Solution Nebulization And(Nanosecond/Femtosecond)Laser Ablation-Multiple Collector Inductively Coupled Plasma Mass Spectrometry And The Application In The Earth Science

In this paper,the solution nebulization,and nanosecond/femtosecond laser ablation coupled with multiple collector inductively coupled plasma mass spectrometry(SN&nsLA/fsLA-MC-ICP-MS)was applied to analyze Sr-Hf-Pb-Mg isotopes and its the application in earth science was also evaluated.The following research work was carried out:Precise determination of Sr isotopic composition after a new Rb calibration method to obtain accurate Sr isotopes of high Rb/Sr ratio samples using both solution nebulization and laser ablation sampling technique was developed,and its application in geological analysis was discussed;accurate analysis of Hf isotopes in zircon was setup based on a new calibration method of Lu and Yb interference correction.The method was evaluated with the zircon samples from Lushan Mountain;Simultaneous determination of major and trace elements and Pb isotopic compositions of silicate minerals was setup using the combination of laser ablation sampling technique and two ICP-MSs,including both quadruple and multiple collector ICP-MS;A purification and determination method was established to measure Mg isotopes in Songshugou dunite olivine inclusion using both solution and fsLA-MC-ICP-MS techniques.1.Accurate determination of Sr isotopes in high Rb/Sr ratio apatite samples based on a new Rb interference correction method using LA—MC-ICP-MS.The Interference of 87Rb on 87Sr was deducted precisely based on the calibrated 87Rb/85Rb ratios in samples.Sr isotopes in high Rb/Sr samples(Rb/Sr≤0.2)could be obtained using the proposed method.Experimental results showed that this correction protocol is valid for Rb/Sr ratios up to 0.2 in real samples in terms of in situ analysis using LA-MC-ICP-MS,which is superior to the limit of conventional calibration method(Rb/Sr<0.0005).The proposed method was evaluated with some international reference materials and the results agreed well with recommended values in analytical uncertainties.This correction method improves the reliability of Sr isotope analysis,and expands the application of the method,especially for micro in-situ laser ablation analysis due to inability to chemically separate Rb offline and only those mineral with low Rb/Sr ratios could be measured.The analyzed Sr isotopic compositions of apatite samples from Qinling Jiu Zi Gou area and Langqiao area using nsLA-MC-ICP-MS showed that,reliable Sr isotopes of vocanic apatite samples with Rb/Sr<0.00021 could be obtained for both conventional or the proposed calibration method.However,Sr results of samples with large variations of Rb/Sr(0.001～0.005)showed remarkable Sr isotope differences(0.71557～0.72378)using conventional calibration method,while Sr results of the proposed Rb interference correction method is 0.71223 ± 0.00021(2SD),which is more reliable.2.Improving the accuracy of Hf isotopic compositions of zircon with high Yb content measured by LA-MC-ICP-MS based on an optimized Yb and Lu isobaric interferences correction strategy.Discrimination and interference correction are the main obstacles to accurate and precise analyses of Hf isotope ratios by in situ Lu-Hf isotope analysis of zircon.The correction method of Yb and Lu interference on Hf was established by SN-MC-ICP-MS and evaluated by natural zircons using LA-MC-ICP-MS.Experiments showed that there was linear correlation between 176Hf/177Hf ratio after conventional interference correction method and 176Yb/177Hf ratio,which indicated that the conventional correction method could not deduct the isobaric interference of 176Yb efficiently.The results of zircon samples from the garnet tonalite in the Lushan Mountain area,Henan,showed that the proposed correction method improved the accuracy of zircons with high Yb/Hf.3.A new method of simultaneous determination of major element,trace element concentration and lead isotopes by laser ablation coupled with two mass spectrometers was established,which provides a powerful technique for geochemisty research of minerals.Major and trace element content and Pb isotopic compositions of silicate minerals and melted glasses were measured simultaneously by an excimer laser ablation system coupled with a quadrupole inductively coupled plasma mass spectrometry(Q-ICP-MC)and an MC-ICP-MS.The optimized parameters were obtained after sufficient experiments.The laser aerosol was distributed in 1:9 ratio to Q-ICP-MS and MC-ICP-MS to measure major/trace elements and Pb isotopes,respectively.The aerosol transporting tubes for the two ICP-MSs were 2mm and 4mm(I.D.)while the laser ablation conditions were frequency 15Hz,spot size 160pm and energy density 18J/cm2.The analytical results of major and trace element contents of standard materials from NIST,USGS and CGSG agreed with recommended values within 10%.The Pb isotopic compositions measured in this work agreed well with recommend ratios within 2s analytical uncertainties.The analytical precision is better than 6.7%(2SD).The proposed method works for the samples which Pb content higher than 20 ppm due to the low sensitivity of current instrumental setup.4.Established Mg isotope purification and SN-MC-ICP-MS analytical method;and an in situ Mg isotopes analyses of minerals and melt glasses using fsLA-MC-ICP-MS.Discovered the fractionation of Mg isotope in olivine of Songshugou dunite.A two-step purification method for Mg isotopes was established using Ln-Spec resin coupled with AG50W-X12 cation exchange resin.The recovery rates of the two steps were more than 99.6%and 99.8%,respectively.The Mg isotopic compositions could be measured precisely by MC-ICP-MS after propriate analytical protocal,including medium resolution mode(M/△M5,95%edge= 3000 RP),dry aerosol sampling(via Aridus Ⅱ membrane desolvation),keep Ca/Mg<2 in samples,concentration matching between sample and standard(0.4<Csample/CStandard<3)and keep consistent total ion content etc.)An in situ Mg isotope analysis method was set up for olivine research using an fsLA-MC-ICP-MS.Experiments revealed that the capacity of ICP load afftected lead isotops dramatically.The laser parameters,including frequency,scanning rate,spot size etc.,caused mass bias and affect the Mg isotopic ratios.However,the femtosecond laser energy showed negligible effect on Mg isotopic compositions.The Mg isotopic ratios of the standard material from USGS were consistent to the recommend values within analytical uncertainties.The external precision was better than 0.17‰(2SD).The Mg isotopic compositions in the olivine of Songshugou dunite,were measured using the in situ analytical method and were consistent with lithology.Samples with consistent lithology showed homogeneous Mg isotopic compositions while those dunite samples with fine-medium grain showed different Mg isotopes.These results indicated that the Mg isotopes fractionated during olivine crystallization.