Characteristics and Geological Significance of Lacustrine Hydrothermal Sedimentary Rocks in the Yingejing Sag in Bayingebi Basin, Inner Mongolia, Northwestern China

In order to promote site screening for high-level radioactive waste (HLW) disposal purposes, the characteristics of argillaceous rock (potential host rock) from the Yingejing Sag of the Bayingebi Basin, Northwest China have been well discussed. Results show that (1) Unlike argillaceous host rocks in foreign countries, the argillaceous rock mainly consists of analcite, dolomite, and albite; the contents of clay minerals are only about 10%. Five typical structures could be categorized, dominating by the massive structure. (2) Geochemical characteristics have the characteristics of abundance in deep source gas and liquid trace elements, a gentle right dip in the distribution pattern of rare-earth elements. (3) Petrological and geochemical characteristics determine the argillaceous rock as the genesis of lacustrine hydrothermal sedimentary rock. The hydrothermal sedimentary model also has been constructed, mainly controlled by tectonic activity of the Altyn Tagh fault from 100 to 120 Ma. The massive argillites with analcite and dolomite would lay the foundation for confirming the site for HLW disposal purposes in China.