摘要
Extended 17α(H),21β(H)-hopanes and three series of 8,14-secohopanes up to C_(40),including 8α(H),14α(H),17α(H),21β(H)-,8α(H),14α(H),17β(H),21α(H)-and 8α(H),14β(H),17β(H),21α(H)-,were detected by GC-MS-MS method in the branched/cyclic hydrocarbon fractions of some unbiodegraded marine oils from the Tazhong uplift in the Tarim Basin,NW China.The coexistence of extended hopanes and 8,14-secohopanes up to C_(40)in unbiodegraded oils suggests that they are primary and independent on biodegradation.The similarity of distribution and composition for extended hopanes and 8,14-secohopanes up to C_(40)in unbiodegraded oils proposes that they could be derived from a similar biological precursor.However,an abrupt decrease up to 3-5 times in the relative abundance from C_(35)to C_(36)in C_(31-40)extended hopanes and extended 8,14-secohopanes suggests that C_(31-35)and C_(36-40)extended hopanes and extended 8,14-secohopanes should have their own biological precursor.The known C35bacteriohopanetetrol should be biological precursor of C_(31-35)extended hopanes and 8,14-secohopanes,but an unknown C_(40)functionalized hopanoid could be biological precursor of C_(36-40)extended hopanes and 8,14-secohopanes.More attention should be paid to their potential roles in oil-source correlation for severely biodegraded oils based on their widespread occurrence in various source rocks,unbiodegraded and severely biodegraded oils.
基金
financially supported by the National Natural Science Foundation of China(Grant No.41772119 and 41272169)
