Exhumation of the Dabie Shan ultra-high-pressure rocks and accumulation of the Songpan-Ganzi flysch sequence, central China

The presence of coesite- and diamond-bearing ultra-high-pressure (UHP) metamorphic rocks in the Dabie and Sulu regions, central China, suggests that a >100-km-thick crustal section (4 x 106 km6 in volume) has been denuded. This volume is comparable to that represented by the 10-15-km-thick Middle to Upper Triassic flysch rocks in the Songpan-Ganzi region. Regional geology and radiometric dates are compatible with an interpretation that the majority of these sedimentary rocks were derived from denudation of the orogenic belt between North and South China blocks following their latest Paleozoic to Triassic collision. This correlation implies a high denudation rate of ∼4 mm/yr that may have been in part promoted by tropical precipitation and extreme topographic relief for as long as 25 m.y.