The morphology and geochemistry of authigenic pyrite formed under methane seepage: Insights from the Laptev Sea
| Parent link: | Marine Geology.— .— Amsterdam: Elsevier Science Publishing Company Inc. Vol. 485.— 2025.— Article number 107558, 13 p. |
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| Other Authors: | , , , , , , |
| Summary: | Title screen In cold seep environments, intense sulfate-driven anaerobic oxidation of methane (SD-AOM) generates significant amounts of hydrogen sulfide, facilitating pyrite precipitation in the sulfate-methane transition zone (SMTZ). To enhance the understanding of pyrite formation processes within the SMTZ, we analyzed the morphology, size distribution, trace element content, and sulfur isotopic composition of framboidal pyrite hosted in methane-derived authigenic carbonate crusts. These crusts were collected from two active cold seep sites in the Laptev Sea: the outer shelf and the continental slope. The main textural forms of authigenic pyrite were found to include spherical and polygonal framboids and their clusters, sunflowers, and rod-like aggregates. The diameter of most measured framboids does not exceed 20 μm, but some reach up to 74 μm. Despite the small size, their association with methane-derived authigenic carbonates indicates that SD-AOM plays a dominant role in pyrite precipitation. Specific pyrite textures, such as rod-like aggregates, and the large size of certain framboids further support that pyrite formation occurred within the SMTZ. Different textural relationships between pyrite aggregates and carbonate cement reflect both pre carbonate and post carbonate pyrite precipitation. Their coexistence within a single carbonate crust sample suggests multiple episodes of pyrite formation. The obtained δ34S values for pyrite (ranging from −35.6 ‰ to −28.1 ‰ V-CDT) reveal a depletion of heavy sulfur isotopes at both sites, which is uncharacteristic of SD-AOM-associated pyrite. This phenomenon is likely attributed to the open-system conditions of pyrite formation, which result from the shallow SMTZ. The content of some trace elements in pyrite from the outer shelf is significantly lower than that in pyrite from the continental slope. This difference in trace element composition may reflect varying conditions under which pyrite precipitated, highlighting the influence of fluid migration regimes on mineral-forming processes. Lower Co/Ni ratios in pyrite from the continental slope indicate its formation under more sulfidic conditions. Our findings suggest that the depth of the SMTZ relative to the seawater-sediment interface is a critical factor controlling the morphological, isotopic, and trace element characteristics of pyrite, which should be taken into account when identifying paleo-seepage Текстовый файл AM_Agreement |
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2025
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| Online Access: | https://doi.org/10.1016/j.margeo.2025.107558 |
| Format: | Electronic Book Chapter |
| KOHA link: | https://koha.lib.tpu.ru/cgi-bin/koha/opac-detail.pl?biblionumber=679670 |