Carbon and Oxygen Isotope Characteristics of the Growth Profile of a Seep Carbonate Chimney from the Northeastern Slope of the South China Sea and Its Formation Model
详细信息
- 责任者：Chen Xuanbo (Key Laboratory of Submarine Geosciences ; State Oceanic Administration ; Hangzhou 310012 ; China) ; Han Xiqiu
- 刊名：Acta Sedimentologica Sinica
- 出版年：2013
- 卷期：31(1)
- 关键词：碳酸盐岩 ; carbonate rocks ; 碳同位素 ; carbon isotopes ; 氧同位素 ; oxygen isotopes ; 南海 ; South China Sea
- 页码：p.50-55
- 图表：illus., 1 table, 29 refs.
- 分类号：0803
- issnNo：ISSN1000-0550
- isbnNo：CN62-1038/P
摘要
This chimney(TVG14-C1-1) was collected by SO177 cruise in 2004 from the northeastern Dongsha,South China Sea.It is composed of Mg-calcite.Author did high resolution sampling on a cross section of the chimney to analyze their C-and O-isotope compositions.Based on their mineral composition,we used carbonate-water fractionation equation to calculate the δ 18 O of the precipitating fluid and discussed the fluid sources.We showed that the δ 13C of the chimney varied from-50.14‰ to-43.92‰,and δ 18O from 2.76‰ to 4.85‰.From the inner to the outer, the δ 13 C increased gradually while δ 18O was decreaseing.The equilibrium δ 18O of the precipitating fluid were in the range of 1.2‰-2.3‰V-SMOW,which were significantly heavier than the modern seawater or glacial water.It is suggested that the water released from gas hydrate dissociation were responsible for the 18O enrichment.According to the two end-member mixing model,it was calculated that the precipitating fluid consisted of 53.6% gas hydrate water and 46.4% seawater during the precipitation stage of the inner layer.It got diluted gradually when it diffused into the sediments to form the outer layer,where the contribution of gas hydrate water decreased to 6.1%.Based on the growth structure and the variation of carbon and oxygen isotope composition,a growth model of the seep carbonate chimney was proposed.
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