Abstract

The Dabie orogen underwent deep continental subduction, rapid exhumation, and the huge amount of erosion during the Mesozoic. Its tectonic evolution, especially how its evolution was recorded by sedimentary basins at the flanks of the Dabie orogen is one of the most important issues of the world’s attention. These years, newly studies of basin sedimentology, combined with structural geology, have shown a fundamental progress. The overall distribution of different basin types in the orogen indicates that shortening and thrusting at the margins of the orogen from the Late Triassic to the Early Cretaceous controlled the foreland basins, and extension, doming and rifting were initiated in the core of the orogen from the Jurassic to the Early Cretaceous and were expanded to the whole orogen after the Late Cretaceous. Therefore, The Dabie orogen records gradual transition from overall shortening and thrusting to dominantly extension and rift basin formation expanded from its core to its margins, although these shortening and extension overlapped in time from the Jurassic through Early Cretaceous at crustal levels. The unroofing ages of the ultra-high pressure (UHP) metamorphic rocks in the Dabie orogen change from Early Jurassic to Late Jurassic westward. The depth of exhumation increases eastwards. The sediment sources for the Hefei basin are mostly composed of the deeply exhumed, axial Dabie metamorphic complex, and the sediment sources for the Middle Yangtze basin are mostly from cover strata in the southern orogen and related strata with subjacent (i.e. subsequently overthrusted) Mianlue suture belt. Geodynamic analysis represents that continental collision between the North China Block and the South China Block along the Shangdan and Mianlue sutures, subsequently northwestward progradation of the Jiangnan fold and thrust belt, and the underthrusting of the North China Block along the Northern Boundary Fault of Qinling Range led to crustal thickening, gravitational spreading and balanced rebound of the resultant thick crustal welt, and multi-episodic exhumation of the HP/UHP metamorphic rocks. The future studies by the methods of tracing the Dabie orogeny through deposition in the marginal basins should focus on eastward extension of the Mianlue suture, thrust and overlap of the Dabie HP/UHP metamorphic block on different lithotectonic zones and basins along the northern South China Block, the structural framework of the source area of the basins in the syn-depositional stage, the basin lateral extension, huge amount of erosion and sediment transportation from the Dabie blanket and basement rocks, and recovery of subducted and removed structural units within the Dabie orogen, etc.

Highlights

  • The Dabie orogen underwent deep continental subduction, rapid exhumation, and the huge amount of erosion during the Mesozoic

  • The Dabie orogen records gradual transition from overall shortening and thrusting to dominantly extension and rift basin formation expanded from its core to its margins, these shortening and extension overlapped in time from the Jurassic through Early Cretaceous at crustal levels

  • Geodynamic analysis represents that continental collision between the North China Block and the South China Block along the Shangdan and Mianlue sutures, subsequently northwestward progradation of the Jiangnan fold and thrust belt, and the underthrusting of the North China Block along the Northern Boundary Fault of Qinling Range led to crustal thickening, gravitational spreading and balanced rebound of the resultant thick crustal welt, and multi-episodic exhumation of the HP/ultra-high pressure (UHP) metamorphic rocks

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Summary

Structural framework of the Dabie orogen

The Dabie orogen is linked westward with the East Qinling orogen across the Nanyang basin, and is connected eastward with the Sulu orogen across the Tanlu fault. Based on exposed geological structures and deep seismic profiles, Zhang et al [36] regarded it as a gigantic thrust fault in the Cretaceous that was traced to the Moho, and was marked by underthrust of the southern North China block. This fault controlled the subsidence and deposition of the southern margin of the Zhoukou basin in the Early Cretaceous [36,37]. The rift deformation expanded northwards from the Early Cretaceous (or latest Jurassic (?)) to Tertiary [5,14]

Axial Dabie structural belt
Basin-filling sequence and its multi-episodically tectonic control
Late Triassic tectonic sequence
Early-Middle Jurassic tectonic sequence
Late Jurassic tectonic sequence
Late Cretaceous tectonic sequence
Isotopic geochemical analysis
Isotopic chronology analysis
Late Triassic syn-collisional peripheral foreland basin system
Late Cretaceous rift basin system
Findings
Analysis of geodynamics
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