. We ascribe this 14-15kyr BP shift in the relative contribution of dust from Patagonia and Southern Africa to (i) long-lasting changes in the hydrology of Patagonian rivers and (ii) a sudden acceleration of sea-level rise at 14.5kyr BP that submerged vast swathes of Patagonian continental shelf, triggering a decline in the supply of Patagonian dust to Antarctica and thus, letting the South Afric, info:eu-repo/semantics/published

Iron oxides are known to play a key role in preserving organic carbon (OC) from mineralization, contributing to its burial, and consequently regulating CO2 and O2 atmospheric concentrations. Approximately 20% of OC in sediments is associated with iron minerals, the so-called “Rusty carbon sink”. Yet, the formation and stability of this organo-mineral association remain unclear, particularly in the natural environment.In this study, quartz grains, ferrihydrite-2-lines (FH2L) and 6-lines (FH6L) coated quartz grains were buried within 4 modified passive autosamplers (peepers) in a mudflat in the Scheldt (Appels, Belgium). Each peeper (~30 cm in length) comprises 3 columns of 12 traversing holes, each row filled with one of the minerals, separated from the sediments by a 63 µm pore size mesh. The peepers were collected after 3, 10, 18, and 23 months of exposure to the sediments. To date, this is the first in situ experiment aimed at following the dynamics of OC-Fe association in sediments over depth.A combination of different techniques, electron microscopic and spectroscopic (FIB, SEM, TEM, TEM-EELS, XPS), thermogravimetric (TGA-DTA coupled with mass spectrometry) and classical solid phase analyses were used to characterize the neo-formed organo-mineral associations. Over time, dissimilatory iron oxide reduction decreased the iron content of both 2L and 6L ferrihydrite, while OC accumulated over the residual iron. The OC pool consisted of thermo-labile (200-400°C), recalcitrant (400-550°C) and refractory carbon (550-650°C), identified via XPS as aromatic, alkene, and aliphatic compounds. FIB sections cut through the iron-coated grains showed the OC localized within the Fe-OC associations. This study sheds new insights onto the least-known processes regulating carbon burial in benthic environments, providing a broader perspective of the Fe-OC association that underlie the so-called 'rusty carbon sink'., info:eu-repo/semantics/published

Southern Hemisphere (SH) dust depositions recorded major changes in origin and flux intensity during the Last Glacial-Interglacial Transition (LGIT) reflecting modifications in atmospheric circulation. Dust archives from ice cores have shown compelling evidence that Southern South America (SSA) is the major dust supplier to Antarctica. However, there is yet no consensus on contributions from secondary Potential Source Areas (PSAs) such as, Australia, New Zealand, Southern Africa (SAF), and Antarctica itself. Among those, SAF is a vast PSA that has been, so far, largely understudied. With a main focus on the Namibian coast in SAF, this work presents an innovative and multi-proxy approach for the identification and quantification of the SH PSAs for Antarctica and the Southern Ocean during the LGIT. We developed a statistical algorithm (complemented with Monte Carlo simulations) combining Rare Earth Elements from well-known PSAs in SH to provide the best fit to the REE patterns measured in EPICA Dronning Maud Land (EDML) allowing for the provenance identification and quantification. Our results provide the first high-resolution and continuous record of the PSAs contribution in the South Atlantic sector of East Antarctica from 26.5kyr to 7.5kyr BP. A major shift is observed at ~14.5kyr BP where the contribution (and thus flux) from Patagonia, the main dust supplier during the Last Glacial Maximum, fell from ̴70% to ̴45%. In the Early Holocene, SAF (~25%) and to a lesser extent Australia and New Zealand became more prevalent[1]. In addition, Sr, Nd and Pb isotopic compositions from the SH PSAs were compared with the East Antarctica dust signature[2]. In agreement with our REE results, during the last glacial climatic periods, East Antarctica dust isotopic composition (EDC & Vostok ice cores) is very uniform converging to an unequivocal SSA signature. In contrast, interglacial dust depositions (in agreement with South Atlantic sediments) show more extreme negative eNd and, info:eu-repo/semantics/published

A 450 km crossing of the Greenland ice sheet on skis, over 400 km sea kayak descent along Greenland’s south and west coast and a 600 m vertical climb to open a new climbing route: this is the atypical triathlon led by the two Belgian explorers of Nanok Expedition, Gilles Denis and Nathan Goffart, between April and September 2022. Beyond their sportive objective, their goal was to serve climate research and engage with and communicate to a non-scientific audience about climate research. In partnership with five scientific institutions, they collected unique data and observations of the elevation changes of the ice sheet, as well as rare in situ samples of snow and fjords water to investigate the influence of ice sheet melting on dust input to the ecosystem. The data and samples collected will be analyzed by the universities and research centers. The expedition was documented with a movie “La Traversée” now shared to a general audience on national television and on different university campus. The two explorers are bridging different scientific disciplines (geophysics, geochemistry, glaciology) and bring the science at the table of a non-scientific audience by sharing their passion. Beyond the science, this is a source of inspiration to communicate about the importance of polar regions in the climate system., info:eu-repo/semantics/published

