Magnetic properties of gas hydrate-bearing sediments and their association with iron geochemistry in the Sea of Marmara, Turkey
Type | Article | ||||||||||||||||
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Date | 2023-03 | ||||||||||||||||
Language | English | ||||||||||||||||
Author(s) | Yang Hailin1, 2, Zhang Peng3, Lu Hailong1, Shi Meinan4, Li Jianming5, Lu Yinghan1, Liu Yujia1, Ruffine Livio6, Poulton Simon W.2 | ||||||||||||||||
Affiliation(s) | 1 : Beijing International Center for Gas Hydrate, School of Earth and Space Sciences, Peking University, Beijing 100871, China 2 : School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK 3 : State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China 4 : School of Ocean Sciences, China University of Geoscience, Beijing 100083, China 5 : Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China 6 : Ifremer, Univ. Brest, CNRS, UMR Geo-Ocean, F-29280 Plouzané, France |
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Source | Chemical Geology (0009-2541) (Elsevier BV), 2023-03 , Vol. 620 , P. 121339 (11p.) | ||||||||||||||||
DOI | 10.1016/j.chemgeo.2023.121339 | ||||||||||||||||
Keyword(s) | Iron geochemistry, Magnetic properties, Sea of Marmara, Seepage activity, Gas hydrate, Sediments | ||||||||||||||||
Abstract | The anaerobic oxidation of methane, a key geochemical process that is involved in the cycling of sulfate and iron (oxyhydr)oxides in marine sediments, results in the formation of iron sulfides. Although ferrimagnetic iron sulfides have been identified in seepage systems, the link between iron migration and sediment magnetic properties remains poorly understood. Here, we investigate two cores from the Sea of Marmara to evaluate biogeochemical iron cycling and iron sulfide mineralogy in gas hydrate-bearing sediments. Magnetic analyses indicate the presence of greigite and pyrrhotite in a core from a hydrate-rich site with a high hydrocarbon flux, which contrasts with a lack of these minerals in a core characterized by only mild seepage. This is supported by the results of rock magnetic and scanning electron microscope analyses of the sediments. The presence of authigenic greigite is critical for assessing local redox records and together with the occurrence of monoclinic pyrrhotite may suggest specific diagenetic processes in gas hydrate environments. Our analysis demonstrates the usefulness of these ferrimagnetic minerals, with a high saturation isothermal remanent magnetization to magnetic susceptibility ratio (SIRM/χ > 15 kAm−1) and a high index of hysteresis parameters (DJH > 0.2) indicative of magnetic mineralogy changes, for evaluating variability in the intensity of seepage fluxes and for estimating gas hydrate distributions. |
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