Crustal Deformation and Detachment in the Sulu Orogenic Belt: New Constraints From Onshore-Offshore Wide-Angle Seismic Data

Abstract

We deployed the first dense onshore-offshore seismic survey profile across the ultrahigh/high-pressure metamorphic Sulu Orogenic Belt (SLOB). By applying multiple seismic and gravity modeling, we obtained the crustal P wave velocity and density model across the SLOB and extending into tectonic units on both sides, including the eastern Sino-Korean Block (SKB), and the lower Yangtze Block (YZB). A ∼120-km-wide high-velocity and high-density upper crust in the southern SLOB reveals the distribution of ultrahigh/high-pressure metamorphism, which should be linking with the deep subduction, detachment, and exhumation of YZB midcrust. In the northern SLOB, the U-shaped velocity contours throughout the crust and the low-density midcrust reveals the downward bending of the crustal deformation due to the collision between SKB and YZB. The crustal deformation and detachment in the SLOB revealed by our results indicate that the orogenic spatial distribution should be wider than what we know before. © 2021. American Geophysical Union. All Rights Reserved.