构造煤变形过程中矿物及元素响应——以朱仙庄矿8号煤为例

摘要

The response characteristics of minerals and elements during coal deformation is a new field in the study of deformed coal and may provide a new method for the prediction of coal and gas outburst.To analyze the response laws as well as the migration and accumulation modes of minerals and elements during deformation,the authors collected some deformed coal samples with different deformation degrees from No.8 coal at a working face of Zhuxianzhuang Mine (the Ⅱ 832 working face) and systematically tested the occurrence characteristics of the minerals and elements by using SEM,XRD,XRF and ICP-MS.As the deformation degrees increase,the mineral layers in the coal are gradually crushed into porphyroclasts,folded deformations even occur in the mineral thin films,and single minerals turn into multi-mineral mixture.The types and contents of minerals in the ductile deformation coal increase significantly.According to the sensitivity of different elements during deformations,the elements in coal are classed into three types such as the brittle-deformation sensitive elements (mainly including Ca,Mg,Zn,Mn,Sb,Hg,etc.),the ductile-deformation sensitive elements (mainly including Si,Al,K,Rb,Th,Cu,U,Sc,Cr,REE,etc.) and the stable or complex variable elements.The migration and accumulation modes of minerals and elements are summarized into three patterns such as dynamic metamorphism driving mode,fracture filling mode,and ductile rheological mode.Dynamic metamorphism mainly influences the organic elements and elements related to organic matters.The development of tectonic fractures and the filling of hydrothermal fluids contribute to the enrichment of carbonate minerals,low temperature hydrothermal sulfide minerals and elements related to these minerals in the coal with brittle deformation.The ductile rheology between the coal seams and surrounding rocks results in the enrichment of clay minerals and related elements in the ductile deformation coal.%煤变形过程中矿物及元素的响应特征是构造煤研究的一个新领域,并可能为煤与瓦斯突出预测提供新的方法和手段.在淮北朱仙庄矿8号煤Ⅱ832工作面不同类型构造煤扫描电镜(SEM),X射线衍射(XRD),X射线荧光光谱(XRF)、电感耦合等离子体质谱(ICP-MS)等实验测试的基础上,分析了煤构造变形过程中矿物及元素的响应特征,并探讨了其迁移聚集模式.结果显示,随着构造变形的增强,煤中矿物由完整的层片状破碎为残斑状,矿物薄膜甚至随煤体发生揉皱变形,同时由单矿物独立分布变为多矿物相互混杂,韧性变形煤中矿物种类及含量均有显著增加;煤中不同种元素对构造变形的敏感程度不同,可划分为脆性变形敏感型元素(主要包括Ca,Mg,Zn,Mn,Sb,Hg等元素)、韧性变形敏感型元素(主要包括Si,Al,K,Rb,Th,Cu,Th,Cu,Cr和REE元素等)和稳定或复杂变化型元素3类;结合不同类型构造煤结构及其应力应变环境的差异,将构造煤中矿物和元素迁移聚集概括为动力变质作用驱动、裂隙充填和韧性变形混合流变等3种模式.动力变质作用主要影响煤中有机元素及与有机质相关的元素类型;构造裂隙的发育及热液流体的充填导致了脆性变形煤中碳酸盐矿物、低温热液型硫化物矿物及相应元素的富集;韧性流变作用使得煤中黏土矿物及相应元素在韧性变形煤中相对富集.