摘要
针对近年来长白山火山下方地幔转换带中是否存在低波速异常指示的太平洋板块"空缺"而引起的不同科学认识的热烈辩论,本文主要回顾了我国东北地区地幔转换带的体波成像结果。使用相对走时残差的远震体波成像结果显示,长白山火山以西地幔转换带中存在低波速异常指示的太平洋板块"空缺";而使用绝对走时残差的区域成像和全球成像结果,尽管展示出长白山火山以西比以东略低的波速异常,但长白山火山以东至我国东北重力梯度带区域下方的地幔转换带均展示出明显的连续的高波速异常。在接收函数分析时,如果以全球平均值660km而非我国东北地区平均值670km作为基准,来分析660km间断面是抬升还是下沉;以全球平均值250km而非我国东北地区平均值260km作为基准,来分析地幔转换带是增厚还是减薄的话,则可以得到长白山火山以东至我国东北重力梯度带区域660km间断面下沉与地幔转换带增厚的认识。这种与绝对走时残差成像结果展示的地幔转换带为连续的高波速异常结果相一致的结果,说明太平洋板块俯冲前缘已由日本海沟抵达我国东北松辽盆地与大兴安岭交界处。结合高温高压实验、数值模拟与岩石地球化学研究结果,本文并不支持长白山火山以西的地幔转换带存在低波速异常指示的板块"空缺"和地幔转换带"减薄"的认识。长白山火山的深部起源与太平洋板块深俯冲至我国东北松辽盆地与大兴安岭交界处形成的"大地幔楔"结构动力学相关。
Some researchers consider that the Changbaishan volcanism is caused by hot and wet upwelling flow in the big mantle wedge （BMW） above the stagnant Pacific slab in the mantle transition zone （MTZ） beneath Northeast （NE） Asia, whereas a recent study suggests that hot upwelling flow from the lower mantle passes through a gap in the Pacific slab in the MTZ and then enters the upper mantle, causing the Changbaishan volcanism. In this article we review recent body-wave tomographic studies of the upper mantle and the MTZ under NE Asia and discuss whether a gap does exist in the Pacific slab under the Changbaishan volcano. To date, only one teleseismic tomographic model inferred from relative travel-time residuals shows a low-velocity anomaly （a gap） in the MTZ to the west of the Changbaishan volcano, whereas all the regional and global tomographic models derived from absolute travel-time residuals show a continuous high-velocity anomaly （i.e., the stagnant Pacific slab） in the MTZ from the region east of the Changbaishan volcano to the North-South Gravity Lineament （NSGL） in NE China. Although a few tomographic models show that seismic velocity is slightly lower to the west than to the east of the Changbaishan volcano, the velocity is still higher than the average velocity in the MTZ. Receiver function studies show that, the average depth of the boundary between the upper mantle and the lower mantle （BULM） is 660km globally, whereas it is 670km under NE China, and the average MTZ thickness is 250km globally, whereas it is 260km under NE China. If these global average values are taken as the criteria, then the receiver function results illustrate a depressed BULM and a thickened MTZ from the region east of the Changbaishan volcano to the NSGL. These receiver-function results are in good agreement with the continuous high-velocity anomaly in the MTZ imaged by most tomographic studies, suggesting that the front of the subducting Pacific slab has reached the boundary between the Songliao basin and the Great Xing＇an range. Integrating all findings from high-temperature and high-pressure experiments, numerical modeling and petrological, geochemical and geophysical studies till now, we deem that a thinned MTZ and a slab gap do not exist to the west of the Changbaishan volcano. To date, much more pieces of evidence support the BMW origin of the Changbaishan volcanism.
作者
雷建设
赵大鹏
徐义刚
樊祺诚
米琦
杜沫霏
鲁明文
LEI JianShe;ZHAO DaPeng;XU YiGang;FAN QiCheng;MI Qi;DU MoFei;LU MingWen(Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;Department of Geophysics, Tohoku University, Sendai 980-8578, Japan;State Key Laboratory of lsotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 51064-0, China;Institute of Geology, CEA, Beijing 100029, China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第1期13-22,共10页
Acta Petrologica Sinica
基金
中国科学院战略性先导科技专项(B类)(XDB18000000)
国家重点研发计划项目(2016YFC 0600408)
国家自然基金重点项目(41530212)和面上项目(41674901)
中国地震局地壳应力研究所基本科研业务专项(ZDJ2017-15)联合资助
关键词
长白山火山
深部起源
地震层析成像
接收函数
岩石地球化学
Changbaishan volcano
Deep origin
Seismic tomography
Receiver function
Petrology and geochemistry
