Ultrahigh-pressure orogeny: Sutures of the Qinling-China

The Qinling-Dabie orogenic belt stretches from the Qin mountain range ("Qinling") south of Xi`an 1500 km westward and further 600 km eastward. To the east, the belt extents through the Tongbai, Dabie, and Sulu areas into the fold belts of Korea. In the west, the Qinling-Dabie orogenic belt continues to the Kunlun and Qilian orogens. With its vast east-west extension, the Qinling-Dabie orogenic belt covers a wide area in east-central China and constitutes the centerpiece of Chinese geology. The major tectonic event in the Qinling-Dabie belt is the Permo-Triassic collision of the Sino-Korean and the Yangtze cratons. Prior to this event, the Qinling-Dabie belt records a complex history: (1) The Yangtze craton was assembled into the supercontinent Rodinia at ~1.0 Ga during the Grenvillian orogeny. (2) In the Ordovician- Silurian, the Sino-Korean craton collided with the Qinling microcontinent, which formerly rifted from the Yangtze craton. (3) In the Devonian-Early Triassic northward subduction created beneath the assembled Qinling microcontinent-Sino-Korean plate an accretionary wedge and an Andean-type magmatic arc. The Late Permian- Early Triassic subduction of the northern edge of the Yangtze craton to >150 km depth is responsible for creating high-pressure and ultrahigh-pressure rocks, the youngest high-pressure event among four (Grenvillian, Devonian, Carboniferous and Triassic). The ultrahigh-pressure rocks mostly crop out in the central part of the fold belt, the Dabie-Sulu area. There, these rocks are characterized by diamond- and coesite-bearing felsic to mafic crustal rocks of the Yangtze craton and were exhumed from mantle depths to the surface during clockwise rotation of the Yangtze craton during the Triassic-Early Jurassic. To the west in the Qinling, the western edge of the Triassic high- pressure and ultrahigh-pressure slab is undefined, possibly represented by alleged "blueschist belts" along the Liuling and Mianlüe sutures and the blueschist-grade "Wudang Shan gneiss dome" between these sutures. Cretaceous and Cenozoic reactivation of the Triassic Qinling-Dabie orogen is locally strong and resulted from far- field collisions, e.g. the Tertiary India-Asia collision. The understanding how high pressure and ultrahigh-pressure metamorphic rocks form and exhume is an outstanding tectonic question. Together with the Caledonides of Norway, eastern China constitutes the archetypes of ultrahigh-pressure orogeny. Thus, the Qinling orogenic belt provides the ideal area to study the exchange of material between the crust and mantle as well as the formation and destruction of mountain belts, the composition of deep continental crust, and tectonic plate motion; most of these processes are still enigmatic. Most enigmatic though, remain the processes and geometries of exhumation along the western edge of the Triassic high-pressure and ultrahigh-pressure slab in the Qinling. Together with structural geologists, petrologists, and geochronologists from the Technische Universität Bergakademie Freiberg, who have gained profound knowledge in this field over the last ten years, I propose to work along the two enigmatic suture zones, the Liuling and Mianlüe sutures. I plan to clarify the geometry and exhumation processes along the western edge of the Qinling-Dabie-Sulu high-pressure and ultrahigh-pressure slab and its relationship to these sutures. The major scientific approaches will be extended field work, geochronology, petrology, and structural geology. Brought in context with the work of the Freiberg group, this project will be an important contribution to the understanding of the formation and exhumation of the western edge of the world`s largest high and ultrahigh- pressure slab.