Discontinuity structure of the mantle transition zone beneath the North China Craton from receiver function migration

Abstract

[1] A better understanding of the significant Phanerozoic tectonic reactivation and destruction of the North China Craton (NCC) demands a detailed knowledge of the deep structural features of the region. We applied the wave equation-based poststack migration technique to a combined receiver function data set from more than 250 broadband seismic stations to construct the structural image of the mantle transition zone beneath the NCC. Our imaging results reveal a relatively simple and flat 410-km discontinuity but a structurally complicated 660-km discontinuity beneath the region. Double discontinuities and a $30-km depression of the 660-km discontinuity are observed locally in the southern part of the eastern NCC, in contrast to the smoothly varying structure to the north and in the central and western parts of the craton. Distinctly rapid variations in both the 660-km discontinuity structure and mantle transition zone thickness were found across the northsouth gravity lineament (NSGL) near the boundary between the eastern and central NCC, which probably reflects different thermal and probably chemical properties on the two sides of the NSGL. These differences are possibly associated with the Pacific slab, which is imaged tomographically as a flat-lying structure in the mantle transition zone under the region east of the NSGL. The structural variation in the deep upper mantle appears to coincide with the sudden changes in surface topography, gravity field, and crustal and lithospheric structures as well, indicating that the two domains may have tectonically deformed differently throughout the whole upper mantle during the Phanerozoic cratonic destruction. The mantle transition zone on the eastern side of the NSGL is up to 30 $ 40 km thicker than the global average; this thickness and the complex structure of the 660-km discontinuity in this region may reflect the strong influence that the deep subduction and stagnancy of the Pacific slab, and its possible sporadic penetration into the lower mantle, have had on mantle dynamics and lithospheric reactivation in the eastern NCC since the Mesozoic time. On the other hand, the less variable structure and normal-to-thin mantle transition zone imaged beneath the central and western NCC may indicate that the IndiaEurasia collision has had a relatively weak effect on the Cenozoic tectonics of these regions.Citation: Chen, L., and Y. Ai (2009), Discontinuity structure of the mantle transition zone beneath the North China Craton from receiver function migration,

Mantle dynamics of the reactivating North China Craton: Constraints from the topographies of the 410-km and 660-km discontinuities

“…Chen and Ai [12] applied the receiver function method to construct a structural image of the MTZ beneath the NCC. The velocity models of the upper mantle S wave, which is a dominant model parameter in the migration imaging of the [12]).…”

“…Changes in temperature or composition shift the pressure of the mineral phase transition, creating the topography of the velocity discontinuity [5,6], which can be used as an indicator of mantle dynamics. The thickened MTZ underlain by a depressed 660-km discontinuity has been generally found to occur near subduction zones and attributed to the stagnancy of the subducted slab or remnants of detached oceanic lithosphere [7][8][9][10][11][12]. The slightly thinned MTZ beneath ridges and hotspots has been attributed to the influence of thermal plumes [13,14].…”

Recycled oceanic crust in the source of 90–40Ma basalts in North and Northeast China: Evidence, provenance and significance

“…These correspond to the subduction of the Pacific plate underneath the Eurasian content and to subsequent extensions, respectively (Wu et al, , 2006. (3) Global tomography studies indicate that the subducted Pacific oceanic slab has become stagnant within the mantle transition zone and extended subhorizontally westward beneath the East Asian continent (Fukao et al, 1992;Huang and Zhao, 2006;Chen and Ai, 2009;Van der Hilst and Li, 2010). The western end of this stagnant slab does not go beyond the NNE-trending NSGL (Huang and Zhao, 2006;Xu, 2007).…”

An experimental study of phase transformations in olivine under pressure and temperature conditions corresponding to the mantle transition zone

“…Numerous studies have focused on the upper mantle structure of eastern China [34,[40][41][42]. Their general conclusion is that the structures under northeastern and northern China are distinct (Figure 6a-c).…”

“…b, Upper mantle structure of the bay area of the Bohai Sea (eastern China) based on receiver function analysis [41]. c, Upper mantle structure under North China Craton (35.3°N, 114.8-120.2°E), based on receiver function migration analysis [42]. d, 410 and 660 km seismic discontinuities under the South African Craton, determined from stacking receiver function analyses [45].…”