关键词: 南海东部, 沉积物, 有机质, 天然气水合物, 奇偶优势指数, 多环芳烃, 正构烷烃, 地球化学特征

Abstract: The organic matters in the sediment core sample HD196A obtained from the eastern South China Sea were measured with GC and GC-MS techniques.More than 90 types of hydrocarbon compounds including n-alkanes,isoprenoid,branched alkanes and polycyclic aromatic hydrocarbons (PAHs) were identified.The HD196A-30 in the middle core sample and HD196A-55 near the bottom of the core sample were analyzed.The distribution curve of n-alkanes,the range of carbon chain,the position of main peaks and the values of CPI and OEP show that the organic matters in the sediments are the mixtures of terrestrial plants,marine phytoplankton algae and bacteria.The organic matters from terrestrial plants are dominated.The organic matters in the sediments are matured in this area.Squalene was identified in the core sample,which showed that biological methane synthesizing and bacteria function occurred in this area.The ubiquity of phenanthrene series,chrysene series compounds,perylene and retene compounds in the sediment indicated that PAHs mainly came from the terrestrial plants.Abundance of perylene designated the fast accumulation of terrestrial organic matter and reductive condition.The geological background and the analysis result showed that HD196A site had the conditions of gas source,temperature and pressure to form gas hydrate.The sampling site fits quite well to the area with high anomalies fueled by hydrocarbon seep,which indicates that this area is favorable for exploration of oil,gas and gas hydrate.

Key words: eastern South China Sea, sediment, organic matter, gas hydrate, odd-even predominance value, polycyclic aromatic hydrocarbon, n-alkane, geochemical characteristics