Upper‐mantle tomography and dynamics beneath the North China Craton

Abstract

[1] A high-resolution tomographic model of the upper mantle beneath the North China Craton (NCC) is determined using a large number of precisely hand-picked teleseismic P wave arrival times. The results are generally consistent with previous results but high-quality arrivals provide new insights into the dynamics beneath the NCC. Obviously north-south trending low-velocity (low-V) zones are revealed down to $300-400 km depth under the Shanxi rift and Tanlu fault zone, while a north-south trending high-velocity (high-V) zone representing the remainder of detached lithosphere is visible down to $200 km depth under the western portion of eastern NCC. High-V anomalies representing the detached lithosphere are detected at 200-400 km depth under central and eastern NCC. Under the Ordos block high-V anomalies are visible above $400 km depth, indicating intact lithosphere. Broad high-V anomalies representing the stagnant Pacific slab are imaged with a low-V anomaly from Datong volcano to the edge of Bohai Sea in the mantle transition zone beneath eastern and central NCC, suggesting that the Pacific slab has subducted to central NCC but with a gap. A continuously Y-shaped low-V structure is clearly imaged under Datong volcano and Bohai Sea from the lower mantle through this gap in the mantle transition zone to the upper mantle, indicating the existence of a lower mantle plume. These results suggest that in addition to the subduction of the Pacific plate, the plume has also played an important role in lithospheric destruction by thermal erosion of the asthenosphere and detachment of the lithosphere beneath the NCC.

Thermal regime of the North China Craton: Implications for craton destruction

“…Such hot material upwelling revealed by tomographic model might help to explain not only the Cenozoic thinning of the eastern and central NCC, formation of Shanxi rift and Datong volcano (Lei, 2012;Lei et al, 2013), but also the high heat flow recorded in the basins. Therefore, the high Cenozoic heat flow, as well as the lithospheric thinning, is probably the comprehensive results of lithospheric extension, magmatism, and or mantle plume (Lei, 2012;Lei et al, 2013).…”

“…The recent tomographic model shows an obviously Y-shaped low-V anomaly under the Datong volcano (situated at the northern end of Shanxi rift in the central NCC) and Bohai Sea, which extends down to the lower mantle, suggesting that the Datong volcano might originate from the lower mantle and could be a volcano of hotspot type (Lei, 2012;Lei et al, 2013). It is also found that the broad high-V anomalies representing the stagnant Pacific slab in the mantle transition zone have a clear gap, which may allow for hot material upwelling.…”

“…Zheng et al, 2006;Deng et al, 2007;Menzies et al, 2007;J.J. Zhang et al, 2009;Zhu and Zheng, 2009;Zhu et al, 2011Zhu et al, , 2012aLei, 2012). Recent research has suggested that the destruction of the eastern NCC was closely linked to the subduction of the Pacific Plate underneath East Asia, starting in the Mesozoic (e.g., Zhao et al, 2007Zhao et al, , 2009; J.J. Zhang et al, 2009;Xu et al, 2009;Zheng and Wu, 2009;Zhu and Zheng, 2009;Zhu et al, 2011Zhu et al, , 2012aXu et al, 2012).…”

“…1) was stable until its destruction in the early Mesozoic (Zhu et al, 2012a). Detailed geochemical and geophysical studies show that the eastern NCC is currently characterized by high surface heat flow, abundant volcanism, large earthquakes, intensive structural deformation and low seismic wave velocities in the upper mantle (Griffin et al, 1998;He et al, 2001;Xu, 2001;Wu et al, 2005a;Zheng et al, 2007;Lei et al, 2008;Yang et al, 2008;Chen et al, 2009;Chen, 2010;Lei, 2012). Numerous studies have been conducted on the timing, scale, and mechanism of the destruction of this craton (Fan and Menzies, 1992;Deng et al, 1994;Griffin et al, 1998;Fan et al, 2000;Xu, 2001;Gao et al, 2002Gao et al, , 2004Wu et al, 2005a;J.P.…”

The bending mechanism of Anping ground fissure in the Hebei Plain, North China

“…The shallow stretching environment provided a favorable release channel for the upward arching of the deep substances. It should be noted that the activities of deep substances are not always uniform (Lei 2012). Under the blocking effect of the Cangxian Uplift, the local stretching activities were nonuniform.…”