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).