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Littérature scientifique sur le sujet « Archean ocean »

Auteur : Grafiati
Publié le 16 novembre 2024

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Articles de revues sur le sujet "Archean ocean"

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Crowe, S. A., C. Jones, S. Katsev, C. Magen, A. H. O'Neill, A. Sturm, D. E. Canfield et al. « Photoferrotrophs thrive in an Archean Ocean analogue ». Proceedings of the National Academy of Sciences 105, no 41 (6 octobre 2008) : 15938–43. http://dx.doi.org/10.1073/pnas.0805313105.

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Busigny, Vincent, Noah J. Planavsky, Didier Jézéquel, Sean Crowe, Pascale Louvat, Julien Moureau, Eric Viollier et Timothy W. Lyons. « Iron isotopes in an Archean ocean analogue ». Geochimica et Cosmochimica Acta 133 (mai 2014) : 443–62. http://dx.doi.org/10.1016/j.gca.2014.03.004.

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Sharma, S. Das, D. J. Patil, R. Srinivasan et K. Gopalan. « Very high18o enrichment in Archean cherts from South India : implications for Archean ocean temperature ». Terra Nova 6, no 4 (juillet 1994) : 385–90. http://dx.doi.org/10.1111/j.1365-3121.1994.tb00511.x.

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Harrison, C. G. A. « Constraints on ocean volume change since the Archean ». Geophysical Research Letters 26, no 13 (1 juillet 1999) : 1913–16. http://dx.doi.org/10.1029/1999gl900425.

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Habicht, K. S. « Calibration of Sulfate Levels in the Archean Ocean ». Science 298, no 5602 (20 décembre 2002) : 2372–74. http://dx.doi.org/10.1126/science.1078265.

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Busigny, Vincent, Oanez Lebeau, Magali Ader, Bryan Krapež et Andrey Bekker. « Nitrogen cycle in the Late Archean ferruginous ocean ». Chemical Geology 362 (décembre 2013) : 115–30. http://dx.doi.org/10.1016/j.chemgeo.2013.06.023.

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Avila-Alonso, Dailé, Jan M. Baetens, Rolando Cardenas et Bernard De Baets. « Assessing the effects of ultraviolet radiation on the photosynthetic potential in Archean marine environments ». International Journal of Astrobiology 16, no 3 (9 septembre 2016) : 271–79. http://dx.doi.org/10.1017/s147355041600032x.

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AbstractIn this work, the photosynthesis model presented by Avilaet al. in 2013 is extended and more scenarios inhabited by ancient cyanobacteria are investigated to quantify the effects of ultraviolet (UV) radiation on their photosynthetic potential in marine environments of the Archean eon. We consider ferrous ions as blockers of UV during the Early Archean, while the absorption spectrum of chlorophyllais used to quantify the fraction of photosynthetically active radiation absorbed by photosynthetic organisms. UV could have induced photoinhibition at the water surface, thereby strongly affecting the species with low light use efficiency. A higher photosynthetic potential in early marine environments was shown than in the Late Archean as a consequence of the attenuation of UVC and UVB by iron ions, which probably played an important role in the protection of ancient free-floating bacteria from high-intensity UV radiation. Photosynthetic organisms in Archean coastal and ocean environments were probably abundant in the first 5 and 25 m of the water column, respectively. However, species with a relatively high efficiency in the use of light could have inhabited ocean waters up to a depth of 200 m and show a Deep Chlorophyll Maximum near 60 m depth. We show that the electromagnetic radiation from the Sun, both UV and visible light, could have determined the vertical distribution of Archean marine photosynthetic organisms.
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Nishizawa, Manabu, Takuya Saito, Akiko Makabe, Hisahiro Ueda, Masafumi Saitoh, Takazo Shibuya et Ken Takai. « Stable Abiotic Production of Ammonia from Nitrate in Komatiite-Hosted Hydrothermal Systems in the Hadean and Archean Oceans ». Minerals 11, no 3 (19 mars 2021) : 321. http://dx.doi.org/10.3390/min11030321.

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Abiotic fixation of atmospheric dinitrogen to ammonia is important in prebiotic chemistry and biological evolution in the Hadean and Archean oceans. Though it is widely accepted that nitrate (NO3−) was generated in the early atmospheres, the stable pathways of ammonia production from nitrate deposited in the early oceans remain unknown. This paper reports results of the first experiments simulating high-temperature, high-pressure reactions between nitrate and komatiite to find probable chemical pathways to deliver ammonia to the vent–ocean interface of komatiite-hosted hydrothermal systems and the global ocean on geological timescales. The fluid chemistry and mineralogy of the komatiite–H2O–NO3− system show iron-mediated production of ammonia from nitrate with yields of 10% at 250 °C and 350 °C, 500 bars. The komatiite–H2O–NO3– system also generated H2-rich and alkaline fluids, well-known prerequisites for prebiotic and primordial metabolisms, at lower temperatures than the komatiite–H2O–CO2 system. We estimate the ammonia flux from the komatiite-hosted systems to be 105–1010 mol/y in the early oceans. If the nitrate concentration in the early oceans was greater than 10 μmol/kg, the long-term production of ammonia through thermochemical nitrate reduction for the first billion years might have allowed the subsequent development of an early biosphere in the global surface ocean. Our results imply that komatiite-hosted systems might have impacted not only H2-based chemosynthetic ecosystems at the vent-ocean interface but also photosynthetic ecosystems on the early Earth.
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Sleep, Norman H. « Archean plate tectonics : what can be learned from continental geology ? » Canadian Journal of Earth Sciences 29, no 10 (1 octobre 1992) : 2066–71. http://dx.doi.org/10.1139/e92-164.

