Retroarc intra-cratonic deformation accommodated by coeval fold-and-thrust belts and strike-slip faults: Insights from the central Tarim craton during the West Kunlun orogeny

Abstract:

Cratons are usually considered as stable blocks with little or no deformation in the interiors and intense structural deformation in the surrounding orogenic belts. However, the coeval deformation history of different types of structures in the cratons and their responses to the formation of orogenic belts is still not well understood due to the quality of data sets, poor exposure, or overprinting. By using the newly acquired 2-D and 3-D seismic reflections and quantitative methods of relief-depth methods, we investigated the thrust and strike-slip structures in the Tarim Craton, and also studied their formation history and relationship with the activities of Western Kunlun Orogeny, to explore the tectonic origin of the intra-cratonic deformation. Our results suggested that the strike-slip faults show as en échelon pattern in the plane view in the Shuntuoguole Low Uplift of the Tarim Basin. In the cross-section view, these strike-slip faults are characterized by the development of superimposed flower structures. The Tazhong Uplift is interpreted as a gentle detachment fold with the structural wedge. Within the uplift, two fold-and-thrust belts were developed, forming the fault-bend and fault-propagation folds. Based on the structural deformation and area-of-relief graphs, the strike-slip faults and Tazhong Uplift has the same evolution history, including the pregrowth stage in the Cambrian, the first growth stage from the Ordovician to the Early Carboniferous, the nongrowth stage from the Late Carboniferous to Late Permian and the second growth stage from the Triassic to the Early Cenozoic. The shortening rates in the Tazhong Uplift are uneven, which may be responsible for the development of the strike-slip fault. Ages and Hf isotopic data of igneous rocks of Western Kunlun Orogeny reflect obvious flux events during the Middle to Late Cambrian and Middle to Late Ordovician, suggesting the coeval defamation of orogenic belts and intra-craton structures. Combined with the seismic interpretation, data of are-of-relief, shortening rates, and tectonic analysis, we build an integrated model to reflect the whole tectonic evolution system from the Western Kunlun Orogeny to the intra-craton basin.