Correlation of lithospheric “de‐rooting” of the Sulu‐Dabie Orogen to tectonic‐sedimentary process of the Hefei Basin: Constraints from Mesozoic coupling of basin and orogen

Abstract

The lithospheric "de-rooting" of the Sulu-Dabie Orogen (SDO) is an important tectonic mechanism for post-orogenic tectono-magmatism, which influenced the sedimentation, evolution, and development of oil-gas accumulation in the Hefei Basin (HB). Combined with seismic, geological, and sedimentary data of the HB and the SDO, this paper studies the coupling of the HB and the SDO since the Late Mesozoic. While the North China Block (NCB) indented south-eastwards under the Greater South China Block (GSCB) since the Mesozoic, the SDO underwent three intense tectonic stages, i.e., subduction, exhumation, and uplift. The upwelling of deep mantle material causes the exhumation of the ultrahigh-pressure metamorphic (UHPM) rocks to the upper crust or surface, forming the UHPM. Influenced by the indentation of the NCB, the "de-rooting" of the SDO lithosphere, caused the delamination and thinning of the lithosphere, accompanied by the continuous flexural subsidence in the HB. The basin underwent at least four stages of tectonic evolution, involving sequentially: the flexural basin, the foreland basin, the strike-slip-related basin, and the faulted graben development periods. The tectonic evolution of the HB was closely coupled with the SDO orogeny. The "de-rooting" of the SDO lithosphere resulted in a strong uplift and erosion of the orogen, providing abundant source of material for the HB and causing the successively northwards migration of basin depocenters at its early stage. Finally, influenced by the subduction retreat of the (Palaeo-) Pacific Plate and the strike-slip movement of the Tanlu Fault, the depocenters migrated to the east.