大别山高压-超高压片麻岩核-边结构锆石成因探讨  

Genesis of zircons with core-rim structure from HP-UHP gneisses of the Dabie Mountains

作　　者：刘文元[1,2,3] 刘景波[1] 柳小明[2] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]西北大学大陆动力学国家重点实验室,西安710069 [3]中国科学院研究生院,北京100039

出　　处：《地质科学》2009年第3期966-982,共17页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:40672054);创新研究群体科学基金项目(编号:40721062);西北大学大陆动力学国家重点开放实验室开放课题基金项目(编号:07LCD15)资助

摘　　要：大别山高压-超高压片麻岩中的锆石在阴极发光(CL)显示核-边结构:韵律环带的岩浆锆石核,较强发光的变质边。本文对核-边结构的锆石进行了包裹体、微区U-Pb年龄和微量元素研究。结果表明变质边由两种不同的机制形成:变质重结晶和变质增生。变质重结晶锆石的U-Pb年龄和稀土总量逐渐降低,稀土配分模式不变。变质增生锆石比变质重结晶锆石具有更低Th/U比值,重稀土严重亏损,Eu负异常不明显,低的Nb、Ta含量。Most of zircons in high-pressure and uhrahigh-pressure gneisses from the Dabie Mountains show the core-rim structures in their Cathodoluminescence（CL） images, consisting of inherited magmatic cores with oscillatory zoning and the rims of metamorphic origin with bright CL images. The researches, on the basis of the incluSion minerals determined by using Laser Raman microprobe,U-Pb ages and trace elements analyzed by using LA-ICP-MS suggest that the metamorphic rims of zircons was formed through two different mechanisms：recrystallization and overgrowth. Recrystallization could result in gradually decreasing U-Pb ages and total contents of rare earth elements （REE）, but the REE pattern remains unchanged. Comparing with the recrystaIlization zircons, the overgrowth zircons have no negative Eu anomaly,lower Th/U ratios and contents of Nb and Ta,more depleted HREE.

关 键 词：锆石 变质重结晶 变质增生 U—Pb年代学 微量元素 

分 类 号：P597[天文地球—地球化学] P588[天文地球—地质学]