Characteristics and formation mechanism of seafloor domes on the north‐eastern continental slope of the <scp>South China Sea</scp>

Wu, Tingting; Wei, Jiangong; Liu, Shengxuan; Guan, Yanan; Zhang, Ruwei; Wang, Hongbin; Zhang, Wei; Meng, Dajiang; Liu, Bin

doi:10.1002/gj.3402

Cited by 15 publications

(6 citation statements)

References 38 publications

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“…Among these changes, the change of sea level has been regarded as the prominent factor, leading to the decomposition of gas hydrate in geological history [61]. The U-Th dates of all samples fall within periods in which the sea level was 110 m lower than the present sea level ( Figure 6) [61,62,[66][67][68]. The coincidence with a low stand is very strong evidence for relationships between seep activity and the sea level.…”

Section: Influence Of Methane Flux On the Formation Of Authigenic Carmentioning

confidence: 93%

“…At cold seeps, the anaerobic oxidation of methane (AOM) typically proceeds in anoxic sub-surface sediments, which leads to increased alkalinity levels in pore waters and, as a consequence, often results in carbonate precipitation [27,31,44,[48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. Occurrences of authigenic carbonate deposits at the sea floor or in sedimentary records are therefore often related to the paleo-seepage of methane-rich fluids at continental margins.…”

Section: Fluid Source and Environment Of Seep Carbonate Formationmentioning

confidence: 99%

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Deeply Buried Authigenic Carbonates in the Qiongdongnan Basin, South China Sea: Implications for Ancient Cold Seep Activities

Wei

Zhang

et al. 2020

Minerals

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Cold seep carbonates are important archives of pore water chemistry and ancient methane seepage activity. They also provide an important contribution to the global carbon sink. Seep carbonates at three sediment layers (3.0, 52.1, and 53.6 mbsf) were collected at site W08B in the Qiongdongnan Basin of the South China Sea. This study investigated the mineralogy, microstructure, stable carbon and oxygen isotopes, trace elements, and U-Th dates of these carbonates to identify the relationship between methane flux and authigenic carbonate precipitation. The results showed that the δ13C and δ18O values of all carbonates are similar, indicating that the carbon source for shallow carbonates and deep carbonates has remained constant over time and included biogenic and thermogenic methane. Although carbonates were found in three sediment layers, the two main stages of methane seepage events were discernible, which was likely caused by the dissociation of gas hydrates. The first methane seep took place at 131.1–136.3 ka BP. During a dramatic drop in the sea level, the seep carbonate at 52.1 mbsf formed at 136.3 ka BP through the anaerobic oxidation of methane (AOM). The carbonate at 53.6 mbsf resulted from the vertical downward movement of the sulfate-methane transition zone with decreasing methane flux at 131.1 ka BP. This is the reason for the age of carbonates at 52.1 mbsf being older than the age of carbonates at 53.6 mbsf. The second methane seep took place at 12.2 ka BP. Shallow carbonate formed at that time via AOM and is now located at 3 mbsf. Moreover, thin-section photomicrographs of deep carbonate mainly consisted of matrix micrite and biological debris and acicular aragonite occurred as vein cement filling the pore spaces between the matrix micrite. The acicular aragonite was mainly influenced by the timing of the carbonate precipitation of minerals. This research identified a long history of methane seep activity reflected by the vertical distribution of carbonates.

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Section: Influence Of Methane Flux On the Formation Of Authigenic Carmentioning

confidence: 93%

Section: Fluid Source and Environment Of Seep Carbonate Formationmentioning

confidence: 99%

Deeply Buried Authigenic Carbonates in the Qiongdongnan Basin, South China Sea: Implications for Ancient Cold Seep Activities

Wei

Zhang

et al. 2020

Minerals

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“…A large number of gas chimneys, mud diapirs, and mud volcanos, which act as gas-bearing fluid migration pathways, have developed in this area. In particular, clusters of gas chimneys have been identified on the seismic profiles in the GMGS2 gas hydrate drilling area [53,64]. Another type of hydrocarbon migration pathway in the Dongsha drilling area is faults, which are mainly inherited faults and small active faults on the top and/or flanks of the large gas chimneys, and some of the inherited faults extend downward into the deeply buried basement.…”

Section: Gas Hydrate Systemmentioning

confidence: 99%

“…The identification of microgeomorphological types related to seafloor seepage and the establishment of gas seepage patterns suitable for specific areas can provide a corresponding basis for gas hydrate prospecting. In addition, there are usually a series of microtopographical features in the seabed in gas hydrate occurrence areas, such as slumps, pockmarks, mounds, mud volcanoes, depressions, and platforms [27,[60][61][62][63][64]. Identifying and characterizing these seafloor features not only is of great significance to the discovery and confirmation of the existence of gas hydrates but also provides basic engineering geological information for the exploration and development of gas hydrate resources.…”

