Pseudotachylytes from the Koktokay-Ertai fault zone, Xinjiang, China, and their seismogeologic implications
Multi-period of pseudotachylytes of variable occurrences and shapes are widely outcropped in Haizikou and Mukurasen sections of the Koktokay-Ertai fault zone. They consist of clasts and matrix. The clasts comprise fine fragments of the host rock (mylonite) and quartz grains, while the matrix consists of cryptocrystalline and glassy materials which contain fibrous and radial microlites. The chemical compositions of the pseudotachylytes resemble those of the host rocks. Their features indicate that the pseudotachylytes were formed from local melting of the mylonites during the rapid movement of the fault, and that the formation depth was 10—12 km. The geologic event that produced pseudotachylytes is believed to be paleoearthquake.