Crustal structure of the North China Craton from deep seismic sounding data

Abstract:

We present a digital crustal structure model of the North China Craton at a resolution of 0.25°×0.25° within the boundaries of 30–45°N and 100–130°E. The new model is based on almost all (except for a few very old and publically unavailable profiles) deep sounding reflection/refraction seismic profiles with a total length of more than 23,000 km. The database includes the depth to Moho, thickness and average P wave velocity of four crustal layers (sediments, upper crust, middle crust, and lower crust), and Pn velocity. We analyze the crustal structure in different tectonic units of the North China Craton. The thickness of sediments correlates strongly with the tectonic setting. It ranges from near-zero to 2 km in the northern and southern orogenic belts, 3–4 km in the central parts of the craton, to more than 6 km in the Ordos basin and the North China Plain. The Moho depth and the thickness of the crystalline crust increase from east to west. The Moho depth varies from 30-32 km along the eastern coast up to 54 km under the western block; Pn velocities range from 7.9 to 8.1 km/s. The upper crust with an average Vp of 6.2-6.3 km/s increases in thickness from 16 km in the east to 22 km in the west. In the eastern block, the thickness of the middle crust is 10-12 km with an average Vp~6.5-6.7 km/s. In the western block, the thickness of the middle crust changes from 13 km in the west to 23 km in the east. The thickness of the lower crust (Vp~ 6.9-7.0 km/s) in most of the eastern block is only 0-2 km, probably due to partial melting of the lower crust in the northern block and delamination in the southern block. In the western block, the lower crust is up to 6 km thick. We illustrate results by a series of maps, which demonstrate strong crustal heterogeneity.