Using sediment geochemistry to infer temporal variation of methane flux at a cold seep in the South China Sea

Niu, Li; Dong, Feng; Chen, Linying; Wang, Hongbin; Chen, Duofu

doi:10.1016/j.marpetgeo.2016.07.026

Cited by 54 publications

(17 citation statements)

References 111 publications

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“…Recent studies have demonstrated that in rapidly depositing methane‐rich marine sedimentary environments, enrichment of CRS (δ 34 S CRS ) and molybdenum (Mo) can be used as proxies to identify paleo‐SMTZs and methane seepage events in marine sediments (Chen et al, ; Hu et al, ; Li et al, ; Lin et al, ; Peketi et al, , ). Negative correlation between CRS content and χ lf in sediment cores MD161/Stn8, MD161/Stn13, and NGHP‐01‐10D (Figure e; Badesab et al, ) suggests that magnetic tracking in combination with geochemical proxies (CRS, δ 34 S CRS , Mo) can be used to constrain paleo‐SMTZ and methane seepage events in marine sediments.…”

Section: Discussionmentioning

confidence: 99%

Magnetic Mineralogical Approach for the Exploration of Gas Hydrates in the Bay of Bengal

et al. 2019

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We evaluate the environmental magnetic, geochemical, and sedimentological records from three sediment cores from potential methane-hydrate bearing sites to unravel linkages between sedimentation, shale tectonics, magnetite enrichment, diagenesis, and gas hydrate formation in the Krishna-Godavari basin. Based on downcore rock magnetic variations, four sedimentary magnetic property zones (I-IV) are demarcated. A uniform band of enhanced magnetic susceptibility (zone III) appears to reflect a period of high-sedimentation events in the Krishna-Godavari basin. Highly pressurized sedimentary strata developed as a result of increased sedimentation that triggered the development of a fault system that provided conduits for upward methane migration to enter the gas hydrate stability zone, leading to the formation of gas hydrate deposits that potentially seal the fault system. Magnetic susceptibility fluctuations and the presence of iron sulfides in a magnetically enhanced zone suggest that fault system growth facilitated episodic methane venting from deeper sources that led to multiple methane seepage events. Pyrite formation along sediment fractures resulted in diagenetic depletion of magnetic signals and potentially indicates paleo sulfate-methane transition zone positions. We demonstrate that a close correlation between magnetic susceptibility and chromium reducible sulfur concentration can be used as a proxy to constrain paleomethane seepage events. Our findings suggest that the interplay between higher sedimentation events and shale tectonism facilitated fluid/gas migration and trapping and the development of the gas hydrate system in the Krishna-Godavari basin. The proposed magnetic mineralogical approach has wider scope to constrain the understanding of gas hydrate systems in marine sediments.

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Section: Discussionmentioning

confidence: 99%

Magnetic Mineralogical Approach for the Exploration of Gas Hydrates in the Bay of Bengal

et al. 2019

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“…However, studies on such carbonate rocks on the seafloor may fail to reveal the complete evolution of past seepage activities due to the somewhat discontinuous occurrence or sampling limitation. Seep-impacted sediment cores can serve as another important archive to reconstruct the evolution of past seepage activities (Bayon et al, 2015;Li et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…However, due to iron limitation in the sedimentary column, low δ 34 S values of pyrites near the SMTZs compromise its ability to recognize seepage activities (Formolo and Lyons, 2013). A few previous studies have used carbon-sulfur-trace element systematics of seep-impacted sediments to trace the SMTZs and seepage activities (Peketi et al, 2012;Sato et al, 2012;Li et al, 2016). A comprehensive study on seep-impacted sediments and hosted authigenic carbonates will thus provide insights into (1) the applicability of sulfur isotopes of pyrite and 2the variations of methane fluxes.…”

Section: Introductionmentioning

confidence: 99%

Geochemical record of methane seepage in authigenic carbonates and surrounding host sediments: A case study from the South China Sea

