科研之友
微信
新浪微博
Facebook
分享链接
摘要
The Triassic Dabie-Sulu collision zone along with recently identified ultrahigh-pressure (UHP) and high-pressure (HP) metamorphic terranes of the western Tianshan, Altyn Tagh, northern Qaidam, and northern Qinling belts forms a huge chain of orogens from northwestern to east-central China. The western Tianshan HP/UHP terrane formed by Pacific-type subduction of a Paleozoic South Tianshan ocean, and was exhumed to higher crustal levels during collision of the Tarim and Yili-central Tianshan plates. HP/UHP recrystallization took place either at similar to 345 Ma or 232-2.15 Ma. The Altyn Tagh, northern Qaidam, and northern Qinling UHP belts are Early Paleozoic collisional orogens. Coesite-bearing eclogites, garnet peridotites, and the country rock gneisses in the Dabie-Sulu UHP terrane were subjected to in situ UHP metamorphism based on the presence of abundant coesite inclusions in zircons and identical metamorphic ages in both eclogite and gneiss. Some garnet peridotites are crust-hosted whereas others were mantle derived. The later are depleted mantle fragments that experienced mantle metasomatism and subduction-zone UHP metamorphism. P-T estimates for eclogites and garnet peridotites combined with investigations of mineral exsolution textures and high-P polymorphs indicate that recovered depths of continental subduction in China reached 200 km or more.
- 出版日期2007-6
