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Articoli di riviste sul tema "Seawater signature"
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Kurzweil, Florian, Corey Archer, Martin Wille, Ronny Schoenberg, Carsten Münker e Olaf Dellwig. "Redox control on the tungsten isotope composition of seawater". Proceedings of the National Academy of Sciences 118, n. 18 (27 aprile 2021): e2023544118. http://dx.doi.org/10.1073/pnas.2023544118.
Testo completoAbstract (sommario):
Free oxygen represents an essential basis for the evolution of complex life forms on a habitable Earth. The isotope composition of redox-sensitive trace elements such as tungsten (W) can possibly trace the earliest rise of oceanic oxygen in Earth’s history. However, the impact of redox changes on the W isotope composition of seawater is still unknown. Here, we report highly variable W isotope compositions in the water column of a redox-stratified basin (δ186/184W between +0.347 and +0.810 ‰) that contrast with the homogenous W isotope composition of the open ocean (refined δ186/184W of +0.543 ± 0.046 ‰). Consistent with experimental studies, the preferential scavenging of isotopically light W by Mn-oxides increases the δ186/184W of surrounding seawater, whereas the redissolution of Mn-oxides causes decreasing seawater δ186/184W. Overall, the distinctly heavy stable W isotopic signature of open ocean seawater mirrors predominantly fully oxic conditions in modern oceans. We expect, however, that the redox evolution from anoxic to hypoxic and finally oxic marine conditions in early Earth’s history would have continuously increased the seawater δ186/184W. Stable W isotope compositions of chemical sediments that potentially preserve changing seawater W isotope signatures might therefore reflect global changes in marine redox conditions.
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Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews e F. von Blanckenburg. "Iron isotope fractionation in marine invertebrates in near shore environments". Biogeosciences Discussions 11, n. 4 (11 aprile 2014): 5533–55. http://dx.doi.org/10.5194/bgd-11-5533-2014.
Testo completoAbstract (sommario):
Abstract. Chitons (Mollusca) are marine invertebrates that produce radula (teeth or rasping tongue) containing high concentrations of biomineralized magnetite and other iron bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radula might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radula collected from different locations in the Atlantic and Pacific oceans to assess the range of isotopic values, and to test whether or not the isotopic signatures reflect seawater values. Furthermore, by comparing two species that have very different feeding habits but collected from the same location, we infer a possible link between diet and Fe isotopic signatures. Values of δ56Fe (relative to IRMM-014) in chiton teeth range from −1.90 to 0.00‰ (±0.05‰ (2σ) uncertainty in δ56Fe), probably reflecting a combination of geographical control and biological fractionation processes. Comparison with published local surface seawater Fe isotope data shows a consistent negative offset of chiton teeth Fe isotope compositions relative to seawater. Strikingly, two different species from the same locality in the North Pacific (Puget Sound, Washington, USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red algae, has a mean δ56Fe of −0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia muscosa, which feeds primarily on green algae, shows lighter isotopic values with a mean δ56Fe of −1.47 ± 0.98‰ (2σ, 5 specimens). Although chitons are not simple recorders of the ambient seawater Fe isotopic signature, these preliminary results suggest that Fe isotopes provide information concerning Fe biogeochemical cycling in near shore environments, and might be used to probe sources of Fe in the diets of different organisms.
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Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews e F. von Blanckenburg. "A preliminary study of iron isotope fractionation in marine invertebrates (chitons, Mollusca) in near-shore environments". Biogeosciences 11, n. 19 (8 ottobre 2014): 5493–502. http://dx.doi.org/10.5194/bg-11-5493-2014.
Testo completoAbstract (sommario):
Abstract. Chitons (Mollusca) are marine invertebrates that produce radulae (teeth or rasping tongues) containing high concentrations of biomineralized magnetite and other iron-bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radulae might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radulae collected from different locations in the Atlantic and Pacific oceans to assess the range of isotopic values, and to test whether or not the isotopic signatures reflect seawater values. Values of δ56Fe (relative to IRMM-014) in chiton teeth range from −1.90 to 0.00 ‰ (±0.05‰ (2σ) uncertainty in δ56Fe), probably reflecting a combination of geographical control and biological fractionation processes. Comparison with published local surface seawater Fe isotope data shows a consistent negative offset of chiton teeth Fe isotope compositions relative to seawater. Strikingly, two different species from the same locality in the North Pacific (Puget Sound, Washington, USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red algae in the sublittoral zone, has a mean δ56Fe of −0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia muscosa, which feeds on both green and red algae in the eulittoral zone, shows lighter isotopic values with a mean δ56Fe of −1.47 ± 0.98‰ (2σ, 5 specimens). Three possible pathways are proposed to account for the different isotopic signatures: (i) physiologically controlled processes within the chitons that lead to species-dependent fractionation; (ii) diet-controlled variability due to different Fe isotope fractionation in the red and green algal food sources; and (iii) environmentally controlled fractionation that causes variation in the isotopic signatures of bioavailable Fe in the different tidal regions. Our preliminary results suggest that while chitons are not simple recorders of the ambient seawater Fe isotopic signature, Fe isotopes provide valuable information concerning Fe biogeochemical cycling in near-shore environments, and may potentially be used to probe sources of Fe recorded in different organisms.
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Renson, Virginie, e Michael D. Glascock. "Lead Isotopes to Identify Underwater Ceramic Contamination: The Example of the Kyrenia Shipwreck (Cyprus)". Minerals 11, n. 6 (12 giugno 2021): 625. http://dx.doi.org/10.3390/min11060625.
