Paleostress Reconstruction of Micangshan Anticlinorium on the Southern Margin of the Qinling Orogenic Belts, China

AbstractBrittle structures in rock of different ages can be used to establish the tectonic evolution of an orogenic belt through paleostress calculations. Micangshan is located at the southern margin of the Qinling orogenic belt, between the SE‐trending Longmenshan fold‐and‐thrust belt and the arcuate Dabashan thrust‐and‐fold belt. Structural observations revealed that the dominant structures are reverse and strike‐slip faults and folds with E–W and NE–SE trends. To increase knowledge of the tectonic evolution of the Micangshan anticlinorium, faults, joints, veins, and folds were measured at more than eighty sites. On the basis of structural analysis, it emerged that the multiphase paleostress fields became established after the oblique collision between the North and South China plates. The earliest stress field with N–S compression was established during the Micangshan uplift associated with the E–W trending faults and folds. Subsequently, a N–S extension occurred when the Qinling orogenic belt collapsed. Then NW–SE compression developed, with NE trending faults and folds forming in relation to Longmenshan thrusting toward southwest on the eastern margin of the Tibetan plateau. With the development of the arcuate Dabashan orogenic belt, the compression stress orientation of the Micangshan anticlinorium altered from NE–SW to E–W.