Tectonic deformation features from Late Indosinian to Yanshanian in southern Guizhou

The tectonic deformations in the southern Guizhou were zoned obviously.To the north of Guiyang-Guiding-Sandu,fault belts distributed in NS direction.The studies of fluid inclusion showed that the present fault belts were active from the late Indosinian to Yanshanian and their tectonic deformation features were in accordance with the general law of progressive(attenuated) deformation caused by the nappe of Xuefeng Mountain from east to west.The rock samples from the fault belts confirmed that rocks were influenced by the squeeze and twist effect from the upper to the lower disk.The faults were compressive.The fault belts were brittle and some were ductile.To the south of Guiyang-Guiding-Sandu,the thrusting of Xuefeng Mountain from east to west led to medium-weak or weak deformations and a gentle anticlinal tectonic framework in NE direction was formed under the influence of Yaziluo squeeze and strike-slip belt.Big difference of stress field existed between the northeast and the southwest of the study area during tectonic evolution.The Anshun and Changshun Sags in the weak deformation belt might be favorable targets for petroleum migration and accumulation.