New geological interpretation of the seismic reflection profile from Huangshi to Liu′an across the Dabie Mountains, China.

There are many subhorizontal reflectors in the Huangshi-Liu′an migrated seismic reflection profile across the Dabie Mountains, which suggests that subhorizontal stratification also occurs in the middle and lower crust below the central part of the Dabie Mountains and shows the difference in rheology and kinematics. This agrees with the understanding of the nature of the lithosphere based on the concept of “thin skin tectonics”. On the basis of the previous geological interpretation of this seismic reflection profile, combined with the classification of the petrologic-tectonic associations of the Dabie Mountains, a more detailed geological interpretation of this profile is made and a 2D geometric architecture of the Dabie orogen along the profile is established in the present paper. In the southern part of the profile, an antiform was formed in the orogenic process, and within 15 km below the surface there occurs the main detachment between the Yangtze block and Sino-Korean block, composed of collisional mélanges. The middle part of the profile is occupied by a post-orogenic intrusion. The northern part is the root zone of the main detachment, cut by the Xiaotian-Mozitan fault formed in the Mesozoic; it is commonly regarded as a suture between the two blocks. The northernmost part is the back thrust belt formed slightly later than the main detachment. It is inferred that the offset of the lower crust and Moho was large during the subduction of the Yangtze block before the Triassic and then was reduced to the present magnitude.