| In this paper,the iron isotopic compositions in geological samples were analyzed using solution nebulization and femtosecond laser ablation-multicollector inductively coupled plasma mass spectrometry(SN/fsLA-MC-ICP-MS).We also determined the iron isotopic compositions of Erlihe lead and zinc ore deposit.Mainly in the following aspects:Chemistry dissolution and Fe isotope purification procedures for geological samples were improved based on previous research.The analytical method of Fe isotopes was established using large-scale MC-ICP-MS(Nu plasma 1700).The detailed experiments were implemented including conditions of the instrument(cone combination,sampling method,etc.)and sample solution(the effects of acidity,concentration matching,etc.).The analytical precision and accuracy of iron isotope data were evaluated using an Ni internal standard coupled with standard-sample bracketing technique(SSB).The Fe isotopic compositions of some international geological reference materials were measured based on the developed method,and agreed well with the published values within 2SD analytical uncertainties.An in situ microanalysis method of iron isotope was established by fsLA-MC-ICP-MS.1.Chemical dissolution and Fe isotope purification procedures for geological samples were further improved based on previous research.Samples can be entirely dissolved with HF and HNO3(3:1),and the melt was fully digested with 8mol/L HCl for resin chromatography.The Fe isotope separation and purification procedures adopted the AGMP-1M anion exchange resin.The recovery of Fe isotopes was higher than 99%according cleaning resin using 2,4,and 8 mol/L HCl and the total procedure blank was less than 7 ng.2.The Fe isotopic compositions were analyzed using Nu plasma 1700 at high mass resolution mode(M/△M=14,000 RP).The interference peaks over Fe isotopes could be resolved completely.The calibration method applied in this work was standard-sample bracketing technique(SSB)coupled with Ni internal standard.The measured Fe isotopic compositions of both dry and wet plasma mode agreed well with reported values within 2s.The external precision of 56Fe obtained by wet plasma(0.029‰,2s)were better than dry plasma(0.084‰,2s).The wet sampling cone plus wet skimmer cone could obtain better stability.The difference of Fe concentration between samples and standard had no effect on Fe isotopic compositions if the Csample/Cstanad ratio was between 0.3-3.However,the difference of acidity between samples and standard affected the Fe isotopic compositions seriously when the difference was larger than 10%.3.Laser ablation spot size and the laser frequency were explored the impact on Fe isotopes and an in situ microanalysis method of Fe isotope was established by a 266nm fsLA-MC-ICP-MS.We analyzed the Fe isotopic compositions of two natural pyrites(Cb and Ly)based on the developed method and the results agreed well with values by solution nebulization method.4.We also studied Fe isotopic compositions of some ore minerals from Erlihe lead and zinc ore deposit and discussed the deposit genesis.The results showed that Fe isotopic compositions of these ore minerals were closed to seawater.So,the Bafang mountain-Erlihe lead and zinc ore deposit had a possible metallogenic characteristics of hydrothermal sediment. |