Chen

Dong

et al. 2017

Journal of Asian Earth Sciences

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Sediments at marine methane seep sites provide potential archives of past fluid flow that serve to explore seepage activities over time. Three gravity cores (D-8, D-F, and D-7) were collected from seep sites on the northern slope of the South China Sea where gas hydrates were drilled in the subsurface. Various carbon and sulfur contents, δ 13 C values of total inorganic carbon (δ 13 C TIC), δ 34 S values of chromium reducible sulfur (δ 34 S CRS), trace element contents, grain size, and AMS 14 C dating of planktonic Foraminifera in the sediments were determined to explore the availability of related proxies at seeps and to trace past methane seepage activities. Evidence for the presence of methane seepage and consequently anaerobic oxidation of methane comes from the occurrence of 13 C-depleted authigenic carbonate nodules (δ 13 C values as low as-49‰) discovered at an interval of 150 cm-200 cm in core D-7. This finding is supported by high S/C ratios and molybdenum enrichment in the same interval. However, low contents of CRS and negative δ 34 S CRS values are present. It is suggested to reflect a transient methane seepage event, which continued for about 1 ka based on the 14 C ages. Cores D-8 and D-F have δ 13 C TIC values close to zero, low S/C ratios and CRS contents, negative δ 34 S CRS values, and no trace element enrichment, suggesting a negligible impact of methane-seepage on the sediments. The negative δ 34 S CRS values of the studied seep-impacted and background sediments suggest that the application of δ 34 S CRS alone as a proxy to identify AOM-related process may be insufficient. Sediment carbon-sulfur-trace element systematics and 14 C ages used here have the potential to be a promising tool to recognize transient methane seepages and constrain their timescales.

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“…The chemical anomalies of bottom seawater comprehensively represent the source and composition of cold seep fluid as well as the biochemical reaction and interaction occurring between the water and the surrounding rock during fluid migration. In recent years, detailed geochemical analyses of cold seeps were performed internationally on columnar sediments and pore water samples obtained through ocean drilling and submarine observation [10][11][12][13][14]. Such research has led to better understanding of the characteristics of pore water in cold seeps and the relationship between cold seeps and gas hydrates [15,16].…”

Section: Introductionmentioning

confidence: 99%

Hydrochemical Characteristics and Evolution Mode of Cold Seeps in the Qiongdongnan Basin, South China Sea

et al. 2020

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Submarine cold seeps have recently attracted significant attention and are among the most effective indicators of gas hydrate in the oceans. In this study, remotely operated vehicle (ROV) observations, seismic profiles, core sediments, bottom seawater, and fluid vented from cold seeps in the deep-water Qiongdongnan Basin were used to investigate the origin and evolution of cold seeps and their relationships with gas hydrate. At stations A, B, and C, inactive cold seeps with dead clams, cold seep leakage with live clams, and active cold seeps with a rich mussel presence, respectively, were observed. The salinity and Na+ and Cl- concentrations of the cold seeps were different from those of typical seawater owing to gas hydrate formation and decomposition and fluid originating from various depths. The main ion concentrations of the bottom seawater at stations B and C were higher than those at station A, indicating the substantial effects of low-salinity cold seep fluids from gas hydrate decomposition. The Na+-Cl-, K+-Cl-, Mg2+-Cl-, and Ca2+-Cl- diagrams and rare earth element distribution curves of the water samples were strongly affected by seawater. The concentrations of trace elements and their ratios to Cl- in the bottom seawater were high at the stations with cold seeps, suggesting the mixing of other fluids rich in those elements. Biochemical reactions may also have caused the chemical anomalies. Samples of HM-ROV-1 indicated a greater effect of upward cold seep fluids with higher B/Cl-, Sr/Cl-, and Ba/Cl- values. Moreover, the Re/Cl- value varied between fluid vents, possibly due to differences in Re precipitation strength. Differences in cold seep intensity are also believed to occur between areas. The cold seep fluxes changed from large to small before finally disappearing, showing a close connection with gas hydrate formation and decomposition, and influenced the local topography and ecosystems.

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Using sediment geochemistry to infer temporal variation of methane flux at a cold seep in the South China Sea

Cited by 54 publications

References 111 publications

Magnetic Mineralogical Approach for the Exploration of Gas Hydrates in the Bay of Bengal

Magnetic Mineralogical Approach for the Exploration of Gas Hydrates in the Bay of Bengal

Geochemical record of methane seepage in authigenic carbonates and surrounding host sediments: A case study from the South China Sea

Hydrochemical Characteristics and Evolution Mode of Cold Seeps in the Qiongdongnan Basin, South China Sea

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