Testo completoAbstract (sommario):
We present the lead isotopic composition of ceramic fragments from the Kyrenia shipwreck (Cyprus), selected from three chemical groups related to the Rhodes and Alimos regions (Greece). Fragments of the lead sheathing covering the ship’s hull and biogenic material formed on some of the ceramic sherds, were analyzed along with sherds from the Rhodes and Alimos source areas for comparison. The objective of this paper was to evaluate the impact of the seawater environment on the isotopic signature of the ceramics, and on our ability to use lead isotopes to source ceramics recovered from seawater. The results showed that the lead isotopic composition of the shipwreck ceramics was modified by its prolonged proximity to the lead hull sheathing. The lead signature of filtering marine organisms encrusted on the ceramics provided support for this hypothesis.
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Resing, Joseph A., e Francis J. Sansone. "The chemistry of lava-seawater interactions II: the elemental signature". Geochimica et Cosmochimica Acta 66, n. 11 (giugno 2002): 1925–41. http://dx.doi.org/10.1016/s0016-7037(01)00897-3.
Testo completo
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Paulukat, Cora, Geoffrey J. Gilleaudeau, Pavel Chernyavskiy e Robert Frei. "The Cr-isotope signature of surface seawater — A global perspective". Chemical Geology 444 (dicembre 2016): 101–9. http://dx.doi.org/10.1016/j.chemgeo.2016.10.004.
Testo completo
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Ripperger, S., M. Rehkämper, D. Porcelli e A. N. Halliday. "Cadmium isotope fractionation in seawater — A signature of biological activity". Earth and Planetary Science Letters 261, n. 3-4 (settembre 2007): 670–84. http://dx.doi.org/10.1016/j.epsl.2007.07.034.
Testo completo
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Bouchard, Laurianne, Ján Veizer, Laura Kennell-Morrison, Mark Jensen, Ken G. Raven e Ian D. Clark. "Origin and 87Rb–87Sr age of porewaters in low permeability Ordovician sediments on the eastern flank of the Michigan Basin, Tiverton, Ontario, Canada". Canadian Journal of Earth Sciences 56, n. 3 (marzo 2019): 201–8. http://dx.doi.org/10.1139/cjes-2018-0061.
Testo completoAbstract (sommario):
Porewater extractions and acid leachates of rock core from a 250 m thick sequence of low-permeability Ordovician-age shales and limestones, on the eastern flank of the Michigan Basin, were analysed for strontium isotope ratios in an attempt to infer porewater ages from observed 87Sr/86Sr enrichments. The porewaters originated as Ordovician seawater, which subsequently mixed with evaporated Silurian seawater infiltrating from above, and, to some extent, with a deep brine—with an enriched 87Sr/86Sr signature—from the underlying crystalline shield or deep basin. The porewater 87Sr/86Sr ratios are more radiogenic than contemporaneous seawater but show no obvious correlation to those leached from the solid rock phases. Accepting that the initial 87Sr/86Sr signatures in porewaters were dominated by Late Silurian brine, potentially with an additional deep brine component, the excess of radiogenic 87Sr appears to represent ingrowth from 87Rb decay over a time span of some 420 million years, approaching the depositional age of the rocks. Similarly, Rb/Sr errochron ages of acid leachates of solid phases, and the calculated initial 87Sr/86Sr isotopic ratios, are consistent with a proposition that the calcites inherited their Sr from Ordovician seawater and were dolomitized shortly afterwards by infiltrating Mg-enriched evaporative brine, indicating long-term conservative behaviour for the enclosing carbonate rocks. The errochron for leachates from (alumino)silicates yields a high initial 87Sr/86Sr, but with an errochron age of about 340 ± 48 Ma, likely owing to variable admixtures of diagenetic illite in the shales. Overall, the data provide evidence for a stable hydrologic regime since Paleozoic time.
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Tignat-Perrier, Romie, Aurélien Dommergue, Alban Thollot, Olivier Magand, Timothy M. Vogel e Catherine Larose. "Microbial functional signature in the atmospheric boundary layer". Biogeosciences 17, n. 23 (4 dicembre 2020): 6081–95. http://dx.doi.org/10.5194/bg-17-6081-2020.
Testo completoAbstract (sommario):
Abstract. Microorganisms are ubiquitous in the atmosphere, and some airborne microbial cells were shown to be particularly resistant to atmospheric physical and chemical conditions (e.g., ultraviolet – UV – radiation, desiccation and the presence of radicals). In addition to surviving, some cultivable microorganisms of airborne origin were shown to be able to grow on atmospheric chemicals in laboratory experiments. Metagenomic investigations have been used to identify specific signatures of microbial functional potential in different ecosystems. We conducted a comparative metagenomic study on the overall microbial functional potential and specific metabolic and stress-related microbial functions of atmospheric microorganisms in order to determine whether airborne microbial communities possess an atmosphere-specific functional potential signature as compared to other ecosystems (i.e., soil, sediment, snow, feces, surface seawater etc.). In the absence of a specific atmospheric signature, the atmospheric samples collected at nine sites around the world were similar to their underlying ecosystems. In addition, atmospheric samples were characterized by a relatively high proportion of fungi. The higher proportion of sequences annotated as genes involved in stress-related functions (i.e., functions related to the response to desiccation, UV radiation, oxidative stress etc.) resulted in part from the high concentrations of fungi that might resist and survive atmospheric physical stress better than bacteria.
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Liang, Cheng Hao, Jing Di Yao, Nai Bao Huang e Jian Hua Wu. "Research on the Shaft-Frequency Electric Field Character of Ship’s Physical Scale Model". Advanced Materials Research 1035 (ottobre 2014): 62–66. http://dx.doi.org/10.4028/www.scientific.net/amr.1035.62.
