scholarly journals Unique Authigenic Mineral Assemblages and Planktonic Foraminifera Reveal Dynamic Cold Seepage in the Southern South China Sea

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 275
Author(s):  
Yang Zhou ◽  
Pengfei Di ◽  
Niu Li ◽  
Fang Chen ◽  
Xin Su ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Gas Hydrate ◽  
Planktonic Foraminifera ◽  
Southern South China Sea ◽  
Globigerinoides Ruber ◽  
Δ13c Values ◽  
Methane Seepage ◽  
Mineral Assemblages ◽  
Authigenic Mineral

Many cold seeps and gas hydrate areas have not been discovered beside the Beikan basin in the southern South China Sea (SCS), and their characteristics and histories also remain poorly known. Here we describe authigenic minerals and the carbon and oxygen isotopic composition of planktonic foraminifera Globigerinoides ruber from sediment core 2PC, recovered from the gas hydrate zone of the Nansha Trough, southern SCS, to elucidate its history of dynamic cold seepage. We infer that the occurrence of authigenic gypsum crystals and pyrite concretions, and anomalously negative δ13C values of Globigerinoides ruber, reflect paleo-methane seepage. Two major methane release events were identified, based on remarkable excursions in foraminifera δ13C at depths of 150–250 cm and 350–370 cm. Euhedral gypsum crystals and tubular pyrite concretions co-occur with extremely negative planktonic foraminifera δ13C values, indicating a shift in the sulfate methane transition zone and a change in the methane flux. Our data suggest that authigenic mineral assemblages and δ13C values of planktonic foraminifera provide a valuable tool in elucidating the characteristics of dynamic methane seepage in a marine environment.

scholarly journals Cold-Water Corals in Gas Hydrate Drilling Cores from the South China Sea: Occurrences, Geochemical Characteristics and Their Relationship to Methane Seepages

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 742
Author(s):  
Yinan Deng ◽  
Fang Chen ◽  
Niu Li ◽  
Meng Jin ◽  
Jun Cao ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Gas Hydrate ◽  
Bottom Water ◽  
Cold Water ◽  
The South China Sea ◽  
Cold Seep ◽  
Authigenic Carbonates ◽  
Δ13c Values ◽  
Fluid Seepage

Cold-water corals (CWCs) are frequently found at cold seep areas. However, the relationship between fluid seepage and CWC development is not clear. Here, for the first time, we report the occurrences, species identification, mineralogy, carbon and oxygen isotopes, as well as elemental compositions of fossil CWC skeletons from gas-hydrate-bearing sediment in drilling cores from the South China Sea (SCS). Three sites (GMGS-08, GMGS-09B, and GMGS-16) were investigated but CWCs were only found at one site (GMGS-09B). Interestingly, the CWCs were found in three horizons and they were all embedded with authigenic carbonates. Three genera of fossil CWCs (Crispatotrochus sp., Solenosmilia sp. and Enallopsammia sp.) were identified. The CWC fragments are predominantly aragonite. The CWCs exhibit δ13C values between −8.4‰ and −0.6‰ that are significantly higher than δ13C values of the associated seep carbonates (δ13C values with an average of −55.6‰, n = 19), which indicates a carbon source other than methane for the CWCs. It appears that authigenic carbonates provide a substratum for coral colonization. Bathymetric high points, appropriate water temperature and stronger bottom-water currents at site GMGS-09B might be crucial to keep conditions favorable for the growth of CWCs in the studied area. In addition, high trace-element concentrations of Cr, Ni, Pb, U, Ba, Th, and Sr suggest that the CWCs are influenced by strong fluid seepage that can reach the water-sediment interface, and associated microbial activity. Hence, it also becomes evident that CWCs in hydrocarbon-rich seepage areas not only provide a critical constraint on the impact of fluid emission on the bottom water chemistry, but also are likely to be very precise recorders of the end time of cold seep activity.

Geophysical evidence for gas hydrate accumulation related to methane seepage in the Taixinan Basin, South China Sea

2018 ◽  
Vol 168 ◽  
pp. 27-37 ◽  
Author(s):  
Xiujuan Wang ◽  
Bo Liu ◽  
Jin Qian ◽  
Xin Zhang ◽  
Yiqun Guo ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Gas Hydrate ◽  
China Sea ◽  
Methane Seepage ◽  
Taixinan Basin

Methane seepage inferred from the porewater geochemistry of shallow sediments in the Beikang Basin of the southern South China Sea

2018 ◽  
Vol 168 ◽  
pp. 77-86 ◽  
Author(s):  
Junxi Feng ◽  
Shengxiong Yang ◽  
Jinqiang Liang ◽  
Yunxin Fang ◽  
Yulin He ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Southern South China Sea ◽  
China Sea ◽  
Methane Seepage ◽  
Shallow Sediments
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