Study on Metamict Zircon from the Koktokay No.3 Granitic Pegmatite Vein

In order to acquire relationships among chemical compositions,structures and metamict degrees of different positions on zircon and evaluate the influence of α-decay on structures of different parts of zircon,in this pater,metamict zircon from the Koktokay No.3 granitic pegmatite,Altai,NW China,was studied by using Electron Microprobe analysis(EPMA) and Raman spectrum analysis.EPMA results revealed that this zircon belongs to hafnian zircon with an evident zonal structure,and the contents of U and Th in the core were higher than those in the border.In addition,non-formula elements such as Ca,Al,and P were discovered in the crack-rich zone,which indicated that this part had altered into a zone with a weak structure.Both Raman spectra andα-radiation showed that the core of zircon was in the range of moderately to highly metamict.Furthermore,the radiation damage of this zone had recovered differently as a result of thermal annealing.In contrast,the border was well-crystallized with just a few isolated defective points in the local zone.