A kinetic model for the thermal evolution of sedimentary and meteoritic organic carbon using Raman spectroscopy

摘要

Small samples of Murchison meteorite were flash pyrolysed at a range of temperatures (250- 1000degrees centigrade) for short durations (10-80s). Raman spectroscopic analysis of the feedstock-pyrolysate revealed that with increased level of thermal alteration the R1 parameter (also known as the ID/IG and D/O ratio) increased in value. This appears to be a phenomena unique to low levels of thermal alteration and is most easily observed in homogeneous materials. An empirically derived kinetic model of the rise of the R1 parameter was obtained from the experimental data and used to successfully reproduce field measurements and experimental work from a number of short duration high temperature heating events. Results indicate that the use of this parameter and its predictor equation are limited to levels of thermal alteration less than that associated with the end of the oil window and the onset of condensate formation. It is also limited to situations where durations of heating are short. Even within these boundaries a high level of variation is observed in data from all settings which can make the parameter imprecise.