Subduction, collision and exhumation in the ultrahigh-pressure Qinling-Dabie orogen

Abstract

Abstract High-pressure metamorphism and ophiolite emplacement (Songshugou ophiolite) attended suturing of the Yangtze craton to Rodinia during the c. 1.0 Ga Grenvillian orogeny. The Qinling microcontinent then rifted from the Yangtze craton at c. 750 Ma. The Erlangping intraoceanic arc formed in the Early Ordovician, was emplaced onto the Qinling microcontinent in the Ordovician-Silurian, and then both units were accreted to the Sino-Korea craton before being stitched together by the c. 400 Ma Andean-style Qinling arc. Subsequent subduction beneath the Qinling-Sino-Korean plate created a Devonian-Triassic accretionary wedge that includes eclogites, and formed a coeval volcano-plutonic arc that stretches from the Longmen Shan to Korea. In the Late Permian-Early Triassic, the northern edge of the South China Block was subducted to >150 km depth, creating the diamond- and coesite-bearing eclogites of the Dabie and Sulu areas. Exhumation from the mantle by lithosphere-scale extension occurred between 245 and 195 Ma during clockwise rotation of the craton. The Yangtze-Sino-Korea suture locally lies tens of km north of the exhumed UHP-HP part of the South China Block, implying perhaps that the very tip of the South China Block was not subducted, or that the UHP-HP rocks rose as a wedge that peeled the upper crust of the unsubducted South China Block from the lower crust. The Tan-Lu fault is an Early Cretaceous to Cenozoic feature. The apparent offset of the Dabie and Sulu UHP terranes by the Tan-Lu fault is a result of this Cretaceous to Cenozoic faulting combined with post-collisional extension north of Dabie.