普通铅对LA-ICP-MS磷灰石U-Pb定年结果的影响及校正方法OA北大核心

Apatite is a widespread U-bearing mineral in igneous,metamorphic,and sedimentary rocks.U-Pb geochronology of apatite can provide significant information for constraining magmatic evolution processes and tracing provenance.Laser ablation inductively coupled plasma-mass spectrometry(LA-ICP-MS)is a crucial technique for in situ U-Pb age analysis of apatite.However,the lack of suitable matrix-matched apatite reference materials and the inevitable presence of common lead in reference materials are major obstacles restricting high-precision determination of apatite U-Pb ages.This study investigates the impact of common lead on LA-ICP-MS apatite U-Pb dating results.The significant systematic biases(6%-30%)in both measured lower intercept ages and initial lead compositions are observed when calibrating against MAD apatite without common lead correction.However,accurate apatite U-Pb ages(within 2%systematic bias)can be obtained by correcting for common lead in MAD using the 207Pb method or Tera-Wasserburg plot method prior to Pb/U fractionation calibration.Furthermore,a vapor-assisted laser ablation method is employed in conjunction with NIST612 glass as an external standard to accurately analyze apatite U-Pb ages.This non-matrix matched method eliminates the need to consider the influence of common lead in the reference materials.Novel high-precision LA-ICP-MS apatite U-Pb dating methods are established with both matrix-matched and non-matrix-matched analyses,which greatly promote the application of apatite U-Pb geochronology in Earth science.The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202404070079.