Development of a Dense Cratonic Keel Prior to the Destruction of the North China Craton: Constraints From Sedimentary Records and Numerical Simulation

Abstract

It remains unclear why some cratonic lithospheres like the North China Craton (NCC) have undergone significant thinning and catastrophic destruction. Here we provide evidence for a dense Phanerozoic cratonic keel beneath the NCC that provides a reason for the craton destruction during the late Mesozoic. We observed two long‐lasting (>100 Myr) episodes of surface subsidence that formed the saucer‐shaped basin topography on the NCC from the Paleozoic to early Mesozoic, which was not associated with lithosphere stretching or a high sea level. Based on a detailed geological and geochemical analysis and 2‐D numerical experiments, we show that this subsidence most likely reflects the secular cooling and eclogitization of iron‐rich materials infiltrated into the cratonic mantle since the early Phanerozoic, a process that is the most prominent over the eastern NCC. This result implies that the lithosphere beneath the eastern NCC became gravitationally unstable prior to its Mesozoic destruction as its keel became progressively denser during the Paleozoic. An early Mesozoic partial removal of this dense keel possibly led to widespread surface uplift of the NCC, as indicated by regional basin inversion. We conclude that the long‐term subsidence of a cratonic basin reflects a gradual increase of the lithospheric density and that this type of subsidence should not be considered a characteristic of stable cratons as previously assumed.

Yanshanian Orogeny During North China's Drifting Away From the Trench: Implications of Numerical Models

“…That lithospheric stretching and rifting basin are widely distributed across eastern North China and adjacent areas during the Early Cretaceous may suggest that the North China lithospheric mantle has already been significantly weakened and thinned (Buck et al, 1999) before the prominent Early Cretaceous rifting event. Mantle thinning before the Cretaceous crustal rifting may be associated with lithospheric delamination or Rayleigh‐Taylor instabilities (Liu, Liu, et al, 2019). Both regimes are associated with a thickened, heavy lithosphere.…”

Nature Versus Nurture: Preservation and Destruction of Archean Cratons

“…The long-lived nature of cratons suggests then that they have a longer period over which to accumulate repeated episodes of metasomatism or progressive refertilization (Griffin & O'Reilly, 2007) that drives gradual increases in the density of the cratonic root (Lee et al, 2011). The increase in density can then drive subsidence of the craton as well as potentially set the stage for future delamination driven by gravitational instabilities (Liu et al, 2019).…”

“…Isotopic systematics can indicate the timing of metasomatism (Carlson et al, 2004). Liu et al (2019) suggest that subsidence could be another possible geologic signal of refertilization: they propose that subsidence and basin formation may result from the progressive infiltration and eclogitization of iron-rich materials within the subcratonic mantle lithosphere and subsequent cooling causing a gradual increase in density. 4.…”

“…If the metasomatism is widespread and infiltrates broad areas, then the effects could be more consequential. It could be a cumulative process that affects cratonic lithosphere over a long period of time, as described by Liu et al (2019) for the North China craton, who describe two prolonged episodes of subsidence that they related to infiltration of metasomatizing melts into the lower cratonic mantle. Or metasomatism may be associated with a discrete event, such as shallow subduction of the Farallon slab followed by rollback and asthenospheric upwelling beneath the Wyoming craton (Carlson et al, 2004;Feeley, 2003).…”

“…Metasomatism appears to be the most effective process for modifying and potentially destroying cratonic mantle. Metasomatism associated with subduction and rollback is most likely responsible for the delamination and loss of cratonic lithosphere beneath the North China craton (e.g., Kusky et al, 2014;Liu et al, 2019) and also has been cited for destruction of the Wyoming cratonic keel (Carlson et al, 2004;Kusky et al, 2014). Evidence of metasomatism is present in mantle xenoliths from both cratons, although the North China mantle lithosphere is more thoroughly destroyed.…”