沉积物和原油中重排藿烷的生物来源和成因机制
摘要
Rearranged hopanes have gradually been reported in sediments deposited in various sedimentary environments and related crude oils, but their biological origins and formation mechanisms are still controversial.In this paper it systematically identified four types of rearranged hopanes in the Mesoproterozoic Xiamaling black shales and Jurassic lacustrine crude oils.Based on the relationship between the relative abundance of rearranged hopanes and their biosynthetic reaction schemes, it is proposed that their relative abundance and generation rate are mainly controlled by the biological origins and times of methyl rearrangement reaction.The formation process of early eluting rearranged hopane and 28-nor-spergulanes is more complicated than that of 17 α (H)-diahopane, which makes their distribution in sediments and crude oil more limited.In addition, 18 α (H)neohopane can not only be derived from the bacteriohopanetetrol of prokaryotic organisms, but also from diplopterol and/or diploptene, so it is widely distributed in geological samples.Importantly, although sediments and crude oils rich in rearranged hopanes are frequently reported, they may not originate from ubiquitous prokaryotic bacteria, but may only exist in a small number of bacterial communities living in a specific environment.