冰碛物电子自旋共振信号测量的基本流程  

Basic procedures of electron spin resonance(ESR) signal measurement for glacial tills

作　　者：毕伟力[1] 杨海军[2] 易朝路[1,3] BI Weili;YANG Haijun;YI Chaolu(Institute of Tibetan Plateau Research,Chinses Academy of Sciences,Beijing 100101,China;Department of Chemistry,Tsinghua University,Beijing 100084,China;CAS Center for Excellence in Tibetan Plateau Earth Sciences,Beijing 100101,China)

机构地区：[1]中国科学院青藏高原研究所,北京100101 [2]清华大学化学系,北京100084 [3]中国科学院青藏高原地球科学卓越创新中心,北京100101

出　　处：《地球环境学报》2018年第6期622-628,共7页Journal of Earth Environment

基　　金：国家自然科学基金项目(41230523);中国科学院战略性先导科技专项(XDA20070102)~~

摘　　要：电子自旋共振(ESR)法是一种用于直接测量和研究含有未成对电子的顺磁性物质的分析方法。ESR测年是应用这种分析方法对沉积物最后一次埋藏以来的年代进行测定。相比于其他方法,它具有测年范围广,测试的样品种类多,样品可以重复测量,测量周期短等优势。20世纪80年代以来我国开始进行沉积物ESR测年与研究,但是在冰碛物ESR测年的制样和测量过程中存在一些问题。本文介绍冰碛物ESR测年的过程:样品野外采集时剖面的选取及其注意事项;详细描述提纯冰碛物中石英颗粒的前处理过程;石英颗粒经过人工辐照后在顺磁波谱仪上测试ESR信号并拟合古剂量过程中的具体方法和需要注意的问题。从实验中得到,用0.063—0.125 mm粒径的组分提纯石英砂比较困难,前处理过程中试剂和时间消耗量大,因此建议ESR测年时:在样品充足的情况下选用细颗粒组分(0.063— 0.125 mm),样品不充足的情况下选用中颗粒部分(0.125— 0.25 mm)。待测样品中存在其他矿物会对石英的ESR信号有影响,因此在提纯石英过程中用重液分选提高石英纯度并可以增强测量的ESR信号的稳定性。经过氢氟酸刻蚀后的样品,石英的纯度要达到95% — 99%或以上。对于冰碛物ESR测年过程中ESR信号的选择需要参照样品自身的特点,综合考虑多次尝试才能确定用常温Ge心信号还是低温的Al心、Ti心作为样品中石英的ESR测年信号。通过规范的采样、制样和ESR信号测量流程,使样品的定年能够被不同的人重复,并能够进行不同区域之间的对比。Background,aim,and scope Electron spin resonance(ESR)as a microwave technology,is an analytical method to detect and research the paramagnetic substance with unpaired electrons.ESR dating is an application of this technique to date sediments since their last burial.Compared to other dating methods,ESR dating has advantages in large time span,different kinds of samples,repeated measurements and the short measurement period.Since 1980s ESR dating has been applied to sediments,however,there exist some problems in sample preparation and ESR signal measurement.The purpose of the paper is to introduce the experimental procedures for those who are interested in ESR dating of glacial till.Materials and methods Sample collection:the quartz was one of the best minerals for detecting ESR signals.In the field,we selected the moraine profiles that had rich in quartz and were not retrofitted.It was better to collect silt and fine sand samples through subglacial grinding or being exposed to the sun.The samples must avoid to the direct sunshine from the field to the laboratory.We gathered samples 2-3 kg and made detailed records and environment descriptions.And we also collect sample using sealed aluminum boxes for water content.If there was not gamma spectrometer for measuring environmental dose rate in situ,the contents of uranium,thorium,potassium from the samples were measured using neutron activation analysis(NAA).The rigorous sampling procedure and detailed field records were of benefit to analysis and comparison of the data.Extraction and purification of quartz from the sediment:we sieved out 0.063-0.25 mm of purified quartz grains from samples for ESR dating.At first,we removed carbonate with hydrochloric acid and organic matter with hydrogen peroxide.Next,we eliminated magnetic mineral with permanent magnet.Then,we separated minerals of different specific gravities with the heavy liquid.Heavy mineral,quartz,feldspar and mica were separated and pure quartz was obtained.Lastly,the residual feldspar and quartz surface dama

关 键 词：ESR测年技术 实验流程 石英矿物 冰碛物 

分 类 号：P597.3[天文地球—地球化学]