P and S wave tomography of east-central China: insight into past and present mantle dynamics

Abstract

East-central China has experienced multi-stage evolution among different tectonic units; thus the present geological structures are superimposed in a long history. But it is still unclear how different tectonic processes interact with each other, especially how the subsequent activity affects the previous structures. In this study, we determined new high-resolution P and S wave tomography of the upper mantle beneath the east-central China. We imaged the stagnant Pacific slab in the mantle transition zone and the hot low-velocity upper mantle in eastern China while cold high-velocity bodies beneath the Archean cratons in central China. More importantly, we newly revealed two important features. Firstly, a high-velocity zone is found in the uppermost mantle (50–150 km) beneath the Southeast China; its location is comparable to the distribution of the Cretaceous igneous rocks. Thus, we propose that the high-velocity anomalies reflect the remnant mafic rocks in the upper mantle after the volcanic eruption. Secondly, a high-velocity body is revealed in the deep upper mantle (300–500 km) beneath the southwestern Yangtze craton, possibly implying the delaminated cratonic lithosphere in the Early Mesozoic.