Testo completoAbstract (sommario):
By signature gathering system, the shaft-frequency electric field of ship’s physical scale model is measured. At the same time, the mechanism of the corrosion related to shaft-frequency electric field is also described. Results show that the shaft-frequency electric field signature arises around a vessel and transmits in the surrounding seawater due to the current flow from impressed current cathodic protection (ICCP) system and the current flow resulting from the corrosion of dissimilar metals during propeller rotation, which contains both shaft fundamental and harmonics. The signature character of electric field is more and more marked with the shaft rotation speed increasing. The amplitude of electric shaft-frequency electric field by modulating the current of ICCP system is 10 times greater than that of corrosion current. It is proved that the using a 1:100 physical scale model of a vessel to study the shaft-frequency electric field character is an effective method and provided an new way.
Tesi sul tema "Seawater signature"
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Aquila, Quentin. "Explorer la géochimie des océans archéens avec les Formations de fer rubanées (BIF) : apport des compositions isotopiques Hf-Nd-Pb". Electronic Thesis or Diss., Université Clermont Auvergne (2021-...), 2024. http://www.theses.fr/2024UCFA0054.
Testo completoAbstract (sommario):
Les Formations de fer Rubanées (BIF) sont des archives sédimentaires uniques pour étudier les océans primitifs de l'Archéen. Cependant, l'environnement de formation et les mécanismes en jeu dans la formation de ces sédiments chimiques riches en fer et en silicium sont peu contraints. Les BIF ont été très peu étudiés pour leurs compositions isotopiques en Nd-Hf alors qu'elles pourraient permettre d'apporter de nouvelles contraintes sur les sources hydrothermales et continentales alimentant les anciens océans. Pour mieux contraindre l'environnement de formation des BIF, j'ai combiné des aspects de terrains et une étude pétro-géochimique sur une succession sédimentaire de la ceinture de Barberton (3,25 Ga, Afrique du Sud). Le modèle de dépôt des BIF de Barberton implique un milieu de dépôt profond, au bas d'une pente et distal du continent. Cet environnement est perturbé ponctuellement par des dépôts gravitaires terrigènes (mafiques) caractéristiques d'un système sédimentaire d'éventail sous-marin profond. J'ai évalué si la signature géochimique de l'eau de mer (REE+Y, faibles HFSE) permettait d'indiquer la préservation des compositions isotopiques Hf-Nd-Pb primaires sur un BIF de la ceinture de Isua (3,7 Ga, Groenland). Le BIF de Isua montre des perturbations post-dépôts des compositions isotopiques Hf-Nd attribués à la présence d'apatites secondaires. Il a cependant préservé un âge 207Pb-206Pb de 3810 ± 7 Ma hérité de zircons détritiques. Le spectre REE+Y typique de l'eau de mer ne garantit donc ni la préservation des compositions isotopiques Hf-Nd primaires de l'eau de mer, ni de l'absence de toute contamination terrigène. Enfin, j'ai exploré l'origine et la source du Nd et de l'Hf dans les BIF à l'échelle des bandes sur des échantillons provenant de la ceinture de Témagami (2,7 Ga, Canada). Les compositions isotopiques initiales en Nd-Hf des bandes de BIF de Témagami riches en Si montrent un découplage des deux systèmes isotopiques. A l'inverse, celles des bandes riches en Fe demeurent couplées en Nd-Hf. Les bandes riches en Si enregistrent une composition isotopique en Hf radiogénique provenant des eaux d'altérations des continents felsiques. A l'inverse, l'Hf et le Nd des bandes riches en Fe pourrait provenir principalement de l'hydrothermalisme sous-marinThe Banded Iron Formations (BIF) are unique sedimentary archives for studying the primitive oceans of the Archean. However, the environment of formation and the mechanisms involved in the formation of these iron- and silicon-rich chemical sediments are poorly constrained. The BIFs have been little studied for their Nd-Hf isotopic compositions, although they could provide new constraints on the hydrothermal and continental sources feeding the ancient oceans. To better constrain the BIFs environment of formation, I combined field observations with a petro-geochemical study on a sedimentary succession from the Barberton belt (3.25 Ga, South Africa). The deposition model of the Barberton BIFs involves a deep depositional environment, at the base of a slope and distal from the continent. This environment is occasionally disturbed by gravity-driven terrigenous deposits (mafic) characteristics of a deep-sea fan system. I evaluated whether the seawater geochemical signature (REE+Y, low HFSE) indicated the preservation of the primary Hf-Nd-Pb isotopic compositions in a BIF from the Isua belt (3.7 Ga, Greenland). The Isua BIF shows post-depositional disturbances in the Hf-Nd isotopic compositions attributed to the presence of secondary apatites. However, it preserved a 207Pb-206Pb age of 3810 ± 7 Ma inherited from detrital zircons. Therefore, the REE+Y spectrum typical of seawater does not guarantee the preservation of the primary Hf-Nd isotopic compositions of seawater, nor the absence of any terrigenous contamination. Finally, I explored the origin and source of Nd and Hf in the BIFs at the scale of the bands on samples from the Témagami belt (2.7 Ga, Canada). The initial Nd-Hf isotopic compositions of the Si-rich bands of the Témagami BIFs show a decoupling of the two isotopic systems. Conversely, those of the Fe-rich bands remain coupled in Nd-Hf. The Si-rich bands record a radiogenic Hf isotopic composition originating from the weathering waters of felsic continents. Conversely, the Hf and Nd in the Fe-rich bands could mainly originate from submarine hydrothermalism
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Miura, Noriko, Yoshihiro Asahara e Iwao Kawabe. "Rare earth element and Sr isotopic study of the Middle Permian limestone-dolostone sequence in Kuzuu area, central Japan: Seawater tetrad sffect and Sr isotopic signatures of seamount-type carbonate rocks". Dept. of Earth and Planetary Sciences, Nagoya University, 2004. http://hdl.handle.net/2237/7643.
Testo completo
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Reboul, Guillaume. "Metabarcoding and metagenomic approaches to decipher microbial communities in suboxic environments Microbial eukaryotes in the suboxic chemosyn- thetic ecosystem of Movile Cave, Romania Hyper- diverse archaea near life limits at the polyextreme geothermal Dallol area Performance of the melting seawater-ice elution method on the metabarcoding characterization of benthic protist communities Core microbial communities of lacustrine microbialites sampled along an alkalinity gradient Environmental drivers of plankton protist communities along latitudinal and vertical gradients in the oldest and deepest freshwater lake Ancient Adaptive Lateral Gene Transfers in the Symbiotic Opalina-Blastocystis Stramenopile Lineage Marine signature taxa and microbial community stability along latitudinal and vertical gradients in sediments of the deepest freshwater lake". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL041.
Testo completoAbstract (sommario):
L’écologie microbienne concerne l’étude des microorganismes et de leurs interactions biotiques et abiotiques dans un écosystème donné. Ces vingt dernières années, l’avancement des techniques moléculaires pour analyser la diversité microbienne et, notamment, les nouvelles technologies de séquençages (NGS) ont permis de surmonter les limitations associées aux approches traditionnelles basées sur la culture et la microscopie. Ces approches moléculaires ont conduit à une accumulation des données de diversité microbienne et de potentiel métabolique dans des communautés microbiennes des écosystèmes variés.Cependant, ces efforts ont été principalement appliqués sur des environnements facilement accessibles ou liés à l’humain, comme le plancton (marin principalement) et la flore intestinale. Néanmoins, ceci a conduit à une très forte augmentation de données environnementales et au développement de la bioinformatique par le biais de nombreux outils. Parmi les environnements délaissés des études, les environnements faibles en oxygène sont probablement également porteurs de nouveautés phylogénique ou métaboliques.Afin de palier à cela, nous avons choisi d’explorer deux environnements suboxiques relativement peu étudiés : la cave Movile (Roumanie) et les sédiments du lac Baikal (Sibérie, Russie). Notre but étant de montrer les diversités phylogénétiques et fonctionnelles des microbes de ces biotopes.Pour cela, j’ai d'abord développé un pipeline d’analyse de données métabarcoding (petite sous-unités ribosomique). Ensuite, j’ai appliqué cet outil sur des données de métabarcoding de protistes provenant d’échantillons d’eau et de tapis microbiens de la cave de Movile, un écosystème chemosynthétique pratiquement fermé. Nous avons montré que la diversité des protistes de la cave s’étendait à quasiment tous les grands groupes eucaryotes et provenait à la fois d’origine d’eaux douces et marines. De plus, la plupart ont été affiliées à des groupes d’organismes typiquement anaérobies, ce qui est concordant avec les paramètres abiotiques de la cave. Écologiquement, ces protistes sont des prédateurs mais aussi vraisemblablement des partenaires symbiotiques avec des espèces procaryotes de la cave.Dans une deuxième étude, j’ai eu l’opportunité d’appliquer ce pipeline de métabarcoding sur des données procaryotes et eucaryotes provenant des couches superficielles des sédiments du lac d’eau douce Baikal. Comme attendu, les communautés microbiennes dans ces sédiments sont particulièrement diverses et relativement enrichis en archées. Nous avons aussi pu mettre en évidence des lignées que l’on pensait exclusivement marines dans ces sédiments. Ces lignées sont probablement planctoniques mais s’accumulent au fond par sédimentation. Enfin, les échantillons ont été prélevés dans le but de tester les influences de la profondeur, du bassin et de la latitude sur les communautés. Aucune d’elles ne s’est révélée significative.Dans une troisième étude, j'ai utilisé une approche métagénomique afin de révéler les acteurs écologiquement majeurs dans les sédiments, leurs rôles et de reconstruire leurs génomes. Cela nous a permis notamment de mettre en évidence le rôle primordial des Thaumarchaeota dans le cycle de l’azote et la production primaire de molécules de carbone. Les chloroflexi et les protéobacteries ont aussi un rôle important dans la surface des sédiments du lac Baikal. Ce travail de thèse participe à la connaissance globale de la diversité microbienne sur la planète en mettant en lumière des environnements peu étudiés. De plus, l’étude de la surface des sédiments du lac Baikal apporte de nouvelles données sur le sujet de la transition eau douces/eau marines des microbes. Enfin, la métagénomique a permis de révéler le cycle des nutriments et les microorganismes y participant dans ces échantillons de sédiment. En résumé, ce travail vient mettre en lumière l’écologie microbienne d’écosystèmes suboxiques, notamment la surface des sédiments du lac BaikalMicrobial ecology is the science of micro-organisms and their biotic and abiotic interactions in a given ecosystem. As technology has advanced, molecular techniques have been widely used to overcome the limitations of classical approaches such as culturing and microscopy. Indeed, the development of Next Generation Sequencing (NGS) technologies in the past twenty years has largely helped to unravel the phylogenetic diversity and functional potential of microbial communities across ecosystems.Nonetheless, most of the environments studied through these techniques concentrated on relatively easily accessible, tractable and host-related ecosystems such as plankton (especially in marine ecosystems), soils and gut microbiomes. This has contributed to the rapid accumulation of a wealth of environmental diversity and metagenomic data along with advances in bioinformatics leading to the development of myriads of tools. Oxygen-depleted environments and especially their microbial eukaryote components are less studied and may lead to future phylogenetic and metabolic discoveries.In order to address this, we conducted analyses on two poorly studied suboxic ecosystems: Movile Cave (Romania) and lake Baikal sediments (Siberia, Russia). In this task, we aimed at unveiling the taxonomic and functional diversity of microorganims in these environments.To do so, I first evaluated the available