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The Chicxulub meteorite impact, ~66 million years ago, marks one of the most catastrophic events inEarth’s history. This event is linked to abrupt climate change and the Cretaceous-Paleogene (K-Pg)boundary mass extinction, responsible for the demise of 75% of life including the iconic non-aviandinosaurs. Fractured, molten, and vaporized rocks from the impact site were rapidly ejected into theatmosphere. This likely triggered the environmental stress at the K-Pg boundary, but the timing and exactmechanisms of these impact-induced processes are still poorly understood. The ~200-km-wide Chicxulubimpact structure, buried below the Yucatán Peninsula in México, forms a unique natural laboratory toinvestigate these processes. This crater is the only impact structure on Earth associated with ejectapreserved worldwide, which allows for a direct comparison between material from the source area and itsglobal deposits. In this PhD thesis, I present new high-resolution geochemical and petrographic analysis onrocks from the Chicxulub crater region and on globally distributed and well-preserved K-Pg boundaryejecta deposits. This work allows for a detailed reconstruction of the sequence of geological and biologicalevents that occurred in the moments prior, during and in the direct aftermath (minutes to years) of theChicxulub impact.The first part of this thesis is centered around crater suevites (impact-melt-bearing breccias)obtained from the Chicxulub northern peak ring by the recent IODP-ICDP Expedition 364 drilling campaign.The peak ring, consisting of granitoid basement, pre-impact dikes and impact melt bodies, was formed dueto the downward and outward collapse of the central uplift and this process took place within the first tenminutes after impact. The ~100 m thick suevite sequence on top is likely formed within 1 day after impactby the rapid arrival of ocean water in the crater that interacted with the underlying melt and subsequentlyflooded the crater basin. The overlying, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

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Antarctic ice cores have revealed the interplay between dust and climate in the Southern Hemisphere. Yet, so far, no continuous record of dust provenance has been established through the last deglaciation. Here, using a new database of 207 Rare Earth Element (REE) patterns measured in dust and sediments/soils from well-known potential source areas (PSA) of the Southern Hemisphere, we developed a statistical model combining those inputs to provide the best fit to the REE patterns measured in EPICA Dronning Maud Land (EDML) ice core (E. Antarctica). Out of 398 samples measured in the EDML core, 386 samples have been un-mixed with statistical significance. Combined with the total atmospheric deposition, we quantified the dust flux from each PSA to EDML between 7 and 27 kyr BP. Our results reveal that the dust composition was relatively uniform up until 14.5 kyr BP despite a large drop in atmospheric deposition at ∼18 kyr with a large contribution from Patagonia yielding ∼68 % of total dust deposition. The remaining dust was supplied from Australia (14–15 %), Southern Africa (∼9 %), New Zealand (∼3–4 %) and Puna-Altiplano (∼2–3 %). The most striking change occurred ∼14.5 kyr BP when Patagonia dropped below 50 % on average while low-latitude PSA increased their contributions to 21–23 % for Southern Africa, 13–21 % for Australia and ∼ 4–10 % for Puna-Altiplano. We argue that this shift is linked to long-lasting changes in the hydrology of Patagonian rivers and to sudden acceleration of the submersion of Patagonian shelf at 14.5 kyr BP, highlighting a relationship between dust composition and eustatic sea level. Early Holocene dust composition is highly variable, with Patagonian contribution being still prevalent, at ∼50 % on average. Provided a good coverage of local and distal PSA, our statistical model based on REE pattern offers a straightforward and cost-effective method to trace dust source in ice cores., SCOPUS: ar.j, info:eu-repo/semantics/published

