Silicalites are distributed widely in the Middle Permian Maokou Formation in the eastern oft-com:office:smarttags" />Sichuan Basin. Detailed observation in the field and the contents of major elements, REE and isotope of silicalites suggest that the Maokou Formation silicalites were hydrothermal origin and were deposited under platform-basin facies environments. The formation of hydrothermal silicalites is closely related to volcanic activities and faulting, the mixed fluid of seawater and magmatic fluid was heated and dissolved a large voluminous of SiO2, and other minerals, which erupted along faults in the form of spring and then deposited in adjacent areas. oft-com:office:office" />