Changbaishan volcanism in northeast China linked to subduction-induced mantle upwelling

Changbaishan volcanism in northeast China linked to subduction-induced mantle upwelling

Youcai Tang, Masayuki Obayashi, Fenglin Niu, Stephen P. Grand, Yongshun John Chen, Hitoshi Kawakatsu, Satoru Tanaka, Jieyuan Ning & James F. Ni

Nature Geoscience Online Edition: 2014/5/18, doi: 10.1038/ngeo2166.

Abstract

Volcanism that occurs far from plate margins is difficult to explain with the current paradigm of plate tectonics. The Changbaishan volcanic complex, located on the border between China and North Korea, lies approximately 1,300 km away from the Japan Trench subduction zone and is unlikely to result from a mantle plume rising from a thermal boundary layer at the base of the mantle. Here we use seismic images and three-dimensional waveform modelling results obtained from the NECESSArray experiment to identify a slow, continuous seismic anomaly in the mantle beneath Changbaishan. The anomaly extends from just below 660 km depth to the surface beneath Changbaishan and occurs within a gap in the stagnant subducted Pacific Plate. We propose that the anomaly represents hot and buoyant sub-lithospheric mantle that has been entrained beneath the sinking lithosphere of the Pacific Plate and is now escaping through a gap in the subducting slab. We suggest that this subduction-induced upwelling process produces decompression melting that feeds the Changbaishan volcanoes. Subduction-induced upwelling may also explain back-arc volcanism observed at other subduction zones.

沈み込んだ太平洋プレート(スラブ)と長白山下のマントル内の上昇流の様子を描いた想像図。スラブ(青)とその西側にあるマントルの低速度領域(赤)。これは滞留しているスラブが途切れ、温かいあるいは軟らかい物質があることを意味している。

*UTokyo Researchhttp://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/enigma-of-changbaishan-volcano-and-a-gap-in-stagnant-slab/

*Newsletter PLUS (digest)”NECESSArray project: Dynamics of earth interior seen from Northeast China