bioinformatics tools and implemented a bioinformatics pipeline for 16S/18S rRNA gene-based metabarcoding analysis, making reasoned methodological choices. Then, as a case study, I carried out metabarcoding analyses of the water and floating microbial mats found in Movile Cave in order to investigate its protist diversity. Our study showed that Movile Cave, a sealed off chemosynthetic ecosystem, harbored a substantial protist diversity with species spanning most of the major eukaryotic super groups. The majority if these protists were related to species of freshwater and marine origins. Most of them were putatively anaerobic, in line with the cave environment, and suggesting that in addition to their predatory role, they might participate in prokaryote-protist symbioses.In a second study, I applied my metabarcoding pipeline to explore unique and relatively unexplored environment of Lake Baikal sediments. I first applied a metabarcoding approach using 16S and 18S rRNA genes to describe prokaryotic as well as protist diversity. Overall, the communities within these ecosystems were very diverse and enriched in ammonia-oxidizing Thaumarchaeota. We also identified several typical marine taxa which are likely planktonic but accumulate in sediments. Finally, our sampling plan allowed us to test whether differences across depth, basin or latitude affected microbial community structure. Our results showed that the composition of sediment microbial communities remained relatively stable across the samples regardless of depth or latitude.In a third study, we applied metagenomics to study the metabolic potential of communities associated to Baikal sediments and to reconstruct metagenome-assembled genomes (MAGs) of dominant organisms. This revealed the considerable ecological importance of Thaumarchaeota lineages in lake Baikal sediments, which were found to be the major autotrophic phyla and also very implicated in the nitrogen cycle. Chloroflexi and Proteobacteria-related species also appeared ecologically important.This PhD thesis reveals the taxonomic diversity of poorly studied suboxic ecosystems and therefore contributes to our knowledge of microbial diversity on Earth. Additionally, the analyses of surface sediment samples in lake Baikal adds new light on freshwater-marine transitions. The metagenomic analyses reported here allowed us to postulate a model of nutrient cycle carried out by microorganismsin these sediments. Overall, this work sheds light on the microbial ecology of oxygen-depleted environments, and most notably lake Baikal surface sediments
Capitoli di libri sul tema "Seawater signature"
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Lobato, Lydia Maria, Rosaline Cristina Figueiredo e Silva, Thomas Angerer, Mônica de Cássia Oliveira Mendes e Steffen G. Hagemann. "Iron Isotopes Applied to BIF-Hosted Iron Deposits". In Isotopes in Economic Geology, Metallogenesis and Exploration, 399–432. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_13.
Testo completoAbstract (sommario):
AbstractPublished and unpublished iron isotope data from banded iron formations (BIF) and their BIF-hosted hypogene (hydrothermal) iron ores from the Quadrilátero Ferrífero (itabirites), Corumbá, and Carajás iron districts in Brazil, as well as from the Hamersley province in Australia are presented and discussed. BIF constitutes a typically thinly bedded or laminated chemical sedimentary rock, with ≥ 15% Fe and layers of chert, chalcedony, jasper, or quartz, whereas itabirite is considered a laminated, metamorphosed iron formation rich in iron oxides, which may contain carbonate minerals, amphiboles, and abundant quartz. For the Paleoproterozoic Quadrilátero Ferrífero district, the range in δ56Fe values of hypogene iron ores is similar to that of the metamorphosed BIFs, and iron isotope variations are better distinguished in different regional deformational domains. Light isotopic compositions dominate in the low deformation domain (δ56Fe = −0.42 ± 0.12 to 0.29 ± 0.04‰), whereas the eastern, high-strain domain is characterized by heavy values (δ56Fe = −0.09 ± 0.08 to 0.37 ± 0.06‰; Mendes et al., Mineral Deposita 52:159–180, 2017). Iron isotope composition for the Neoproterozoic iron formations of the Corumbá region (hematitic, dolomite-rich: −1.83 and −0.83‰; cherty-hematite: δ56Fe −0.49‰) are controlled by: (1) primary seawater signature, (2) microbial activity, and (3) supergene goethite alteration. Hydrothermal alteration is reflected in the oxygen isotope data, but apparently not in the iron isotope fractionation. Iron and oxygen isotope pairing shows that δ56Fe values increase, while δ18O values decrease. In the Archean jaspilites of Carajás, hypogene ores tend to display lighter δ56Fe values than their host BIF counterparts. Also, there is a correlation between coupled iron and oxygen isotope values that is clearer towards lighter isotopic values, especially for δ18O. In the Paleoproterozoic Hamersley deposits, correlation between δ18O and δ56Fe values suggests a direct correlation of both isotope systems during low-grade, greenschist-facies metamorphism. On the other hand, despite the evident shift to negative δ18O values and apparent preservation of the metamorphic δ56Fe signature, iron ore and hydrothermally modified BIF show a correlation between δ18O and δ56Fe values. In contrast, in supergene-modified samples a negative correlation is apparent. The Carajás (+1.24 to + 0.44; one sample − 0.30‰) and Hamersley (+ 1.02 to − 0.29‰) hypogene ores display δ56Fe in a similar interval, reaching positive values, whereas ores from the Quadrilátero Ferrífero show a tendency towards lower values (to − 0.80‰). This review indicates that the application of iron isotopes in exploration is presently limited mainly due to the restricted dataset available for ore samples. Nevertheless, and despite all local differences, there is a general tendency for hypogene ores to display moderately lighter δ56Fe values for all deposits compared to precursor BIF. In contrast, a strong supergene imprint in ore leads to moderately heavier δ56Fe values. As more data become available, and if these trends are confirmed, the use of this tool may be valuable in the future, for instance to decipher the hypogene or supergene origin of specific ore zones, and as a consequence the probable depth extension or interpretation of concealed, deep orebodies.
