A number of cold seeps have been discovered in the northern South China Sea(SCS) including the Haiyang 4 cold-seep area where Core 973-5 was collected. Intact polar lipids(IPLs) and core lipids(CLs) were analyzed sepa...A number of cold seeps have been discovered in the northern South China Sea(SCS) including the Haiyang 4 cold-seep area where Core 973-5 was collected. Intact polar lipids(IPLs) and core lipids(CLs) were analyzed separately in sediments from Core 973-5. The most abundant lipid biomarkers were isoprenoidal GDGTs(iso GDGTs), with Crenarchaeol and GDGT-0 predominating. IPL-iso GDGTs and CL-iso GDGTs were mainly derived from Thaumarchaeota. IPL-iso GDGTs were mainly produced and retained in situ thus containing most of the in situ microbiological information. Branched GDGTs were predominantly derived from generated in marine production, and mixed with some terrestrial inputs. All IPLs groups presented a high value in the sulfate-methane transition zone(SMTZ). Furthermore, IPL and CL-MI, IPL-R;showed the highest values within the SMTZ, while IPL and CL-R;had the lowest values at the SMTZ, suggesting that the contribution of Methanophila and methanogenic to GDGTs increased, while the contribution of ammonia-oxidizing Archaea to GDGTs decreased at the SMTZ.展开更多
Cold seeps spread worldwide along the continental margins,which are closely related to the exploration of gas hydrates.Cold-seep carbonates have been reported to record the nature of seepage,including fluid source,sed...Cold seeps spread worldwide along the continental margins,which are closely related to the exploration of gas hydrates.Cold-seep carbonates have been reported to record the nature of seepage,including fluid source,sedimentary environment,and variation of seepage activity.We investigated the morphology,mineralogy,element compositions,and carbon and oxygen isotopes of 15 cold-seep carbonates collected from the Shenhu area,and compared them with 2 carbonates from the Haima cold seep,the South China Sea(SCS),to promote our knowledge of cold-seep system in SCS.Most of the Shenhu carbonates exhibit crust morphology,and some are in the form of chimneys and blocks.Their absolute(20%–65%)and relative carbonate mineral contents(mainly aragonite and calcite,with minor samples containing dolomite)vary significantly,indicating the multi-stage methane leakage in our study area.Some samples show a slight negative Ce anomaly,suggesting either the mixing of seawater or variation of the redox condition during the precipitation;the cooccurrence of strongly enriched U and Mo demonstrates anoxic condition during precipitation.The mixed genetic methane source was interpreted by δ^(13)C of the Shenhu carbonates to range from-22.34‰to-59.30‰Vienna PeeDee Belemnite(VPDB),and the slight ^(18)O-enrichment imprinted on the carbonates suggests the possible influence from hydrate dissociation.The Haima carbonates,with biogenic methane as the main gas source,were presumably formed in a stronger fluid flux by compared with our Shenhu samples.展开更多
基金supported by the Natural Science Foundation of China(Grant Nos.40672005 and 41776066)。
文摘A number of cold seeps have been discovered in the northern South China Sea(SCS) including the Haiyang 4 cold-seep area where Core 973-5 was collected. Intact polar lipids(IPLs) and core lipids(CLs) were analyzed separately in sediments from Core 973-5. The most abundant lipid biomarkers were isoprenoidal GDGTs(iso GDGTs), with Crenarchaeol and GDGT-0 predominating. IPL-iso GDGTs and CL-iso GDGTs were mainly derived from Thaumarchaeota. IPL-iso GDGTs were mainly produced and retained in situ thus containing most of the in situ microbiological information. Branched GDGTs were predominantly derived from generated in marine production, and mixed with some terrestrial inputs. All IPLs groups presented a high value in the sulfate-methane transition zone(SMTZ). Furthermore, IPL and CL-MI, IPL-R;showed the highest values within the SMTZ, while IPL and CL-R;had the lowest values at the SMTZ, suggesting that the contribution of Methanophila and methanogenic to GDGTs increased, while the contribution of ammonia-oxidizing Archaea to GDGTs decreased at the SMTZ.
基金Supported by the Guangdong Province Marine Economic Development(Six Major Marine Industries)Special Fund Project(No.[2021]No.58)the National Key R&D Program of China(No.2018YFC0310000)the National Natural Science Foundation of China(Nos.41776056,42076054)。
文摘Cold seeps spread worldwide along the continental margins,which are closely related to the exploration of gas hydrates.Cold-seep carbonates have been reported to record the nature of seepage,including fluid source,sedimentary environment,and variation of seepage activity.We investigated the morphology,mineralogy,element compositions,and carbon and oxygen isotopes of 15 cold-seep carbonates collected from the Shenhu area,and compared them with 2 carbonates from the Haima cold seep,the South China Sea(SCS),to promote our knowledge of cold-seep system in SCS.Most of the Shenhu carbonates exhibit crust morphology,and some are in the form of chimneys and blocks.Their absolute(20%–65%)and relative carbonate mineral contents(mainly aragonite and calcite,with minor samples containing dolomite)vary significantly,indicating the multi-stage methane leakage in our study area.Some samples show a slight negative Ce anomaly,suggesting either the mixing of seawater or variation of the redox condition during the precipitation;the cooccurrence of strongly enriched U and Mo demonstrates anoxic condition during precipitation.The mixed genetic methane source was interpreted by δ^(13)C of the Shenhu carbonates to range from-22.34‰to-59.30‰Vienna PeeDee Belemnite(VPDB),and the slight ^(18)O-enrichment imprinted on the carbonates suggests the possible influence from hydrate dissociation.The Haima carbonates,with biogenic methane as the main gas source,were presumably formed in a stronger fluid flux by compared with our Shenhu samples.
