Composition And Optical Property Evolution Of Macerals In Meta-Anthracite From Yongan,Fujian,China

Meta-anthracite may have natural advantages in preparing the raw material of graphene.Meta-anthracite in Fujian province accounts for about 97% of the coal resources in the whole province.Unique history and geological condition of coalification creates a natural laboratory to carry out studies on the conversion of coal to graphite.In this paper,therefore,we take Tongziyan Formation of Middle Permian Series as the object to analyze the maceral features of meta-anthracite,to study the evolution law of maceral reflectance,to discuss the deformation mechanism of maceral structure and finally to gain systematic knowledge.We find that apart from the original macerals of meta-anthracite,the derived nascent(secondary)macerals with a series of strong optical changes constitute the unique maceral types of meta-anthracite.The original macerals of meta-anthracite has different evolution rates and degrees,where,the evolution of the exinite precedes the one of the vitrinite,and the inertinite lags behind.The optical anisotropy of the nascent macerals is significantly different.It can be seen the anisotropy of flow structure and the graphite-like body generated from the epigenetic fissure.The results show that the maximum reflectivity of the exinite is higher than that of the vitrinite,and the inertinite is the lowest in original macerals,optical properties are "reversed" compared to low to medium coal.The minimum reflectivity and bireflectance of all kinds of macerals "reversed" with the increase of the maximum reflectivity of vitrinite,and the turning point position corresponds to the rate of evolution of macerals.It is suggested that graphitization process and graphitization degree of different macerals are not alike.The reflectivity parameters have a common rule in the same macerals,the difference among different macerals is obvious,corresponding to the jumps and stages of metraanthracite.The evolution of macerals is controlled by the formation temperature,pressure,coal-forming environment and the type of coal-forming parent material.the structure of coal is obviously transformed into long-range ordered graphite structure,making-up action is an important mechanism of its evolution.