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Huston, David L., Robert B. Trumbull, Georges Beaudoin e Trevor Ireland. "Light Stable Isotopes (H, B, C, O and S) in Ore Studies—Methods, Theory, Applications and Uncertainties". In Isotopes in Economic Geology, Metallogenesis and Exploration, 209–44. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_8.
Testo completoAbstract (sommario):
AbstractVariations in the abundances of light stable isotopes, particularly those of hydrogen, boron, carbon, oxygen and sulfur, were essential in developing mineralization models. The data provide constraints on sources of hydrothermal fluids, carbon, boron and sulfur, track interaction of these fluids with the rocks at both the deposit and district scales, and establish processes of ore deposition. In providing such constraints, isotopic data have been integral in developing genetic models for porphyry-epithermal, volcanic-hosted massive sulfide, orogenic gold, sediment-hosted base metal and banded-iron formation-hosted iron ore systems, as discussed here and in other chapters in this book. After providing conventions, definitions and standards used to present stable isotope data, this chapter summarizes analytical methods, both bulk and in situ, discusses processes that fractionate stable isotopes, documents the isotopic characteristics of major fluid and rock reservoirs, and then shows how stable isotope data have been used to better understand ore-forming processes and to provide vectors to ore. Analytical procedures, initially developed in the 1940s for carbon–oxygen analysis of bulk samples of carbonate minerals, have developed so that, for most stable isotopic systems, spots as small as a few tens of μm are routinely analyzed. This precision provides the paragenetic and spatial resolution necessary to answer previously unresolvable genetic questions (and create new questions). Stable isotope fractionation reflects geological and geochemical processes important in ore formation, including: (1) phase changes such as boiling, (2) water–rock interaction, (3) cooling, (4) fluid mixing, (5) devolatilization, and (6) redox reactions, including SO2 disproportionation caused by the cooling of magmatic-hydrothermal fluids and photolytic dissociation in the atmosphere. These processes commonly produce gradients in isotopic data, both in time and in space. These gradients, commonly mappable in space, provide not only evidence of process but also exploration vectors. Stable isotope data can be used to estimate the conditions of alteration or mineralization when data for coexisting minerals are available. These estimates use experimentally- or theoretically-determined fractionation equations to estimate temperatures of mineral formation. If the temperature is known from isotopic or other data (e.g., fluid inclusion data or chemical geothermometers), the isotopic composition of the hydrothermal fluid components can be estimated. If fluid inclusion homogenization and compositional data exist, the pressure and depth of mineralization can be estimated. One of the most common uses of stable isotope data has been to determine, or more correctly delimit, fluid and sulfur sources. Estimates of the isotopic compositions of hydrothermal fluids, in most cases, do not define unequivocal sources, but, rather, eliminate sources. As an example, the field of magmatic fluids largely overlap that of metamorphic fluids in δ18O-δD space, but are significantly different to the fields of meteoric waters and seawater. As such, a meteoric or seawater origin for a fluid source may be resolvable, but a magmatic source cannot be resolved from a metamorphic source. Similarly, although δ34S ~ 0‰ is consistent with a magmatic-hydrothermal sulfur source, the signature can also be produced by leaching of an igneous source. Recent analytical and conceptual advances have enabled gathering of new types of isotopic data and application of these data to resolve new problems in mineral deposit genesis and geosciences in general. Recent developments such as rapid isotopic analysis of geological materials or clumped isotopes will continue to increase the utility of stable isotope data in mineral deposit genesis and metallogeny, and, importantly, for mineral exploration.
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Joseph, Antony. "Imaging of Seawater Motion Signatures Using Remote Sensors". In Measuring Ocean Currents, 139–75. Elsevier, 2014. http://dx.doi.org/10.1016/b978-0-12-415990-7.00005-3.
Testo completoAtti di convegni sul tema "Seawater signature"
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Barré, Guillaume, Georges Beaudoin, Crystal LaFlamme, Jean Goutier e Pierre Cartigny. "The Archean seawater sulfate isotopic signature determined from VMS deposits". In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.12186.
Testo completo
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Bertrand, A., C. Ribeiro e C. MacBeth. "Uncertainties in the 4D Seismic Signature Due to Seawater Velocity Variations". In 66th EAGE Conference & Exhibition. European Association of Geoscientists & Engineers, 2004. http://dx.doi.org/10.3997/2214-4609.201405662.
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Bertrand, Alexandre, Christophe Ribeiro e Colin MacBeth. "Uncertainties in the 4D seismic signature due to seawater velocity variations". In SEG Technical Program Expanded Abstracts 2004. Society of Exploration Geophysicists, 2004. http://dx.doi.org/10.1190/1.1851214.
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Zheng, Xinyuan, Guy Evans, Xinyang Chen, Soisiri Charin, William Seyfried e Tianyu Chen. "Can hydrothermal alteration explain the heavy K isotope signature of seawater?" In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.12314.
