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- Lorand, Jean-Pierre, et al.
(författare)
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The sulfur budget and sulfur isotopic composition of Martian regolith breccia NWA 7533
- 2020
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Ingår i: Meteoritics and Planetary Science. - : John Wiley & Sons, Ltd. - 1086-9379 .- 1945-5100. ; 55:9, s. 2097-2116
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Tidskriftsartikel (refereegranskat)abstract
- The sulfur isotope budget of Martian regolith breccia (NWA 7533) has been addressed from conventional fluorination bulk rock analyses and ion microprobe in situ analyses. The bulk rock analyses yield 865 ± 50 ppm S in agreement with LA-ICP-MS analyses. These new data support previous estimates of 80% S loss resulting from terrestrial weathering of NWA 7533 pyrite. Pyrite is by far the major S host. Apatite and Fe oxyhydroxides are negligible S carriers, as are the few tiny igneous pyrrhotite-pentlandite sulfide grains included in lithic clasts so far identified. A small nonzero delta-33S (-0.029 ± 0.010) signal is clearly resolved at the 2σ level in the bulk rock analyses, coupled with negative CDT-normalized δ34S (-2.54 ± 0.10 permil) and near-zero delta-36S (0.002 ± 0.09 permil). In situ analyses also yield negative delta-33S values (-0.05 to -0.30 permil) with only a few positive delta-33S up to +0.38 permil. The slight discrepancy compared to the bulk rock results is attributed to a possible sampling bias. The occurrence of mass-independent fractionation (MIF) supports a model of NWA 7533 pyrite formation from surface sulfur that experienced photochemical reaction(s). The driving force that recycled crustal S in NWA 7533 lithologies - magmatic intrusions or impact-induced heat - is presently unclear. However, in situ analyses also gave negative δ34S values (+1 to -5.8 permil). Such negative values in the hydrothermal setting of NWA 7533 are reflective of hydrothermal sulfides precipitated from H2S/HS- aqueous fluid produced via open-system thermochemical reduction of sulfates at high temperatures (>300 °C).
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| 2. |
- Wilson, Samuel T., et al.
(författare)
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Ideas and perspectives : A strategic assessment of methane and nitrous oxide measurements in the marine environment
- 2020
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 17:22, s. 5809-5828
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Tidskriftsartikel (refereegranskat)abstract
- In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics – namely production, consumption, and net emissions – is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climate-active trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment.
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