STABLE ISOTOPE GEOCHEMISTRY OF A MIDDLE PENNSYLVANIAN COAL
The present study is undertaken to evaluate the controls on carbon isotope variability in macerals from Illinois coals. We separated macerals by using density-gradient centrifugation techniques. In this way we were able to concentrate relatively pure macerals within a single coal (purities up to 99%) and measure their isotopic composition.
Our preliminary carbon isotope results of macerals separated from an individual sample of the Springfield No. 5 coal show that significant differences exist among macerals. We measure an increase in ä13C values from liptinites (ä13C resinite = -27.2 and ä13C sporite = -26.9 ) to inertinites [ä13C fusinite = -25.3 and ä13C semifusinity = -25.2 ] and finely to vitrinites (ä13C vitrinite = -24.9 ). These results confirm previous findings that significant isotope differences exist among different macerals within a single coal, likely recording the original composition of plant tissues from which the macerals originated and the changes that occur during coalification.