MICROSTRUCTURES AND AGES OF ACTIVITY OF THE REVERSE FAULTS ALONG THE SOUTHERN MARGIN OF THE JUNGGAR BASIN

The microstructures of fault gouge and tectonite in the Huo'erguosi-Manas-Tugulu reverse fault zones along the southern margin of the Junggar basin are studied and twelve samples of gypsum,fault gouge and quartz veins were collected and dated by using the electronic spin resonance(ESR) method.The results show that the gouges underwent at least three deformation stages.Many stick-slip microstructural marks such as slickenside striations and steps appear in gouges and on quartz grains.In addition,many creep deformation marks such as shear slip and oriented arrangement of clay minerals are also found.The results show that the Huo'erguosi-Manas-Tugulu reverse fault zones formed about 1.5 Ma ago and were readjusted at 0.4-1.0 and 0.08-0.12 Ma respectively.The time of faulting is consistent with the time of uplift of the Qinghai-Tibet Plateau,suggesting that the formation of the Huo'erguosi-Manas-Tugulu reverse fault zones on the southern margin of the Junggar basin is closely related to the uplift process of the Qinghai-Tibet Plateau.