Quantification of radiation damage in natural and synthetic zircon by Raman spectroscopy:application to low-temperature thermochronology  

作　　者：Ke Su Shao-Bing Zhang John MHanchar Zhen-Xin Li Fang-Yuan Sun Ting Liang Xiao-Ying Gao 

机构地区：[1]CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China [2]Center of Excellence for Comparative Planetology,Chinese Academy of Sciences(CAS),Hefei 230026,China [3]Frontiers Science Center for Planetary Exploration and Emerging Technologies,University of Science and Technology of China,Hefei 230026,China [4]Department of Earth Sciences,Memorial University of Newfoundland,St John’s,NL A1B 3X5,Canada

出　　处：《Acta Geochimica》2023年第4期673-688,共16页地球化学学报（英文）

基　　金：supported by funds from the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB 41000000);the National Natural Science Foundation of China(41973002,41772187);the Fundamental Research Funds for the Central Universities;Natural Sciences and Engineering Research Council of Canada(NSERC)Discovery Grant to J.M Hanchar(RGPIN/004649-2015)。

摘　　要：Due to its ubiquitous occurrence in igneous,metamorphic,and sedimentary rocks and its wide application in geochronology and geochemistry,zircon has become the most widely used accessory mineral in the geological community.Nevertheless,the decay of U and Th causes radiation damage to the zircon structure,resulting in various degrees of metamictization,which can affect the accuracy of U–Pb dates and Hf and O isotope results.If the degree of zircon radiation damage can be quantified,the influence on geochemical analyses can be evaluated,and the results can be corrected more precisely.In this paper,synthetic and natural zircon crystals with different crystallization ages were selected for Raman spectroscopy analysis,cathodoluminescence imaging,and determination of the U and Th concentrations.The results show that Raman FWHM(full width at half bandmaximum)and Raman shift correlate with alpha dose(Da)ofzirconsfollowingtheseequations,FWHM=44.36(±2.32)×[1-exp(-2.74×Da)]-+1.7(±0.19),Raman Shift=-6.53×Da+1007.69.Analysis of synthetic zircon crystals shows that doped REEs(rare earth elements and P)can also lead to an increase in the FWHM.However,this effect can be ignored for natural zircon samples with REE contents at a normal level of hundreds to a few thousand ppm.The FWHM and Raman shift can be used as proxies to measure the degree of zircon radiation damage.Using the updated equations to calculate the latest age when zircon began to accumulate radiation damage,a more accurate and more meaningful“radiation damage age”can be obtained.

关 键 词：ZIRCON Radiation damage Raman spectroscopy FWHM(full width at half-maximum) Raman shift Raman isochron age 

分 类 号：P597.3[天文地球—地球化学]