The Structural Analysis On Transformation From Orogenic Period To Post-orogeny Of The South Edge Of Northern Dabie Belt

The Wuhe-Shuihou shear zone (WSSZ) is located between the southern andnorthern Dabie belts. Since the time of formation for the southern and northern Dabiebelts is different, this shear zone as a boundary between them should record thestructural evidences from orogenic to post-orogenic period.This work focuses on the detailed measurement and recording of geometric andkinematic characteristics on the field at the southern edge of northern Dabie belt. NearShuihou, the WSSZ strikes NE and the mylonitic foliations trends SE or SEE with thepreferred direction of145°SE. The mineral lineation inclines SE or SEE havingapproximately160°SSE as its preferred direction. Based on the observation in thefield, the rotated porphyroclast and the anisomerous folds all indicate shear oftop-to-the-NW. According to the microstructure of the samples collected, the trailingof the mineral aggregate, the rotated porphyroclast, the S-C fabrics, the mica fish andother microstructures all indicate a shear of top-to-the-NW. A conclusion has beendrawn from the kinematic vorticity measurement using Mohr’s Circle that the WSSZshows a movement dominated by simple shear. The same result is gotted from thekinematic vorticity measurement using critical form method. We get the differentialstress of the WSSZ and the southern edge of the northern Dabie belt. Thedifferential stress of the southern edge of the northern Dabie belt is10.28-14.86MPa, that of the WSSZ is9.96-16.11MPa. The Fllin graphy in theWSSZ shows its strain is elongated strain. The main stress ratio of the WSSZ isbetween4.300and18.667.This work compares the WSSZ with the Xiaotian-Mozitan ductile shear belt, theTanlu fault belt, the northern Dabie belt and the southern Dabie belt on their structuralcharacteristics, and finds that the WSSZ and southern Dabie belt are in consistency,while are largely different from others. Therefore, it is inferred that the WSSZ andsouthern Dabie belt developed in the same period.