质谱学报2018，Vol.39Issue(3)：295-309,15.DOI:10.7538/zpxb.2017.0072
MC-ICP-MS标样-样品交叉测试法测定石笋样品的230Th/U年龄
Measurement of U/Th Isotopic Compositions in Stalagmites for 230Th/U Geochronology Using MC-ICP-MS by Standard-Sample Bracketing Method
摘要
Abstract
Over the past two decades,multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS)has gradually become the most commonly used technique for high-precision U/Th dating studies in the world.Based on the previously established methods,this study presents a simplified chemical procedure for U/Th separation and purification using the UTEVA resin columns and a standard-sample bracketing method for U/Th isotope measurements by MC-ICP-MS.In routing measurements,the daily variations of instrumental mass discrimination and SEM/Faraday cup gain are less than 0.1 and 1 %,respectively.By the use of rigorous arid washout,potential contribution of instrumental background to U/Th isotopes measurements is less than 0.2‰,or even negligible.The precision and accuracy of this method were tested by the repeated meas-urements of Harwell uraninite (HU-1)as an unknown sample,the averagedδ234U in HU-1 is (-1.27±2.14)‰ (±2σ,n=29),which is in agreement with the values that reported previously by different international laboratories with various analytical tech-niques.The repeatability of this method was assessed by a large number of replicate an-alyses using the in-house U/Th standard MFT,which hasδ234U of (408.2±3.2)‰, 230 Th/238U activity ratio of 1.002±0.003 and 230Th/U age of (124.3±0.5)ka,respec-tively.We also analyzed 47 stalagmite samples with known ages to test the accuracy of our method.For these stalagmite samples,the measured 234U/238U and 230Th/238U activ-ity ratios and the age have averaged uncertainties (± 2σ)of 0.6‰,2.4‰ and 0.5 %, respectively,and they are consistent well with the previously published data.In addi-tion,this study shows that the reliability of standard-sample bracketing method is large-ly influenced by the stability of SEM/Faraday cup yield,which in turn is sensitive to the stability of room temperature and humidity and is sensitive to the presence of organics or any other matrix materials in the U/Th fractions.关键词
多接收电感耦合等离子体质谱(MC-ICP-MS)/230Th/U定年/UTEVA树脂/U/Th分离纯化/石笋Key words
multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS)/230 Th/U dating/UTEVA resin/U/Th separation and purification/stalagmites分类
化学化工引用本文复制引用
廖泽波,邵庆丰,李春华,孔兴功,汪永进..MC-ICP-MS标样-样品交叉测试法测定石笋样品的230Th/U年龄[J].质谱学报,2018,39(3):295-309,15.基金项目
江苏省高等学校自然科学研究项目(17KJA170001)资助 （17KJA170001）
