The tectonic framework and controlling mechanism of coal-based graphite in Lutang mining area, Hunan Province

Lutang mining area, one of the famous coal-based graphite mining areas in China, is controlled by both the magmatic intrusions and tectonic activities. Both the graphitization of coal and occurrence are closely related to the tectonic framework. To study the influence of tectonic activity on the formation of coal-based graphite, based on the filed geological survey, observation under microscope, X-ray diffraction and Raman spectroscopy experiments, structural characteristics of the research area and characteristics of coal-based graphite were analyzed. The effect of structural control of ore on the coal-based graphite was discussed in this paper. The tectonic framework of the study area is characterized by divisional and zonal structure due to the influence of regional tectonic activities. Three belts along the EW direction and three zones along the NS direction were divided separately. From the west to the east, the graphitization degree gradually increases with the decreasing distance from the intrusion. From the south to the north, the tectonic deformation degree is enhanced, resulting in the closed metallogenic environment in the northern zone which has high temperature and high pressure; moreover, tectonic stress promoted the coal graphitization, causing higher graphitization degree of coal. The complex tectonic condition in the central zone developed different temperature and pressure environment, which induced different graphitization degree of coal. In the southern zone, simple tectonic conditions tended to form open environment with the result of poor graphitization degree of coal. Semi-graphite occurs only occurred near the intrusion. The research provides a strong and convincing evidence for the exploration of coal-based graphite.