Subduction age of Neo-Tethys oceanic crust in southwest Yunnan, China: Laser micro-area 40Ar-39Ar dating

The basic granulite, which is considered to be the MORE based on geochemistry and isotopic characteristics([1]), has been discovered recently as the enclaves in the Yingjiang island-arc magmatic suite on the border of Burma and west Yunnan, east of Myitkyina suture in the eastern Burma. The laser micro-area 40Ar-(39)A. technique is used to date the age of garnet and cliopyroxene that is the result of the early metamorphic event. The isochron outcome is similar to 74.4 Ma which is induced to be the age of the suduction event of the Myitkyina oceanic crust on the basis of the Cenozoic lithosphere tectonic evolution, tectonic thermal events and the age of deformation and metamorphism. The discovery of the high-grade or high-pressure metamophic rocks in the island-are magmatic suite by the way of studying its P-T-t paths can provide a good way to study the age and process of oceanic crust subduction, slab break-off, metamorphic terrain exhumation and the evolution of paleoocean basin.