My PhD research aims to encompass a detailed chemical and isotopic characterization of “well-preserved” Antarctic meteorites to improve our understanding of the (re-)distribution of various trace elements in specific meteorite types and the effects of the (re-)distribution on radiogenic isotope systematics. As Antarctic meteorites can be affected by alteration, prior to the investigation of the elemental distribution in meteorites and the isotopic effects of the (re-)distribution, the first task of this work has been dedicated to assessing the effects of Antarctic alteration on the chemical and isotopic compositions of ordinary chondrites, the most abundant class of meteorites, and more specifically on H group of ordinary chondrites. The main focus is placed on the systematic study of rare earth elements including their isotope systematics such as Sm-Nd and Lu-Hf.This PhD thesis first demonstrates that the effects of Antarctic alteration on the Sm-Nd and Lu-Hf systems in bulk H chondrites are generally limited and thus the Sm-Nd and Lu-Hf systems preserve their original compositions during Antarctic alteration. Secondly, the underlying mechanism of Antarctic alteration observed in the first part of the PhD study is investigated using in-situ measurement techniques including state-of-the-art laser ablation-inductively coupled plasma-time of flight-mass spectrometry (LA-ICP-TOF-MS). Simultaneously, the potential of LA-ICP-TOF-MS as a novel technique to study the elemental distribution is examined and evaluated. Finally, the distribution of lithophile elements among the constituent minerals in H chondrites is documented at the microscale and their re-distribution during thermal metamorphism in the parent body(ies), i.e. the thermal effects of the lithophile element distribution are quantified and discussed, with a direct link to the heterogeneity recorded in the Sm-Nd and Lu-Hf isotope systematics of bulk chondrites. Overall, this thesis confirms the generally pristine, Cette thèse de doctorat vise à apporter une caractérisation chimique et isotopique détaillée des météorites antarctiques considérées comme « bien conservées" afin d'améliorer notre compréhension de la (re-)distribution de divers éléments en traces dans des types de météorites spécifiques ainsi que pour les systèmes isotopiques radiogéniques. Comme les météorites antarctiques peuvent être affectées par l'altération, avant l'étude de la distribution élémentaire dans les météorites et les effets isotopiques de la (re-)distribution, la première tâche de ce travail a été consacrée à l'évaluation des effets de l'altération antarctique sur les compositions chimiques et isotopiques des chondrites ordinaires, la classe la plus abondante de météorites, et plus précisément du groupe H des chondrites ordinaires. L'accent est mis sur l'étude systématique des éléments des terres rares, y compris leur systématique isotopique Sm-Nd et Lu-Hf.Ce travail démontre d'abord que les effets de l'altération antarctique pour les systèmes Sm-Nd et Lu-Hf dans les chondrites de type H sont généralement limités et donc que ces systèmes conservent leurs compositions d'origine lors de l'altération antarctique. Deuxièmement, le mécanisme sous-jacent de l'altération antarctique a été étudié à l'aide de techniques de mesure in situ, notamment l'ablation laser et la spectrométrie de masse plasma-temps de vol à couplage inductif (LA-ICP-TOF -MS). Simultanément, le potentiel du LA-ICP-TOF-MS en tant que nouvelle technique pour étudier la distribution élémentaire a été examiné et évalué. Enfin, la distribution des éléments lithophiles parmi les minéraux constitutifs des chondrites H est documentée à l'échelle microscopique et leur redistribution lors du métamorphisme thermique dans le ou les corps parents. Ainsi, les effets thermiques de la distribution des éléments lithophiles sont quantifiés et discutés, avec un lien direct avec l'hétérogénéité enregistrée dans la systématique isotopique Sm-Nd et Lu-Hf, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

This chapter illustrates the role of watersheds and estuaries in the biogeochemical functioning of coastal zones, specifically in terms ofeutrophication, which is a widespread phenomenon. Along the land–ocean aquatic continuums, estuaries are receptacles of thepollution generated by human activities (e.g. domestic wastewater, agriculture) in watersheds; they can further modify the riverinenutrient delivery before it reaches the marine zone. We present several applications of a chain of modeling tools able to simulate waterquality transfers and transformations for a reference situation in a variety of systems to be compared with scenarios involvingimprovement of domestic wastewater and structural changes in agriculture., info:eu-repo/semantics/published

