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| Mänd, Kaarel; Lalonde, Stefan; Paiste, Kärt; Thoby, Marie; Lumiste, Kaarel; Robbins, Leslie J.; Kreitsmann, Timmu; Romashkin, Alexander E.; Kirsimäe, Kalle; Lepland, Aivo; Konhauser, Kurt O.. |
| The Zaonega Formation in northwest Russia (~2.0 billion years old) is amongst the most complete successions that record the middle of the Palaeoproterozoic era. As such, geochemical data from the formation have played a central role in framing the debate over redox dynamics in the aftermath of the Great Oxidation Event (GOE). However, uncertainty over local redox conditions and the degree of hydrographic restriction in the formation has led to contradictory interpretations regarding global oxygen (O2) fugacity. Here, we provide new iron (Fe) isotope data together with major and trace element concentrations to constrain the local physiochemical conditions. The Zaonega Formation sediments show authigenic Fe accumulation (Fe/Al ≫ 1 wt.%/wt.%) and δ56Fe... |
| Tipo: Text |
Palavras-chave: Isotope geochemistry; Redox stratification; Benthic Fe shuttle; Dissimilatory iron reduction. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00688/79959/82885.pdf |
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| Paquet, Marine; Hamelin, Cédric; Moreira, Manuel; Cannat, Mathilde. |
| The eastern Southwest Indian Ridge, between 61° and 67°E, has a very low melt supply and comprises several corridors of nearly amagmatic spreading that expose mantle-derived serpentinized peridotite. More volcanically active ridge portions separate these corridors. He, Ne, Pb, Nd, Hf and Sr isotopes were analyzed in basalt glasses dredged on two types of seafloor: volcanic and ultramafic. Basalts dredged in ultramafic seafloor on-axis tend to be slightly more depleted for heavy radiogenic isotopes and show slightly higher 3He/4He isotope ratios than basalts dredged in volcanic seafloor, with no systematic difference in neon isotope ratios. We propose that both types of basalts are derived from the same mantle source, but that the basalts dredged on... |
| Tipo: Text |
Palavras-chave: Mid-Ocean Ridge Basalts; Mantle heterogeneity; Noble gases; Isotope geochemistry; Melt/mantle interactions. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00633/74525/74360.jpg |
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| Revillon, Sidonie; Teagle, Damon A. H.; Boulvais, Philippe; Shafer, John; Neal, Clive R.. |
| Hole 1205A was drilled on Nintoku Seamount, which lies in the midportion of the Emperor Seamount Chain. This seamount was emergent similar to 56 Myr ago but was submerged by 54 Ma, so the lavas have endured weathering in both subaerial and submarine environments. We have studied the petrology, mineralogy, and geochemistry of intercalated altered basalts, breccias, and soil samples recovered at Hole 1205A to quantify the chemical exchanges between the seamount and seawater and/ or meteoric fluids. The secondary mineralogy is relatively uniform throughout the section and comprises smectite, Feoxyhydroxides, iddingsite, and Ca-carbonates. Soils are composed of variably altered basaltic clasts in a matrix of kaolinite, smectite, and vermiculite with minor... |
| Tipo: Text |
Palavras-chave: Geochemistry : major and trace element geochemistry; Geochemistry : alteration and weathering processes; Geochemistry : geochemical cycles; Oceanic island; Isotope geochemistry; Chemical fluxes; Alteration; Hole 1205A; Ocean Drilling Program. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2435.pdf |
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