Ultrahigh-pressure metamorphic evidence for gneiss from the northern Dabie complex, central China: message from zircon.

Micro-inclusions and the U-Pb age of zircons were investigated from the banded gneiss in the northern Dabie complex, central China Mineral inclusions in zircon from the gneiss,combined with cathodoluminescene images and isotopic dating, can be divided into three generations, i. e. primary magma assemblage of feldspar + biotite + quartz + apatite, ultrahigh-pressure ( UHP) metamorphic assemblage of diamond + garnet + rutile, and granulite-facies retrograde assemblage such as diopside. Diamond and garnet occurred as inclusion in diopside, which is representative retrograde mineral of granulite-facies in the northern Dabie complex. The zircons from the studied gneiss, analyzed by SHRIMP U-Pb, yielded peak metamorphic age of 218±3Ma and granulite-facies retrograde age of 199±10Ma. The evidences for UHP metamorphism were firstly discovered on the gneiss from the northern Dabie complex, indicating the banded gneiss of northern Dabie complex suffered Triassic UHP metamorphism as well as the enclosed eclogites.