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首页> 外文期刊>Geochemical Journal >Non-destructive potassium measurement in minerals by gamma-ray spectrometry: Toward an enhanced K-Ar dating method
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Non-destructive potassium measurement in minerals by gamma-ray spectrometry: Toward an enhanced K-Ar dating method

机译：γ射线光谱法测定矿物中的无损钾：改进的K-Ar定年法

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We performed a calibration of a Ge-detector gamma ray spectrometer to measure the activity of K-40 in natural volcanic glass and minerals. The goal of this experimental study is to demonstrate that non-destructive measurements of K-40 in rocks and minerals can be obtained with a good precision, comparable at 2 sigma to that obtained by classical atomic absorption spectroscopy. This is the first step toward an enhanced K-Ar dating method in which both parent (K-40) and daughter (Ar-40*) nuclides are measured in the same sample aliquot. This method should minimize the undeterminable internal error produced by the natural chemical heterogeneity of the measured sample. The efficiency of the Ge-detector was calibrated at 1461 keV, corresponding to the emission energy of K-40, on five geostandards of biotite, feldspar, trachyte, glauconite and a synthetic glass. Calculated efficiency ranges from 0.0403 to 0.0442 with a mean value of 0.0418 +/- 0.0018. Comparison between K2O contents calculated after measurements on the gamma ray detector (K2O gamma) of nineteen natural volcanic mineral and groundmass samples and those obtained by classical atomic absorption spectroscopy (K2OAAS) are identical within 2 sigma uncertainties. Best results are obtained by calibrating the natural sample measurements with the efficiency obtained for the synthetic glass geostandard VS-N with a K2O gamma/K2OAAS of 1.040 +/- 0.060.
机译：我们对锗探测器伽马射线光谱仪进行了校准，以测量天然火山玻璃和矿物中K-40的活性。这项实验研究的目的是证明可以以良好的精度获得岩石和矿物中K-40的无损测量值，与传统原子吸收光谱法获得的精度相差2σ。这是迈向增强型K-Ar定年方法的第一步，在该方法中，在同一等分试样中同时测量了母体（K-40）和子体（Ar-40 *）核素。此方法应将被测样品的自然化学异质性所产生的无法确定的内部误差降至最低。在黑云母，长石，菱铁矿，青钙石和合成玻璃的五个地球标准上，将Ge检测器的效率校准为1461 keV，对应于K-40的发射能量。计算效率范围为0.0403至0.0442，平均值为0.0418 +/- 0.0018。在2σ不确定度内，使用19种天然火山矿物和地面质量样品的伽马射线检测器（K2O gamma）进行测量后计算出的K2O含量与通过经典原子吸收光谱法（K2OAAS）获得的K2O含量之间的比较相同。通过以1.040 +/- 0.060的K2Oγ/ K2OAAS对合成玻璃地球标准VS-N所获得的效率进行校准来校准天然样品，可以获得最佳结果。

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