Source-sink process of reactive iron in mud sediments controlled by holocene depositional environments and redox states: Insight from the Central Yellow Sea Mud

Chemical Geology, Journal Year: 2025, Volume and Issue: unknown, P. 122780 - 122780

Published: April 1, 2025

Language: Английский

---

Multiple Sulfur Isotopes of Iron Sulfides From Thick Greigite‐Bearing Sediments Indicate Anaerobic Oxidation and Possible Leakages of Coastal Methane

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(16)

Published: Aug. 17, 2023

Abstract Magnetic greigite may be a valuable indicator for methane emissions in the geological past, if its formation pathway and diagenetic environment can unambiguously defined. Here, we investigate sulfur isotopic compositions of iron sulfides ferrous concentrations thick greigite‐bearing sediments (TGBSs) South Yellow Sea, shallow marginal sea with strong emissions. For first time, isotopically heavy (up to 28.7‰ δ 34 S 0.19‰ Δ 33 S) enrichments TGBSs are observed. We interpret data as indicating synchronic occurrences anaerobic oxidation coupled sulfate reductions, which occur coastal methanic zones limited availability therefore probably imply leakages methane. Consequently, suggest that is promising tracing liberated from sediments, accounting ∼60% currently rising global marine budget.

Language: Английский

---

Depositional control on the fate of reactive iron in shelf sediments since the last deglaciation: A case study of the East China Sea

Marine Geology, Journal Year: 2024, Volume and Issue: 475, P. 107358 - 107358

Published: Sept. 1, 2024

Language: Английский

---

Iron species and sulfur isotopic compositions of authigenic pyrite in deep-sea sediments at southern Hydrate Ridge, Cascadia margin (ODP Leg 204): implications for non-steady-state depositional and diagenetic processes

Frontiers in Marine Science, Journal Year: 2024, Volume and Issue: 11

Published: July 24, 2024

Two accretionary sediment sequences from Sites 1245 and 1252 recovered during Ocean Drilling Program (ODP) Leg 204 at southern Hydrate Ridge were investigated to explore the response of geochemical partitioning iron sulfur isotopic composition authigenic pyrite non-steady-state depositional diagenetic scenarios. Five species characterized by a modified sequential extraction procedure that covers almost all iron-bearing minerals in cores, including: (1) carbonates, mainly siderite; (2) ferric (hydr)oxides, probably ferrihydrite and/or lepidocrocite; (3) magnetite; (4) silicates; (5) pyrite. Highly reactive has been accumulated for long-term steady-state history its pyritization, varying degrees, is limited availability dissolved sulfide. This causes siderite occurred same sedimentary layer shows an inverse relationship between their concentrations. From this, proportions highly can be chosen evaluating degree sulfidization. A significant change (-42.4 +16.8‰ VCDT) indicates conditions are dramatically limited, where δ 34 S values higher than -20‰ may result upward shift SMT zone close seafloor or sudden, massive event. To explain downcore sulfidization effects values, we developed two categories conceptual scenarios based on variations sedimentation rate methane flux. The features similar those derived each scenario searched columns events behind proved consistent with real observations. Thus, regarded as proxy differentiate different controls record.

Language: Английский

---

Geochemical behavior of C, N, and S in sediments of Hangzhou Bay, Southeastern China: implications for the study of paleoclimate and sea-level changes

Frontiers in Marine Science, Journal Year: 2024, Volume and Issue: 11

Published: March 11, 2024

The correlation between the amount of organic carbon (OC) and sulfur (S) in sediments has been widely used as a paleosalinity indicator to distinguish marine freshwater environments. However, whether ratio total OC S (TOC/TS) can be identify unsteady or dynamic environments across sedimentary strata is still contended. An HZW1907 sediment core 80 m length was successfully collected middle Hangzhou Bay (HZB), serving one few boreholes that are crucial for study geologic geo-environment changes coastal regions eastern China since Last Glacial Maximum (LGM). Total (TOC), stable isotope, TS 82 subsamples from were analyzed reconstruct history shallow water biological pump preservation record bay Late Pleistocene. Our results indicate samples had low concentrations TOC (0.21%) nitrogen (TN) (0.02%), high mass TOC/TN (10.8), δ 13 C (−24.9‰), content (0.06%), TOC/TS (9.1) 33.6 ka BP 12.3 BP, implying matter (OM), algae, C3 plant fragments main sources OM relatively cold environment. abundances TOC, TN, increased 0.56%, 0.07%, 0.4%, respectively, while (−23.9‰) (2.7) decreased Holocene sediments, suggesting seawater began influence composition HZB. Climate warming, which likely have impacted results, experienced BP. isotope mixing model indicated Mid-late Holocene, more than 70% riverine accounted OM. identified an effective intrusion, with C/S ratios 1–6 being considered “sea–land transitional zone” environment, >6 indicating freshwater, C/S<1 normal facies. These findings provide evidence using enhance our understanding past climate changes. Therefore, these geochemical indicators conjunction other records obtain accurate about evolution.

Language: Английский

---

The relationships between vertical variations of shallow gas and pore water geochemical characteristics in boreholes from the inner shelf of the East China Sea

Frontiers in Marine Science, Journal Year: 2024, Volume and Issue: 11

Published: March 22, 2024

Shallow gas was widely recognized in the coastal region, especially estuarine delta areas with high organic matter (OM) burial flux. In this study, vertical variations of shallow and related geochemical indicators from two boreholes region East China Sea (ECS) were investigated. Two gas-bearing layers identified sediments Holocene late Pleistocene series. Both exhibit a “typical” an “inverse” Sulfate Methane Transition Zone (SMTZ). The SMTZs (SMTZ1 SMTZ3) upper part layers, where sulfate levels decrease methane increase depth. Conversely, (SMTZ2 SMTZ4) lower exhibiting depth, phenomenon rarely documented previous research. downward pore water characteristics indicates that these ions to Anaerobic Oxidation (AOM) processes. Ca 2+ Ba concentrations gradual at SMTZ reflect series biogeochemical processes resulting dissolution carbonate other minerals by AOM. research AOM may originate multiple sources. Through analyzing distribution properties water, study elucidates formation mechanism features SMTZ, laying groundwork for further investigations.

Language: Английский

---

Anaerobic oxidation of methane and greigite formation: Evidence of isotopically heavy pyrite in Pleistocene coastal sediments from the South Yellow Sea

Global and Planetary Change, Journal Year: 2024, Volume and Issue: 240, P. 104530 - 104530

Published: July 26, 2024

Language: Английский

---

Transportation and transformation of sedimentary Fe speciation in the northern South China Sea

Journal of Asian Earth Sciences, Journal Year: 2024, Volume and Issue: 276, P. 106371 - 106371

Published: Oct. 19, 2024

Language: Английский

---

Carbon, iron and sulfur records of lacustrine paleo-environments during the middle Eocene in eastern China

The Science of The Total Environment, Journal Year: 2024, Volume and Issue: 956, P. 177270 - 177270

Published: Nov. 9, 2024

Language: Английский

---