FOLDING INVOLVED IN STRUCTURAL DOMING TECTONICS

Folding is a common deformation mechanism whose effects can be observed at multiple scales. The southwest margin of the Yangtze Block underwent multiple tectonic events including the collision between the Yangtze and the South China Plate, Caledonian folding and uplift of South China, subduction of the western Pacific Plate, and Cenozoic continental escape during the Indo–Asia collision. Through field petrologic and structural studies, microstructures within the deformed units, and estimates of the temperature of deformation, we constrain the conditions of deformation and further classify at least four-stage deformation. The first stage involved northeastward thrusting that produced folds, mylonites. The second stage of deformation involved uplift, extension, and the generation of a domal structure. During the third event, high-angle normal faults formed within the cover sequence that surrounds the dome. The fourth stage of deformation occurred in the Cenozoic and involved motion along sinistral and dextral strike–slip faults. The dome in the study area represents a transitional structure between a metamorphic core complex and a gneissic dome, which we refer to as structural doming. During doming, local extension occurred along a ~50–100-m-thick layer within the cover sequence, forming down-dipping fold axial planes to different directions, carbonate mylonite, and muscovite neoblasts. Subsequent far-field compression resulted in uplift and passive extension of the dome. This structural doming can be used and formed in multiple stages deformation in intracontinental tectonics.