High‐ to ultrahigh‐pressure (HP‐UHP) metamorphic rocks that resulted from deep continental subduction and subsequent exhumation in the Sulu orogenic belt, China, have experienced multiphase deformation and metamorphic overprint during its long journey to the mantle and return to the surface. HP‐UHP shear zones are strain‐localized weak zones on which the UHP slab is transported over long distances. HP‐UHP shear zones are well exposed along a 200‐km belt in the Sulu UHP metamorphic belt. The shear zones lie structurally below the UHP rocks and above the non‐UHP rocks, suggesting the early exhumation of the UHP rocks by thrusting. The large area distribution, HP‐UHP nature, high strain and structural association of the shear zones with the UHP rocks suggest that the shear zones are probably a regional detachment developed during the early stage of exhumation of the UHP rocks. Kinematic indicators suggest top‐to‐the N–NW motion of the UHP slab during the exhumation, which, combined with isotope signature in Mesozoic igneous rocks, leads us to the interpretation that the subduction polarity is the North China plate down to the south rather than the Yangtze plate down to the north in the Sulu region.
The detailed P-wave velocity structure of the crust in the southern Kanto-Tokai region was analyzed using the tomographic method for seismic refraction survey in this paper. A total of 332 P-wave arrival times received from 13 seismic explosion surveys were used in the analysis. The results indicate that analyses of travel-time curves are probably useful for the evaluation of inverted structures. The lateral heterogeneity of the velocity structure is obviously related to tectonics. The crust in the eastern region is thinner than that in the western region. The Conrad discontinuity obviously fluctuates.The granitic layer is thinner beneath the oceanic region to the east of Oshima. The layer becomes about 16 km thick beneath Suruga Bay. The Conrad discontinuity drops nearly 17 km in depth beneath Suruga Bay, and velocity is relatively low there. The Conrad discontinuity rises 6 km beneath MTL and its vicinity. The Moho discontinuity is located at a depth of around 34 km beneath the region to the west of ISTL and roughly coincides with the upper boundary of the seismic zone due to subduction of the Philippine Sea Plate under the Eurasian Plate. It becomes shallow across the Suruga trough toward the eastern region. The discontinuity is located about 27 km in depth beneath the oceanic region east of Oshima.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.