he micro-strain mechanism of Jiaochang arc structure in Songpan-Garze fold belt, Sichuan, China.

The Jiaochang arc belt is characterized by synorogenic, multiphasic, coaxial compressional deformation and metamorphism, which is under the mid-shallow layer setting, and has some typical microtectonics, such as rotated helicitic structure, symmetric pressure shadow and kind structure etc. Based on 15 orientated samples′ microscopic features, dominant striking micro-strain feature of Jiaochang is symmetry, meanwhile magnitude of strain is roughly similar(γ≌1.8) in the western and eastern arc limbs, and percentage of compression is roughly equal(C≌27%) too. There is increasing tendency for micro-strain feature in the same unit from north to south, while there is decreasing tendency in different units, as well as the Flinn index (K>1). The strain pattern is triaxial prolate strain. The symmetrically micro-structural feature in Jiaochang is significantly different to the unsymmetrical feature about "strike-slip" mechanism of arc belt, attributed to differential stress-strain mechanism controlled by the north to south main stress.