干酪根化学降解产物的碳同位素组成研究

采用一系列温和的化学降解法对松辽盆地南部嫩江组烃源岩的干酪根进行连续的选择性化学降解，并对不同降解产物进行色谱—同位素比值质谱分析。研究表明碱性水解和脱硫产物以一元脂肪酸和正构烷烃为主，其中正构烷烃碳同位素分布曲线呈现一定的“负倾”（即随碳数增加呈现逐渐贫13C）趋势；一元脂肪酸以C16和C18为主，具有明显的偶碳优势，与同碳数的正构烷烃具有相似的碳同位素组成。氧化产物则以一元脂肪酸和α,ω 二元脂肪酸为主，一元脂肪酸低碳数部分呈现“负倾”趋势，高碳数部分则呈现“正倾”的趋势；α,ω 二元脂肪酸与低碳数的一元脂肪酸具有相似的分布，表明它们可能具有相同的母源。对比研究表明JL 30抽提物中正构烷烃可能存在混源的影响，其碳同位素组成是多源混合的结果。

Carbon Isotopic Compositions of Kerogen Chemical Degradation Products

A sequential selective chemical degradation was performed for the kerogen from the Nenjiang Formation of the southern Songliao Basin by using a series of mild chemical degradations. Subsequently, GC MS analyses were carried out for different degradation products. The results show that products of alkaline hydrolysis and desulfurization mainly comprise monocarboxylic acids and n alkanes. The carbon isotope curve of n alkanes displays a “negative sloping” (i.e. gradually depleted in 13C with increasing carbon number). Monocarboxylic acids, mainly including C16 and C18 acids, have an obvious even carbon numbered predominance. Their carbon isotope compositions are similar to those of the corresponding n alkanes with same carbon number. Monocarboxylic acids and α, ω dicarboxylic acids are the dominant products of RuO4 oxidation. Carbon isotopic composition of monocarboxylic acids fall between －28.3% and －33.7‰, and a "negative sloping" is shown in the range of light carbon number, while a “positive sloping” in high carbon number part. δ13C values of α,ω dicarboxylic acid is similar to those of monocarboxylic acids in the range of light carbon number, indicating that they have the same source. The comparison shows that the n alkanes in the extracts from sample JL 30 possibly have the mixing of other sources, and their carbon isotopic compositions present the mixing characteristics.