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

Abstract

The continents on the earth are formed by several ancient continental blocks through millions of years of divergence and convergence. North China (Figure 1a) was mainly formed by the convergence of the Sino-Korean Block (SKB) and the Yangtze Block (YZB) in the Triassic (Wan, 2012). The collision between SKB and YZB formed the famous Qingling-Dabie-Sulu orogenic belt (QDSOB), which has been proven to be the world's largest ultrahigh-pressure metamorphism (UHPM) and high-pressure metamorphism (HPM) belt

Integrated Geophysical Study of the Collision Between the North China Craton and the Yangtze Craton and Its Links With Craton Lithospheric Thinning

“…After pre-processing the data, including linear time drift correction, OBS relocation, denoising, and deconvolution (Figure 4), we picked the travel-times of the refraction and reflection seismic phases from all the useful OBSs and land stations (Liu et al, 2015;Liu et al, 2021). We found that most of the OBS stations provided useful data at offsets of up to 100 km (Figure 5), although a few OBS stations only provided effective observations within 60 km offsets.…”

“…Most of the phases in the Bohai Sea and SYS had the same distribution, but the refractions within the upper crust of the northern SYS had lower travel times and larger apparent velocities than those in the Bohai Sea from offset 0 km to about 120 km, indicating a roughly 120-km scale high-velocity anomaly in the upper crust of the northern SYS. The high-velocity anomaly was linked to the exhumation of the UHPM rocks in the SLOB (Liu et al, 2021).…”

“…We estimated the resolution of the models for the four lines by applying differently sized checkerboard tests (Figure 8) for the inversion models and perturbation analysis and the F-test for the forward models (Liu et al, 2015;Liu et al, 2021). In general, the uncertainty in the velocity was between −0.3 and 0.3 km/s, the uncertainty in the depth of the Moho was <1 km, and our models were able to effectively recover checkerboard patterns larger than (30 km × 10 km) throughout the crust.…”

“…The SLOB is located on the southern Jiaodong Peninsula and in the northern SYS (Figure 2) and retains a large number of structural traces generated during the collision between the NCC and YZC (Hao et al, 2010). As the eastern extension of the QDSOB, the SLOB is an important region for studying the dynamics of continent-continent collision, subduction, and reentry (Liu et al, 2021). Based on petrological chronology research, geochemical analysis, and deep structural geophysical observations around the SLOB, early research constrained the exhumation time of the UHPM to about 120 Ma in the Cretaceous (Li et al, 2009).…”

“…Like the NCC, the YZC is divided into three parts from west to east: the upper, middle, and lower YZC. Based on magnetotelluric sounding (Xiao et al, 2014), active-source seismic sounding (Xu et al, 2014;Lü et al, 2015;Liu et al, 2021), earthquake tomography (Jiang et al, 2013;Ouyang et al, 2014;Bao et al, 2015), and receiver function analysis (Shi et al, 2013;Zheng et al, 2014), previous studies reached a consensus that the lithosphere of the YZC has undergone significant thinning from west to east (Figure 1D) and that the thinning reaches a maximum in the eastern YZC, with a lithospheric thickness of <80 km (An and Shi, 2006) and a crustal thickness <35 km (Zhang et al, 2009).…”