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Some basic questions about Archean plate tectonics can be addressed by examining accretionary Archean margins, in particular fault zones with significant strike-slip components on the Canadian Shield. (1) Were the oceanic plates typically rigid like modern plates? Yes. Significant lateral viscosity contrasts in the lithosphere between plates and plate boundaries are required for major strike-slip faults to exist. Conversely, strike-slip faults are a kinematic consequence of rigid plates. (2) Did large oceanic plates exist in the Archean? Probably. First, the length and offset of the longest preserved segments of Archean faults are similar to modern examples such as in Alaska. Less directly, the duration of a period with a consistent sense of strike slip at a point on the continental side of an accretionary margin should be related to the time that a typical oceanic plate remains outboard of the margin. This time varies proportionally with size of typical ocean plates and inversely with their velocity. The duration of an example of persistent strike slip on the Canadian Shield is comparable to that of Cenozoic examples. (3) Did old oceanic crust and hence moderate plate velocities occur in the Archean? Perhaps. Paleomagnetic poles are the most direct line of evidence, but they usually relate to continental blocks. The duration of consistent strike-slip motion, preserved alkalic seamounts which record eruption on old oceanic crust, and the duration of ocean basins are potential indirect indications. Overall, the hotter mantle does not appear to have had a great effect on Archean plate motions. Thus, the geometry and rate of plate tectonics are strongly influenced by the lithosphere.
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Olson, Haley C., Nadja Drabon et David T. Johnston. « Oxygen isotope insights into the Archean ocean and atmosphere ». Earth and Planetary Science Letters 591 (août 2022) : 117603. http://dx.doi.org/10.1016/j.epsl.2022.117603.

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Plus de sources

Thèses sur le sujet "Archean ocean"

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Koeksoy, Elif [Verfasser], et Andreas [Akademischer Betreuer] Kappler. « Biogeochemical Fe-S-cycling in a late Archean and Proterozoic ocean model habitat - the high alpine Arvadi Spring / Elif Koeksoy ; Betreuer : Andreas Kappler ». Tübingen : Universitätsbibliothek Tübingen, 2018. http://d-nb.info/1198973374/34.

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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.

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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-marin
The 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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Mayaga-Mikolo, Francis. « Chronologie des evenements sedimentaires, magmatiques et tectono-metamorphiques du precambrien d'afrique centrale occidentale (gabon) : tectogenese ogooue et heritage archeen ». Clermont-Ferrand 2, 1996. http://www.theses.fr/1996CLF21824.

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Le precambrien du gabon est compose de terrains archeens des massifs du nord-gabon et du chaillu, des formations reputees d'age paleoproterozoique de l'ogooue, des sediments paleoproterozoiques du francevillien, des plutons d'age eburneen du mayombe (ou chaine ouest-congolienne). Des datations radiometriques (pb-pb, u-pb, rb-sr et sm-nd, ar-ar) ont ete utilisees afin de contraindre l'age des evenements sedimentaires, magmatiques, tectoniques et metamorphiques qui ont affecte ces differentes entites. L'etude geochronologique montre que l'accretion des terrains paleoproterozoiques se fait autour des noyaux archeens dont les plus vieux temoins, d'age anterieur a 3100 ma, seraient presents dans les monts de cristal au nord-gabon. L'histoire archeenne se deroulerait ensuite de la facon suivante: entre 3100-3000 ma: premier metamorphisme de haut grade ; 3000-2950 ma: mise en place diachrone des greenstone belts. Durant la meme periode et jusqu'a 2850 ma des intrusions granitiques a tonalitiques se mettent en place. Elles provoquent dans l'encaissant, soit des recristallisations dans des conditions granulitiques, soit des retromorphoses. L'evolution archeenne s'acheve entre 2800 et 2500 ma, avec la mise en place des ultrabasiques de kinguele, des leucogranites, des pegmatites, des monzonites et des granites. Ces processus diapiriques fini-archeens de grande ampleur associes a une tectonique verticale vont favoriser l'apparition, a partir de 2500 ma, des premiers bassins sedimentaires tels que l'ogooue. Ce dernier sera ensuite engage dans un orogene paleoproterozoique qui s'accompagne d'une remobilisation de materiel archeen. Les trois phases tectono-metamorphiques d1, d2 et d3 responsables de sa structuration en domaine orogenique collisionnel sont respectivement posterieure a 2440 ma, syn-2120 ma et syn-a post 2040-2000 ma. Parallelement les metabasites de l'ogooue, reputees pre-orogeniques s'avereraient etre d'age archeen. Les contraintes ar-ar sur l'age des mineralisations d'eteke associees a l'evolution tectono-metamorphique du domaine de l'ogooue n'ont revele que des ages de refroidissement autour de 1850-1870 ma. Les sediments fluvio-deltaiques du francevillien moyen a superieur (2050-1780 ma) s'individualisent a la fin de cette evolution tectonique collisionnelle, en position d'avant-pays. Parallelement, les investigations rb-sr dans la faille syn-d3 de l'ikoye-ikobe ont revele un rejeu panafricain de celle-ci vers 530 ma. Enfin, la comparaison de l'histoire geologique de la partie occidentale du craton du congo avec le craton de sao francisco (bresil), montre qu'en ce qui concerne les blocs archeens, les plus vieux temoins de l'histoire archeenne precoce ne sont nettement reconnus qu'au bresil (3200-3400 ma), en revanche au paleoproterozoique, de part et d'autre de l'atlantique, les processus geodynamiques et orogeniques sont similaires
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Barbeau, David Longfellow Jr. « Application of Growth Strata and Detrital-Zircon Geochronology to Stratigraphic Architecture and Kinematic History ». Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/244092.

