Laser-ablation MC-ICP-MS lead isotope microanalysis down to 10 μm: application to K-feldspar inclusions within zircon†,Journal of Analytical Atomic Spectrometry

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Laser-ablation MC-ICP-MS lead isotope microanalysis down to 10 μm: application to K-feldspar inclusions within zircon†
Journal of Analytical Atomic Spectrometry ( IF 3.1 ) Pub Date : 2017-12-18 00:00:00 , DOI: 10.1039/c7ja00276a
Hélène Delavault _{1,

2,

3,

4,

5} , Bruno Dhuime _{1,

2,

3,

4,

5} , Chris Hawkesworth _{1,

2,

3,

4,

5} , Horst R. Marschall _{6,

7,

8,

9}

Affiliation

The geochemical information preserved in mineral inclusions within zircon provides new ways to decipher the evolution of the continental crust. We present a routine procedure to analyse Pb isotopes in K-feldspar minerals and mineral inclusions in zircon by LA-MC-ICP-MS, with a spot size down to 10 μm diameter. Natural K-feldspar grains from the Shap granite (north England) were selected for their homogenous Pb isotope composition to validate the method. The Faraday cups of the Thermo Scientific Neptune Plus MC-ICP-MS were used to collect the beams for spot sizes of 150 μm and 40 μm. The average ²⁰⁶Pb/²⁰⁴Pb ratios were respectively 18.255 ± 0.27% and 18.24 ± 1.3% (2 s.d.), and they agree within their analytical uncertainties. Ion counters (MIC) were used at 10 μm to allow better determination of the low intensity signal for Pb isotopes. The ²⁰⁶Pb/²⁰⁴Pb average ratio is 18.29 ± 1.3% (2 s.d.), which is within error of the average values at spot sizes of 150 μm and 40 μm. For a 10 μm spot size internal errors on individual measurements are typically better than 1.1% (2 s.e.). K-feldspar inclusions in zircons from a monzonite intrusion in Dronning Maud Land (East Antarctica), were analysed by MIC-LA-MC-ICP-MS (10 μm spot and ∼12 μm depth). The Pb isotope ratios are similar to those previously obtained by SIMS with a Cameca IMS 1270 (∼40 × 20 μm elliptic spot and ∼2 μm depth). These SIMS data are used to validate the robustness of MIC-LA-MC-ICP-MS measurements in minute mineral inclusions.

中文翻译：

激光烧蚀MC-ICP-MS铅同位素显微分析低至10μm：适用于锆石中的钾长石夹杂物†

锆石中矿物包裹体中保存的地球化学信息为解密大陆壳的演化提供了新途径。我们提出了一种常规程序，可通过LA-MC-ICP-MS分析钾长石矿物和锆石中锆石中的矿物包裹体中的Pb同位素，其光斑直径小至10μm。选择了来自Shap花岗岩（英格兰北部）的天然钾长石晶粒，以证明其均一的Pb同位素组成，从而验证了该方法的有效性。使用Thermo Scientific Neptune Plus MC-ICP-MS的法拉第杯收集光斑大小为150μm和40μm的光束。平均值²⁰⁶ Pb / ²⁰⁴铅的比例分别为18.255±0.27％和18.24±1.3％（2 sd），并且在分析不确定性范围内是一致的。使用10μm的离子计数器（MIC）可以更好地确定Pb同位素的低强度信号。的²⁰⁶铅/ ²⁰⁴铅的平均比率为18.29±1.3％（2 sd），这在150μm和40μm的光斑尺寸的平均值的误差范围内。对于10μm的光斑尺寸，单个测量的内部误差通常优于1.1％（2 se）。通过MIC-LA-MC-ICP-MS（10μm斑点和约12μm深度）分析了Dronning Maud Land（East Antarctica）蒙脱石入侵中锆石中的钾长石包裹体。铅的同位素比率类似于先前通过SIMS使用Cameca IMS 1270获得的同位素比率（约40×20μm椭圆形斑点和约2μm深度）。这些SIMS数据用于验证MIC-LA-MC-ICP-MS在微小矿物夹杂物中测量的稳健性。

更新日期：2017-12-18

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