Response of minerals and elements during coal deformation:Taking Zhuxianzhuang Mine No. 8 coal as an example

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 Ⅱ832 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. Ac-cording 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-de-formation 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 metamor-phism 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 hy-drothermal sulfide minerals and elements related to these minerals in the coal with brittle deformation. The ductile rhe-ology between the coal seams and surrounding rocks results in the enrichment of clay minerals and related elements in the ductile deformation coal.