Lithospheric structure below Dabie Shan, China
Final Report Abstract
P and S receiver functions obtained from a portable array of 34 broadband stations in east central China provided a detailed image of the crust-mantle and lithosphere-asthenosphere boundaries in the Dabie Shan and its adjacent areas. P receiver function study beneath the Dabie Shan proposed a complicated pattern for the Moho boundary and suggested several crustal blocks beneath this orogen. Our results also showed that the crust beneath the Dabie Shan orogen has an obviously asymmetric blocked structure in the direction perpendicular to the mountain strike. The maximal crustal thickness reaches to 42 km, however the crust-mantle boundary shows a dislocation structure correlated to the crustal blocks and the largest offset reaches to 8 km. A low velocity body inside the crust of the orogen separating into two parts corresponded to the South Dabie and North Dabie on the structure is also visible in our data. The crust below this low velocity area has a positive gradient velocity structure with depth, even though the upper mantle down to the depth of 70 km shows a lower S-wave velocity than its both sides. Clear S-to-P converted waves produced at the lithosphere-asthenosphere boundary showed a thin lithosphere beneath the whole study area. Based on our results, the thickest lithosphere of 72 km was observed beneath the southern part of the area within the Yangtze craton, whereas beneath the North-China platform, the lithosphere is only 60 km thick. S receiver functions also revealed, in good agreement with P receiver functions, a maximum depth of the Moho beneath the Dabie Shan orogen at approximately 40-42 km. Based on our results, the general pattern of lithospheric variations is quite similar to that of Moho depth variations showing also similar recent tectonic processes which involved the Yangtze craton and the Sino-Korean craton. However, in small scale, distinctive lithospheric characteristics imply the existence of two lithospheric blocks. The resulting LAB depth map showed a good correlation with known geological and tectonic features, separating the Yangtze lithosphere at 32° latitude from the Sino-Korean lithosphere with approximately 60 km thickness in the north. This boundary at 32° latitude may draw the location of the mantle suture between two cratons, which has also been strongly influenced by tectonic processes affecting this area.
Publications
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Liu, Q., Kind, R., Chen, J., Yuan, X., Li, S., Guo, B., Wylegalla, K. & Lai, Y., 2005. Dislocation structure of the crust-mantle boundary and low-velocity body within the crust beneath the Dabie Shan collision orogen, Science in China, 48(7), 875-885.
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Sodoudi, F., X. Yuan, Q. Liu, R. Kind and J. Chen, 2006. Lithospheric thickness beneath the Dabie Shan, central eastern from S receiver functions. GeophysicalJournal International, 166, NO. 3, 1363 - 1367 (Siehe online unter: doi: 10.1111/j. 1365-246X.2006.03080.X)