Les minéralisations de « type Opémiska » sont localisées dans la partie nord-est de la ceinture de roche verte archéennes de la Sous-province de l’Abitibi, à proximité de la ville de Chapais. Elles sont encaissées au sein d’un réseau de fractures localisées dans le nez de plis du Filon-couche de Ventures appartenant à la Suite intrusive de Cummings (~2716 Ma). Ces minéralisations représentent une catégorie de gisement Cu-Au filonien atypique et caractéristique du camp de Chibougamau-Chapais. Ces minéralisations ont historiquement représenté une part très importante de la métallogénie et de l’économie régionale. Avec une production de plus de 475 000 tonnes de Cu à partir des mines Springer et Perry, elles équivalent à elles seules à plus de la moitié de la production en Cu du camp minier de Chibougamau (~737 000 tonnes Cu). La formation de ces veines riches en Cu, Au, Ag est néanmoins restée énigmatique en raison de son caractère assez unique en Abitibi. Le nouvel intérêt pour ce camp minier depuis les années 2000 et les projets de réouverture des anciennes mines ont motivé la nécessité d’améliorer la compréhension de ce type de gisement « inclassable ». L’étude pétrologique et géochimique à la mine Springer, a mis en évidence 2 types de minéralisations. Le premier type correspond aux veines de quartz-sulfures qui ont constituées le minerai principal. Elles représentent un type de minéralisation Cu-Au-Mo avec une paragénèse principale à chalcopyrite, pyrite, magnétite et molybdénite, et une association Cu, Au, Ag, Bi, Mo. Elles s’accompagnent d’une altération sodique-potassique proximale à biotite, stilpnomélane, feldspaths Na-K et propyllitique distale à chlorite-épidote. Les signatures en éléments traces des pyrites de Springer, Perry et de l’indice Chibougamau-Copper présentent des associations à Se, Te, Bi, Cu, Co, Ag comparables aux minéralisations magmatiques-hydrothermales, ainsi qu’à celles des veines Cu-Au filoniens et porphyriques du Camp minier du lac Dor

Le lithium (Li) est présentement considéré comme une ressource « critique » ou « stratégique » en raison de son utilisation dans la fabrication de batteries pour véhicules électriques. Cet élément peut être extrait de plusieurs sources, dont le spodumène (LiAlSi2O6), un minéral trouvé dans certains types de pegmatites. Malgré l’ancienneté de l’exploitation des pegmatites à spodumène, les impacts environnementaux de cette exploitation et leurs effets sur la qualité de l’eau sont encore peu documentés. Il ressort d’une revue critique de la littérature disponible que l’une des principales caractéristiques des rejets de mines de pegmatite à spodumène est la présence de spodumène résiduel à des niveaux atteignant quelques points de pourcentage massique. Cela est à la source de concentrations peu communes en Li dans les eaux de drainage, de l’ordre de 0,1 à plus de 10 mg/L. Bien que l’extraction du Li du spodumène soit difficile et nécessite notamment un traitement thermique à plus de 1 000 °C selon les procédés conventionnels, ce minéral est paradoxalement reconnu depuis longtemps pour être sujet à l’altération météorique, perdant son contenu en Li et se transformant éventuellement en minéraux argileux. L’effet des microorganismes sur la dégradation du spodumène semble limité et souvent indirect et les quelques essais réalisés à des fins hydrométallurgiques jusqu’à maintenant sont peu concluants. Face à ce constat et à l’intérêt grandissant pour cette ressource, l’objectif principal de cette thèse est d’évaluer le comportement géochimique et hydrogéologique de lithologies et rejets provenant de l’exploitation minière des pegmatites à spodumène. Les échantillons étudiés proviennent de deux sites miniers situés au Québec. Le site Whabouchi, près de Nemaska dans le Nord-du-Québec, est une mine en développement d’où quelques milliers de tonnes de roches ont été extraites pour la réalisation d’essais de traitement du minerai à l’échelle pilote. De ce site, le minerai brut, le

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Understanding the process of continental break-up requires knowledge of the geodynamics of mature rift systems close to the point of plate rupture. In Ethiopia, late-stage continental rifting occurs in a magma-rich setting where extensional processes correlate closely with magmatic and volcanic activity. Unravelling the role that mantle and lithospheric dynamics play in sustaining rifting in Ethiopia is key to improving models of late-stage continental rift evolution. In this study we provide petrological constraints on the physical characteristics of magma production using volcanic samples from the northern Main Ethiopian Rift (MER) and central Afar. Olivine crystallisation temperatures provide information about the thermal state of mantle-derived magmas generated by the mantle during upwelling and melting. These temperatures, determined by Al-exchange thermometry, are used in conjunction with other geochemical and geophysical constraints in inversion models of melting a multi-lithology mantle to find the best-fitting geodynamic parameters that can reproduce observed magma compositions and melt volumes. Our model results suggest that the potential temperature of the Ethiopian mantle is hotter than ambient mantle by ≥ 150∘C, and is elevated to a similar degree across the MER and Afar. We predict significant variations in lithospheric thickness between the MER (90 km) and Afar (50-70 km), with Afar also likely to have a higher portion of fusible mantle domains. This thinner lithosphere and/or more productive mantle is required to generate the larger volumes of magma inferred to have been intruded into the Afar crust. The geodynamic differences between these two settings can be attributed to the more-evolved state of the Afar rift and its proximity to the centre of the Afar plume., SCOPUS: ar.j, info:eu-repo/semantics/published

