PHENGITE IN THE NORTHERN MARGINAL DUCTILE SHEAR ZONE OF EAST PAMIR AND ITS IMPLICATIONS
Wang Daoxuan; Sun Shiqun(Department of Resources and Environment of Hefei University of Technology,Hefei 230009)
This paper deals with phengite of mylonite in the northern marginal ductile nappe shear zone of East Pamir. The electronic probe analysis and X-ray diffraction show that the rise from 3. 2043 to 3. 3609 for the contents of phengite in average depends on the change from the margin to the centre of the shear zone and the unit cell parameters are from 9. 024 to 9. 027,9. 041 and 9.045 with identical facies pattern 2M1. Sillimanite was locally found in mylonite.Several beds of piemontite quartzite were developed upon the mylonite association. The mean value of K-Ar age for phengite is 36. 95+1. 2Ma. So,it is determined that the mylonite formed in low temperature(locally high)and mid to high-pressure environment of late Eocene epoch(37Ma).