塔里木盆地煤岩生物降解的生物标志化合物证据

Biomarker evidences of biodegradation for Jurassic coal in Tarim Basin

对塔里木盆地煤岩及显微组分中可溶有机质生物标志化合物的分析表明,正构烷烃、类异戊二稀烷烃、萜烷系列以及甾烷系列中均检测出一些代表煤岩发生生物降解的生物标志化合物。正构烷烃呈双峰分布,且∑n-C21-/∑n-C22+>1.0,同时检测出较丰富的三环二萜烷、四环二萜烷以及C32—C34苯并藿烷系列化合物。在低成熟样品中,甾烷C29-5αββ/(ββ+αα)值为0.59。通过对这些指标的综合分析,可以推断塔里木盆地满加尔凹陷煤系曾遭受较强烈的生物降解。煤岩遭遇细菌微生物降解时,最先降解的是惰质组,其次为镜质组,而壳质组中的正构烷烃不易受到细菌微生物降解。

The analysis on soluble organic matters from Jurassic coal and its maeerals in Tarim Basin showed that there were some biomarker evidences for biodegradation of Jurassic coal, such as n-alkanes, isoprenoids, terpanes and steranes. The mass chromatogram for n-alkanes was characterized by a bimodal distribution in relative proportions of mid-chain and long-chain n-alkanes and ratio of ∑n-C21- to ∑n-C22＋ above 1.0. In the GC-MS traces of the saturated hydrocarbons, some chemical compounds were identified, such as tricyclic diterpenoids （C19-C29） at low intensities, tetraeycloclicterpane and C32--C34-benzohopane. For the low mature coal samples, the ββ-to-（ββ ＋ αα） ratio was 0.59 and almost reached the equilibrium value. The comprehensive analysis of above features showed that there was a strong biodegradation of saturated hydrocarbon fractions in Jurassic coal rock in Manjiaer Depression of Tarim Basin. In the micro-process of coal rock, the rough biodegradation sequence is inertinite first and vitrinite is followed. The n-alkane on exinite is hard to be biodegraded.