The Dabie UHP unit, Central China: a Cretaceous extensional allochthon superposed on a Triassic orogen |
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Authors: | Wang Neubauer Genser & Yang |
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Institution: | Department of Geology and Palaeontology, University of Salzburg, Hellbrunner Straße 34, A-5020 Salzburg, Austria, and Faculty of Earth Sciences, China University of Geosciences, Wuhan city, Hubei province, 430074, China; Department of Geology and Palaeontology, University of Salzburg, Hellbrunner Straße 34, A-5020 Salzburg, Austria; ADepartment of Geology and Palaeontology, University of Salzburg, Hellbrunner Straße 34, A-5020 Salzburg, Austria; Faculty of Earth Sciences, China University of Geosciences, Wuhan city, Hubei province, 430074, China |
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Abstract: | Petrological, geochronological and structural data show that the eastern Dabie 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 subsequently exhumed by distributed, ESE-directed shearing during Triassic time. In contrast, rocks of the Dabie orthogneiss domes, now in a footwall tectonic position, were penetratively deformed during temperature-dominated, Early Cretaceous tectonic events, that are likely related to magmatic underplating. The Dabie orthogneiss domes and the UHP/HP units were juxtaposed during Early Cretaceous exhumation of Dabie orthogneiss domes by the formation of an ESE-directed low-angle ductile normal shear zone. Consequently, the 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 regional 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. |
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