Coesite inclusions in zircon from gneisses identified by laser Raman microspectrometer in ultrahigh pressure zone of Dabie Mountains, China

Abstract

The mineral inclusions in zircon from gneisses in ultra-high pressure (UHP) zone of the Dabie Mountains were identified by using a laser Raman microspectrometer. Coesite occurs as inclusions in zircons from all types of gneiss. Other important minerals, such as jadeite, omphacite, aragonite, barite, and anhydrite were also found as inclusion minerals. These discoveries indicate that (i) gneissic country rocks had metamorphosed at the same time as the enclosed eclogites; and (ii) SO4−2-bearing fluids were present in the UHP metamorphic process, which is manifested by occurrence of barite and anhydrite coexisting with coesite.