altered by rapid heating events (i.e., those intruded by dikes and sills) are thought to follow a different geochemical maturation pathway than coals altered through diagenesis. If an igneous intrusion alters the petrographic and geochemical properties of a coal, the effect should also be observable in the coal's molecular structure. In this study, we evaluate whether coals altered by rapid heating follow distinct maturation trends from coals that were altered by slower heating (burial maturation). Petrographic, geochemical, and micro-FTIR analyses were performed on a series of Pennsylvanian Illinois Basin coal samples, collected at various distances from a Permian igneous dike. Standard coal characterization techniques including vitrinite reflectance and proximate and ultimate analyses provide valuable insights on the maturation pathways experienced.by rapidly heated coals. These techniques were coupled with reflectance micro-FTIR to provide a better understanding of the molecular changes that occur in the coal structure during relatively short-lived, intensive heating events. With decreasing distance to the intrusion, coals have higher mean random vitrinite reflectance values (R-r) within the dike alteration zone. Coking textures similar to those observed in industrial cokes are observed within 2 m of the intrusion. Geochemical data for HCl-treated coals indicate an overall loss of H, 0, and N and an increase in C approaching the dike. Intruded coals have higher volatile matter (VM) yields at high rank than coals of similar rank that result from normal burial maturation. When plotted on a van Krevelen diagram or Seyler chart, intruded coals follow different coalification trends than coals matured through normal burial diagenesis. Reflectance micro-FTIR analysis of collotelinite shows increased aromaticity with rank: both the ratio of the aromatic CH stretching band at similar to 3100-3000 cm(-1) versus the aliphatic CHx stretching bands between 3000 and 2800 cm(-1) (AR1), and the ratio of the aromatic out-of-plane deformation bands between similar to 900-700 cm(-1) versus the aliphatic CHx band (AR2) increase with increasing R-r. Within the 3000-2800 cm(-1) region, there is an increase in the area under the asymmetric CH3 peak at similar to 2960 cm(-1) relative to the asymmetric CH2 peak at similar to 2920 cm(-1) with increased rank. Within the 900-700 cm(-1) region, the overall intensity of the similar to 750 cm(-1) peak (aromatic rings with four adjacent H atoms) relative to the similar to 870 cm(-1) peak (aromatic rings with one isolated H atom) increases up to 2.5%R-r, likely reflecting a lower degree of substitution (DOS) of alkyl groups on aromatic ring sites. The prevalence of the 750 cm(-1) peak at high rank may represent a lower degree of condensation of aromatic rings in the structure of intruded coals compared to normally matured coals. (C) 2016 Elsevier B.V. All rights reserved.