Li, Sanzhong, Kusky, Timothy M., Zhao, Guochun, Liu, Xiaochun, Wang, Lu, Kopp, Heidrun, Hoernle, Kaj, Zhang, Guowei and Dai, Liming (2011) Thermochronological constraints on two-stage extrusion of HP/UHP terranes in the Dabie–Sulu orogen, east-central China Tectonophysics, 504 . pp. 25-42. DOI 10.1016/j.tecto.2011.01.017.

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Abstract

Along the Qinling–Dabie–Sulu orogenic belt in China crops out the world's largest terrane composed of
ultrahigh-pressure (UHP) metamorphic rocks. Differences in the timing and mechanisms of oceanic and
continental subductions are assumed to be responsible for different ages of high-pressure (HP) and UHP slices
in different parts of the belt. The western part of the Dabie orogen (western Dabie terrane) holds a key to
understanding of the transition from oceanic to continental subduction. This paper reports geochronological
results to test a two-stage tectonic model for the exhumation of HP/UHP rocks in western Dabie. This model
involves two different stages and types of extrusion for exhumation of the HP/UHP rocks in east-central China.
Mica Ar/Ar ages, ranging from 241 to 231 Ma, indicate a general middle Triassic cooling probably driven by
early upward extrusion during the collision between the North and South China Blocks. Late Triassic–Early
Jurassic cooling was associated with later eastward extrusion, ranging from 200 to 184 Ma. The second event
is recorded also in mica in the region that was not affected by later deformation and magmatism. The lateral
movement along lithosphere-scale faults resulted in the eastward extrusion of the HP–UHP metamorphic
terrane, which was followed, in the Late Triassic–Early Jurassic time, by a major compressive event. These two
extrusion events are correlative with the two stages of Triassic exhumation of the western Dabie HP–UHP
rocks, respectively. Wintin the framework of the Qinling–Dabie–Sulu orogenic belt, it is suggested for western
Dabie that the subduction/exhumation of blueschist-facies unit is related to the Mianlue suture, whereas the
subduction/exhumation of HP/UHP eclogite-facies units is related to the Shangdan suture.

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