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Growth strata analysis and detrital-zircon geochronology are useful applications of stratigraphy to tectonic problems. Whereas both tools can contribute to kinematic analyses of supracrustal rock bodies, growth strata are also useful for analyzing the influence of tectonics on stratigraphic architecture. This study reports: 1) a conceptual model for growth strata development; 2) stratigraphic and kinematic analyses of growth strata architectures from growth structures in southeastern Utah, the Gulf of Mexico, and northeastern Spain; and 3) the detrital-zircon geochronology of the Salinian block of central coastal California. Kinematic sequence stratigraphy subdivides growth strata into kinematic sequences that are separated by kinematic sequence boundaries. Kinematic sequences can be further partitioned into kinematic domains based on the termination patterns of strata within a kinematic sequence. Salt- related fluvial growth strata from the Gulf of Mexico and southeastern Utah contain stratigraphic architectures that are unique to different kinematic domains. Offlap kinematic domains contain fluvial strata indicative of high slopes, low accommodation rates, and strong structural influence on paleocurrent direction. Onlap kinematic domains contain fluvial strata indicative of moderate slopes, high accommodation rates, and decreased structural influence on paleocurrent direction. The stratigraphic architecture of alluvial -fan thrust -belt growth strata in northeastern Spain does not display a marked correlation with kinematic domain, and is most easily interpreted using existing models for autocyclic alluvial -fan evolution. Detrital- zircon (U -Pb) geochronologic data from basement and cover rocks of Salinia suggest that Salinia originated along the southwestern margin of North America, likely in the vicinity of the Mojave Desert. The presence of Neoproterozoic and Late Archean detrital zircons in Salinian basement rocks also suggest that Salinian sediments were recycled from miogeoclinal sediments of the western margin of North America.
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Lincoln, Sara Ann Lincoln Ph D. Massachusetts Institute of Technology. « Molecular studies of the sources and significance of archaeal lipids in the oceans ». Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84916.

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Thesis (Ph. D. in Geochemistry)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013.
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Includes bibliographical references.
Marine archaea are ubiquitous and abundant in the modem oceans and have a geologic record extending >100 million years. However, factors influencing the populations of the major clades - chemolithoautotrophic Marine Group I Thaumarchaeota (MG-I) and heterotrophic Marine Group II Euryarchaeota (MG-II) - and their membrane lipid signatures are not well understood. Here, I paired techniques of organic geochemistry and molecular biology to explore the sources and significance of archaeal tetraether lipids in the marine water column. Using metagenomics, 16S rDNA pyrosequencing, QPCR and mass spectrometric analyses, I found that uncultivated MG-IL Euryarchaeota synthesize glycerol dialkyl glycerol tetraether (GDGT) lipids - including crenarchaeol, previously thought limited to autotrophic Thaumarchaeota. This finding has important implications for paleoenvironmental proxies reliant upon GDGTs. To investigate the effects of organic matter and bicarbonate + ammonia amendments on archaeal tetraether lipids and microbial community composition, I conducted large scale microcosm experiments. Experimental conditions did not promote the overall growth of archaea, but several changes in tetraether lipid abundance and relative ring distribution suggest that future incubation labeling studies using whole seawater may be valuable in probing the metabolism of individual archaeal clades in mixed populations. A rapid decrease in GDGT concentrations was observed within the first 44 h of the experiment, suggesting that the residence time of these compounds in the open ocean may be short. Changes in functional gene representation and microbial community composition over the course of the experiment provide potential insight into mechanisms of copiotrophy and the identity of bacteria that may degrade GDGTs. Finally, I present the results of a study of the sources and patterns of bacterial and archaeal GDGTs detected in the Lost City Hydrothermal Vent Field. Branched GDGTs, generally considered markers of terrestrial input to marine sediments, were detected in carbonate chimneys of this alkaline site near the mid-Atlantic Ridge. A relatively uncommon H-shaped GDGT was also present, and appears to be a marker of hydrothermal archaeal input rather than a mesophilic euryarchaeotal signal. Taken together, the work presented in this thesis emphasizes the necessity of understanding the biological underpinnings of archaeal lipids in the environment, increasingly used as biomarkers in microbial ecology and paleoenvironmental reconstruction.
by Sara Ann Lincoln.
Ph.D.in Geochemistry
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Halter, Ghislaine. « Zonalite des alterations dans l'environnement des gisements d'uranium associes a la discordance du proterozoique moyen (saskatchewan, canada) ». Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13078.

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Cette etude porte sur les conditions des gisements d'uranium du saskatchewan de la region de waterbury lake, qui sont associes a la discordance entre le socle archeen/aphebien et la couverture sedimentaire helikienne. Deux episodes tardi-hudsoniens gouvernent la remobilisation in situ de l'uranium: une retromorphose (facies schiste vert) et une alteration hydrothermale affectant les zones tectonisees du socle. Les donnees isotopiques des phyllites revelent que la diagenese des gres est realisee en presence d'une saumure qui est egalement a l'origine du fluide mineralisateur
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Cámara, Mor Patricia. « Radionuclides in the Arctic Ocean : tracing sea ice origin, drifting and interception of atmospheric fluxes ». Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/123297.

