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Sharpness of the Midlithospheric Discontinuities and Craton Evolution in North China
Journal of Geophysical Research: Solid Earth ( IF 3.9 ) Pub Date : 2020-09-13 , DOI: 10.1029/2019jb018594
Weijia Sun 1, 2 , Liang Zhao 2, 3, 4 , Huaiyu Yuan 5, 6 , Li‐Yun Fu 7
Affiliation  

The lithospheric layering and evolution of Archean cratons can be effectively constrained by seismic properties. We present fine‐scale lithospheric discontinuity images of the North China Craton (NCC) using the seismic daylight imaging (SDI) technique, which is also known as the autocorrelogram method. With the aid of large‐scale surface‐wave velocity models, the characters of autocorrelograms related to lithospheric discontinuities in the NCC are investigated. Spatial variation in discontinuity characteristics is revealed across the craton. In the modified/destroyed eastern NCC, both the midlithospheric discontinuity (MLD) and the lithosphere‐asthenosphere boundary (LAB) are rather sharp (~2 km). Various dynamic processes, including juvenile underplating, asthenospheric upwelling, and corner flow induced by paleo‐Pacific Plate subduction, may contribute to such sharp interfaces. In the stable western NCC, P wave reflections cannot easily reveal the LAB, suggesting a diffuse (thicker than 30 km) lithosphere‐asthenosphere transition (LAT). Multiple MLDs are also found that may have arisen during craton formation and multiple phases of rejuvenation of the cratonic lithosphere as evidenced by the petrological results. The use of higher‐frequency data enables us to distinguish among the lithospheric discontinuity styles and favor multiple origins of the MLDs and LAB in the cratonic lithosphere.

中文翻译:

华北岩圈中部间断的锐度与克拉通演化

太古代克拉通的岩石圈分层和演化可以受到地震作用的有效限制。我们使用地震日光成像(SDI)技术(也称为自相关图法)呈现了华北克拉通(NCC)的精细尺度岩石圈间断图像。借助大规模的表面波速度模型,研究了与NCC中岩石圈不连续性有关的自相关图的特征。整个克拉通都显示出不连续性特征的空间变化。在经过改造/破坏的东部NCC中,岩圈中部的不连续面(MLD)和岩石圈-软流圈边界(LAB)都非常陡峭(〜2 km)。古太平洋板块俯冲引起的各种动力学过程,包括青少年的底盘活动,软流圈上升以及角流,可能有助于实现如此尖锐的界面。在稳定的西部NCC中,P波反射不能轻易地揭示出LAB,这表明岩石圈-软流圈之间存在弥漫性的变化(厚度小于30 km)。岩石学结果表明,在克拉通形成和克拉通岩石圈回春的多个阶段中可能还出现了多个MLD。高频数据的使用使我们能够区分岩石圈不连续性样式,并支持克拉通岩石圈中MLD和LAB的多个起源。
更新日期:2020-09-22
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