Abstract
AbstractWe obtained the crustal thickness and average crustal Vp/Vs ratio along the profiles across the Liaodong anteclise, Yanshan belt and Xingmeng orogenic belt using H‐к stacking of receiver functions. The result shows that the average crustal thicknesses of these three tectonic units are 32, 33 and 35 km, respectively, indicative of slight differences, and display distinct transverse variations in the crustal structure. The crust is thicker in the middle and thinner on each side in the Liaodong anteclise, whereas the thickness of the crust varies smoothly in the Yanshan belt. In the Xingmeng orogenic belt, the crust thickens sharply from southeast to northwest near the Solonker suture. The Vp/Vs ratio also fluctuates obviously in the study region. In particular, it varies laterally in the Yanshan belt and increases markedly nearby the boundary area between the Yanshan belt and the Xingmeng orogenic belt (near the north‐south gravity gradient zone). However, the Vp/Vs ratio is relatively low and has small change in the Xingmeng orogenic belt. The distinct crustal structures of the Yanshan belt and the Xingmeng orogenic belt are probably indicative of a more intense crustal modification in the Yanshan belt compared with the Xingmeng orogenic belt during Mesozoic‐Cenozoic time. Significant changes in the crustal structure roughly coincide with the north‐south gravity gradient zone aforementioned. This together with the concordant change in the deep lithospheric structure observed previously suggests that this gravity gradient zone may be a lithospheric‐scale intra‐continental tectonic boundary, the opposite sides of which may have evolved differently in the Phanerozoic. The thickening of the crust in the Xingmeng orogenic belt (near the Solonker suture) and the Liaodong anteclise appears to mirror the surface topography, and corresponds to relatively stable Vp/Vs ratios. This feature probably indicates relatively even Phanerozoic modifications of the crust in each region, resulting in minor lateral variations in the crustal structure and components at present.
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