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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS013 Poster presentation 2243
Exhumation of the Dabie UHP Metamorphic Terrane, China
Prof. Qingchen Wang
Institute of Geology and Geophysics Chinese Academy of Sciences IASPEI
Exhumation of deeply buried Ultra-high-pressure (UHP) terranes remains a puzzle in understanding
lithospheric dynamic process. New evidence that constrains the exhumation process of the Dabie UHP
terrane includes: (1) Structural geological data record the architecture of the Dabie UHP terrane. Three
slices are recognized, i.e., from top to bottom, the Susong blueschist slice, the Huangzhen-Huangweihe
(HH) HP slice, and the Jinheqiao-Shuanghe-Bixiling (JSB) UHP slice. These slices have been stacked and
domed. (2) Geophysical data depict two offsets in the Moho. Offset-I separates the Dabie UHP terrane
from the North China Craton and has served as a subduction channel, as well as an exhumation
channel. Offset-II, separating the Dabie UHP terrane from the foreland belt, developed due to
geodynamic regime reorganization. (3) Geochronological data reveal that the HP slice was exhumed
earlier that the UHP slice. A northward younging exhumation polarity is implied with younger
exhumation age closer to the exhumation channel. These evidences point to a multistage exhumation
process. The Yangtze Craton collided with and subducted beneath the North China Craton in the very
beginning of Triassic time. By 230 Ma, the Susong blueschist slice and the south end of the HH HP slice
had arrived at a middle crustal level, while its north part was still at mantle depth. Such processes
continued until the JSB UHP slice was exhumed to mid-crustal levels at 210 Ma. After geodynamic
regime reorganization during 210~180 Ma, continuing compression of the Yangtze Craton and
underthrusting along the offset-II in the Moho caused the dome structure and eventually brought the
UHP rocks to the Earths surface.
Keywords: uhp, dabieshan, exhumation