Articles de revues : « Archean ocean »

1

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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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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Krissansen-Totton, Joshua, Giada N. Arney et David C. Catling. « Constraining the climate and ocean pH of the early Earth with a geological carbon cycle model ». Proceedings of the National Academy of Sciences 115, n^o 16 (2 avril 2018) : 4105–10. http://dx.doi.org/10.1073/pnas.1721296115.

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The early Earth’s environment is controversial. Climatic estimates range from hot to glacial, and inferred marine pH spans strongly alkaline to acidic. Better understanding of early climate and ocean chemistry would improve our knowledge of the origin of life and its coevolution with the environment. Here, we use a geological carbon cycle model with ocean chemistry to calculate self-consistent histories of climate and ocean pH. Our carbon cycle model includes an empirically justified temperature and pH dependence of seafloor weathering, allowing the relative importance of continental and seafloor weathering to be evaluated. We find that the Archean climate was likely temperate (0–50 °C) due to the combined negative feedbacks of continental and seafloor weathering. Ocean pH evolves monotonically from 6.6−0.4+0.6 (2σ) at 4.0 Ga to 7.0−0.5+0.7 (2σ) at the Archean–Proterozoic boundary, and to 7.9−0.2+0.1 (2σ) at the Proterozoic–Phanerozoic boundary. This evolution is driven by the secular decline of pCO2, which in turn is a consequence of increasing solar luminosity, but is moderated by carbonate alkalinity delivered from continental and seafloor weathering. Archean seafloor weathering may have been a comparable carbon sink to continental weathering, but is less dominant than previously assumed, and would not have induced global glaciation. We show how these conclusions are robust to a wide range of scenarios for continental growth, internal heat flow evolution and outgassing history, greenhouse gas abundances, and changes in the biotic enhancement of weathering.

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Dey, S., et J. F. Moyen. « About this title - Archean Granitoids of India : Windows into Early Earth Tectonics ». Geological Society, London, Special Publications 489, n^o 1 (2020) : NP. http://dx.doi.org/10.1144/sp489.

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Granitoids form the bulk of the Archean continental crust and preserve key information on early Earth evolution. India hosts five main Archean cratonic blocks (Aravalli, Bundelkhand, Singhbhum, Bastar and Dharwar). This book summarizes the available information on Archean granitoids of Indian cratons. The chapters cover a broad spectrum of themes related to granitoid typology, emplacement mechanism, petrogenesis, phase-equilibria modelling, temporal distribution, tectonic setting, and their roles in fluid evolution, metal delivery and mineralizations. The book presents a broader picture incorporating regional- to cratons-scale comparisons, implications for Archean geodynamic processes, and temporal changes thereof. This synthesis work, integrating modern concepts on granite petrology and crustal evolution, offers an irreplaceable body of reference information for any geologist interested in Archean Indian granitoids.

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Kienert, H., G. Feulner et V. Petoukhov. « Albedo and heat transport in 3-D model simulations of the early Archean climate ». Climate of the Past 9, n^o 4 (7 août 2013) : 1841–62. http://dx.doi.org/10.5194/cp-9-1841-2013.

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Abstract. At the beginning of the Archean eon (ca. 3.8 billion years ago), the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics) to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth"). We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.

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Gifford, Jennifer N., Shawn J. Malone et Paul A. Mueller. « The Medicine Hat Block and the Early Paleoproterozoic Assembly of Western Laurentia ». Geosciences 10, n^o 7 (15 juillet 2020) : 271. http://dx.doi.org/10.3390/geosciences10070271.

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The accretion of the Wyoming, Hearne, and Superior Provinces to form the Archean core of western Laurentia occurred rapidly in the Paleoproterozoic. Missing from Hoffman’s (1988) original rapid aggregation model was the Medicine Hat block (MHB). The MHB is a structurally distinct, complex block of Precambrian crystalline crust located between the Archean Wyoming Craton and the Archean Hearne Province and overlain by an extensive Phanerozoic cover. It is distinguished on the basis of geophysical evidence and limited geochemical data from crustal xenoliths and drill core. New U-Pb ages and Lu-Hf data from zircons reveal protolith crystallization ages from 2.50 to 3.28 Ga, magmatism/metamorphism at 1.76 to 1.81 Ga, and εHfT values from −23.3 to 8.5 in the Archean and Proterozoic rocks of the MHB. These data suggest that the MHB played a pivotal role in the complex assembly of western Laurentia in the Paleoproterozoic as a conjugate or extension to the Montana Metasedimentary Terrane (MMT) of the northwestern Wyoming Province. This MMT–MHB connection likely existed in the Mesoarchean, but it was broken sometime during the earliest Paleoproterozoic with the formation and closure of a small ocean basin. Closure of the ocean led to formation of the Little Belt arc along the southern margin of the MHB beginning at approximately 1.9 Ga. The MHB and MMT re-joined at this time as they amalgamated into the supercontinent Laurentia during the Great Falls orogeny (1.7–1.9 Ga), which formed the Great Falls tectonic zone (GFTZ). The GFTZ developed in the same timeframe as the better-known Trans-Hudson orogen to the east that marks the merger of the Wyoming, Hearne, and Superior Provinces, which along with the MHB, formed the Archean core of western Laurentia.

