大别山榴辉岩带片麻岩的锆石拉曼光谱研究  

Laser-Raman spectroscopic studies on zircons of gneisses from the eclogitic zone of the Dabie Mountains.

作　　者：刘景波[1] 叶凯[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈构造演化国家重点实验室,北京100029

出　　处：《岩石学报》2005年第4期1094-1100,共7页Acta Petrologica Sinica

基　　金：基金项目(40272037);973项目(G1999075501);中国科学院创新项目(KZCX3-SW-135)资助

摘　　要：我们对来自大别山榴辉岩带11个片麻岩样品的锆石进行了拉曼光谱研究,这些研究集中在1008和356cm^(-1)峰和它们的半高宽上。依据阴极发光(CL)图像特征,锆石可分为三种结构类型:(1)核边结构,由一个老的岩浆锆石核和一个变质边构成,也可由两期变质锆石构成;(2)CL 不均匀强反差发光的锆石,这些锆石的一些部位明显发亮,这些发亮的部分是在早期岩浆锆石发育而来的;(3)CL 总体是均匀的或弱反差发光锆石。在 CL 图像的基础上,我们用拉曼扫描的方法分析了这3类不同结构的锆石。1008和356cm^(-1)峰显示了相同或相似的图像特征,而它们的半高宽图像有相同或相似的图像特征。峰和半高宽图像可以有一定差异。核边结构的和 CL 不均匀强反差发光的锆石的 CL 结构也反映在拉曼光谱的图像上,半高宽的图像更相似于锆石的 CL 图像。CL 总体是均匀的或弱反差发光锆石的拉曼光谱图像通常也是相对均匀的。11个样品锆石的1008cm^(-1)峰位值和它的半高宽落在放射破坏趋势上,我们认为早期继承的锆石在超高压变质过程中发生了完全退火和重结晶。一粒锆石拉曼光谱图像的结构反映的是不同的部分蜕晶化程度的差异,由于有相同的蜕晶化历史,这些部分的蜕晶化程度与这些部分的 U 和 Th 含量应该是正相关的。The bands of 1008 and 356cm^ -1 and haff-widths of zircons of eleven gneissic samples from the eclogitic zone of the Dabie Mountains have been studied by using laser-Raman spectroscopy. Zircons in samples can be divided into three types on the basis of their CL images ： the core-rim structural zircon, either consisting of an early igneous inherited core and an overgrowth metamorphic rim or two-stages metamorphic growth; strongly contrasting CL zircon, which the bright CL domains developed within an early inherited zircon; and homogeneous or weak contrasting CL zircon. We analyzed the zircons with different CL structures by laser-Raman scanning through the guide of CL image. The laser-Raman images of 1008 and 356cm^-1 bands exhibit the same or similar images, and their half-widths display the same or similar images. However there may be some difference between the images of a band and its half-width. For the core-rim and strongly contrasting CL zircons, the CL structure of zircon is also manifested by the laser-Raman images, and the image of the half-width is more similar to the CL image than one of band. The homogeneous or weak contrasting CL zircon has usually relatively homogeneous images of laser-Raman. The band of 1008cm^-1 and its half-width of zircons of eleven samples displays the radiation damage trend （RDT） , which we interpret that early inherited zircons had experienced complete annealing and recrystallization during the ultrahigh pressure metamorphism. The structures shown by images of laser-Raman in a zircon grain reflect the different metamict degree in different domains, and the metamict degree in different domains must be positively correlated with U and Th contents in the domains due to that these domains had the same metamict history.

关 键 词：锆石 拉曼光谱 片麻岩 超高压变质作用 大别山 

分 类 号：P588.348[天文地球—岩石学] P588.345[天文地球—地质学]