不同变形机制下煤中应力敏感元素的迁移聚散过程及机理

Based on the scientific theory that the tectonically sensitive elements (TSES) can be migrated and aggregated by rock deformation, making full use of the tectono-geochemistry research methods and results, this project will be centered on the scientific question of TSES migration and aggregation mechanism in the process of coal deformation. The Pingdingshan mining area, characterized by the typical structure and tectonically deformed coal (TDC), will be chosen as the main researched area. According to the elements differentiation phenomena in different structural positions and deformation degree of TDCs, the dynamical mechanism of elements migration and aggregation will be demonstrated from the perspective of tectonic stress – coal deformation – stress drive – elements migration, accumulation and dispersion, and even mineralization. According to the coal deformation experiments at high temperature and pressure and analysis on different deformation degrees of TDC samples collected from different structural positions in coal mine, the elements differential distributions of TDC in different scales and different deformation mechanism before and after the coal deformation test will be comparatively studied, controls of tectonic stress on the elements migration and aggregation characteristics will be specially discussed, the identification method and technical process of TSES will be established, and then the TSES will be identified and determined. Combining the results of the Organic-inorganic two-phase sequential extraction experiment and stress and strain analysis of TDC formation, the TSES migration, accumulation and dispersion process and its mechanism will be revealed. The research results will provide the scientific foundation for rare metal mineralization, coal clean and utilization and coal resource evaluation in TDC development areas.

基于岩石变形可使元素迁移的科学论断，充分借鉴和利用构造地球化学的研究方法与成果，围绕煤变形过程中存在的应力敏感元素及其迁移、聚散机理这一科学问题，选择构造和构造煤发育典型的平顶山矿区为研究对象，针对构造不同部位、不同类型构造煤中出现的元素分异现象，从构造应力－煤体变形－应力驱动－元素迁移、聚散甚至成矿的视角揭示煤变形过程中元素迁移的动力学机制。通过实验室煤的高温高压变形实验和井下不同构造部位及不同变形程度构造煤系统采样，对比分析煤体变形试验前后不同尺度变形区域和不同变形机制构造煤中元素分布的系统差异性，阐释应力对元素迁移的控制作用，建立应力敏感元素识别方法与技术流程，甄别并确定构造煤中的应力敏感元素；利用有机－无机两相逐级提取实验并结合构造煤形成的应力－应变环境分析，揭示应力敏感元素迁移、聚散过程及机理，为构造复杂区煤中稀有金属成矿、构造煤清洁利用和煤炭资源评价提供理论基础和科学依据。

岩石变形会促使岩石中的元素发生迁移，构造煤变形-变质过程可能也同样伴随敏感元素迁移现象，研究基础薄弱。项目系统采集淮北和新密矿区典型构造煤样品，结合区域构造发育特征和构造煤形成的动力学机制，分析构造煤中矿物的分布特征。借助ICP-MS、SEM-EDX、XRF和CVAS等测试方法，测定并分析不同类型构造和不同变形程度构造煤中常量、微量和稀土元素的迁移聚集和散失规律，揭示构造煤中应力敏感元素迁移聚集的动力学机制。研究成果如下：（1）建立并深化了构造煤演化模型，将构造煤分为3个变形序列9种变形类型；（2）发现煤中矿物的分布、变形和迁移与构造煤流变作用有关。脆性变形煤中后生矿物的裂隙填充作用，碎斑煤中矿物的机械混合作用及剪切滑面上的压溶流变作用，是煤中矿物分布迁移的主要因素；（3）不同类型构造煤中矿物赋存和形态受构造煤变形机制影响，在脆性变形阶段产生的碎裂作用为煤中矿物的形成和赋存提供了良好空间；在韧性变形阶段煤体变形及其伴随产生的动力变质作用，促使煤元素迁移聚集并为矿物形成提供了动力学条件；（4）以构造煤中硫和汞为例，揭示了不同类型构造煤中元素的迁移聚集规律，将敏感元素分布分为聚集型、对称型、散失型和稳定型4类；（5）系统探讨了构造煤中应力敏感元素迁移聚集的动力学机制，应力敏感元素的迁移聚集过程分为迁移和聚集两个阶段，存在物理和化学两种途径，包括断裂填充、应力驱动、动热迁移、力化学驱动和机械混合流变等5种迁移聚集机制。研究成果为富集元素的资源评价与回收利用、有害元素防治和矿井瓦斯突出预测提供理论依据。