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Rüpke, Lars, et Fabrice Gaillard. « The Geological History of Water : From Earth’s Accretion to the Modern Deep Water Cycle ». Elements 20, n^o 4 (1 août 2024) : 253–58. http://dx.doi.org/10.2138/gselements.20.4.253.

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The abundance of water on Earth and its distribution between surficial and deep reservoirs are the outcome of 4.6 billion years of geological history involving various mechanisms of water in and outgassing. Here, we use the metaphor of a pipeline connecting Earth’s deep and surface water reservoirs. The net flux through this pipeline has changed over time due to contrasting Hadean, Archean, and modern geodynamic regimes. Most water was dissolved in the primordial magma ocean, entrapped in the solidifying mantle, and massively released by volcanism during the Hadean and Archaean. As Earth cooled, plate tectonics enabled water ingassing into the mantle, which appears to exceed outgassing under the modern tectonic regime, implying that Earth’s surface has been drying out and will continue to do so.

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Kienert, H., G. Feulner et V. Petoukhov. « Albedo and heat transport in 3-dimensional model simulations of the early Archean climate ». Climate of the Past Discussions 9, n^o 1 (24 janvier 2013) : 525–82. http://dx.doi.org/10.5194/cpd-9-525-2013.

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Abstract. At the beginning of the Archean eon (ca. 3.8 billion yr ago), the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun problem" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-dimensional model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth"). We find a reduction in meridional heat transport compared to today which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterisation of the ice-albedo feedback for 1-dimensional model simulations of the early Archean and thus the faint young Sun problem.

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Mukherjee, Indrani, et Ross R. Large. « Co-evolution of trace elements and life in Precambrian oceans : The pyrite edition ». Geology 48, n^o 10 (19 juin 2020) : 1018–22. http://dx.doi.org/10.1130/g47890.1.

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Abstract The significance of trace elements in initiating origins and driving evolution of life on Earth is indisputable. Trace element (TE) trends in the oceans through time broadly reflect their availability and allow speculation on all possible influences on early life. A comprehensive sedimentary pyrite–TE database, covering 3000 m.y. of the Precambrian, has improved our understanding of the sequence of bio-essential TE availability in the ocean. This study probed how changing availability (and scarcity) of critical TEs in the marine environment influenced early life. The pyrite-shale matrix TE sequence shows relatively elevated concentrations of Ni, Co, Cu, and Fe, Cr, respectively, in the Archean and Paleoproterozoic. Abundances of these elements in the Archean potentially facilitated their widespread utilization by prokaryotes. The Paleoproterozoic–Mesoproterozoic saw increases in Zn and Mo but a marked decline in Ni, Co, Cu, Se, and Fe. Our data suggest the evolution of the first complex cell in the Paleoproterozoic was probably triggered by this major change in TE composition of the oceans. A decline of elements prompted alternative utilization strategies by organisms as a response to TE deficits in the middle Proterozoic. An overall increase in a multitude of elements (Ni, Co, Cu, Cr, Se, V, Mo, and P) in the Neoproterozoic and Cambrian was highly advantageous to the various micro– and macro–life forms. Without questioning the importance of macronutrients and atmosphere-ocean redox state, multi-TE availability would have induced substantial heterogenous biological responses, owing to the effects of optimal, deficient, toxic, lethal, and survival levels of TEs on life.

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Vérard, Christian, et Ján Veizer. « On plate tectonics and ocean temperatures ». Geology 47, n^o 9 (2 août 2019) : 881–85. http://dx.doi.org/10.1130/g46376.1.

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Abstract Plate tectonics, the principal vehicle for dissipation of planetary energy, is believed to buffer the δ18O of seawater at its near-modern value of 0‰ SMOW (Standard Mean Ocean Water) because the hot and cold cells of hydrothermal circulation at oceanic ridges cancel each other. The persistence of plate tectonics over eons apparently favors attribution of the well-documented oxygen isotope secular trends for carbonates (cherts, phosphates) to progressively warmer oceans, from 40–70 °C in the early Paleozoic to 60–100 °C in the Archean. We argue that these oceanic hydrothermal systems are dominated by low-temperature (<350 °C) cells that deplete the percolating water in 18O. Seawater δ18O is therefore a proxy for, rather than being buffered by, the intensity of plate tectonics. Detrending the Phanerozoic carbonate δ18Oc secular trend for its “tectonic” component yields a stationary time series that, interpreted as a proxy for Phanerozoic climate, indicates low-latitude shallow ocean temperatures oscillating between 10 and 30 °C around a baseline of 17 °C, attributes comparable to modern temperature values.

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Rey, Patrice F., Nicolas Coltice et Nicolas Flament. « Archean Geodynamics Underneath Weak, Flat, and Flooded Continents ». Elements 20, n^o 3 (1 juin 2024) : 180–86. http://dx.doi.org/10.2138/gselements.20.3.180.

