Abstract: The studied segment shows its major,transcurrent ductile shear zone with a considerable sinistral displacement.The rock formation (Pt-T₁₊₂) at a depth of 5—15km may have cropped out in this area during its and subsequent erosion,many plastic-deformed strctures in it.The deformed zone was involved in the Indo-China orogeny.On the basis of measurements and analyses on a lot of pebbles within the shear zone,it is known that K₁ (the Flinn') is 1.178 and 1.053,which suggests a variation of simple shear and a plain strain with a constant volume of the studied zone.The intensely deformed belts are generally 40—50km in width,with an average a/c ratio of 27.68 and the maximum more than 87.37.The intensity of strain decreases rapidly with increasing distance from the shear fault zone,as well as with decreasing".depth to which the fault goes.For the Pt formation at the greatest depth,a/c value ranges from 30.58,Z₁-12.71-12.98,Z₂-2.54,and G-1.50.It follows that the differential horizontal slip may occur between various structures.On the condition that the elongation strain e1 and e3 are 4.95 and -0.817 within the intensely deformed belt,respectively,the belt in question has been elongated 164.23km in length and shortened 272.5km in width,to a corresponding 200km and 50km for the time being.The deformed belt was associated with syntectonic dynamothermal metamorphism,represented by greenschist facies and retrogressive metamorphism of early amphibolite ones.The internal belt was formed by high shear strain,with an angle ranging from 0—20°and a shear strain culculated to be more than 11.34.Developed here are four sorts of models involving viscous shear,ductile shear,ductile-brittle shear and brittle shear within the earth's crust.