The Dabie–Sulu continental collision zone: A comprehensive review
The Dabie–Sulu Triassic orogen in central-eastern China was created by northward subduction of the Yangtze cratonal plate beneath the Sino-Korean craton. Eclogites, garnet peridotites and the surrounding country rock gneisses in the collision zone were subjected to in situ ultrahigh-pressure (UHP) metamorphism based on the presence of widespread coesite inclusions in eclogitic minerals and in gneissic zircons, and on virtually identical metamorphic ages of the various UHP rocks. P–T estimates combined with investigations of mineral exsolution textures and high-P polymorphs indicate that recovered depths of continental subduction in east-central China may have reached 200 km or more. Parageneses of mineral inclusions reflecting pre-peak, peak, and retrograde metamorphism in zoned zircon prisms, combined with SHRIMP U–Pb age data imply exhumation rates of 5–10 km/Myr for the Dabie–Sulu UHP terrane. Petrochemical and zircon U–Pb + Hf isotopic studies of various rocks suggest that initial crustal growth of the Yangtze craton occurred in the Archean, but significant Neoproterozoic addition of continental crust along the northern margins of the Yangtze craton is indicated by the formation of abundant bimodal igneous rocks during supercontinental rifting in response to the breakup of Rodinia at about 750–780 Ma. Mineral oxygen isotope and zircon U–Pb data from many surface specimens, and CCSD-main hole core samples over a 3.3 km depth range indicate that three-dimensional 18O depletion took place in more than 100,000 km3 in the Dabie–Sulu collision zone; the northern edge of the Yangtze craton was attended by Snowball Earth conditions, and extensive meteoric water-rock interactions occurred during the Neoproterozoic. Most Sulu garnet peridotites were derived from a depleted and metasomatized mantle, representing the subcontinental lithosphere beneath the southern margin of the Sino-Korean craton. Although significant progress has been made in studies of the Dabie–Sulu orogenic belt, critical questions remain unanswered. With new approaches and advanced technologic applications, many petrochemical, mineralogical and isotopic surprises and new tectonic models are anticipated for the years to come.