The Distribution Characteristics And Geological Significance Of Trace Elements In Coals From The Deep Of Panji Huainan Area

To research the distribution characteristics and geological significance of trace elements in coals from the deep of Panji Huainan area,19 samples from three coal bearing members of Upper Shihezi.Formation and Lower Shihezi Formation were collected. Geochemical analysis methods and mathematical statistical methods were used to research the distribution characteristics and occurrence modes of trace elements in coal. The content of 44 trace elements was determined by inductively coupled plasma mass spectrometry (ICP-MS).Compared to the arithmetic average of trace elements in coal of North China and China, it shows that the content of trace elements in deep of Panji area are richer in Li, V, Cr, Cu, Sr and Ba, and are lower in Mo、Cd、W、Tl、Bi、U、Nb and Ta. The content of Cs and Th are similar to coal of North China and China.When compared to average content of the upper continent crust (UCC) of China, the results show that Mo is the richest trace elements in coal of the Upper Shihezi Formation, the content of Rb and Cs is remarkable depleted. While Mo is also the richest trace elements in coal of the Lower Shihezi Formation, but its content is lower than the Upper Shihezi Formation, none of the trace elements in coal of Lower Shihezi Formation is remarkable depleted.Redox conditions, paleosalinity characteristics and paleoclimate characteristics are inverted by geochemical indexes of trace elements. The results show that the water transit from brackish water to fresh water started from Shihezi Formation, salt content of the water declined gradually. Sedimentary environment changed from marine-continental transitional facies to terrestrial facies. The climate during sedimentary period of Shihezi Formation was mainly warm and humid-semi-dry, and had the tendency of changing from warm and humid to hot and arid. The results of analyzing trace elements show that the sedimentary environment was in weak oxidizing conditions all this period. Two reasons are thought to be responded. For one thing, the climate of Shihezi Formation became hot and dry gradually, because of water evaporation, sedimentary organic matter were exposed to the air above the water. Some parts of them were oxidized so that the oxidation of the sedimentary environment was enhanced. For another, with the retreat of the sea, sedimentation happened in the redox interface because of the depth of the overlying water decreased gradually.Through the research of rare earth elements(REE), it comes to the conclusion that negative Eu anomaly is mainly influenced by the terrestrial sources, it is related to the geochemical features of terrigenous clastic rock, it may also influenced by the leaching of coal-bed gangue, groundwater circulation, and redox of lake water. Slightly negative 8Ce anomaly may caused by sea water.