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El Océano Ártico está caracterizado por la presencia de una cobertura de hielo marino, cuya extensión varía entre verano e invierno. El hielo marino incorpora material particulado y especies químicas asociadas (nutrientes, metales, contaminantes, etc.) durante su formación en las plataformas continentales. A lo largo de su ciclo de vida, diversos procesos físicos, químicos y biológicos determinan la concentración tanto de sedimentos del hielo marino (SIS) como de las especies químicas atrapados a ellos. Durante su deriva desde la costa a la cuenca ártica, el hielo intercepta/acumula especies químicas procedentes de la atmosfera, aunque SIS también puede incorporar especies químicas disueltas del agua superficial. Finalmente, durante el deshielo las especies químicas y SIS transportados son liberados al agua. Así, el hielo marino se convierte en un importante agente de transporte y distribución. Sin embargo, se desconoce cual es la eficiencia de intercepción de flujos atmosféricos, el origen tanto de SIS como de los radionúclidos incorporados, el tiempo de transito del hielo en el Océano ártico, así como la importancia del transporte de especies químicas y SIS y su liberación en las zonas de ablación. Para responder a dichas preguntas, un grupo de radionúclidos naturales (7Be, 210Po-210Pb y 234Th) y artificiales (137Cs, 239,240Pu), caracterizados por tener sus fuentes bien definidas y diferente vidas medias, fueron analizados en muestras de precipitación, hielo marino, agua superficial y por debajo del hielo, SIS muestreadas durante ARK XXII/2 (2007) a lo largo de la Cuenca ártica central. La distribución de 7Be muestra un enriquecimiento en el hielo marino con respecto al agua superficial. Puesto que todo 7Be incorporado el hielo durante su formación se ha desintegrado durante su deriva, el flujo atmosférico aparece como la fuente más importante de 7Be en el hielo. Mediante un balance de masa se estimó que el hielo intercepta aproximadamente 30% del flujo atmosférico de 7Be. Esta estimación podría ser extrapolada para otras especies químicas atmosféricas, como nutrientes o contaminantes. Dado que el hielo intercepta/acumula 7Be y 210Pb durante su deriva, éstos también podrían ser arrastrados por SIS, y por tanto ser utilizados para estimar su tiempo de transito. La presencia de radionúclidos artificiales en SIS (240Pu/239Pu ratio atómica, en combinación con las actividades de 137Cs y 239,240Pu) permiten delimitar su origen geográfico. SIS procedentes del mar de Laptev y Kara tienen 240Pu/239Pu ratios atómicas inferiores al global fallout (0.18), mientras que SIS procedentes de las plataformas de Alaska presentan 240Pu/239Pu ratios atómicos superiores al global fallout. Los datos muestran que la mayoría de SIS en la Cuenca Euroasiática vienen de las plataformas siberianas, en concordancia con los análisis de retro-trayectorias y los principales patrones de deriva. El uso de radionúclidos en SIS como trazadores para estimar el tiempo de transito y el origen del hielo, juntamente con el hecho que SIS no contenga 234Thxs o que sólo una pequeña fracción del 7Be en SIS sea explicada por el arrastre del agua superficial si todo 210Pb en SIS viene de esta fuente, hace que la deposición atmosférica sea la principal fuente de radionúclidos en SIS. La relevancia del hielo como agente de transporte y fuente de radionúclidos en las áreas de deshielo, como el Estrecho de Fram, se demuestra en que los flujos anuales de 7Be disuelto en hielo (67±55Bq·m-2·y-1) son comparables a los input atmosféricos en esta región (113-131Bq·m-2·y-1). Además, el flujo anual de SIS en este área, calculado usando el balance de masa de 7Be y el flujo promedio anual de área de hielo a través éste, es de media 240(4.5-1700)·106 toneladas, comparable descargadas anualmente por los ríos árticos (115·106 toneladas).
The Arctic Ocean is characterized by being covered by sea ice with a large variability between summer and winter. Sea ice incorporates particles and associated chemical species (metals, nutrients, contaminants, etc.) during its formation mainly in the continental shelves, while dissolved solutes are excluded. Along the whole life cycle of sea ice, diverse physical, chemical and biological processes determine the concentration of the sea-ice sediments (SIS) and chemical species entrapped in it. During its drifts offshore to the central Arctic Basin, sea ice also intercepts/incorporates chemical species from the atmosphere although, SIS may also incorporate some chemical solute compounds from the surface waters. Eventually, transported chemical species and SIS, are released to the underlying water column during melting process. Thus, sea ice becomes an important transport and distribution agent. However, the interception efficiency of atmospheric fluxes by sea ice, the origin of the entrapped SIS and radionuclides, the transit times of sea ice in the Arctic Ocean, as well as the importance of the transport of chemical species and SIS and its release in the ablation area are all poorly understood. To address these questions, a suite of natural (7Be, 210Po-210Pb and 234Th) and artificial (137Cs, 239,240Pu) radionuclides, characterized to have well-known sources and different half-lives, were analysed in samples from precipitation, sea ice, surface water, water beneath ice and SIS collected during the ARK XXII/2 expedition in 2007 along the central Arctic. The distributions of 7Be showed enrichment in sea ice (129±90Bq·m-3) with respect to surface water (7.1±1.3Bq·m-3). Since any 7Be incorporated to sea ice during its formation has decayed during drift, the direct atmospheric flux appears as the most important source of 7Be in sea ice. A mass balance was used to calculate that sea ice intercepts about 30% of the 7Be atmospheric flux. This estimation may be extrapolated to other atmospheric chemical species, such as nutrients or contaminants. Given that 7Be and 210Pb are intercepted and accumulated during sea ice transit and may also scavenge by SIS, both radionuclides can be used to assess sea ice transit time. The presence of SIS indicates that ice floes are formed in continental shelves. The presence of artificial radionuclides in SIS (240Pu/239Pu atom ratio, in combination with 137Cs and 239,240Pu activity) allow constraining their geographical origin. SIS originating in the Laptev and Kara Seas has 240Pu/239Pu atom ratios lower than those imprinted by global fallout (0.18), while SIS originating from the Alaskan shelf present 240Pu/239Pu atom ratios greater than global fallout. Data showed that most of the SIS in the Eurasian Basin originated from the Siberian shelves, in agreement with back-trajectory analyses and main drift patterns. The evidence of using 7Be/210Pb ratio, 137Cs and 239,240Pu in SIS as tracers to estimate sea ice transit time and origin, and the fact that SIS did not contain 234Thxs or that a small fraction of 7Be activity in SIS is explained by scavenging of seawater if all 210Pb in SIS does, make the atmospheric deposition the main source of radionuclides in SIS. The relevance of sea ice as a significant transport and source of radionuclides in melting areas, such as the Fram Strait, is reflected in the annual fluxes of dissolved 7Be carried by sea ice (67±55Bq·m-2·y-1), which are comparable to atmospheric inputs in this region (113-131Bq·m-2·y-1). In addition, the annual mass flux of SIS at the Fram Strait, assessed using a 7Be mass balance and the mean annual ice area efflux through it, is on average 240 (4.5-1700)·106 tons, value comparable to 115·106 tons discharged annually by Arctic rivers.
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Yamaguchi, Kosei. « Geochemistry of Archean-Paleoproterozoic black shales the early evolution of the atmosphere, oceans, and biosphere / ». 2002. http://www.etda.libraries.psu.edu/theses/approved/PSUonlyIndex/ETD-128/index.html.

