铼-锇定年法中碱熔分解样品方法的改进

The Re-Os Dating Using Modified Alkali Fusion Method

为改进铼锇测年的准确度 ,试验了 4种熔样和稀释剂加入方式 ,最后选择了锆埚熔样和加入混合稀释剂溶液的方法。先用NaOH溶液中和混合稀释剂溶液 ,在碱性稀释剂溶液烤干后 ,再分层加入NaOH、样品、NaOH、Na2 O2 进行高温熔融。采用同位素稀释 -等离子体质谱 (ID-ICP -MS)对所研制的Re -Os年龄参考样辉钼矿JDC的年龄进行了 4次测定 ,测定值为1 39.1 0± 0 .2 6Ma ,相对标准偏差为 0 .2 %。采用 φ =5 %的NH3·H2 O和浓H2 O2 交替清洗测量系统 ,可更有效地消除ICP -MS测量中Os的记忆效应。浓HNO3浸煮和加热烘烤可较有效地除去Teflon器皿中残留的Os。

Four types of alkali fusion methods and spike adding mode have been tested for improving the precision in Re Os dating. In the selected method the mixed spikes is neutralized with NaOH solution in Zr crucible and heated to dryness and then NaOH, sample, NaOH, and Na 2O 2 are added in sequence and fused in high temperature. Four molybdenites JDC powder as standard reference materials are analyzed using ID ICP MS with this fusion method. The Re Os age is 139.10±0.26 Ma with precision of 0.2% RSD.Memory effect from Os can be greatly reduced by alternately rinsing the ICP MS system with 1%～2 % ammonia and peroxide hydrogen. Remains of Os in Teflon vessel could be clear up using soaking in boiling con. HNO 3 and heated in oven at 110℃.