Rock weathering is a key process in global elemental cycling. Life participates in this process with tangible consequences observed from the mineral interface to the planetary scale. Multiple lines of evidence show that microorganisms may play a pivotal—yet overlooked—role in weathering. This topic is reviewed here with an emphasis on the following questions that remain unanswered: What is the quantitative contribution of bacteria and fungi to weathering? What are the associated mechanisms and do they leave characteristic imprints on mineral surfaces or in the geological record? Does biogenic weathering fulfill an ecological function, or does it occur as a side effect of unrelated metabolic functions and biological processes? An overview of efforts to integrate the contribution of living organisms into reactive transport models is provided. We also highlight prospective opportunities to harness microbial weathering in order to support sustainable agroforestry practices and mining activities, soil remediation, and carbon sequestration., SCOPUS: re.j, info:eu-repo/semantics/published

Achondritic micrometeorites represent one of the rarest (ca. 0.5–2.1%) particle types among Antarctic micrometeorite collections. Here, we present major, trace element and oxygen isotope compositions on five vitreous, achondritic cosmic spherules (341–526 µm in size) recovered from the Widerøefjellet sedimentary trap in the Sør Rondane Mountains (SRMs) of East Antarctica. We also present the first iron isotope data for four of these achondritic cosmic spherules. The particles were initially identified based on the atomic concentrations of Fe-Mg-Mn and their distribution in Fe/Mg versus Fe/Mn space, spanning a relatively wide range in Fe/Mg ratios (ca. 0.48–1.72). The Fe/Mn ratios cover a more restricted range (22.4–31.7), comparable to or slightly below the values measured for howardite-eucrite-diogenite (HED) and martian meteorites. One particle (WF1801-AC3) displays an elevated Fe/Mn ratio of ∼78, comparable to the values determined for lunar rocks. The negative correlation observed between the CaO + Al2O3 contents and the Fe/Si ratios of achondritic spherules reflects both the mineralogy of the precursor materials, as well as the extent of volatilization experienced during atmospheric entry heating. This trend suggests that the primary mineralogy of precursor materials may have been compositionally similar to basaltic achondrites. Based on their distribution in Ca/Si versus Al/Si space, we argue that the majority of achondritic cosmic spherules predominantly sample pyroxene- and/or plagioclase-rich (i.e. basaltic) precursor bodies. Such precursor mineralogy is also inferred from their rare earth element (REE) patterns, which show resemblances to fine-grained basaltic eucrites or Type 1 achondritic spherules (n = 3 – av. REEN = 11.2–15.5, (La/Yb)N = 0.93–1.21), pigeonite-rich equilibrated eucrite precursors or Type 2 achondritic spherules (n = 1 – av. REEN = 27.9, (La/Yb)N = 0.10), and possibly Ca-phosphates from (primitive) achondritic bodies (n = 1 – av. REEN =, SCOPUS: ar.j, DecretOANoAutActif, info:eu-repo/semantics/published

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The Earth’s climate is strongly affected by the partitioning of carbon between its mobile reservoirs, primarily between the atmosphere and the ocean. The distribution between the reservoirs is being massively perturbed by human activities, primarily due to fossil fuel emissions, with a range of consequences, including ocean warming and acidification, sea-level rise and coastal erosion, and changes in ocean productivity. These changes directly impact valuable habitats in many coastal regions and threaten the important services the habitats provide to mankind. Among the most productive and diverse systems are coral reefs and vegetated habitats, including saltmarshes, seagrass meadows, and mangroves. Coral reefs are particularly vulnerable to ocean warming and acidification. Vegetated habitats are receiving heightened attention for their ability to sequester carbon, but they are being impacted by land-use change, sea-level rise, and climate change. Overall, coasts play an important, but poorly quantified, role in the global cycling of carbon. Carbon reservoirs on land and in the ocean are connected through the so-called land–ocean aquatic continuum, which includes rivers, estuaries, and the coastal ocean. Terrestrial carbon from soils and rocks enters this continuum via inland water networks and is subject to transformations and exchanges with the atmosphere and sediments during its journey along the aquatic continuum. The expansive permafrost regions, comprised of ground on land and in the seabed that has been frozen for many years, are of increasing concern because they store vast amounts of carbon that is being mobilized due to warming. Quantitative estimates of these transformations and exchanges are relatively uncertain, in large part because the systems are diverse and the fluxes are highly variable in space and time, making observation at the necessary spatial and temporal coverage challenging. But despite their uncertainty, existing estimates point to an import, info:eu-repo/semantics/published