1.1. Geological background of the NCC
The NCC is bounded by the late Palaeozoic to Mesozoic Central Asian orogen in the north, the early Palaeozoic Qilian orogen in the west, and the Mesozoic Qinling–Dabie–Sulu orogen in the south (Zhao et al., 2001). During the Paleoproterozoic between 1.92 and 1.85 Ga, the Ordos and Yinshan Blocks were amalgamated along the Inner Mongolia suture zone, forming the unified Western Block (Zhao and Zheng, 2005), and the Eastern and Western Blocks collided along the Trans-North China orogen (Zhao and Zhai, 2013) (Fig. 1a, red rectangular region, Fig. 1b).
The thick, old and refractory lithospheric keel is widely accepted to have been largely replaced by fertile and young lithospheric mantle beneath the eastern part of the NCC during the Mesozoic and Cenozoic (Wu et al., 2019; Zhao et al., 2020), which implies lithospheric thinning or destruction of the NCC (Zhai et al., 2007). Models of craton destruction in the NCC involve two schools of thought: one proposes that lower crustal and/or lithospheric delamination resulted in lithospheric thinning or craton destruction (Liu et al., 2019; He, 2020), and the other suggests that upwelling asthenosphere led to thermal or mechanical erosion beneath the lithosphere and ultimately craton destruction (Zhang et al., 2002).
Geologists have studied the abundant gold deposits generated by the destruction of the NCC, which was accompanied by widespread crustal/lithospheric deformation and magmatic activity (Yang et al., 2003). In particular, the consistency between the time of lithospheric thinning and the ages of most gold ores in the NCC suggests that the destruction of the craton exerted a major control on gold mineralization in the late Mesozoic (Li et al., 2013).