Development of detachment fault system associated with a mature metamorphic core complex: Insight from the Kaiping Sag, northern South China Sea rifted margin

AbstractDetachment fault system associated with a mature metamorphic core complex (MCC) is still not well understood. Using high‐resolution 3D seismic data, we analyse the geometries and kinematic development of detachment fault system associated with a mature and exhumated MCC in the northern South China Sea rifted margin, with an emphasis on the MCC‐associated faults within the supra‐detachment basin. Faults within the supra‐detachment basin can be classified into three stages, the pre‐MCC, syn‐MCC and post‐MCC faults, based on their formation time relative to the MCC. The NE to NEE‐striking pre‐MCC faults developed in the early syn‐rift 1 stage, and the NW to WNW‐striking post‐MCC faults were both dominated by the regional tectonics and are perpendicular to the extension directions. While the syn‐MCC faults, synchronous with the MCC development in the late syn‐rift 1 stage, show overall EW‐striking, consistent with the long axis of the KP MCC. These syn‐MCC faults were well developed and are significant in shaping the basin architecture. Besides, the syn‐MCC faults are regularly distributed in the four zones overlying the convex‐upward master detachment fault surface, and are defined in this study as a synthetic fault zone, an upper collapse synformal‐graben fault zone, a lower collapse antiformal‐graben fault zone and an antithetic fault zone respectively. These four fault zones show distinct features and evolutionary patterns, and have a closed relationship with the rolling‐hinge process of the KP MCC. An evolutionary model is established for the development of MCC‐associated detachment fault system which should have global implications.