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Although a significant volume of crust was extracted from the mantle early in Earth’s history, the contribution of felsic rocks to the sedimentary record was minimal until ~3.0 Ga. On a hotter Earth, this conundrum dissipates if we consider that the felsic crust was buried under thick basaltic covers, continents were flooded by a near-global ocean, and the crust was too weak to sustain high mountains, making it largely unavailable to erosion. Gravitational forces destabilized basaltic covers within these weak, flat, and flooded continents, driving intra-crustal tectonics and forcing episodic subduction at the edges of continents. Through secular cooling, this dual-mode geodynamics progressively transitioned to plate tectonics.

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Heard, Andy W., Nicolas Dauphas, Romain Guilbaud, Olivier J. Rouxel, Ian B. Butler, Nicole X. Nie et Andrey Bekker. « Triple iron isotope constraints on the role of ocean iron sinks in early atmospheric oxygenation ». Science 370, n^o 6515 (22 octobre 2020) : 446–49. http://dx.doi.org/10.1126/science.aaz8821.

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The role that iron played in the oxygenation of Earth’s surface is equivocal. Iron could have consumed molecular oxygen when Fe3+-oxyhydroxides formed in the oceans, or it could have promoted atmospheric oxidation by means of pyrite burial. Through high-precision iron isotopic measurements of Archean-Paleoproterozoic sediments and laboratory grown pyrites, we show that the triple iron isotopic composition of Neoarchean-Paleoproterozoic pyrites requires both extensive marine iron oxidation and sulfide-limited pyritization. Using an isotopic fractionation model informed by these data, we constrain the relative sizes of sedimentary Fe3+-oxyhydroxide and pyrite sinks for Neoarchean marine iron. We show that pyrite burial could have resulted in molecular oxygen export exceeding local Fe2+ oxidation sinks, thereby contributing to early episodes of transient oxygenation of Archean surface environments.

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Pasek, M. A., J. P. Harnmeijer, R. Buick, M. Gull et Z. Atlas. « Evidence for reactive reduced phosphorus species in the early Archean ocean ». Proceedings of the National Academy of Sciences 110, n^o 25 (3 juin 2013) : 10089–94. http://dx.doi.org/10.1073/pnas.1303904110.

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Shibuya, Takazo, Tsuyoshi Komiya, Kentaro Nakamura, Ken Takai et Shigenori Maruyama. « Highly alkaline, high-temperature hydrothermal fluids in the early Archean ocean ». Precambrian Research 182, n^o 3 (1 octobre 2010) : 230–38. http://dx.doi.org/10.1016/j.precamres.2010.08.011.

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Rouxel, O. J. « Iron Isotope Constraints on the Archean and Paleoproterozoic Ocean Redox State ». Science 307, n^o 5712 (18 février 2005) : 1088–91. http://dx.doi.org/10.1126/science.1105692.

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Moyen, Jean-François. « Archean granitoids : classification, petrology, geochemistry and origin ». Geological Society, London, Special Publications 489, n^o 1 (1 avril 2019) : 15–49. http://dx.doi.org/10.1144/sp489-2018-34.

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AbstractThis paper describes the petrology, geochemistry and petrogenesis of Archean granitoids. Archean granites define a continuum of compositions between several end members: (i) magmas that originated by partial melting of a range of crustal sources, from amphibolites to metasediments (‘C-type’ granitoids); and (ii) magmas that formed by partial melting of an enriched mantle source, the most common agent of enrichment being felsic (TTG) melts. Differences in the degree of metasomatism results in different primitive liquids for these ‘M-type’ granitoids.Mixed sources, differentiation and interactions between different melts resulted in a continuous range of compositions, defined by variable proportions of each end member.During the Archean, evolved crustal sources (sediments or felsic crust) and metasomatized mantle sources become increasingly more important, mirroring the progressive maturation of crustal segments and the stabilization of the global tectonic system.

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Kusky, Timothy M. « Evidence for Archean ocean opening and closing in the Southern Slave Province ». Tectonics 9, n^o 6 (décembre 1990) : 1533–63. http://dx.doi.org/10.1029/tc009i006p01533.

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Kamber, Balz S. « Archean mafic–ultramafic volcanic landmasses and their effect on ocean–atmosphere chemistry ». Chemical Geology 274, n^o 1-2 (juin 2010) : 19–28. http://dx.doi.org/10.1016/j.chemgeo.2010.03.009.

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Knoll, Andrew H., Kristin D. Bergmann et Justin V. Strauss. « Life : the first two billion years ». Philosophical Transactions of the Royal Society B : Biological Sciences 371, n^o 1707 (5 novembre 2016) : 20150493. http://dx.doi.org/10.1098/rstb.2015.0493.

