对墨西哥湾北部水深2 200m 的Alaminos Canyon 645区块（AC 645区）和水深540m的Green Canyon 185区块（GC 185区）冷泉碳酸盐岩的有机质进行了研究，结果显示深水和浅水区冷泉碳酸盐岩的有机质丰度和烷烃组成差别较大，下陆坡深水AC区样品有机质含量低，正构烷烃、萜烷、甾烷各组分的含量相对较高，正构烷烃以低碳数占绝对优势，并含有种类丰富的三环萜烷和五环三萜烷，且以17α(H)，21β(H)-藿烷为主峰碳，反映了深水区冷泉碳酸盐岩的有机质来源于细菌和低等藻类，有少量的深部油气藏有机质的渗漏输入，并受微弱的微生物作用改造。上陆坡浅水GC区样品有机质含量较高，其中正构烷烃含量较低，并且以难以分开的复杂混合物(UCM)为主，同样含有种类丰富的以17α(H)，21β(H)-降藿烷为主峰碳的三环萜烷和五环三萜烷，表明有机质主要来源于深部油气藏渗漏的有机质，并遭受了强烈的微生物降解。本文系统地研究了冷泉碳酸盐岩中正构烷烃、萜烷、甾烷的组成和分布特征，并探讨了有机质来源和冷泉渗漏的关系。

The authors report the organic matter in seep-carbonates from the block GC 185 (Sample GC-F) of the upper slope and the block AC 645 (Sample AC-E) of the lower slope of Gulf of Mexico, where water depth is 540 m and 2200 m, respectively. Their results show that both organic contents and alkane compositions are different between Samples AC-E and GC-F. Sample AC-E has low organic content, with relatively high fraction contents of normal alkanes, steranes and terpanes. It is dominated by low molecular weight alkanes and also with kinds of tricyclic terpanes and pentacyclic triterpanes that are maximized at 17α(H)，21β(H)-hoptane, indicating that the organic matter of the lower slope (Sample AC-E) mainly originated from bacteria and marine algae, with a little hydrocarbon seep from the underlying reservoir and slight microbial degradation. Sample GC-F has higher organic content, but its content of normal alkanes is low with mainly unresolved complex mixture (UCM). It also has kinds of tricyclic terpanes and pentacyclic triterpanes that are maximized at 17α(H)，21β(H)-nor-hoptane, suggesting that the organic matter of the upper slope (Sample GC-F) is microbial-degraded and mainly from seep hydrocarbon of the underlying reservoir. They also investigate the composition and distribution of normal alkanes, steranes and terpanes in seep carbonates, and discuss the relationship between organic matter source and cold seep.

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