煤成石墨化作用的构造应力控制机理研究

Coal-formed graphite, also known as graphite in coal-bearing strata, is the main type of cryptocrystalline graphite and accounted for about 40% of graphite resources in China, belongs to the emerging strategic minerals. Coal-formed graphite was generally considered to be the product of contact thermal metamorphism, and the research of its formation condition was focused on the temperature factor, but the study of tectonic influence was relatively lacked of, which severely hindered the complete understanding of the graphitization of coal. From the coalfield structure characteristics and coal metamorphism types in China, and based on the research results of deformed coals and carbon materials graphitization in metamorphic rocks, Hunan Lutang and Southwest Fujian as the typical cryptocrystalline graphite deposits in coal-bearing strata, will be deeply studied on the metallogenic mechanism of coal-formed graphite, to investigate the relationship between macro-micro deformation of coal and degree of graphitization, to identify the differential graphitization characteristics and their controlling geological factors. The High temperature and high pressure simulation experiments of meta-anthracite and semi-graphite samples will be carried out to experimentally establish the quantitative correspondence between the molecular structure ordered evolution of coal-formed graphite and the conditions of temperature and pressure. Through comparative analysis of typical geological examples and simulation experiments, the mechanism of tectonic stress control on the graphitization of coal will be revealed, and the metallogenic model of coal-formed graphite will be established, to provide the scientific basis for identifying the occurrence regularity of coal-formed graphite and evaluation and reasonable exploitation of coal-formed graphite resources.

煤成石墨又称煤系石墨，是隐晶质石墨的主要类型，其潜在资源量占我国石墨资源总量的40%左右，属于战略性新兴矿产。煤成石墨通常被认为是接触热变质的产物，其形成条件研究多注重温度因素，但构造影响研究却相对较薄弱，从而严重阻碍了对煤成石墨化作用的全面认识。本项目从中国煤田构造特征和煤变质作用类型出发，借鉴构造煤和变质岩中碳物质石墨化作用研究成果，选择湖南鲁塘和福建闽西南两处典型煤系隐晶质石墨矿区深入进行石墨成矿机制研究，探讨煤岩宏/微观变形与石墨化程度的关系，查明差异石墨化作用特征及其地质控制因素；开展高变质无烟煤和半石墨样品的高温高压模拟实验，从实验角度建立煤成石墨大分子结构有序度演化与温/压条件的定量关系；通过典型地质实例与模拟实验的对比分析，揭示构造应力对煤成石墨化作用的控制机理，建立煤系隐晶质石墨成矿模式；为查明煤系石墨赋存规律、开展资源评价和合理开发利用提供科学依据。

煤成石墨又称煤系石墨，是隐晶质石墨的主要类型，属于战略性新兴矿产。煤成石墨通常被认为是接触热变质的产物，其形成条件研究多注重温度因素，但构造影响研究相对较薄弱，从而阻碍了对煤成石墨化作用的全面认识。本项目从中国煤田构造特征和煤变质作用类型出发，采用典型型煤系石墨矿区实例研究与煤石墨化模拟实验相结合的技术路线，深入开展石墨成矿机制研究，揭示构造应力对煤成石墨化作用的控制机理，建立煤系隐晶质石墨成矿模式。取得以下重要成果：.（1）查明了煤石墨化结构演化规律，煤石墨化的实质是大分子结构由无序向有序转化、晶体结构结晶度增加和缺陷消亡的过程，经历晶格构建预备、雏晶形成、晶格生长优化等3阶段，演变为三维有序结构的石墨矿物。（2）煤石墨高温和高温高压实验证实了构造应力在石墨结构形成过程中具有显著的催化作用，并发现石墨结构演化的温度-压力耦合效应，提出应变诱导石墨化机制。（3）探讨了显微组分大分子结构演化差异性及其动力学机制，高温热模拟实验显示惰质组存在石墨化启动阈值，惰质组属于动力学控制下的石墨化进程，镜质组属于热力学控制下的石墨化进程。（4）发现煤系石墨具有矿物学和岩石学或矿石学双重属性，据此建立了煤系石墨分类分级体系；以成矿机制研究和实测数据统计分析结果为依据，制定了科学合理的煤系石墨鉴别指标。（5）建立了煤石墨化成矿模式，根据煤系石墨成矿控制因素，将成矿构造-热环境归纳为封闭式、半封闭-半开放式和开放式等3种基本类型。（6）提出煤系石墨找矿方向（找矿标志），划分了全国煤系石墨成矿区带，包括5个成矿域和11个成矿带。（7）在国内外期刊发表学术论文共20篇，其中，SCI收录5篇、EI收录5篇、北大中文核心期刊6篇；学术会议报告10次；培养毕业研究生6名，其中，博士2名、硕士4名。.上述工作成果深化了对煤成石墨形成机制及其控制因素的认识，可以为我国煤系石墨资源评价和合理开发利用提供科学依据。