The Dabie UHP unit, Central China: a Cretaceous extensional allochthon superposed on a Triassic orogen

Petrological, geochronological and structural data show that the eastern Da bie metamorphic complex resulted from two orogenic stages. Precursor rocks of the ultrahigh-pressure (UHP) and high-pressure (HP) units in the present hanging wall tectonic position were buried, penetratively deformed and sub sequently exhumed by distributed, ESE-directed shearing during Triassic tim e. In contrast, rocks of the Dabie orthogneiss domes, now in a footwall tec tonic position, were penetratively deformed during temperature-dominated, E arly Cretaceous tectonic events, that are likely related to magmatic underp lating. The Dabie orthogneiss domes and the UHP/HP units were juxtaposed du ring Early Cretaceous exhumation of: Dabie orthogneiss domes by the formati on of an ESE-directed low-angle ductile normal sheer zone. Consequently, th e UHP/HP units now represent an extensional allochthon in the hanging wall of the younger normal shear zone. The Cretaceous extensional structures are limited by boundary strike-slip faults. Consistent with the South China re gional tectonic framework, ESE-directed lateral extrusion is considered to be the driving mechanism for extension and the present-day structure of the Dabie metamorphic complex.