Coal deformation, metamorphism and tectonic environment in Xinhua, Hunan

This paper discusses in detail chemical composition, molecular structure, microstructure phenomena, estimates the palaeo-stress, paleo-temperature and the strain rate to deepen the knowledge for the correlation of coal deformation and metamorphism with structural environment in Xinhua Hunan by coal quality analysis, XRD and SEM methods.The results show that d₀₀₂ value of coal samples is from 3.36 to 3.39 nm, coal changed gradually into aphanitic graphite with the increase of coal rank during coalification, which is characterized by graphite flakes, and the crystallite size is from 50 nm to 250 nm; A certain degree of 3R-structure content increased and the crystallite size extended with the coalification process, but Rh-structure content decreased; the tectonic environment of the study area belongs to the ductile-brittle deformation, which is characterized by low temperature, low stress, high strain rate; Tianlongshan magmatic intrusion provided heat source, its side-extrusion made the molecules structure of coal ordering, distance between layers decreased, finally it caused the formation of aphanitic graphite.