Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (1): 439-448.DOI: 10.13745/j.esf.sf.2020.12.11

Previous Articles     Next Articles

Control of coal metamorphism by tectonic physicochemical conditions

CAO Daiyong1(), LIU Zhifei2, WANG Anmin1, WANG Lu3, DING Zhengyun1, LI Yang1   

  1. 1. College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
    2. Mine Safety Technology Branch, China Coal Research Institute, Beijing 100013, China
    3. Department of Geological and Surveying Engineering, Shanxi Institute of Energy, Jinzhong 030600, China
  • Received:2020-04-15 Revised:2020-08-14 Online:2022-01-25 Published:2022-02-22

Abstract:

Coal is an organic rock very sensitive to geological factors such as temperature and pressure, and the physicochemical conditions associated with various tectonic thermal events are the fundamental driving force promoting the evolution of coal. In this paper, the current research status of coal metamorphism is reviewed; the control factors and evolutionary process and mechanism of coal in the stage from high rank coal to graphite are emphatically discussed. Coal metamorphism includes coalification stage and graphitization stage, which together constitute a continuous organic matter evolution process. The general trend of evolution is chemical constituents progressively simplifying and structure ordering, finally the graphite with three-dimensional ordered structure is evolved. Temperature and pressure (shear stress) are two major factors controlling coal metamorphism, their functions and evolution mechanism are different in different evolution stages. In the low and middle rank evolution stage, temperature is the main controlling factor of coal chemical structure evolution, which provides activation energy for chemical bond fracture, while stress polycondensation and stress degradation have catalytic effect on chemical structure evolution. The main mechanism from the high rank coal to graphite is that the basic structural units (BSUs) are interconnected and the short-range ordering range is increased,structural stress plays a key role in the evolution of the physical structure of macromolecules, it will promote the physical structure evolution of macromolecules by the orientation arrangement of BSUs and the distance decrease of carbon layer. It will enrich and deepen the understanding of the complete evolution sequence of the physical and chemical structure of coal by strengthening the research on the stage from high rank coal to graphite, the high-temperature and high-pressure simulation experiment of the coal-based graphite forming mechanism provides a feasible technical means for the study of the physical and chemical conditions of coal metamorphism.

Key words: coal metamorphism, coalification, graphitization, tectonic physicochemical, evolution mechanism

CLC Number: