CHARACTERISTICS OF TRACE ELEMENTS IN OIL SHALE AND PALEOENVIRONMENT RECOVERY IN THE METALLOGENIC PERIOD IN SOUTHERN SONGLIAO BASIN

The paleoenvironment in the metallogenic period of oil shale controls the organic type and abundance of oil shale, which is important for research of the origin and enrichment regularity of oil shale. In southern Songliao Basin, the oil shale formations are generally stable deep lake to semi-deep lake facies. The characteristics of trace elements are sensitive to the changes of ancient environment. Therefore, the contents of trace elements in oil shale and their ratios can be used to restore the paleoenvironment of oil shale in metallogenic period. This article, through test of more than 20 trace elements and analysis for their ratios of the oil shale samples from southern Songliao Basin, restores the paleoenvironment of the Qingshankou Formation and Nenjiang Formation. The results show that the oil shale in the metallogenic period experienced a warm humid-subhumid and dry heat climate, in a reduction environment of brackish water. To compare with the counterparts of Nenjiang period, the climate and salinity changes of Qingshankou period are more stable, with a slightly drier climate and a higher salinity.