Vitrinite Reflectance & Kerogen Microscopy

Kerogen Microscopy Awesomest Photo Ever

Trilete spores such as this can yield much information about a sample's thermal maturity and age.

Trilete spores such as this one can be used to determine a sample’s thermal maturity and age.

Preserved organic matter can also be used to determine thermal maturity in the absence of spores.

Preserved organic matter can also be used to determine thermal maturity in the absence of spores.

Rock samples are ground to pass a 40-mesh sieve and then treated with a 30-37% hydrochloric acid solution. After the reaction ceases, the samples are rinsed to neutral and treated with a 70% hydrofluoric (HF) acid solution. The sample is stirred intermittently for 24 hours, then the HF is carefully poured off and a second 70% HF allotment is added and the digestion repeated as before. The sample is then rinsed to neutral and the organic matter floats on a heavy liquid, is removed, and prepared as a kerogen slide (by fixing on the slide cover) and a vitrinite plug (by mixing the sample with epoxy, then drying and polishing it).  Examined under halogen light, the plug reveals the percentage of reflectivity of the vitrinite, which is then cross-referenced on the Thermal Alteration Index to determine the maturity of the sample’s source based on the color of the light, from pale yellow (immature) to black (very mature).  The kerogen slide is also subjected to further visual analysis, with the differing types of organic matter and spores present yielding additional information about thermal maturity, age, and depositional environment.