Controls on migration and aggregation for tectonically sensitive elements in tectonically deformed coal：An example from the Haizi mine, Huaibei coalfield, China

• Published in: Science China. Earth sciences 2014-06, Vol.57 (6), p.1180-1191
• Main Authors: Li, YunBo, Jiang, Bo, Qu, ZhengHui
• Format: Article
• Language: English
• Subjects: Coal; Coal mining; Deformation; Earth and Environmental Science; Earth Sciences; Geophysics; Metamorphism; Minerals; Plate tectonics; Rare earth elements; Research Paper; Seismology; Tectonics; Trace elements; 元素迁移; 地质控制; 敏感元件; 构造变形; 构造煤; 淮北煤田; 煤矿; 聚集
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-014-4857-9

Tectonically deformed coal（TDC） develops because of the superimposed deformation and metamorphism of a coal seam by tectonic movements. The migration and accumulation of trace elements in TDC is largely in response to stress-strain conditions. To develop a law governing the migration and aggregation of sensitive elements and investigate the geological controls on TDC, coal samples from different deformation sequences were collected from the Haizi mine, in the Huaibei coalfield in Anhui Province, China, and the concentrations of 49 elements were determined by XRF and ICP-MS, and then microscopically analyzed. The results show that the distribution and morphology of minerals in coal is related to the deformation degree of TDC. The evolutionary process runs from orderly distribution of minerals in a weak brittle deformed coal to disordered distributions in ductile deformed coal. According to the elemental distribution characteristics in TDC, four types of element migration can be identified： stable, aggregate, declining, and undulate types, which are closely related to the deformation degree of TDC. Present data indicate that the overall distribution of rare earth elements（REE） does not change with metamorphism and deformation, but it shows obvious dynamic differentiation phenomena along with the deformation of TDC. Tectonic action after coal-formation, brittle or ductile deformation, and the metamorphic mechanism and its accompanying dynamic thermal effects are the main factors that influence the redistribution of elements in TDC. We conclude that tectonic movements provide the motivation and basis for the redistribution of elements and the paths and modes of element migration are controlled by brittle and ductile deformation metamorphic processes. The dynamic thermal effect has the most significant effect on coal metamorphism and tectonic-stress-accelerated element migration and accumulation. These factors then induce the tectonic-dynamic differentiation phenomenon of element migration.