Rare earth element and Yttrium (REY) geochemistry of Cenozoic carbonates on the Xuande Atoll of the Xisha Archipelago, the South China Sea: Implications of the impact of dolomitization on REY

2017 ◽  
Vol 51 (6) ◽  
pp. 507-523
Author(s):  
Zhenfeng Wang ◽  
Keke Huang ◽  
Daojun Zhang ◽  
Xinyu Liu ◽  
Wei Luo ◽  
...  
Keyword(s):  
Rare Earth ◽  
South China Sea ◽  
Rare Earth Element ◽  
South China ◽  
Earth Element ◽  
The South China Sea ◽  
China Sea ◽  
Xisha Archipelago ◽  
The Impact ◽  
Rey Geochemistry

scholarly journals Formation of Tubular Carbonates within the Seabed of the Northern South China Sea

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 768
Author(s):  
Yuedong Sun ◽  
Jörn Peckmann ◽  
Yu Hu ◽  
Xudong Wang ◽  
Shanggui Gong ◽  
...  
Keyword(s):  
Rare Earth ◽  
South China Sea ◽  
Rare Earth Element ◽  
South China ◽  
Earth Element ◽  
Anaerobic Oxidation Of Methane ◽  
Fluid Migration ◽  
Bottom Currents ◽  
China Sea ◽  
Carbonate Formation

A remarkable exposure of tubular authigenic carbonates was found on the seafloor in the Dongsha area of the South China Sea (SCS). The tubular carbonates, around 2–3 cm in diameter and usually less than 10 cm in length, represent broken fragments of once-larger pipes that now protrude from muddy sediments. The morphology, carbon and oxygen stable isotope compositions, and trace and rare earth element contents of the carbonates were analyzed to decipher the mode of carbonate formation. The tubular carbonates exhibit a dark brown coating of iron and manganese hydrous oxides, indicating prolonged exposure to oxic bottom waters. The carbonate content of the micritic pipes falls between 12.5 and 67.3 wt.% with an average of 42.0 wt.%, suggesting formation within the sediment. This inference is supported by trace and rare earth element patterns including a moderate enrichment of middle rare earth elements. Low δ13C values (as low as −50.3‰, Vienna Pee Dee Belemnite (VPDB)) suggest that carbonate precipitation was induced by the anaerobic oxidation of methane. The unusually positive δ18O values of the carbonates (as high as +5.3‰, VPDB) are believed to reflect the destabilization of locally abundant gas hydrate. Taken together, it is suggested that pipe formation was initiated by sediment-dwelling organisms, such as crustaceans or bivalves. The burrows subsequently acted as conduits for upward fluid migration. The lithification of the sediment directly surrounding the conduits and the partial filling of the conduits with carbonate cement resulted in the formation of tubular carbonates. Turbidity currents, sediment slumps, or the vigorous emission of fluids probably induced the fragmentation of tubular carbonates within the sediment. The carbonate fragments had been further subjected to winnowing by bottom currents. This study provides insight into the interaction of megafauna burrowing with fluid migration and carbonate formation at hydrocarbon seeps, highlighting the role of bottom currents and mass wasting on the formation of fragmented tubular carbonates.

scholarly journals The Current Environmental Situation and Green Solutions for Vietnam's East Sea

2019 ◽  
Vol 4 (9) ◽  
pp. 70-74
Author(s):  
Thi Minh Hao Dong ◽  
Huu Cuong Le ◽  
Thanh Hai Truong
Keyword(s):  
Climate Change ◽  
South China Sea ◽  
South China ◽  
Natural Capital ◽  
Action Plan ◽  
The South China Sea ◽  
East Sea ◽  
The South ◽  
China Sea ◽  
The Impact

The South China Sea, including the Vietnam Sea, is witnessing significant changes under the impact of both nature and man. These are the impacts of climate change and ocean change with "extreme" signs such as increasing storms, coastal floods, sea level rise, sea acidification, pollution and environmental incidents, ... occur thicker, more intense and irregular. Especially serious degradation of the environment and biodiversity of the sea, increasing environmental incidents, including oil spills, ... due to human impact. Especially the large-scale destruction of coral reefs, seagrass beds in island clusters off the South China Sea has been happening at a worrying rate. The destructive fishing activities of humans in the South China Sea have caused ecosystem degradation and the extinction of some species, such as sea turtles, some sharks and another species. Other fish, especially the giant mussel, the consequence is a decrease in the natural capital of the sea, leading too prolonged "ecological disturbances". The reserves of seafood in the Spratly region (of Vietnam) and the West Sea in the East Sea have decreased by about 19% compared to before 2017. Therefore, the improvement of marine environment quality, including biodiversity conservation and major marine ecosystems are to preserve marine natural assets, contributing to the implementation of Vietnam's green growth strategy and action plan. This is the path that Vietnam has chosen to both grow marine economy, adapt to climate change, and protect the environment both in the short and long term, towards sustainable development.

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