Syn-collisional channel flow and exhumation of paleoproterozoic High Pressure rocks in the Trans-North China Orogen: the critical role of partial-melting and orogenic bending

Pierre Trap (1) , Michel Faure (2) , Wei Lin (3) , Romain Augier (2) , Antoine Fouassier (2)

1 LCE - Laboratoire Chrono-environnement (UMR 6249)
2 ISTO - Institut des Sciences de la Terre d'Orléans
3 SKL - State Key Laboratory of Lithospheric Evolution

Within the paleoproterozoic Trans-North China Orogen, the High-Pressure Belt (HPB) is made of high-pressure (~ 15 kbar) mafic granulites hosted in migmatitic gneisses. In this contribution, we document a set of structural analyses acquired over the whole HPB. We also proposed a morphological subdivision of the partially molten rocks that compose the HPB according to changes in melt fraction. A compilation of the P-T and radiochronological data carried out over the last 15 years is presented. The results highlight the concurrent effect of oroclinal bending and partial-melting in controlling the exhumation of the deeply buried continental crust. During ongoing compression of the thickening orogenic root, onset of partial-melting at peak metamorphism is responsible for a first strength drop that enhanced an eastward lateral flow. Radiometric ages show that the deep crust was partially molten over a 50 Ma lasting period during which it evolved in a diatexite core mantled by metatexites. This was responsible for a second strength drop with strain concentrated along the diatexite/metatexite boundaries, as exemplified by the newly documented Datong-Chengde Shear Zone, a ~ 400 km-long normal shear zone with a sinistral strike-slip component that accommodated the final uprise of the high-pressure rocks.

Mots clés: High-pressure rocks; Exhumation; Partial melting; Channel flow; Trans-North China Orogen

Domaines: Tectonique; Milieux et Changements globaux

Pierre Trap, Michel Faure, Wei Lin, Romain Augier, Antoine Fouassier. Syn-collisional channel flow and exhumation of paleoproterozoic High Pressure rocks in the Trans-North China Orogen: the critical role of partial-melting and orogenic bending. Gondwana Research, 2011, 20, pp.498-515. ⟨10.1016/j.gr.2011.02.013⟩. ⟨insu-00576322⟩