Effects of rapid thermal alteration on coal: Geochemical and petrographic signatures in the Springfield (No. 5) Coal, Illinois Basin

摘要: Abstract Igneous intrusion into a coal bed can change the geochemical and petrographic properties of including vitrinite reflectance, maceral composition, optical texture, mineralogy, stable isotope trace element bulk geochemistry. The intent this study was to evaluate changes in an intruded compare them trends seen coals altered by normal burial maturation, thereby evaluating whether or not followed different maturation pathway. current reports petrographic, (proximate, ultimate), Leco total organic carbon (TOC), Rock-Eval pyrolysis data for suite samples from Springfield (No. 5) Coal (Pennsylvanian, Desmoinesian) southern part Illinois Basin where had been Permian-age peridotite dike. Petrographic analysis shows increase reflectance (Rm) background levels 0.55–0.63% up ~ 4.80%, loss ability differentiate liptinite macerals, formation isotropic coke and, at dike/coal contact, development fine-grained mosaic anisotropic texture. Volatile matter (VM) content decreases fixed (FC) content, ash, mineral (Parr formula) approaching contact. Carbon increases whereas nitrogen, hydrogen, oxygen decrease intrusion. presence carbonate minerals (confirmed X-ray diffraction analysis) has significant impact on proximate ultimate data. However, even after removal carbonates, VM vs. Rm, %C H C do follow typical associated with coalification. Approaching TOC, free oil (S1), remaining hydrocarbon potential (S2), CO2 (S3), hydrogen (HI) (OI) indices thermal maturity (Tmax, °C) increases. S2 Rm Tmax diverge pathways previous studies that have undergone maturation. Geochemical suggest may track differed under perhaps due geologically rapid, high heating event emplacement It is also suggested here natural textures produced rapid geological differ those observed metallurgical cokes standard industrial coking conditions. Typically, oven, initial rank (Ro = ~ 0.6%) would produce coke, rather than circular here. as variations rate, duration heating, maximum temperatures attained, hydrothermal conditions, pressure are mostly unknown intrusive event, it unreasonable differences these variables contributed higher anisotropy coke. Alternatively, texture reflect “pre-heating” during event.