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Livres sur le sujet "Archean ocean"

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Enright, Joseph F. Shinano ! : The sinking of Japan's secret supership. London : Bodley Head, 1987.

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Enright, Joseph F. Shinano ! : The sinking of Japan's secret supership. Taiwan : Xing Guang, 1987.

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La Busqueda De Archelon/ the Search for Archelon. Alfaguara, 2006.

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Robinson, Carol. Phytoplankton Biogeochemical Cycles. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199233267.003.0005.

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This chapter describes how the activity of phytoplankton, bacteria, and Archaea drive the marine biogeochemical cycles of carbon, nitrogen, and phosphorus, and how climate driven changes in plankton abundance and community composition influence these biogeochemical cycles in the North Atlantic Ocean and adjacent seas. Carbon, nitrogen, and phosphorus are essential elements required for all life on Earth. In the marine environment, dissolved inorganic carbon, nitrogen, and phosphorus are utilized during phytoplankton growth to form organic material, which is respired and remineralized back to inorganic forms by the activity of bacteria, Archaea, and zooplankton. The net result of the photosynthesis, calcification, and respiration of marine plankton is the uptake of carbon dioxide from the atmosphere, its sequestration to the deep ocean as organic and inorganic carbon, and its availability to fuel all fish and shellfish production.
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Money, Nicholas P. 6. Microbial ecology and evolution. Oxford University Press, 2014. http://dx.doi.org/10.1093/actrade/9780199681686.003.0006.

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Many ecosystems are wholly microbial and the activities of microorganisms provide the biochemical foundation for plant and animal life. ‘Microbial ecology and evolution’ describes how plants depend upon the complex redox reactions of microbes that fertilize the soil by fixing nitrogen, converting nitrites to nitrates, enhancing the availability of phosphorus and trace elements, and recycling organic matter. Eukaryotic microorganisms are similarly plentiful and essential for the sustenance of plants and animals. Bacteria, archaea, and single-celled eukaryotes are the masters of the marine environment, harnessing the energy that supports complex ecological interactions between aquatic animals. Bacteria and archaea form 90% of the ocean biomass and surface waters are filled with eukaryotic algae.
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Kirchman, David L. Community structure of microbes in natural environments. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0004.

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Community structure refers to the taxonomic types of microbes and their relative abundance in an environment. This chapter focuses on bacteria with a few words about fungi; protists and viruses are discussed in Chapters 9 and 10. Traditional methods for identifying microbes rely on biochemical testing of phenotype observable in the laboratory. Even for cultivated microbes and larger organisms, the traditional, phenotype approach has been replaced by comparing sequences of specific genes, those for 16S rRNA (archaea and bacteria) or 18S rRNA (microbial eukaryotes). Cultivation-independent approaches based on 16S rRNA gene sequencing have revealed that natural microbial communities have a few abundant types and many rare ones. These organisms differ substantially from those that can be grown in the laboratory using cultivation-dependent approaches. The abundant types of microbes found in soils, freshwater lakes, and oceans all differ. Once thought to be confined to extreme habitats, Archaea are now known to occur everywhere, but are particularly abundant in the deep ocean, where they make up as much as 50% of the total microbial abundance. Dispersal of bacteria and other small microbes is thought to be easy, leading to the Bass Becking hypothesis that “everything is everywhere, but the environment selects.” Among several factors known to affect community structure, salinity and temperature are very important, as is pH especially in soils. In addition to bottom-up factors, both top-down factors, grazing and viral lysis, also shape community structure. According to the Kill the Winner hypothesis, viruses select for fast-growing types, allowing slower growing defensive specialists to survive. Cultivation-independent approaches indicate that fungi are more diverse than previously appreciated, but they are less diverse than bacteria, especially in aquatic habitats. The community structure of fungi is affected by many of the same factors shaping bacterial community structure, but the dispersal of fungi is more limited than that of bacteria. The chapter ends with a discussion about the relationship between community structure and biogeochemical processes. The value of community structure information varies with the process and the degree of metabolic redundancy among the community members for the process.
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Kirchman, David L. The nitrogen cycle. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0012.

