Geochemistry characteristics of trace elements of mud shale of Shanxi Formation in Huainan coalfield and its significance

The characteristics of trace elements in mud shale have significant importance for invesion of paleao-geog-raphic and paleo-chimate during formation of mud shale. The geochemical characteristics and its significance of trace elements of Shanxi Formation mud shale in Huainan coalfield were discussed by collection of mud shale samples and testing the content of the trace elements in shale with ICP-MS. The results show that elements B, Cr, U, Ga, Li, Sn, Pb, Mo, Th, W are enriched, and Cd, Co, Cu, Ti, Zn, Sc, Ba, Mn, Ni, Sr are of deficit; The results revealed that Shanxi Formation in Huainan coalfield was formed in a warm and humid and brackish-high saltwater sedimentary environment. The deposition system was open, the depositional environment was of weak oxidation-reduction. It was mainly the weak reduction-reducing environment, showing the characteristics of the evolution from the early weak oxidative environment to the later reductive environment. Correlation analysis of the results of U/Th, Ni/Co, Sr/Cu, B/Ga, Sr/Ba, TOC and other geochemical parameters indicate that salinity and redox conditions may be affected by many factors, the original amount of organic matter accumulation was the main affecting factor on the content of organic matter in the mud shale from Shanxi Formation, salinity and redox conditions affected the evolution of organic matter toward different macerals. Warm moist climate and reducing environmental provided favorable conditions for organic matter accumulation and preservation, provided the mate-rial basis for the shale gas reservoir.