Optimizationof the Working Parameters of LA-ICP-MS and Its Application to Zircon U-Pb Dating

Laser Ablation (LA) combined with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) avoids cumbersome analysis of solution and time-consuming pre process, thus reducing possible pollution during sample preparation. Moreover, LA-ICP-MS has the advantages of low cost, rapid determination, and high precision of analysis data. The lower fractionation effect of elements is discussed by combing laser energy density and denudation frequency. Meanwhile, the main working parameters such as RF power, sampling depth, carrier gas and He gas flow rate are matched to obtain high sensitivity and stability of the signal. Based on these, the optimal parameters of the instrument are obtained and reliable zircon U-Pb dating method is established. By mutual determination of zircon age standard substance 91500, GJ-1, and Plešovic, the respective weighted average ages of ²⁰⁶Pb/²³⁸U were 1063.9±6.0 Ma (2σ, n=20), 600.3±2.6 Ma (2σ, n=27), and 337.6±1.7 Ma (2σ, n=20). The accuracy and precision are within 1%, consistent with previous studies. Using the optimized parameters of the instrument, the quartz-orthoclase diorite porphyrite from the Tonglushan Orefield in Southeast Hubei has the ²⁰⁶Pb/²³⁸U age of zircon, basically consistent with the previous results, indicating that this method can be used for zircon U-Pb dating.