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Microfossils, stromatolites, preserved lipids and biologically informative isotopic ratios provide a substantial record of bacterial diversity and biogeochemical cycles in Proterozoic (2500–541 Ma) oceans that can be interpreted, at least broadly, in terms of present-day organisms and metabolic processes. Archean (more than 2500 Ma) sedimentary rocks add at least a billion years to the recorded history of life, with sedimentological and biogeochemical evidence for life at 3500 Ma, and possibly earlier; phylogenetic and functional details, however, are limited. Geochemistry provides a major constraint on early evolution, indicating that the first bacteria were shaped by anoxic environments, with distinct patterns of major and micronutrient availability. Archean rocks appear to record the Earth's first iron age, with reduced Fe as the principal electron donor for photosynthesis, oxidized Fe the most abundant terminal electron acceptor for respiration, and Fe a key cofactor in proteins. With the permanent oxygenation of the atmosphere and surface ocean ca 2400 Ma, photic zone O 2 limited the access of photosynthetic bacteria to electron donors other than water, while expanding the inventory of oxidants available for respiration and chemoautotrophy. Thus, halfway through Earth history, the microbial underpinnings of modern marine ecosystems began to take shape. This article is part of the themed issue ‘The new bacteriology’.

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Machado, N., H. Zwanzig et M. Parent. « U-Pb ages of plutonism, sedimentation, and metamorphism of the Paleoproterozoic Kisseynew metasedimentary belt, Trans-Hudson Orogen (Manitoba, Canada) ». Canadian Journal of Earth Sciences 36, n^o 11 (10 novembre 1999) : 1829–42. http://dx.doi.org/10.1139/e99-012.

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The Kisseynew Domain is a metasedimentary belt in the central Reindeer Zone of the Trans-Hudson Orogen. It is bounded by 1.92-1.86 Ga volcanic-plutonic belts to the north and south, by an Archean terrane to the east (Superior Province), and by a volcanic-plutonic terrane underlain by an Archean terrane to the southwest (Glennie Domain). The Kisseynew Domain developed in an arc-related setting in the final stages of plate convergence involving the northward migration of arc-ocean floor complexes toward the Archean Hearne Craton. Terminal collision, involving also the Superior Craton, originated multiple fold-thrust systems and high-grade metamorphism. U-Pb ages of 1874-1860 Ma for pretectonic plutonic units in southern Kisseynew Domain are identical to ages of plutonism intruding the arc-ocean floor accretionary complex in the Flin Flon domain (Amisk collage) and indicate its northern extension. Deposition of the Burntwood Group turbidites started at ca. 1860 Ma, indicating uplift and erosion of the volcanic complexes and was coeval with arc magmatism that succeeded the Amisk collage. From 1848 Ma, Burntwood sedimentation was coeval with deposition of Missi Group continental sediments, with continental arc magmatism and early deformation. New and published ages for detrital zircon indicate that sediments were derived both from local 1.89-1.84 Ga units and also from 2.55-2.36 Ga sources. The latter suggest that a Neoarchean-Paleoproterozoic cratonic block was undergoing erosion, remnants of which occur in the Flin Flon Belt. Basin closure started after 1823 Ma and is marked by regional high-grade metamorphism lasting for ca. 30 million years from 1818 Ma to 1785 Ma; late- to posttectonic metamorphic activity lasted until ca. 1775 Ma.

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Hernández, Claudeth, et Karo Michaelian. « Dissipative Photochemical Abiogenesis of the Purines ». Entropy 24, n^o 8 (26 juillet 2022) : 1027. http://dx.doi.org/10.3390/e24081027.

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We have proposed that the abiogenesis of life around the beginning of the Archean may have been an example of “spontaneous” microscopic dissipative structuring of UV-C pigments under the prevailing surface ultraviolet solar spectrum. The thermodynamic function of these Archean pigments (the “fundamental molecules of life”), as for the visible pigments of today, was to dissipate the incident solar light into heat. We have previously described the non-equilibrium thermodynamics and the photochemical mechanisms which may have been involved in the dissipative structuring of the purines adenine and hypoxanthine from the common precursor molecules of hydrogen cyanide and water under this UV light. In this article, we extend our analysis to include the production of the other two important purines, guanine and xanthine. The photochemical reactions are presumed to occur within a fatty acid vesicle floating on a hot (∼80 ∘C) neutral pH ocean surface exposed to the prevailing UV-C light. Reaction–diffusion equations are resolved under different environmental conditions. Significant amounts of adenine (∼10−5 M) and guanine (∼10−6 M) are obtained within 60 Archean days, starting from realistic concentrations of the precursors hydrogen cyanide and cyanogen (∼10−5 M).

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Muller, Élodie, Pascal Philippot, Claire Rollion-Bard et Pierre Cartigny. « Multiple sulfur-isotope signatures in Archean sulfates and their implications for the chemistry and dynamics of the early atmosphere ». Proceedings of the National Academy of Sciences 113, n^o 27 (21 juin 2016) : 7432–37. http://dx.doi.org/10.1073/pnas.1520522113.

