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| Heller, Maija Iris; Lam, Phoebe J.; Moffett, James W.; Till, Claire P.; Lee, Jong-mi; Toner, Brandy M.; Marcus, Matthew A.. |
| Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here we have measured the redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES... |
| Tipo: Text |
Palavras-chave: Oxygen minimum zone; Oxygen deficient zone; OMZ; ODZ; Fe redox cycling; Synchrotron XAS. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00386/49714/50242.pdf |
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| Marcus, Matthew A.; Edwards, Katrina J.; Gueguen, Bleuenn; Fakra, Sirine C.; Horn, Gregory; Jelinski, Nicolas A.; Rouxel, Olivier; Sorensen, Jeffry; Toner, Brandy M.. |
| Deep-sea ferromanganese nodules accumulate trace elements from seawater and underlying sediment porewaters during the growth of concentric mineral layers over millions of years. These trace elements have the potential to record past ocean geochemical conditions. The goal of this study was to determine whether Fe mineral alteration occurs and how the speciation of trace elements responds to alteration over ∼3.7 Ma of marine ferromanganese nodule (MFN) formation, a timeline constrained by estimates from 9Be/10Be concentrations in the nodule material. We determined Fe-bearing phases and Fe isotope composition in a South Pacific Gyre (SPG) nodule. Specifically, the distribution patterns and speciation of trace element uptake by these Fe phases were... |
| Tipo: Text |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00278/38965/37505.pdf |
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| Toner, Brandy M.; Rouxel, Olivier; Santelli, Cara M.; Bach, Wolfgang; Edwards, Katrina J.. |
| Hydrothermal sulfide chimneys located along the global system of oceanic spreading centers are habitats for microbial life during active venting. Hydrothermally extinct, or inactive, sulfide deposits also host microbial communities at globally distributed sites. The main goal of this study is to describe Fe transformation pathways, through precipitation and oxidation-reduction (redox) reactions, and examine transformation products for signatures of biological activity using Fe mineralogy and stable isotope approaches. The study includes active and inactive sulfides from the East Pacific Rise 9 degrees 50'N vent field. First, the mineralogy of Fe(III)-bearing precipitates is investigated using microprobe X-ray absorption spectroscopy (RXAS) and X-ray... |
| Tipo: Text |
Palavras-chave: Hydrothermal; East Pacific Rise; X-ray absorption spectroscopy; Stable isotopes; Micro-environment; Mineral alteration; Iron; Biosignature. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00337/44810/44375.pdf |
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