Authigenic carbonates from newly discovered active cold seeps on the northwestern slope of the South China Sea: Constraints on fluid sources, formation environments, and seepage dynamics

Liang

Mitochondrial DNA Part B

et al. 2018

Self Cite

Section: Mitogenome Announcementmentioning

confidence: 99%

The mitochondrial genome of the deep-sea tubeworm Paraescarpia echinospica (Siboglinidae, Annelida) and its phylogenetic implications

Liang

Mitochondrial DNA Part B

et al. 2018

Self Cite

Limnology & Oceanography

“…High sedimentation rates during the late Pliocene led to considerable accumulation of organic matter in the SCS, and this material likely drives early diagenetic microbial methane production and, subsequently, gas hydrate formation (Suess ). Geophysical and geological investigations detected active methane seepage and gas hydrate samples along the northern slope of SCS (Suess ; Zhang et al ; Wu et al ; Liang et al ). Although sparse studies on the microbial diversity or carbonate geochemistry existed (Zhang et al ; Feng and Chen ; Jiao et al ; Niu et al , b ), little is known of the sediment biogeochemistry and metabolic activity that occurs in deep‐sea sediments of the SCS.…”

mentioning

confidence: 99%

Biogeochemistry, microbial activity, and diversity in surface and subsurface deep‐sea sediments of South China Sea

Zhuang

Liu

Liang

et al. 2019

Self Cite

Deep‐sea environments are the largest ecosystem of the global biosphere and constitute a crucial role in global biogeochemical cycles. We integrated biogeochemical and molecular ecological approaches to investigate microbial activity and diversity, with the goal of elucidating pathways and regulations of methane cycling and low molecular weight (LMW) compounds metabolism in different deep‐sea sediments of the South China Sea. We found that methanogenesis, anaerobic oxidation of methane, and sulfate reduction occurred concurrently with low rates in surface sediments of the Haima area (~ 50 cm push cores) and in subsurface sediments of the Shenhu area (~ 8 m piston core). In the presence of sulfate, methanogenesis was fueled by methylotrophic substrates, in agreement with thermodynamic calculations as well as the detection of the methylotrophic methanogenic genus Methanococcoides. Higher oxidation rates of LMW compounds than methanogenesis rates, suggested acetate, and to a lesser extent, methanol and methylamine, were predominantly utilized as an energy source by nonmethanogenic microorganisms (e.g., sulfate‐reducing bacteria). Diverse methanotrophic archaea (e.g., ANME‐1a/b and ANME‐2a/b) and sulfate‐reducing bacteria (e.g., Desulfarculaceae and Desulfobacteraceae) were observed and the abundance of mcrA and dsrA genes varied over depth and between sites. Dominant archaeal groups, such as Bathyarchaeota, Thermoplasmatale, Woesearchaeota, Lokiarchaeota, were consistently detected at both areas. Multivariate statistical analysis demonstrated sulfate was the most relevant environmental variable that correlated with the archaeal community composition. These results suggested that the presence of sulfate controlled methane cycling and LMW carbon metabolism pathways, and also affected the composition of the microbial community.

“…ROV diving and piston coring have been conducted in the cold seep area discovered in the southern low uplift in the QDNB in 2015 (Liang et al, ). The coring sites are just on the top of a gas chimney with approximately 4 km in diameter (Figure ).…”

Section: Discussionmentioning

confidence: 99%

“…The Qiongdongnan Basin (QDNB), located on the northern continental margin of the South China Sea (SCS), is not only a petroleum‐enriched basin but also a favourable gas hydrate accumulation district (Chen, Li, & Xia, ; Huang, Tian, Li, Wang, & Xiao, ; Liang et al, ; Wang et al, ; Wu et al, ; Xie, Wang, & Tong, ; Zhang et al, ; Zhu et al, ). Petroleum geology and natural gas hydrate studies on the QDNB have shown that in addition to various types of faults (Hu et al, ; Hui et al, ; Lei et al, ; Zhang, ), a number of mud diapirs, gas chimneys, and associated diapiric structures, that may have a relationship with oil and gas, developed in the deepwater QDNB (Wang et al, ; Wang, Wu, Dong, Gong, & Chai, ; Zhang, ; Zhang et al, ; Zhang et al, ; Zhao, ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Distribution and characteristics of mud diapirs, gas chimneys, and bottom simulating reflectors associated with hydrocarbon migration and gas hydrate accumulation in the Qiongdongnan Basin, northern slope of the South China Sea

Zhang

Gong

et al. 2018

Geological Journal

Self Cite

A comprehensive analysis on high‐resolution seismic data and the geological characteristics of the Qiongdongnan Basin (QDNB) in the northern South China Sea reveals multiple seismic evidence indicative of hydrocarbon migration and gas hydrate accumulation, including mud diapirs, gas chimneys, bottom simulating reflectors (BSRs), acoustic blanking, enhanced reflections, V‐AMP structures, elevated stacking velocity of sediments, and seafloor expressions. Mud diapirs and gas chimneys, which are characterized by acoustic turbidity, fuzziness, and blanking reflections on seismic profiles, with a diversity of structures and scales, are widespread and concentrated in the centres of sags and the transitional zones between sags and uplifts. Five BSR regions, with a total area of approximately 11,000 km2, have been delineated in the QDNB. They have high or medium‐high continuity amplitudes with overlying acoustic blanking on seismic profiles, indicating the occurrence of gas hydrate. Distinct fluid seepage phenomena are common below the BSRs, demonstrating that abundant free gas has migrated and accumulated beneath the gas hydrate. The distribution of BSRs and the developed zones of mud diapirs and gas chimneys presents a spatial superposition feature, and the BSRs are usually located on top of or within the structural highs of the mud diapirs and gas chimneys, indicating a close relationship between them. Mud diapirs, gas chimneys, and associated faults are efficient pathways for migrating hydrocarbons, through which the mature to highly mature thermogenic gas of the Palaeogene strata and the biogenic gas of the Neogene sediments migrate to the gas hydrate stability zones and form gas hydrate. Gas hydrate samples were recovered from the gas chimney area during the remote operated vehicle (ROV) investigation in deepwater QDNB in 2015. Based on the seismic interpretation and geochemical results, we propose two models of gas hydrate accumulation in the deepwater area of the QDNB: (a) near source biogenic gas hydrate with self‐generation and self‐accumulation, and (b) distal source thermogenic gas hydrate with lower generation and upper accumulation. We believe that the areas with a fine spatial coupling configuration between the mud diapirs, gas chimneys, and BSRs are favourable exploration targets for gas hydrate in the QDNB.