Abstract:

The research on the element characteristics of Chang 9 shale in Erdos Basin is inadequate, and the sedimentary environment is not fully revealed.Based on energy dispersive X-ray fluorescence technology, we used the optimized energy setting method to characterize the major and trace elements, which increases the number of measured effective elements to 29.Based on the element composition characteristics of the Chang 9 shale, the sedimentary environment (incl.paleo-climate, paleo-salinity, paleo-redox state, paleo-productivity, and provenance input) is systematically analyzed.The results show that the average content of 11 major elements in Chang 9 shale is 38,341.54 μg/g; the average content of 18 trace elements is 160.12 μg/g.Si, Al, Fe, Ca and K have the highest contents among the major elements; Ba, Rb, Sr and Zr have the highest contents among the trace elements.For the trace elements of the Chang 9 shale, elements including V, Cu, Th, Rb, Zr and Nb are relatively depleted; elements including Co, Ni, Zn, Ga, Pb, U, Y and Cr are weakly enriched; elements including Ba, Sr and Mo are moderately enriched; arsenic is highly enriched.The sedimentary environment of Chang 9 shale has the following characteristics: humid climate, freshwater water and weakly oxidized, medium to weak closing lake, stable terrigenous materials input, and strong primary productivity.

Key words: major element, trace element, sedimentary environment, Chang 9 shale, Ordos Basin