Title: Progresses on petrology, mineralogy and geochemistry of cold seep carbonates in the northern South China Sea
Abstract: Cold seep carbonates are known to be commonly developed in the northern South China Sea.Authigenic carbonate samples were collected from thirty sites in the region.These carbonates consist of concretions,nodules,chimneys,fragments or massive blocks.Mineralogically,the carbonates are dominated by aragonite and Mg calcite.However,a certain amount of dolomites are present in some samples.The carbon isotopic compositions(δ13CPDB) of the carbonates range from 29.6‰ to 13.3‰ in the Xisha samples,from 40.4‰ to 38.7‰ in the Shenhu samples,from 36.1‰ to 18.2‰ in the southwestern Dongsha samples,from 61.4‰ to 32.8‰ in the northeastern Dongsha samples,and from 57.6‰ to 35.7‰ in the southwestern Taiwan samples.The variable δ13C values indicate complex carbon sources that include 13C-depleted biogenic and thermogenic methane.A similarly large variability in δ18O PDBvalues(0.4‰ to 7.5‰) demonstrates 18O-enriched fluids possibly associated with dissociation of locally abundant gas hydrate.The shale-normalized REE(rare positive and negative Cerium anomalies,suggesting that the redox conditions changed significantly.Samples from different regions and from the same sites show variations in mineralogical,isotopic and elemental features,indicating that different regions,even the same sites,developed various seep fluids and gas hydrate stability.
Publication Year: 2012
Publication Date: 2012-01-01
Language: en
Type: article
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Cited By Count: 1
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