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Sulfur isotopic anomalies (∆33S and ∆36S) have been used to trace the redox evolution of the Precambrian atmosphere and to document the photochemistry and transport properties of the modern atmosphere. Recently, it was shown that modern sulfate aerosols formed in an oxidizing atmosphere can display important isotopic anomalies, thus questioning the significance of Archean sulfate deposits. Here, we performed in situ 4S-isotope measurements of 3.2- and 3.5-billion-year (Ga)-old sulfates. This in situ approach allows us to investigate the diversity of Archean sulfate texture and mineralogy with unprecedented resolution and from then on to deconvolute the ocean and atmosphere Archean sulfur cycle. A striking feature of our data is a bimodal distribution of δ34S values at ∼+5‰ and +9‰, which is matched by modern sulfate aerosols. The peak at +5‰ represents barite of different ages and host-rock lithology showing a wide range of ∆33S between −1.77‰ and +0.24‰. These barites are interpreted as primary volcanic emissions formed by SO2 photochemical processes with variable contribution of carbonyl sulfide (OCS) shielding in an evolving volcanic plume. The δ34S peak at +9‰ is associated with non–33S-anomalous barites displaying negative ∆36S values, which are best interpreted as volcanic sulfate aerosols formed from OCS photolysis. Our findings confirm the occurrence of a volcanic photochemical pathway specific to the early reduced atmosphere but identify variability within the Archean sulfate isotope record that suggests persistence throughout Earth history of photochemical reactions characteristic of the present-day stratosphere.

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Ciscato, Emily R., Tomaso R. R. Bontognali, Simon W. Poulton et Derek Vance. « Copper and its Isotopes in Organic-Rich Sediments : From the Modern Peru Margin to Archean Shales ». Geosciences 9, n^o 8 (25 juillet 2019) : 325. http://dx.doi.org/10.3390/geosciences9080325.

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The cycling of copper (Cu) and its isotopes in the modern ocean is controlled by the interplay of biology, redox settings, and organic complexation. To help build a robust understanding of Cu cycling in the modern ocean and investigate the potential processes controlling its behavior in the geological past, this study presents Cu abundance and isotope data from modern Peru Margin sediments as well as from a suite of ancient, mostly organic-rich, shales. Analyses of an organic-pyrite fraction extracted from bulk modern sediments suggest that sulphidation is the main control on authigenic Cu enrichments in this setting. This organic-pyrite fraction contains, in most cases, >50% of the bulk Cu reservoir. This is in contrast to ancient samples, for which a hydrogen fluoride (HF)-dissolvable fraction dominates the total Cu reservoir. With <20% of Cu found in the organic-pyrite fraction of most ancient sediments, interpretation of the associated Cu isotope composition is challenging, as primary signatures may be masked by secondary processes. But the Cu isotope composition of the organic-pyrite fraction in ancient sediments hints at the potential importance of a significant Cu(I) reservoir in ancient seawater, perhaps suggesting that the ancient ocean was characterized by different redox conditions and a different Cu isotope composition to that of the modern ocean.

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Ahmad, Iftikhar, M. E. A. Mondal, Md Sayad Rahaman, Rajneesh Bhutani et M. Satyanarayanan. « Archean granitoids of the Aravalli Craton, northwest India ». Geological Society, London, Special Publications 489, n^o 1 (2020) : 215–34. http://dx.doi.org/10.1144/sp489-2018-195.

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AbstractThe Archean granitoids of the Aravalli Craton (NW India) are represented by orthogneisses (3.3–2.6 Ga) and undeformed granitoids (c. 2.5 Ga). Here we present whole-rock geochemical (elemental and Nd-isotope) data of the granitoids from the Aravalli Craton with an aim of understanding the evolution of the continental crust during the Archean. These Archean granitoids have been classified into three compositional groups: (1) TTG – tonalite–trondhjemite–granodiorite; (2) t-TTG – transitional TTG; and (3) sanukitoids. Based on the geochemical characteristics, it is proposed that the TTGs have formed from the partial melting of subducting oceanic plateau. The t-TTG formed owing to reworking of an older continental crust (approximately heterogeneous) in response to tectonothermal events in the craton. For the formation of the sanukitoids, a two-stage petrogenetic model is invoked which involves metasomatization of the mantle wedge, followed by slab breakoff and asthenospheric upwelling, which leads to the melting of asthenosphere and the metasomatized mantle wedge. It is also proposed that subducted sediments contributed to the genesis of sanukitoid magma.

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Yang, Xi, Qingjun Guo, Valeria Boyko, Khoren Avetisyan, Alyssa J. Findlay, Fang Huang, Zhongliang Wang et Zhenwu Chen. « Isotopic reconstruction of iron oxidation-reduction process based on an Archean Ocean analogue ». Science of The Total Environment 817 (avril 2022) : 152609. http://dx.doi.org/10.1016/j.scitotenv.2021.152609.

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Yamaguchi, K. E. « Comment on "Iron Isotope Constraints on the Archean and Paleoproterozoic Ocean Redox State" ». Science 311, n^o 5758 (13 janvier 2006) : 177a. http://dx.doi.org/10.1126/science.1118221.

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Terabayashi, Masaru, Yuki Masada et Hiroaki Ozawa. « Archean ocean-floor metamorphism in the North Pole area, Pilbara Craton, Western Australia ». Precambrian Research 127, n^o 1-3 (novembre 2003) : 167–80. http://dx.doi.org/10.1016/s0301-9268(03)00186-4.

