【摘要】 天然气水合物是一种赋存在低温、高压条件下海底沉积物中的规模巨大的新型能源。研究表明,地球化学是识别海底天然气水合物赋存的一种有效方法。国际上通过分析由大洋钻探采上来的柱状沉积物和孔隙水的地球化学异常,己建立了一套较为成熟的地球化学识别方法。但是,在没有钻井岩心的情况下,如何通过浅表层(<20m)沉积物和孔隙水及底层海水的地球化学分析来识别海底可能存在的天然气水合物,是国际国内天然气水合物勘查中面临的一道难题。通过对国际上己有数据和资料的全面总结,尝试提出了一系列在海底浅表层条件下识别天然气水合物赋存的地球化学异常标志,包括底层海水的烃类气体及其同位素组成异常,沉积物中有机碳和水的含量异常,沉积物中孔隙水的元素和同位素组成异常,沉积物中气体含量异常及沉积物中自生碳酸盐矿物的化学和同位素组成异常等。这些标志的建立将有助于在我国海域开展天然气水合物的勘查工作。更多还原

【Abstract】 Gas hydrate is a new type of potential energy that occurs within marine sediments under lowtemperature and highpressure conditions. Recent researches have revealed that geochemical method is an efficient way to indicate the gas hydrate occurrence in marine sediments. According to sediment and pore water samples collected from ODP drill cores, a series of geochemical anomalies have been identified which are related to the existence of gas hydrates in deep marine sediments.However, difficulties still remain to use geochemical analysis of very shallow marine sediments and pore waters in exploring gas hydrates at places where no ODP drill cores are available. In this paper, we use available data from literatures and point out a series of geochemical anomalies that may have been caused by gas hydrates and can be used to assist gas hydrate exploration. These anomalies include ① anomaly of gas contents and their isotopic compositions in bottom seawater, ② anomaly of organic carbon and water contents in shallow marine sediments, ③ anomaly of element and isotopic compositions of pore water, ④ anomaly of gas contents in marine sediments, and ⑤ occurrence of authigenic carbonates and their carbon and oxygen isotopic composition anomaly. All these anomalies recognized in shallow marine sediments may help us search gas hydrates in the South China Sea.更多还原