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Bertrand, A., C. Ribeiro e C. MacBeth. "Uncertainties in the 4D Seismic Signature due to Seawater Velocity Variations". In 66th EAGE Conference & Exhibition. European Association of Geoscientists & Engineers, 2004. http://dx.doi.org/10.3997/2214-4609-pdb.3.a041.
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Drummond, Drew, Robert Blakeman, John H. Ashton, Ian Farrelly, Jonathan Cloutier, Lola Yesares e Adrian Boyce. "Ore depositional processes at the carbonate-hosted Tara Deep Zn-Pb deposit, Navan, Ireland". In Irish-type Zn-Pb deposits around the world. Irish Association for Economic Geology, 2023. http://dx.doi.org/10.61153/dqcn2038.
Testo completoAbstract (sommario):
The Tara Deep Zn-Pb deposit (currently 26.2 Mt @ 8.4% Zn, 1.6% Pb) is the latest major discovery by Boliden Tara Mines (first announced in 2016) which significantly adds to the existing world-class Navan deposit. Located 2 km south of the Navan deposit in Co. Meath, Ireland, economic mineralization is hosted by upper Tournaisian carbonates (Pale Beds; 87% of the total economic resource), within a degraded footwall of a major south-dipping normal fault, and also within lower Visean sedimentary breccias (‘S Fault’ Conglomerates; SFC). Sphalerite and galena are the dominant sulphides, with massive, cavity fill and brecciated textures dominating. These textures attest complex, subsurface, episodic mineralization events that display considerable reworking, fracturing, dolomitization, open-space infill and selective replacement. Lower Visean syn-rift sliding, erosion, and deposition of thick debrites and calc-turbidites at Tara Deep record basin margin processes near extensional faulting associated with formation of the Dublin Basin. These debrites host detrital sulphide-rich clasts and offer unambiguous evidence that the onset of mineralization occurred during the upper Tournaisian. δ34S values of base metal sulphides have a bimodal distribution suggesting both bacteriogenic (-13.5 to -3.6‰) and hydrothermal sulphur sources (+3.4 to +16.2‰). Both textural and sulphur isotope data reveal the dynamic nature of mineralization at Tara Deep and infer fluid mixing. Lead isotope analyses display remarkably homogeneous 206Pb/204Pb of 18.23 ±0.006 (2σ, n=25), which is coincident with Pb isotope data across the Navan deposit. Subsequently, Tara Deep and Navan are isotopically similar, showing both a statistically identical Pb isotopic signature and a bimodal sulphide S isotopic distribution and homogeneous sulphate signature. In particular, the Pb isotopes and the hydrothermal S signature, correlate with Navan and support the view that base-metals were leached from the underlying Lower Palaeozoic basement, and suggest that similar deep, circulating metalliferous fluids were also involved at Tara Deep. However, despite these similarities, key differences can be recognized within the S isotope data; around 5‰ shifts to higher δ34S in the surface-derived S isotope signatures (both bacteriogenic sulphide and sulphate) indicate that Tara Deep’s sulphur was sourced from a distinct seawater/connate fluid signature. The Tara Deep deposit has many similarities with the neighbouring Navan deposit reflecting comparable controls on the mineralizing processes in terms of host rocks, Pb and S sources, and tectonic environment. Mineralization initiated during an early phase of the developing Dublin Basin (syn-diagenetically) and kept pace with rifting and subsequently an evolving basin.
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Drummond, Drew, Robert Blakeman, John H. Ashton, Ian Farrelly, Jonathan Cloutier, Lola Yesares e Adrian Boyce. "Ore depositional processes at the carbonate-hosted Tara Deep Zn-Pb deposit, Navan, Ireland". In Irish-type Zn-Pb deposits around the world. Irish Association for Economic Geology, 2023. http://dx.doi.org/10.61153/dpcd8412.
Testo completoAbstract (sommario):
The Tara Deep Zn-Pb deposit (currently 26.2 Mt @ 8.4% Zn, 1.6% Pb) is the latest major discovery by Boliden Tara Mines (first announced in 2016) which significantly adds to the existing world-class Navan deposit. Located 2 km south of the Navan deposit in Co. Meath, Ireland, economic mineralization is hosted by upper Tour-naisian carbonates (Pale Beds; 87% of the total economic resource), within a degraded footwall of a major south-dipping normal fault, and also within lower Visean sedimentary breccias (‘S Fault’ Conglomerates; SFC). Sphalerite and galena are the dominant sulphides, with massive, cavity fill and brecciated textures dominating. These textures attest complex, subsurface, episodic mineralization events that display considerable reworking, fracturing, dolomitization, open-space infill and selective replacement. Lower Visean syn-rift sliding, erosion, and deposition of thick debrites and calc-turbidites at Tara Deep record basin margin processes near extensional faulting associated with formation of the Dublin Basin. These debrites host detrital sulphide-rich clasts and offer unambiguous evidence that the onset of mineralization occurred during the upper Tournaisian. δ34S values of base metal sulphides have a bimodal distribution suggesting both bacteriogenic (-13.5 to -3.6‰) and hydrothermal sulphur sources (+3.4 to +16.2‰). Both textural and sulphur isotope data reveal the dynamic nature of mineralization at Tara Deep and infer fluid mixing. Lead isotope analyses display remarkably homogeneous 206Pb/204Pb of 18.23 ±0.006 (2σ, n=25), which is coincident with Pb isotope data across the Navan deposit. Subsequently, Tara Deep and Navan are isotopically similar, showing both a statistically identical Pb isotopic signature and a bimodal sulphide S isotopic distribution and homogeneous sulphate signature. In particular, the Pb isotopes and the hydrothermal S signature, correlate with Navan and support the view that base-metals were leached from the underlying Lower Palaeozoic basement, and suggest that similar deep, circulating metalliferous fluids were also involved at Tara Deep. However, despite these similarities, key differences can be recognized within the S isotope data; around 5‰ shifts to higher δ34S in the surface-derived S isotope signatures (both bacteriogenic sulphide and sulphate) indicate that Tara Deep’s sulphur was sourced from a distinct seawater/connate fluid signature. The Tara Deep deposit has many similarities with the neighbouring Navan deposit reflecting comparable controls on the mineralizing processes in terms of host rocks, Pb and S sources, and tectonic environment. Mineralization initiated during an early phase of the developing Dublin Basin (syn-diagenetically) and kept pace with rifting and subsequently an evolving basin.
