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

The basic granulite, which is considered to be the MORE based on geochemist ry and isotopic characteristics([1]), has been discovered recently as the e nclaves in the Yingjiang island-arc magmatic suite on the border of Burma a nd west Yunnan, east of Myitkyina suture in the eastern Burma. The laser mi cro-area Ar-40-(39)A. technique is used to date the age of garnet and cliop yroxene that is the result of the early metamorphic event. The isochron out come 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 lithosphe re tectonic evolution, tectonic thermal events and the age of deformation a nd metamorphism. The discovery of the high-grade or high-pressure metamophi c rocks in the island-are magmatic suite by the way of studying its P-T-t p aths can provide a good way to study the age and process of oceanic crust s ubduction, slab break-off, metamorphic terrain exhumation and the evolution of paleoocean basin.