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BARBOSA, JOHILDO S. F., et PIERRE SABATÉ. « Geological features and the Paleoproterozoic collision of four Archean crustal segments of the São Francisco Craton, Bahia, Brazil : a synthesis ». Anais da Academia Brasileira de Ciências 74, n^o 2 (juin 2002) : 343–59. http://dx.doi.org/10.1590/s0001-37652002000200009.

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Recent geological, geochronological and isotopic research has identified four important Archean crustal segments in the basement of the São Francisco Craton in the State of Bahia. The oldest Gavião Block occurs in the WSW part, composed essentially of granitic, granodioritic and migmatitic rocks. It includes remnants of TTG suites, considered to represent the oldest rocks in the South American continent (~ 3,4Ga) and associated Archean greenstone belt sequences. The youngest segment, termed the Itabuna-Salvador-Curaçá Belt is exposed along the Atlantic Coast, from the SE part of Bahia up to Salvador and then along a NE trend. It is mainly composed of tonalite/trondhjemites, but also includes stripes of intercalated metasediments and ocean-floor/back-arc gabbros and basalts. The Jequié Block, the third segment, is exposed in the SE-SSW area, being characterized by Archean granulitic migmatites with supracrustal inclusions and several charnockitic intrusions. The Serrinha Block (fourth segment) occurs to the NE, composed of orthogneisses and migmatites, which represent the basement of Paleoproterozoic greenstone belts sequences. During the Paleoproterozoic Transamazonian Orogeny, these four crustal segments collided, resulting in the formation of an important mountain belt. Geochronological constrains indicate that the regional metamorphism resulting from crustal thickening associated with the collision process took place around 2.0 Ga.

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Mondal, M. E. A., M. Faruque Hussain et Talat Ahmad. « Archean granitoids of the Bastar Craton, Central India ». Geological Society, London, Special Publications 489, n^o 1 (8 janvier 2019) : 135–55. http://dx.doi.org/10.1144/sp489-2019-311.

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AbstractArchean granitoids of the Bastar Craton mainly occur as gneisses (3.56, 3.50 Ga) and undeformed granitoids (c. 2.5–2.48 Ga). Based on detailed geochemical characteristics two compositional types of gneisses: tonalite–trondhjemite–granodiorite (TTG) and transitional TTG (t-TTG) have been identified. The TTG rocks are further classified into low-HREE (heavy rare earth element) type and high-HREE type. It is proposed that melting of a thick enriched oceanic plateau basalt at deeper level may have generated the low-HREE TTG, whereas melting at shallower depth of the thick plateau can explain the geochemical signatures of the high-HREE TTG. The t-TTG was formed as a result of reworking of the older TTG crust. These two gneisses were probably formed at different time at 3.56 and 3.50 Ga as manifested from the age of the gneisses. The granitoids were formed at a later stage (c. 2.5–2.48 Ga) by reworking of the pre-existing gneissic crust consisting of TTG and t-TTG. Presence of a small 3.58 Ga undeformed K-rich granitoid from the northern part of the craton might indicate yet another earlier crustal reworking event.

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Chian, Deping, et Keith Louden. « The structure of Archean–Ketilidian crust along the continental shelf of southwestern Greenland from a seismic refraction profile ». Canadian Journal of Earth Sciences 29, n^o 2 (1 février 1992) : 301–13. http://dx.doi.org/10.1139/e92-027.

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The velocity structure of the continental crust on the outer shelf of southwestern Greenland is determined from dense wide-angle reflection–refraction data obtained with large air-gun sources and ocean bottom seismometers along a 230 km seismic line. This line crosses the geological boundary between the Archean block and the Ketilidian mobile belt. Although the data have high noise levels, P- and S-wave arrivals from within the upper, intermediate, and lower crust, and at the Moho boundary, can be consistently identified and correlated with one-dimensional WKBJ synthetic seismograms. In the Archean, P- and S-wave velocities in the upper crust are 6.0 and 3.4 km/s, while in the intermediate crust they are 6.4 and 3.6 km/s. These velocities match for the upper crust a quartz–feldspar gneiss composition and for the intermediate crust an amphibolitized pyroxene granulite. In the Ketilidian mobile belt, P- and S-wave velocities are 5.6 and 3.3 km/s for the upper crust and 6.3 and 3.6 km/s for the intermediate crust. These velocities may represent quartz granite in the upper crust and granite and granitic gneiss in the intermediate crust. The upper crust is ~5 km thick in the Archean block and the Ketilidian mobile belt, and thickens to ~9 km in the southern part of the Archean. This velocity structure supports a Precambrian collisional mechanism between the Archean block and Ketilidian mobile belt. The lower crust has a small vertical velocity gradient from 6.6 km/s at 15 km depth to 6.9 km/s at 30 km depth (Moho) along the refraction line, with a nearly constant S-wave velocity around 3.8 km/s. These velocities likely represent a gabbroic and hornblende granulite composition for the lower crust. This typical (but somewhat thin) Precambrian crustal velocity structure in southwestern Greenland shows no evidence for a high-velocity, lower crustal, underplated layer caused by the Mesozoic opening of the Labrador Sea.

