川东北固体沥青的有机地球化学

Organic Geochemical of Solid Bitumen from the Northeastern Sichuan Basin

采用选择性化学降解方法并结合多种有机地球化学测定手段对川东北固体沥青的成因进行研究。生物标志化合物参数和沥青反射率数据表明,此类固体沥青经历了相对较高的热演化程度。化学降解释放出的生标化合物以C16和C18一元脂肪酸为主,具有明显的偶碳优势,揭示这类固体沥青的母质可能以菌藻类低等水生生物输入为主。降解产物中还含有一定的正构烷烃及甾萜类化合物,与抽提物中的相应组分对比表明,它们可能具有相同的来源,但经历的热演化程度明显较抽提物中的组分偏低。单体碳同位素组成特征表明,这类母质可能形成于一个半深水—深水的沉积环境,单体氢同位素组成特征则揭示出是一个环境水为富D的海相环境。

Solid bitumen from the Northeastern Sichuan Basin is investigated by the present authors using selective chemical degradation combined with various organic geochemical analyses. Biomarker parameters and bitumen reflectivity indicate that the solid bitumen has experienced a relatively high thermal maturity. The facts that C16 and C18 fatty acids are the predominant biomarkers released by chemical degradation and fatty acids are of remarkable even-odd predominance suggest that the precursor of the solid bitumen may mainly derived from bacteria and algae input. The products of chemical degradation also contain some n-alkanes, steranoids and terpenoids. Comparison reveals that they possibly have same source as the corresponding components in the extracts of solid bitumen, but display a relatively lower thermal maturity than the latter. Carbon isotopic compositions of the individual compounds suggest that the precursor of the solid bitumen was mainly formed in a half deep water-deep water environment, and hydrogen isotopic composition indicates a possibly D-enriched marine environment.