The Springfield (No.5) coal, a Pennsylvanian-age high volatile B bituminous rank coal in the Carbondale Formation, is mined in the southeastern section of the Illinois Basin. intruded into this coal is a 10.1-m-wide basic dike that is near vertical through the extent of the mined coal bed, and strikes N 22 W, The intrusion and the effects it had on the coal were studied petrographically and geochemically. Using a published heat flow model by Carslaw and Jaeger (1959) [Carslaw, H.S., Jaeger, J.C., 1959. Conduction of Heats in Solids. Oxford University Press] in conjunction with thin-section microscope analysis, a contact temperature of similar to 600 C was determined, Vitrinite reflectance wits measured for a suite of coal samples collected distal to the intrusion. Vitrinite reflectance values rose Uniformly from the ambient reflectance values of similar to 0.69%, at just greater than one-dike thickness away. to similar to 5% at the dike/coal contact. The increase in reflectance values for samples within similar to 1.2 times dike thickness is concordant with data published by Bostick and Pawlewicz (1984) [Bostick, N.H., Pawlewicz. M.J., 1984. Paleotemperatures based on vitrinite reflectance of shales and limestones in igneous dike aureoles in the Upper Cretaceous Pierre shale, Walsenburg, Colorado. In: Woodward, J.G,, Meissner, F.F., Clayton, J.L. (Eds.). Hydrocarbon Source Rocks of the Greater Rocky Mountain Region, Rocky Mountain Association of Geologists, pp. 387-392] on the effects of mafic intrusions into Cretaceous-age, shales in Walsenburg, Colorado. Comparison of Colorado data with data from these sites indicates that, despite difterences in intrusion temperature, timing, or coal rank at time of the intrusion, ambient mean vitrinite reflectance values remain unchanged at just greater than one-dike width from an intrusion. (c)(c) 2005 Elsevier B.V. All rights reserved.