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Burgess, Ray, Sarah L. Goldsmith, Hirochika Sumino, Jamie D. Gilmour, Bernard Marty, Magali Pujol et Kurt O. Konhauser. « Archean to Paleoproterozoic seawater halogen ratios recorded by fluid inclusions in chert and hydrothermal quartz ». American Mineralogist 105, n^o 9 (1 septembre 2020) : 1317–25. http://dx.doi.org/10.2138/am-2020-7238.

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Abstract Past changes in the halogen composition of seawater are anticipated based on the differing behavior of chlorine and bromine that are strongly partitioned into seawater, relative to iodine, which is extremely depleted in modern seawater and enriched in marine sediments due to biological uptake. Here we assess the use of chert, a chemical sediment that precipitated throughout the Precambrian, as a proxy for halide ratios in ancient seawater. We determine a set of criteria that can be used to assess the primary nature of halogens and show that ancient seawater Br/Cl and I/Cl ratios can be resolved in chert samples from the 2.5 Ga Dales Gorge Member of the Brockman Banded Iron Formation, Hamersley Group, Western Australia. The values determined of Br/Cl ~2 × 10-3 M and I/Cl ~30 × 10-6 M are comparable to fluid inclusions in hydrothermal quartz from the 3.5 Ga North Pole area, Pilbara Craton, Western Australia, that were the subject of previous reconstructions of ancient ocean salinity and atmospheric isotopic composition. While the similar Br/Cl and I/Cl values indicate no substantial change in the ocean halide system over the interval 2.5–3.5Ga, compared to modern seawater, the ancient ocean was enriched in Br and I relative to Cl. The I/Cl value is intermediate between bulk Earth (assumed chondritic) and the modern seawater ratio, which can be explained by a smaller organic reservoir because this is the major control on marine iodine at the present day. Br/Cl ratios are about 30% higher than both modern seawater and contemporary seafloor hydrothermal systems, perhaps indicating a stronger mantle buffering of seawater halogens during the Archean.

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Singh, M. M., et Vinod K. Singh. « Geochemistry and tectonic setting of the supracrustal rocks from the central part of the Bundelkhand craton, India ». Journal of Geoscience, Engineering, Environment, and Technology 4, n^o 2-2 (25 juillet 2019) : 3. http://dx.doi.org/10.25299/jgeet.2019.4.2-2.2175.

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Supracrustal rocks (mafics and ultramafics) occurs along with banded iron formation, and felsic volcanics around Babina, Dhaura, and Mauranipur linear east-west trends in central part of the Bundelkhand craton represent Archean crust. The mafic and ultramafic rocks geochemically classified into Komatiite and Basaltic Komatiite and have high-Fe Tholeiitic in composition which may relate with the primitive mantle. The major and trace element geochemistry of mafic and ultramafic rocks correspond to hydrated mantle with wedge tectonic sources and ocean ridge geological characteristics.

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Peck, William H., et John W. Valley. « The Fiskenaesset Anorthosite Complex : Stable isotope evidence for shallow emplacement into Archean ocean crust ». Geology 24, n^o 6 (1996) : 523. http://dx.doi.org/10.1130/0091-7613(1996)024<0523:tfacsi>2.3.co;2.

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Carbonne, Johanna Marin. « Fe isotope composition of Archean sulfides do not record progressive oxygenation of the ocean ». Geology 48, n^o 4 (1 avril 2020) : 415–16. http://dx.doi.org/10.1130/focus042020.1.

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François, Louis M., et Jean-Claude Gérard. « Reducing power of ferrous iron in the Archean Ocean, 1. Contribution of photosynthetic oxygen ». Paleoceanography 1, n^o 4 (décembre 1986) : 355–68. http://dx.doi.org/10.1029/pa001i004p00355.

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François, L. M. « Reducing power of ferrous iron in the Archean Ocean, 2. Role of FEOH+photooxidation ». Paleoceanography 2, n^o 4 (août 1987) : 395–408. http://dx.doi.org/10.1029/pa002i004p00395.

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Thurston, P. C., B. S. Kamber et M. Whitehouse. « Archean cherts in banded iron formation : Insight into Neoarchean ocean chemistry and depositional processes ». Precambrian Research 214-215 (septembre 2012) : 227–57. http://dx.doi.org/10.1016/j.precamres.2012.04.004.

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de Wit, Maarten J., et Harald Furnes. « 3.5-Ga hydrothermal fields and diamictites in the Barberton Greenstone Belt—Paleoarchean crust in cold environments ». Science Advances 2, n^o 2 (février 2016) : e1500368. http://dx.doi.org/10.1126/sciadv.1500368.