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Nitrogen is required for the biosynthesis of many cellular components and can take on many oxidation states, ranging from −3 to +5. Consequently, nitrogen compounds can act as either electron donors (chemolithotrophy) or electron acceptors (anaerobic respiration). The nitrogen cycle starts with nitrogen fixation, the reduction of nitrogen gas to ammonium. Nitrogen fixation is carried out only by prokaryotes, mainly some cyanobacteria and heterotrophic bacteria. The ammonium resulting from nitrogen fixation is quickly used by many organisms for biosynthesis, being preferred over nitrate as a nitrogen source. It is also oxidized aerobically by chemolithoautotrophic bacteria and archaea during the first step of nitrification. The second step, nitrite oxidation, is carried out by other bacteria not involved in ammonia oxidation, resulting in the formation of nitrate. Some bacteria are capable of carrying out both steps (“comammox”). This nitrate can then be reduced to nitrogen gas or nitrous oxide during denitrification. It can be reduced to ammonium, a process called “dissimilatory nitrate reduction to ammonium.” Nitrogen gas is also released by anaerobic oxidation of ammonium (“anammox”) which is carried out by bacteria in the Planctomycetes phylum. The theoretical contribution of anammox to total nitrogen gas release is 29%, but the actual contribution varies greatly. Another gas in the nitrogen cycle, nitrous oxide, is a greenhouse gas produced by ammonia-oxidizing bacteria and archaea. The available data indicate that the global nitrogen cycle is in balance, with losses from nitrogen gas production equaling gains via nitrogen fixation. But excess nitrogen from fertilizers is contributing to local imbalances and several environmental problems in drinking waters, reservoirs, lakes, and coastal oceans.
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Chapitres de livres sur le sujet "Archean ocean"

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Shen, Yanan, Daniele L. Pinti et Ko Hashizume. « Biogeochemical cycles of sulfur and nitrogen in the Archean ocean and atmosphere ». Dans Archean Geodynamics and Environments, 305–20. Washington, D. C. : American Geophysical Union, 2006. http://dx.doi.org/10.1029/164gm19.

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Volk, Tyler, et Martin I. Hoffert. « Ocean Carbon Pumps : Analysis of Relative Strengths and Efficiencies in Ocean-Driven Atmospheric CO2 Changes ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 99–110. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0099.

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Hsü, Kenneth J., et Judith A. Mckenzie. « A “Strangelove” Ocean in the Earliest Tertiary ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 487–92. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0487.

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Wenk, T., et U. Siegenthaler. « The High-Latitude Ocean as a Control of Atmospheric CO2 ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 185–94. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0185.

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Mclean, Dewey M. « Mantle Degassing Induced Dead Ocean in the Cretaceous-Tertiary Transition ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 493–503. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0493.

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Herring, James R. « Charcoal Fluxes into Sediments of the North Pacific Ocean : The Cenozoic Record of Burning ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 419–42. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0419.

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Peterson, L. C., et W. L. Prell. « Carbonate Preservation and Rates of Climatic Change : An 800 KYR Record from the Indian Ocean ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 251–69. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0251.

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Toggweiler, J. R., et J. L. Sarmiento. « Glacial to Interglacial Changes in Atmospheric Carbon Dioxide : The Critical Role of Ocean Surface Water in High Latitudes ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 163–84. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0163.

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Curry, W. B., et G. P. Lohmann. « Carbon Deposition Rates and Deep Water Residence Time in the Equatorial Atlantic Ocean Throughout the Last 160,000 Years ». Dans The Carbon Cycle and Atmospheric CO2 : Natural Variations Archean to Present, 285–301. Washington, D. C. : American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm032p0285.

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Takai, Ken, Fumio Inagaki et Koki Horikoshi. « Distribution of unusual archaea in subsurface biosphere ». Dans The Subseafloor Biosphere at Mid-Ocean Ridges, 369–81. Washington, D. C. : American Geophysical Union, 2004. http://dx.doi.org/10.1029/144gm23.

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Actes de conférences sur le sujet "Archean ocean"

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Lambrecht, Nicholas, Elizabeth Swanner, Chad Wittkop, Cody Sheik et Sergei Katsev. « MICROBIAL COMMUNITIES OF TWO ARCHEAN OCEAN ANALOGS ». Dans 52nd Annual North-Central GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018nc-312978.

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Zheng, Xin-Yuan, Aaron M. Satkoski, Brian L. Beard, Thiruchelvi R. Reddy, Nicolas J. Beukes et Clark M. Johnson. « TRACING OF THE COUPLED SI AND FE CYCLE IN THE ARCHEAN OCEAN ». Dans GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-300243.

