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

Ling Chen,Yinshuang Ai

doi:10.1029/2008jb006221

Abstract

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 north‐south 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 India‐Eurasia collision has had a relatively weak effect on the Cenozoic tectonics of these regions.

Highlights

[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
[2] The North China Craton (NCC) in east Asia is composed of the eastern and western NCC of Archean age and the intervening Trans-North China Orogen, which was formed by the collision of the eastern and western NCC in the Late Paleoproterozoic [G
To what extent the NCC was affected by the Mesozoic-Cenozoic tectonics of the surrounding plates, such as the Triassic north-south China collision, the deep subduction of the oceanic Pacific plate since Mesozoic, and the intercontinental collision between India and Eurasia in the Cenozoic etc., is hotly debated [e.g., Menzies et al, 1993; Yin and Nie, 1996; Griffin et al, 1998; Xu, 2001; Liu et al, 2004; Deng et al, 2004]

Summary

Introduction

[2] The North China Craton (NCC) in east Asia is composed of the eastern and western NCC of Archean age and the intervening Trans-North China Orogen (central NCC), which was formed by the collision of the eastern and western NCC in the Late Paleoproterozoic [G. In this regard, detailed knowledge about the discontinuity structure of the mantle transition zone beneath the NCC can help us to gain deeper insights into both the Phanerozoic reactivation of the overlying craton and the deep subduction and fate of the oceanic Pacific plate, and the correlation between the two processes. The ways in which the mantle transition zone west of the stagnant slab beneath the central and western NCC differs structurally from that under the eastern NCC are unclear These structural differences are important for constraining the thermal regime in the deep upper mantle and deciphering the factors that have controlled the tectonic evolution in both regions. On the basis of our migrated receiver function images and comparisons with tomography results, we discuss the structural differences between the eastern NCC and the central and western NCC, variations in the morphology of the subducting Pacific slab under the eastern NCC, and possible influences of the deep Pacific subduction and the IndiaEurasia collision on the tectonic reactivation and destruction of the craton

Data and Method

Discussion

Conclusions