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Hawco, Nicholas, Shun-Chung Yang, Rhea Foreman, Carolina Funkey, Mathilde Dugenne, Angelicque White, Samuel Wilson et al. "Unique Metal Isotope Signatures from Lava-Seawater Interaction during the 2018 Eruption of Kīlauea". In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.981.
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Rolle, Francesca, e Michela Sega. "Stable carbon isotope signatures in atmosphere and seawater as a basis for climate change studies". In 2018 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea). IEEE, 2018. http://dx.doi.org/10.1109/metrosea.2018.8657888.
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Yue, Ruiyong, Ping Hu e Jing Zhang. "The influence of the seawater and seabed interface on the underwater low frequency electromagnetic field signatures". In 2016 IEEE/OES China Ocean Acoustics (COA). IEEE, 2016. http://dx.doi.org/10.1109/coa.2016.7535694.
Testo completoRapporti di organizzazioni sul tema "Seawater signature"
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Mueller, C., S. J. Piercey, M. G. Babechuk e D. Copeland. Stratigraphy and lithogeochemistry of the Goldenville horizon and associated rocks, Baie Verte Peninsula, Newfoundland. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328990.
Testo completoAbstract (sommario):
The Goldenville horizon in the Baie Verte Peninsula is an important stratigraphic horizon that hosts primary (Cambrian to Ordovician) exhalative magnetite and pyrite and was a chemical trap for younger (Silurian to Devonian) orogenic gold mineralization. The horizon is overlain by basaltic flows and volcaniclastic rocks, is intercalated with variably coloured argillites and cherts, and underlain by mafic volcaniclastic rocks; the entire stratigraphy is cut by younger fine-grained mafic dykes and coarser gabbro. Lithogeochemical signatures of the Goldenville horizon allow it to be divided into high-Fe iron formation (HIF; >50% Fe2O3), low-Fe iron formation (LIF; 15-50% Fe2O3), and argillite with iron minerals (AIF; <15% Fe2O3). These variably Fe-rich rocks have Fe-Ti-Mn-Al systematics consistent with element derivation from varying mineral contributions from hydrothermal venting and ambient detrital sedimentation. Post-Archean Australian Shale (PAAS)-normalized rare earth element (REE) signatures for the HIF samples have negative Ce anomalies and patterns similar to modern hydrothermal sediment deposited under oxygenated ocean conditions. The PAAS-normalized REE signatures of LIF samples have positive Ce anomalies, similar to hydrothermal sediment deposited under anoxic to sub-oxic conditions. The paradoxical Ce behaviour is potentially explained by the Mn geochemistry of the LIF samples. The LIF have elevated MnO contents (2.0-7.5 weight %), suggesting that Mn from hydrothermal fluids was oxidized in an oxygenated water column during hydrothermal venting, Mn-oxides then scavenged Ce from seawater, and these Mn-oxides were subsequently deposited in the hydrothermal sediment. The Mn-rich LIF samples with positive Ce anomalies are intercalated with HIF with negative Ce anomalies, both regionally and on a metre scale within drill holes. Thus, the LIF positive Ce anomaly signature may record extended and particle-specific scavenging rather than sub-oxic/redox-stratified marine conditions. Collectively, results suggest that the Cambro-Ordovician Taconic seaway along the Laurentian margin may have been completely or near-completely oxygenated at the time of Goldenville horizon deposition.
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Simandl, G. J., R. J. D'Souza, S. Paradis e J. Spence. Rare-earth element content of carbonate minerals in sediment-hosted Pb-Zn deposits, southern Canadian Rocky Mountains. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/328001.
Testo completoAbstract (sommario):
Paleozoic platform carbonate rocks of the Rocky Mountains host Mississippi Valley-type (MVT), magnesite, barite, and REE-barite-fluorite deposits. Farther west, platform carbonate rocks of the Kootenay Arc host MVT and fracture-controlled replacement (FCR) deposits. This is the first systematic LA-ICP-MS study of carbonates in MVT and FCR deposits. We investigated seven MVT deposits in the Rocky Mountains, and five MVT deposits in the Kootenay Arc. None of the post-Archean Australian shale (PAAS)-normalized REE profiles show light REE (LREE) depletion and strong negative Ce anomalies characteristic of modern seawater: some profiles are nearly flat; others show depletion in LREE similar to seawater but without negative Ce anomalies; others are middle REE enriched. Carbonates with a strong positive Eu anomaly precipitated from or interacted with different fluids than carbonates with flatter profiles without a strong positive Eu anomaly. REE signatures reflect crystallization conditions of primary carbonates, and crystallization and re-equilibration conditions of carbonates with ambient fluids during diagenesis, deep burial, and/or metamorphic recrystallization. Chemical evolution of fluids along their migration path, fluid-to-rock ratio, fluid acidity, redox, and temperature also influence REE profile shape, which helps establish genetic and timing constraints on studied deposits and improves knowledge of the metallogeny of the Kootenay Arc and Rocky Mountains.