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Heard, Andy W.; Dauphas, Nicolas; Guilbaud, Romain; Rouxel, Olivier; Butler, Ian B.; Nie, Nicole X.; Bekker, Andrey. |
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... |
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Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00657/76889/78193.pdf |
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Greenwood, Richard C.; Barrat, Jean-alix; Miller, Martin F.; Anand, Mahesh; Dauphas, Nicolas; Franchi, Ian A.; Sillard, Patrick; Starkey, Natalie A.. |
The Earth-Moon system likely formed as a result of a collision between two large planetary objects. Debate about their relative masses, the impact energy involved, and the extent of isotopic homogenization continues. We present the results of a high-precision oxygen isotope study of an extensive suite of lunar and terrestrial samples. We demonstrate that lunar rocks and terrestrial basalts show a 3 to 4 ppm (parts per million), statistically resolvable, difference in Delta O-17. Taking aubrite meteorites as a candidate impactor material, we show that the giant impact scenario involved nearly complete mixing between the target and impactor. Alternatively, the degree of similarity between the Delta O-17 values of the impactor and the proto-Earth must have... |
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Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00638/74995/75750.pdf |
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