Geophysical Evidence for the Ancient Suture Within the Cathaysia Block

The Zhenghe-Dapu fault zone, which has a length of ~800 km and is located in southeastern China, has been mapped as a suture. Geological and geochronological data indicate that the suture is filled with chaotic pelagic sedimentary rocks and ophiolite mélange that separated the Cathaysia block at ~860 Ma by rifting and later closed as one block at ~240 Ma. However, the crustal structure corresponding to this ancient suture has seldom been reported. In this study, we investigate this suture based on four east–west reflected/refracted P-wave velocity structures, along with data of Bouguer and magnetic anomalies in Fujian province in China. The results indicate that the suture has imprinted in the crustal structure, as shown by the low velocity zone and thicker crust beneath the suture as well as the low Bouguer anomalies. Additionally, a negative magnetic anomaly zone is located beneath the Zhenghe-Dapu fault zone and is consistent with a low-Vp velocity zone. This fault zone is suggested to be a rift basin filled with chaotic sedimentation. The compressional force may therefore have caused these low-susceptibility and low-density materials to move to deeper depths in Fujian province. These geological and geophysical data indicate that this suture is an important feature in southeastern China and they advance our knowledge of plate reconstruction.