A natural pyrolysis experiment — hopanes from hopanoic acids?

The formation or generation of hopanes are important processes during both the natural heating of organic-rich sediments and laboratory pyrolysis experiments. Molecular maturity parameters as well as the amounts (ng/g rock) of the C31 hopanes and C30–C32 hopanoic acids were quantified in a Jurassic silty shale horizon (Isle of Skye, Scotland) as a function of distance from an igneous intrusion. The maturity profiles of the homohopanes and the hopanoic acids are comparable. There is also a correlation between the decreasing amounts of C30–C32 hopanoic acids and concomitant increases in C29–C31 hopanes suggesting that free hopanoic acids could be one potential source of hopanes in this particular horizon. Other possible sources could include hopanoic acids that are bound into the macromolecular fraction.