沉积有机质中稳定碳同位素逆转现象初探

本文研究了沉积有机质的可溶部分（抽提物）和不溶部分（干酪根）及抽提物的族组分（饱和烃、芳烃、非烃、沥青质）的碳同位素组成特征。通过其δ13C的分布为:干酪根>抽提物;沥青质 >非烃 >芳烃 >饱和烃。研究表明由于生源物质的不同,沉积环境的差异可构沉积有机质碳同位素组成异常。如非烃 >沥青质 >芳烃 >非烃、本文称为沉积有机质碳同位素局部逆转。当沉积有机质可溶部分>干酪根时,称之为总体逆转。湖沼相或河间湖相高等植物来源常为正常组或型;经细菌强烈改造生源以高等植物为主有低等生物为类脂组分加入常形成局部逆转的碳同位素组成。总体逆转则常现于有机质演化程度很高的海相沉积岩中。

Preliminary Study on the Reversed Distribution of Stable Carbon Isotopes in Sedimentary Organic Matter

In the present paper, the distribution of carbon isotopes of sedimentary organic matter are studied in the aspects of soluable portion (i.e., abstracts) and insoluble component (i.e., kerogen) as well as in the groups of EOM (i. e. , saturated hydrocarbon, aromatic hydrocarbon, non- hydrocarbon and asphaltene), results show that the distribation of δ~(13)C value are as follows: it is higher in kerogen than in abstracts, and for the abstracts, it decreases in the proper order of asphaltene, non-hydrocarbon, aromatic hydrocarbon and saturated hydrocarbon. The study revealed that different sedimentary environment that fed by different biologic group may resulted in the abnormal distribution of carbon isotopic composition, for instance, it may be havier in non-hydrocarbon than in asphaltene, and aromatic hydrocarbon havier than non-hydrocarbon, the authors defined these phenominon as partially reversed carbon isotopic distribution of sedimentary organic matter; and if the carbon isotop is havier in soluble sedimentary organic matter than in kerogen, it would be called as totally reversed distribution. Normal carbon istopic composition are usually found in higher plant input limnetic facies and interfluval lacustrine, Partially reversed distribution is usually found in the facies that input mainly by higher plant but suffered intensivly bacterial action and input also by lipid of lower biomass. Totally reversed carbon isotopic distribution is often found in marine sedimentaty rocks that with a very high evolution degree of organic matter.