鄂尔多斯盆地不同沉积环境中煤系烃源岩重排藿烷的组成特征及其意义

Composition Characteristics and Significance of Rearranged Hopanes in Coal-bearing Source Rocks in Different Sedimentary in North Ordos Basin

鄂尔多斯盆地上古生界煤系烃源岩中重排藿烷类化合物异常丰富,经GC/MS分析,检测出17α(H)-重排藿烷系列相对丰度最高,这类化合物以C30重排藿烷为主峰,C29重排化合物次之,分布模式与正常藿烷类似。从烃源岩的生源构成、沉积环境的氧化还原性和有机质的热演化程度3个方面来探讨高丰度的17α(H)-重排藿烷的成因。研究表明,烃源岩中高丰度17α(H)-重排藿烷的母质来源可能是低等水生菌藻类弱氧化-弱还原、微咸水的扇缘泥炭沼泽相有利于高丰度17α(H)-重排藿烷形成;其形成不完全取决有机质的热演化程度。

The upper-Palaeozoic coal-bearing source rocks in north Ordos Basin were found to be extremely rich in rearranged hopanes. By GC/MS analysis, the highest relative abundance of rearranged hopane series is 17α（H）-diahopanes. The main peak of this class of compounds is the C30-diahopane. The abundance of C29-diaho- pane is lower than the abundance of C30-diahopane. 17α（H）-diahopanes show a similar distribution pattern with regular hopanes. The main controlling factors of extremely abundant 17α（H）-diahopanes are discussed from the composition of organic materials, maturity and oxidation reduction of depositional environments. The result shows the source of parent material of high abundance of 17α（H） -diahopanes in source rocks may be low aquatic alage. Weak oxidation to weak reduction and brackish weak fan marginal peat bog facies is beneficial to the high abun- dance of 17α（H）-diahopanes formation. The origin and accumulation of 17α（ H）-diahopanes do not entirely de- pend on the maturity of the organic matter.