Chemical environment of cold seep carbonate formation on the northern continental slope of South China Sea: Evidence from trace and rare earth element geochemistry

Ge, Liu; Jiang, Shao-Yong; Swennen, Rudy; Yang, Tao; Yang, Jinghong; Wu, N.; Liu, Jian; Chen, Daohua

doi:10.1016/j.margeo.2010.08.008

Cited by 115 publications

(46 citation statements)

References 45 publications

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“…There are extensive bottom-simulating reflectors (BSRs) covered most of the study area ( Fig. 1), indicating gas hydrate in the strata (Suess et al, 2005;Ge et al, 2010). In addition to authigenic carbonates, chemosynthetic communities were visually observed, and shallow SMTZS were observed in this area (Lim et al, 2011;Feng and Chen, 2015b).…”

Section: Study Areamentioning

confidence: 95%

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

Niu

Dong

Chen

et al. 2016

Marine and Petroleum Geology

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Section: Study Areamentioning

confidence: 95%

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

Niu

Dong

Chen

et al. 2016

Marine and Petroleum Geology

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“…Additionally, all carbonate nodules develop pyrites, which can reveal that they precipitated under anaerobic conditions. Therefore, Xigaze seep carbonates have great consistency with lots of modern and ancient seep carbonates in primary reducing formation environments [50,[54][55][56].…”

Section: Formation Conditions Of Xigaze Seep Carbonatesmentioning

confidence: 99%

“…Ce anomalies are used to indicate redox conditions of seep carbonate precipitation environments [50,[54][55][56]. The negative Ce anomaly indicates oxidizing environments while no or positive Ce anomaly indicates reducing environments.…”

Section: Formation Conditions Of Xigaze Seep Carbonatesmentioning

confidence: 99%

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

Tong

Chen

2012

Chin. Sci. Bull.

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Hydrocarbon seeps, widely occurring in continental margins, have become increasingly focused owing to their close relationships with gas hydrates, strong greenhouse gas methane, and biological resources in extreme environments. Ancient hydrocarbon seeps have already been recognized from Devonian to Quaternary strata worldwide based on seep carbonates or seep-related fossil chemosynthetic assemblages. However, seep-related deposits are rarely found from ancient strata in the mainland China. Here, we report the first discovery of an ancient seep deposit, specifically late Cretaceous seep carbonates from Xigaze in Tibet, China. Xigaze seep carbonates, occurring as nodules, are enclosed in upper Cretaceous turbidite strata in Xigaze forearc basin. These carbonates are composed of authigenic carbonate (56.2% on average), clastic quartz and feldspar (27.3% on average), and clay minerals (chlorite, illite and smectite, 16.5% on average). Clotted micrites, peloids and framboid pyrites are frequently observed, all of which are common in modern seep carbonates. The carbonates have negative  13 C values varying from 27.7‰ to 4.0‰ (V-PDB), suggesting that thermogenic methane is the primary carbon source. Ce/Ce* values revised by eliminating La effects show no real Ce anomaly, indicating the carbonates were primarily precipitated in a weak reducing environment. Overall, these features provide unequivocal evidences that the seafloor of Xigaze forearc basin developed hydrocarbon seeps in late Cretaceous. seep carbonate, carbon isotope, sedimentary fabric, Xigaze, late Cretaceous Citation:Tong H P, Chen D F. First discovery and characterizations of late Cretaceous seep carbonates

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“…The chimney samples are dominated by high Mg-calcite with abundant quartz and feldspar detritus indicating that they were formed from pore water in the sediments. REE analysis showed that the chimneys have positive Ce-anomalies, this indicates that they were formed in a reducing environment [15]. When the chimneys became exposed to the seafloor, the environment changed from the more reducing pore water to the more oxidative seawater.…”

Section: Petrology and Mineralogymentioning

confidence: 96%

“…A TV-guided grab sampler was used to collect seep carbonates [9,10]. Previous studies have addressed many aspects of the seep carbonate samples, including their characteristic morphology, petrology, mineralogy, C-and O-isotope compositions, rare Earth element geochemistry, preserved microbial structures, biomarkers, ages as well as model of chimney-like carbonate formations [5,[9][10][11][12][13][14][15][16][17][18][19]. However, the origin and nature of the fluid flow and its relationship with gas hydrate deposits have not been studied thoroughly.…”

Section: South China Sea Seep Carbonate Chimneys Carbon and Oxygen mentioning

confidence: 99%

Origin and nature of cold seep in northeastern Dongsha area, South China Sea: Evidence from chimney-like seep carbonates

2013

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The occurrence of seep carbonates is one of the characteristic features for cold seep sites at continental margins. The carbonates documented the venting history of methane-rich fluid. Compared to the chemoherm carbonates and carbonate pavements which formed on the sediment-water interface, chimney-like seep carbonates precipitated around fluid conduits below the sediment-water interface therefore better recording information of the past fluid flow and composition. Here the chimney-like seep carbonate samples from the northeastern Dongsha area of the South China Sea were studied to understand the origin and nature of the venting fluids and their potential relationship with gas hydrate deposits underneath the seafloor. Based on the occurrence, morphology, petrology, mineralogy and C-and O-isotope compositions, combined with present and past bottom water temperatures and the timing of methane release events, the oxygen isotopic fractionation between calcite and water were used to estimate the equilibrium δ18 O values of the precipitating fluids. The δ 13 C values ranging from −56.33‰ to −42.70‰ V-PDB and thus clearly show that the studied chimneys were mainly derived from biogenic methane oxidation. The calculated equilibrium δ 18 O values of the precipitating fluids ranged from 1.9‰  0.3‰ to 0.6‰  0.3‰ V-SMOW, with an average of 1.4‰  0.3‰ V-SMOW which is heavier than those of seawater even at the last glacial maximum. It is considered that the formation of chimney-like carbonates was closely related to methane hydrate dissociation in the area. The methane hydrates contributed as much as 45.7% of water to the venting fluids. It is suggested that the climate and environmental changes (e.g. sea-level lowering, down-cutting canyons and mass wasting) are the major mechanisms maybe responsible for the destabilization of methane hydrates in the study area. The extensive occurrence of seep carbonates indicates that a large amount of the methane released from methane hydrate dissociation has been effectively captured and sequestered by microbial anaerobic oxidation of methane (AOM) before it escapes into the water column.South China Sea, seep carbonate chimneys, carbon and oxygen isotopes, gas hydrate deposits, methane-rich fluids Citation:

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Chemical environment of cold seep carbonate formation on the northern continental slope of South China Sea: Evidence from trace and rare earth element geochemistry

Cited by 115 publications

References 45 publications

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

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

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

Origin and nature of cold seep in northeastern Dongsha area, South China Sea: Evidence from chimney-like seep carbonates

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