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Estimates of ocean temperatures on Earth 3.5 billion years ago (Ga) range between 26° and 85°C. We present new data from 3.47- to 3.43-Ga volcanic rocks and cherts in South Africa suggesting that these temperatures reflect mixing of hot hydrothermal fluids with cold marine and terrestrial waters. We describe fossil hydrothermal pipes that formed at ~200°C on the sea floor >2 km below sea level. This ocean floor was uplifted tectonically to sea level where a subaerial hydrothermal system was active at 30° to 270°C. We also describe shallow-water glacial diamictites and diagenetic sulfate mineral growth in abyssal muds. These new observations reveal that both hydrothermal systems operated in relatively cold environments and that Earth’s surface temperatures in the early Archean were similar to those in more recent times.

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Ossa Ossa, Frantz, Axel Hofmann, Jorge E. Spangenberg, Simon W. Poulton, Eva E. Stüeken, Ronny Schoenberg, Benjamin Eickmann, Martin Wille, Mike Butler et Andrey Bekker. « Limited oxygen production in the Mesoarchean ocean ». Proceedings of the National Academy of Sciences 116, n^o 14 (20 mars 2019) : 6647–52. http://dx.doi.org/10.1073/pnas.1818762116.

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The Archean Eon was a time of predominantly anoxic Earth surface conditions, where anaerobic processes controlled bioessential element cycles. In contrast to “oxygen oases” well documented for the Neoarchean [2.8 to 2.5 billion years ago (Ga)], the magnitude, spatial extent, and underlying causes of possible Mesoarchean (3.2 to 2.8 Ga) surface-ocean oxygenation remain controversial. Here, we report δ15N and δ13C values coupled with local seawater redox data for Mesoarchean shales of the Mozaan Group (Pongola Supergroup, South Africa) that were deposited during an episode of enhanced Mn (oxyhydr)oxide precipitation between ∼2.95 and 2.85 Ga. Iron and Mn redox systematics are consistent with an oxygen oasis in the Mesoarchean anoxic ocean, but δ15N data indicate a Mo-based diazotrophic biosphere with no compelling evidence for a significant aerobic nitrogen cycle. We propose that in contrast to the Neoarchean, dissolved O2levels were either too low or too limited in extent to develop a large and stable nitrate reservoir in the Mesoarchean ocean. Since biological N2fixation was evidently active in this environment, the growth and proliferation of O2-producing organisms were likely suppressed by nutrients other than nitrogen (e.g., phosphorus), which would have limited the expansion of oxygenated conditions during the Mesoarchean.

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Rouxel, O. J. « Response to Comment on "Iron Isotope Constraints on the Archean and Paleoproterozoic Ocean Redox State" ». Science 311, n^o 5758 (13 janvier 2006) : 177b. http://dx.doi.org/10.1126/science.1118420.

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Reid, Ian. « Crustal structure across the Nain – Makkovik boundary on the continental shelf off Labrador from seismic refraction data ». Canadian Journal of Earth Sciences 33, n^o 3 (1 mars 1996) : 460–71. http://dx.doi.org/10.1139/e96-036.

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A detailed seismic refraction profile was shot along the continental shelf off Labrador, across the boundary between the Archean Nain Province to the north and the Proterozoic Makkovik orogenic zone to the south. A large air-gun source was used, with five ocean-bottom seismometers as receivers. The data were analysed by forward modelling of traveltimes and amplitudes and provided a well-determined seismic velocity structure of the crust along the profile. Within the Nain province, thin postrift sediments are underlain by crust with a P-wave velocity of 6.1 km/s, which increases with depth and reaches 6.6 km/s at about 8 km. Moho is at around 28 km, and there is no evidence for a high-velocity (>7 km/s) lower crust. The P- and S-wave velocity structure is consistent with a gneissic composition for the Archean upper crust, and with granulites becoming gradually more mafic with depth for the intermediate and lower crust. In the Makkovik zone, the sediments are thicker, and a basement layer of P-wave velocity 5.5–5.7 km/s is present, probably due to reworking of the crust and the presence of Early Proterozoic volcanics and metasediments. Upper crustal velocities are lower than in the Nain Province. The crustal thickness, at 23 km, is less, possibly due in part to greater crustal stretching during the Mesozoic rifting of the Labrador Sea. The crustal structure across the Nain–Makkovik boundary is similar to that across the corresponding Archean–Ketilidian boundary off southwest Greenland.

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Janoušek, Vojtěch, Bernard Bonin, William J. Collins, Federico Farina et Peter Bowden. « Post-Archean granitic rocks : contrasting petrogenetic processes and tectonic environments ». Geological Society, London, Special Publications 491, n^o 1 (6 décembre 2019) : 1–8. http://dx.doi.org/10.1144/sp491-2019-197.

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AbstractGranitic rocks represent a ubiquitous component of upper continental crust but their origin remains highly controversial. This controversy stems from the fact that the granites may result from fractionation of mantle-derived basaltic magmas or partial melting of different crustal protoliths at contrasting pressure–temperature conditions, either water-fluxed or fluid-absent. Consequently, many different mechanisms have been proposed to explain the compositional variability of granites ranging from whole igneous suites down to mineral scale. This Special Publication presents an overview of the state of the art and envisages future avenues towards a better understanding of granite petrogenesis.

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