通过C27/C29甾烷和有机碳同位素来判断早古生代和前寒武纪的烃源岩的生物来源

在早古生代与前寒武纪的石油与源岩中,经常出现令人困惑的C29甾烷优势,而在有机地球化学中C29甾烷优势被认为是陆相有机质输入的标志。作者通过对比文献中各种海相藻类的热模拟产物分析,提出了早古生代与前寒武纪的石油与源岩中C29甾烷优势主要来源于浮游绿藻的观点,并通过C27甾烷/C29甾烷的比值提出了区分早古生代及前寒武纪石油源岩沉积环境的方法,对中国南方前寒武纪和早寒武世黑色岩系的有机地球化学分析也支持上述推断。此外,本文还提出了用有机碳同位素来进一步区分C29甾烷优势生物来源的方法。

BIOLOGICAL ORIGIN OF EARLY PALAEOZOIC AND PRECAMBRIAN HYDROCARBON SOURCE ROCKS BASED ON C27/C29STERANE RATIO AND ORGANIC CARBON ISOTOPE

The predominance of C_ 29 sterane in early Paleozoic and Precambrian rocks and crude oils is puzzling, because the predominance of C_ 29 sterane is often taken as the result of high terrestrial plant input. Based on mainly the previously published investigations on various algae pyrolytic products , we proposed that the predominance of C_ 29 sterane in early Paleozoic and Precambrian source rocks and crude oils may have come from planktonic green algae, and the different sedimentary environments can be distinguished through C_ 27/C_ 29 sterane ratios. The organic geochemistry results of Precambrian and early Cambrian black shales from South China support this conclusion. We also bring forward a new method to recognize the different biological source for C_ 29 sterane predominance using organic carbon isotope.