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Hinz, Isaac L., Christine Nims, Christine Nims, Samantha Theuer, Samantha Theuer, Alexis S. Templeton, Alexis S. Templeton, Jena E. Johnson et Jena E. Johnson. « FERRIC IRON CATALYZES THE FORMATION OF IRON-RICH SILICATES UNDER ARCHEAN OCEAN-LIKE CONDITIONS ». Dans 54th Annual GSA North-Central Section Meeting - 2020. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020nc-347861.

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Johnson, Aleisha C., Stephen J. Romaniello, Chadlin M. Ostrander, Christopher T. Reinhard, Timothy W. Lyons et Ariel D. Anbar. « ASSESSING THE BIOAVAILABILITY OF MO IN ARCHEAN OCEANS ». Dans GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-341070.

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Katsev, Sergei, Mojtaba Fakhraee, Emily Hyde, Madelyn Petersen, Cody Sheik et Kathryn Schreiner. « Sulfide, Sulfite, and Sulfate Production from Organic Sulfur in Archean Oceans and Modern Lakes ». Dans Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.1256.

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Osterhout, Jeffrey T., et Andrew D. Czaja. « STABLE ISOTOPE GEOCHEMISTRY OF A LATE ARCHEAN MICROBIAL ECOSYSTEM : DIVERSITY IN THE PRE-GOE OCEANS ». Dans GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-307829.

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Ribeiro, Elton J. B., Edson Luiz Labanca, Cesar Bartz et Andre Iwane. « Tubarão Martelo Field Development : Lazy S Riser Configuration Using Mid Water Arch (MWA) ». Dans ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41873.

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Mid-Water Arches (MWAs) have been used as alternative to distributed buoyancy systems in flexible riser designs worldwide. Those structures usually involve complex lifting requirements for installation, as the Buoyancy Tank Assemblies (BTAs) are lightweight compared to its volume and footprint area. Handling those odd-sized structures in the deck of a construction vessel and crossing the splash-zone are frequently challenging engineering tasks. This paper will present a case study of MWA installation performed by GE/WSC as part of the OGX Tubarão Martelo field development, offshore Brazil. The location is prone to swell from South Atlantic and hence a flat sea is a rare event, even when no local wind generated are present. This makes any delicate and weather sensitive operation a critical schedule issue. Still, 8 MWA were installed with minor Waiting on Weather thanks to an extensive analysis envelope and to an engineered installation method aiming to minimize the time the operation was limited by weather condition. Also, as the scope involved a large number of MWAs, a “mass production” method was developed for the operations, not only covering the offshore installation but also the mobilization and logistic aspects of handling large and heavy items ashore. To allow road transportation by trucks, the BTAs and Gravity Bases (GBs) were shipped to the mobilization port in sub-components for site integration.
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Murray, John J., Harish Mukundan, Apurva Gupta et Guibog Choi. « Dry Disconnectable Riser System for Low Keel Clearance Floaters ». Dans ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79734.

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Fixed structures operating in extreme offshore environments (eg: arctic) have to resist and survive the challenging conditions like large ice forces. On the other hand, the floating systems in such environments benefit from their ability to be evacuated and transported in the event of severe condition. However, such an ice-management scheme requires the moorings and risers to be disconnected in the severe conditions and reconnected during more clement conditions. Among the floater designs typically considered for extreme offshore applications is the Spar. The Spar offers low extreme motion responses than other shallower draft floaters and as a result, low fatigue damage on the risers. However, this design has versions with open centerwells that can contain leaked product and cause a potential hazardous condition. Furthermore, most designs that require the risers to be disconnected below the mean water line (wet-disconnection mechanism) not only carry the risk of leakage but have poor access for visual inspection. One solution is to use a continuous flexible riser without in-line connections or terminations in the flexible riser between the seafloor pipe line end manifolds (PLEM) and the production deck manifolds (dry-disconnection mechanism). The risers disconnect at an elevation above the water line and the termination point is lowered to a disconnect buoy supported at the keel. Subsequently the floater is moved away. The main difficulty is that the lowered flexible riser has to be suspended from the disconnect buoy and at the same time avoid contact with the seafloor. This paper describes and discusses a design of a dry-disconnectable flexible riser system comprised of a buoy supporting arches to control the bending in the risers during operation and disconnect. The system is particularly effective when the clearance between the keel and the seafloor is restricted. The rationale is based on strength, control of the minimum allowable bend radius and interference among the risers.
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Rapports d'organisations sur le sujet "Archean ocean"

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Mueller, C., S. J. Piercey, M. G. Babechuk et D. Copeland. Stratigraphy and lithogeochemistry of rocks from the Nugget Pond Deposit area, Baie Verte Peninsula, Newfoundland. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328989.

