This poster will be presented at the joint meeting of the Canadian Society for Coal Science and Organic Petrology, The Society for Organic Petrology, and the International Committee for Coal and Organic Petrology at the University of Victoria, Victoria, British Columbia, Canada, on August 19-25, 2007.Changes in high-volatile bituminous coal (Pennsylvanian) near contacts with volcanic intrusions in Illinois were investigated with
respect to coal chemistry, carbon and hydrogen stable isotope ratios, and pore structure. Vitrinite reflectance (Ro) increases from
~0.6% to ~5% within 4.7 m from the dike. Elemental chemistry of
the coal shows distinct reduction in hydrogen and nitrogen content
approaching the intrusions. No trend was noticed for total sulfur
content, but decreases in sulfate and organic sulfur contents
towards the dikes indicate thermal sulfur reduction (TSR). Carbon
isotopic values did not show significant changes, whereas
hydrogen isotopic values showed a distinct trend of becoming
more negative toward the dikes. Contact metamorphism has a
dramatic effect on coal porosity. The mesopore volume decreases
3 3 from 0.01 cm /g in the unaffected coal to 0.004 cm /g at a distance
3 of 4.5 m away from the contact, then hovers around 0.004 cm /g
closer to the contact. In contrast, the micropore volume shows a
3 progressive decrease from 0.04 cm /g in unaffected coal to almost
3 0.01 cm /g at the contact. Strongly decreasing mesopore and
micropore volumes in the altered zone, together with frequent
cleat and fracture-filling by calcite, indicate deteriorating
conditions for both coalbed gas sorption and gas transmissibility
