Tectonics of the Dabieshan (eastern China) and possible exhumation mechanism of ultra high-pressure rocks


Michel Faure E-mail: michel.faure@univ-orleans.fr


The Dabieshan is divided into three tectonic domains. The Southern Dabieshan is a stack of allochtons, from top to bottom: (i) unmetamorphosed Cambrian–Early Triassic series unconformably covered by Jurassic sandstone; (ii) weakly metamorphosed Proterozoic slate; (iii) HP rocks mostly retrogressed into greenschist facies; (iv) UHP allochton; (v) UHP-free gneisses. These units exhibit a NW–SE lineation and top-to-the-NW shearing reworked by S-verging folds. The Central Dabieshan is a migmatitic dome superimposed on UHP metamorphism and bounded by a detachement fault responsible for the exhumation of the UHP unit during its retrogression into amphibolite facies. In the Northern Dabieshan, early foliation and N–S trending compressional lineation are deformed by N-verging folds coeval to the syn-exhumation ductile structures of the Central Dabieshan. A geodynamic model involving coeval thrusting and normal faulting is discussed.