Section: Introductionmentioning

confidence: 99%

Gas Hydrate Accumulation and Occurrence Associated with Cold Seep Systems in the Northern South China Sea: An Overview

Zhang

Liang

et al. 2021

Geofluids

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Studying deep-water cold seep systems is of great significance to gas hydrate exploration due to their close relationship. Various cold seep systems and related gas hydrate accumulations have been discovered in the northern South China Sea in the past three decades. Based on high-resolution seismic data, subbottom profiles, in situ submergence observations, deep drilling and coring, and hydrate gas geochemical analyses, the geological and geophysical characteristics of these cold seep systems and their associated gas hydrate accumulations in the Qiongdongnan Basin, the Shenhu area, the Dongsha area, and the Taixinan Basin have been investigated. Cold seep systems are present in diverse stages of evolution and exhibit various seabed microgeomorphic, geological, and geochemical features. Active cold seep systems with a large amount of gas leakage, gas plumes, and microbial communities and inactive cold seep systems with authigenic carbonate pavements are related to the variable intensity of the gas-bearing fluid, which is usually derived from the deep strata through mud diapirs, mud volcanoes, gas chimneys, and faults. Gas hydrates are usually precipitated in cold seep vents and deeper vertical fluid migration pathways, indicating that deep gas-bearing fluid activities control the formation and accumulation of gas hydrates. The hydrocarbons collected from cold seep systems and their associated gas hydrate reservoirs are generally mixtures of biogenic gas and thermogenic gas, the origin of which is generally consistent with that of deep conventional gas. We also discuss the paragenetic relationship between the gas-bearing fluid and the seafloor morphology of cold seeps and the deep-shallow coupling of gas hydrates, cold seeps, and deep petroleum reservoirs. It is reasonable to conclude that the deep petroleum systems and gas-bearing fluid activity jointly control the development of cold seep systems and the accumulation of gas hydrates in the northern South China Sea. Therefore, the favorable areas for conventional oil and gas enrichment are also prospective areas for exploring active cold seeps and gas hydrates.

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“…The OT is an incipient back-arc basin and formed after the middle Miocene due to the crustal stretching of the Eurasian lithosphere [29]. The geology of the seeps in the OT is less structurally and bathymetrically complex than those in the other oceans (e.g., South China Sea) [30][31][32]. The most striking feature of the cold seeps in the OT is the impact from the nearby hydrothermal activities that can provide abundant metal oxides to react in the microbially mediated processes of the seeping environment [25].…”

Section: Introductionmentioning

confidence: 99%

Review of Methane Seepages in the Okinawa Trough: Progress and Outlook

et al. 2021

Geofluids

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It has been two decades since the cold seeps were firstly found in the Okinawa Trough (OT). The scientific cruises and the geological surveys since then have unveiled the currently active submarine methane seeps and significantly improved the understanding of methane seeps in the back-arc basin of the OT. In this paper, we review the up-to-date progress of the research of methane seepages then put forward the promising, yet challenging, outlook by listing the unsolved questions of the cold seeps in the OT. Multiple approaches and techniques, including seismic and echo-sounder recording, dredging, gravity-piston and ROV coring, seafloor drilling, and isotopic and microarray-based genomic analysis, have been used to reveal the geological processes responsible for the seeping activities and the biogeochemical processes related to them. The geophysical signature associated with gas seeps mainly includes the acoustic turbidity in the subsurface, the anomaly of the backscattering intensity at the seabed, and the gas plumes observed in the water column. Pore water and methane-derived authigenic carbonate archive the intensification of methane seepage and the paleoenvironment changes at different time scales. The methane feeding of the seeps in the OT was generated mostly via the microbially mediated process and has an origin mixed by thermogenic hydrocarbon gas in the middle OT. Sulfate-driven and Fe-driven anaerobic oxidations of methane are suggested to be the key biogeochemical processes, which would shape the material cycling in the seeping environment. The future research on the cold seeps in the OT is worth looking forward to due to its geographic and potential geologic links with the nearby hydrothermal activities. Multidisciplinary studies are expected to concentrate on their link with the undiscovered gas hydrates, the amount of methane transferring into the oceans and its impact on the climatic change, and the evolution of the seeping activities accompanied by the biogeochemical processes.

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Characteristics and formation mechanism of seafloor domes on the north‐eastern continental slope of the South China Sea

Cited by 15 publications

References 38 publications

Deeply Buried Authigenic Carbonates in the Qiongdongnan Basin, South China Sea: Implications for Ancient Cold Seep Activities

Deeply Buried Authigenic Carbonates in the Qiongdongnan Basin, South China Sea: Implications for Ancient Cold Seep Activities

Gas Hydrate Accumulation and Occurrence Associated with Cold Seep Systems in the Northern South China Sea: An Overview

Review of Methane Seepages in the Okinawa Trough: Progress and Outlook

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