PSEUDOTACHYLYTES FROM THE KOKTOKAY-ERTAI FAULT ZONE, XINJIANG, CHINA,AND THEIR SEISMOGEOLOGIC IMPLICATIONS

Multi-period of pseudotachylytes of variable occurrences and shapes ar e widely outcropped in Haizikou and Mukurasen sections of the Koktokay -Ertai fault zone. They consist of clasts and matrix. The clasts compr ise fine fragments of the host rock (mylonite) and quartz grains, whil e the matrix consists of cryptocrystalline and glassy materials which contain fibrous and radial microlites. The chemical compositions of th e pseudotachylytes resemble those of the host rocks. Their features in dicate that the pseudotachylytes were formed from local melting of the mylonites during the rapid movement of the fault, and that the format ion depth was 10-12 km. The geologic event that produced pseudotachyly tes is believed to be paleoearthquake.