Deformation metamorphism of bituminous and anthracite coals from China

Tectonic displacement of coal seams in China has resulted in faulting paral lel to coal bedding. Displacement along these faults caused significant com minution of the coal on the footwall contributing to various mining problem s, the worst of which is catastrophic failure, or "outbursting" of the work ing face during mining. The granular texture and mostly unconsolidated natu re of the coal suggests that faulting occurred relatively late in the coali fication sequence, at a time of maximum tectonic stress. Coal samples taken on either side of the fault plane (normal and deformed coal layers) were o btained in an effort to establish what influence these tectonic stresses mi ght have had on coal properties as well as what they might reveal about the influence of tectonic pressure on organic maturity. Sample sets were colle cted within coal beds from undisturbed and adjacent deformed layers, includ ing 21 bituminous samples from the Pingding-shan coal field and nine anthra cite samples from the Jiaozuo coal field, the Tieshenggou coal mine of the Yuxi coal field in Henan province, the Beijing Xishan coal field, the Baiji ao mine of the Furong coal field in Sichuang province and the Baisha coal f ield in Hunan province, China. Results from vitrinite reflectance, proximat e and ultimate analyses show some differences in reflectance, hydrogen cont ent and nitrogen content of anthracite coal. No significant difference was found between volatile matter yields of normal and deformed coal specimens. GC measurements of the saturated hydrocarbon fraction of chloroform extrac ts from bituminous coals showed that lower molecular weight carbon fragment s were concentrated in the deformed samples. Therefore, although changes in the gross chemical properties of the deformed coal were insignificant, som e modification of the chemical structure is seen to have occurred as a resu lt of exposure to tectonic pressure. (C) 2000 Elsevier Science B.V. All rig hts reserved.