可可托海3号伟晶岩脉中蜕晶质化锆石微区研究

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

通过电子探针和激光拉曼光谱分析技术系统研究了阿尔泰可可托海3号伟晶岩中蜕晶质化锆石各部位的成分特征、结构变化和蜕晶质化程度间的关系,定量评测了放射性衰变对锆石不同部位结构的影响程度。成分分析结果表明此锆石为铪质锆石,具有明显的环带,其中核部U、Th含量高,边部U、Th含量低,而且锆石破碎区富含非化学式元素Ca、Al、P等,表明此处为锆石的薄弱区,已发生热液蚀变。拉曼光谱特征和锆石的辐射剂量值都表明,锆石核部发生了中度-高度的蜕晶质化,且由于热事件发生退火,辐照损伤程度得到一定的愈合;而边部晶体结构保持较好,只局部出现点缺陷和零星非晶质区。

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.