Tectonics of an ultrahigh‐pressure metamorphic terrane: The Dabie Shan/Tongbai Shan Orogen, China

Abstract

Ultrahigh‐pressure metamorphic rocks with coesite and diamond form a tectonic slice over 20 km thick, called the eclogite zone, within the Dabie Shan complex in the Qinling orogen in central China. The orogen separates the Sino‐Korean block in the north from the Yangtze block in the south. The Dabie Shan Complex is a composite terrane made up of eclogite facies and amphibolite facies gneiss slices and represents fragments of the lower continental crust of the Yangtze block. The Dabie Shan Complex is bounded in the south by a Triassic foreland fold‐thrust belt and in the north by a greenschist facies metaclastic unit, the Foziling Group, which probably represents the passive continental apron deposits of the Yangtze block. Farther north is a granulite facies gneiss complex, the Qinling Group, which has ultramafic slivers and includes the remnants of an island arc with two bounding suture zones. North of the Qinling Group are early Paleozoic active margin deposits of the Sino‐Korean block. The eclogite zone in the Dabie Shan Complex is sandwiched between amphibolite facies gneiss slices. Dating by Sm‐Nd, Rb‐Sr, and Ar‐Ar of two eclogite samples from the eclogite zone gives early to middle Triassic ages (236–246 Ma); the initial εNd values indicate reworking of a 2.11 and 1.55 Ga continental crust. A Himalayan‐type tectonic evolution is envisaged for the Qinling orogen with the creation of a 100‐km‐thick crustal thrust wedge through continuous underplating during the subduction of the Yangtze continental lithosphere. Exhumation of the ultrahigh‐pressure metamorphic rocks was chiefly achieved by the southward propagation of the thrust planes, thereby isostatically uplifting and eroding the earlier deeply subducted parts of the orogen. A total of 680 km of southward thrusting in front of Dabie Shan is inferred, based on the abrupt termination of the Tanlu fault. Normal faulting possibly caused by gravitational collapse probably also had a role in the exhumation process.

Sedimentary provenance of the Hengyang and Mayang basins, SE China, and implications for the Mesozoic topographic change in South China Craton: Evidence from detrital zircon geochronology

“…Intra-continental collision between the Yangtze Block and the North China Craton has been accepted as a crucial event during Triassic (Zhao and Coe, 1987;Ames et al, 1993;Okay et al, 1993;Yin and Nie, 1993;Zhang et al, 2000;Li et al, 1989Li et al, , 2000Li et al, , 2003. Jurassic was a time of the second rapid exhumation event (180-170 Ma) in the Dabieshan core and shortening along the north and south flanks of the range .…”

“…The collision between the North and South China blocks occurred in a diachronous manner from east to west since Early Mesozoic (Zhao and Coe, 1987;Yin and Nie, 1993;Okay et al, 1993;Faure et al, 1996;Liu et al, 2003;Katsube et al, 2009). A total of about 4.0 Â 10 6 km 3 was estimated to have been eroded from the suture zone during the Early Mesozoic (Okay et al, 1993;Li et al, 1999aLi et al, , 2000Li et al, , 2002a.…”

“…A total of about 4.0 Â 10 6 km 3 was estimated to have been eroded from the suture zone during the Early Mesozoic (Okay et al, 1993;Li et al, 1999aLi et al, , 2000Li et al, , 2002a. It is important to determine where such a great volume of sediment was eventually deposited and if the extensive denudation of the suture zone constituted the source for the basin sediment in the South China Craton.…”

Triassic polyphase deformation in the Feidong-Zhangbaling Massif (eastern China) and its place in the collision between the North China and South China blocks

“…The Dabieshan and Sulu areas are famous worldwide for the occurrence of ultra high-pressure (UHP) coesite-bearing eclogite facies metamorphic rocks (e.g. Wang et al, 1992;Okay et al, 1993;Liou et al, 1996 andCong, 1996). Abundant petrologic and geochemical data related to the UHP metamorphism have been published.…”

“…1; e.g. Mattauer et al, 1985;Okay et al, 1993 andCong, 1996). The Dabieshan and Sulu areas are famous worldwide for the occurrence of ultra high-pressure (UHP) coesite-bearing eclogite facies metamorphic rocks (e.g.…”