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Stratigraphic and lithogeochemical data were collected from selected drill core from the Nugget Pond gold deposit in the Betts Cove area, Newfoundland. The stratigraphy consists of a lower unit of basaltic rocks that are massive to pillowed (Mount Misery Formation). This is overlain by sedimentary rocks of the Scrape Point Formation that consist of lower unit of turbiditic siltstone and hematitic cherts/iron formations (the Nugget Pond member); the unit locally has a volcaniclastic rich-unit at its base and grades upwards into finer grained volcaniclastic/turbiditic rocks. This is capped by basaltic rocks of the Scrape Point Formation that contain pillowed and massive mafic flows that are distinctively plagioclase porphyritic to glomeroporphyritic. The mafic rocks of the Mount Misery Formation have island arc tholeiitic affinities, whereas Scrape Point Formation mafic rocks have normal mid-ocean ridge (N-MORB) to backarc basin basalt (BABB) affinities. One sample of the latter formation has a calc-alkalic affinity. All of these geochemical features are consistent with results and conclusions from previous workers in the area. Clastic sedimentary rocks and Fe-rich sedimentary rocks of the Scrape Point Formation have features consistent with derivation from local, juvenile sources (i.e., intra-basinal mafic rocks). The Scrape Point Formation sedimentary rocks with the highest Fe/Al ratios, inferred to have greatest amount of hydrothermally derived Fe, have positive Ce anomalies on Post-Archean Australian Shale (PAAS)-normalized trace element plots. These features are consistent with having formed via hydrothermal venting into an anoxic/ sub-oxic water column. Further work is needed to test whether these redox features are a localized feature (i.e., restricted basin) or a widespread feature of the late Cambrian-early Ordovician Iapetus Ocean, as well as to delineate the role that these Fe-rich sedimentary rocks have played in the localization of gold mineralization within the Nugget Pond deposit.
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Thomas, M. D. Magnetic and gravity characteristics of the Thelon and Taltson orogens, northern Canada : tectonic implications. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329250.

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Differences of opinion concerning the relationship between the Thelon tectonic zone and the Taltson magmatic zone, as to whether they are individual tectonic elements or two independent elements, have generated various plate tectonic models explaining their creation. Magnetic and gravity signatures indicate that they are separate entities and that the Thelon tectonic zone and the Great Slave Lake shear zone form a single element. Adopting the single-element concept and available age dates, a temporally evolving plate tectonic model of Slave-Rae interaction is presented. At 2350 Ma, an Archean supercontinent rifted along the eastern and southern margins of the Slave Craton. Subsequent ocean closure, apparently diachronous, began with subduction at 2070 Ma in the northern Thelon tectonic zone, followed by subduction under the Great Slave Lake shear zone at 2051 Ma. Subduction related to closure of an ocean between the Buffalo Head terrane and the Rae Craton initiated under the Taltson magmatic zone at 1986 Ma, at which time subduction continued along the Thelon tectonic zone. At 1970 Ma, collision in the northern Thelon tectonic zone is evidenced in the Kilohigok Basin. From 1957 to 1920 Ma, plutonism was active in the Taltson magmatic zone, Great Slave Lake shear zone, and southern Thelon tectonic zone. The plutonism terminated in the northern Thelon tectonic zone at 1950 Ma, but it resumed at 1910 Ma and continued until 1880 Ma. The East Arm Basin witnessed igneous activity as early as 2046 Ma, though this took place more continuously from 1928 to 1861 Ma; some igneous rocks bear subduction-related trace element signatures. These signatures, and the presence of northwest-verging nappes, may signify collision with the Great Slave Lake shear zone as a result of southeastward subduction, completing closure between the Slave and Rae cratons.
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Barbie, Alexander. ARCHES Digital Twin Framework. GEOMAR, décembre 2022. http://dx.doi.org/10.3289/sw_arches_core_1.0.0.

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In the Helmholtz Future Project ARCHES (Autonomous Robotic Networks to Help Modern Societies) with a consortium of partners from AWI (Alfred- Wegener-Institute Helmholtz Centre for Polar and Marine Research), DLR (German Aerospace Center), KIT (Karlsruhe Institute of Technology), and the GEOMAR (Helmholtz Centre for Ocean Research Kiel), several Digital Twins of ocean observation systems were developed by the GEOMAR and AWI. The ARCHES Digital Twin Framework is one of the results of this project. The software is based on the Robot Operating System (ROS) and is written in Python.
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Mueller, C., S. J. Piercey, M. G. Babechuk et 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.

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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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Sommer, Stefan, Sascha Flögel, Michael Walter et Frank Wenzhöfer. Autonomous Robotic Network to Resolve Coastal Oxygen Dynamics : Cruise No. AL547, 20.10. – 31.10.2020, Kiel – Kiel, ARCODYN. GEOMAR Helmholtz Centre for Ocean Research Kiel, 2022. http://dx.doi.org/10.3289/cr_al547.

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The ALKOR cruise AL547 represents a concluding milestone of the Helmholtz innovation project ARCHES (Autonomous Robotic Networks to Help Modern Societies). The aim was to implement a heterogeneous robotic sensing network to simultaneously monitor changes in the water column and at the seafloor. The network has been developed by a consortium of partners from AWI, DLR, GEOMAR and the University of Kiel. The participating sensing platforms allow for real-time data transfer and the entire network shall be able to autonomously respond to environmental changes in the ocean. The network comprised seven different mobile and stationary platforms. Tests were conducted at the Mittelgrund working area in the entrance of the Eckernförde Bay (western Baltic Sea). During 47 stations the various sensing platforms were deployed and recovered for maintenance. A total of 87853 messages were sent using hydro-acoustics, of which 71734 messages contained O 2 data, 15177 were status messages, 926 messages were commands to trigger a change of the measurement behavior of a platform and 16 messages represented broadcasts about the environmental status. We synoptically recorded short-term O 2 time series on the different platforms, which were placed along a depth gradient in the working area. As the Eckernförde Bay is known for sporadic fish kills by anoxia we hope to contribute to a better understanding of the O 2 dynamics in coastal areas. - (ALKOR-Berichte ; AL547)
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