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张佳, 刘汉彬, 李军杰, 金贵善, 韩娟, 张建锋, 石晓. K-Ar稀释法中40Ar含量测量过程中实验参数的确定[J]. 岩矿测试, 2021, 40(3): 451-459. DOI: 10.15898/j.cnki.11-2131/td.202012040158
引用本文: 张佳, 刘汉彬, 李军杰, 金贵善, 韩娟, 张建锋, 石晓. K-Ar稀释法中40Ar含量测量过程中实验参数的确定[J]. 岩矿测试, 2021, 40(3): 451-459. DOI: 10.15898/j.cnki.11-2131/td.202012040158
ZHANG Jia, LIU Han-bin, LI Jun-jie, JIN Gui-shan, HAN Juan, ZHANG Jian-feng, SHI Xiao. Determination of Experimental Parameters during Measurement of 40Ar Content in K-Ar Dilution Method[J]. Rock and Mineral Analysis, 2021, 40(3): 451-459. DOI: 10.15898/j.cnki.11-2131/td.202012040158
Citation: ZHANG Jia, LIU Han-bin, LI Jun-jie, JIN Gui-shan, HAN Juan, ZHANG Jian-feng, SHI Xiao. Determination of Experimental Parameters during Measurement of 40Ar Content in K-Ar Dilution Method[J]. Rock and Mineral Analysis, 2021, 40(3): 451-459. DOI: 10.15898/j.cnki.11-2131/td.202012040158

K-Ar稀释法中40Ar含量测量过程中实验参数的确定

Determination of Experimental Parameters during Measurement of 40Ar Content in K-Ar Dilution Method

  • 摘要: K-Ar稀释法中40Ar含量的测量需经过样品熔融释气、气体纯化富集、质谱测量等步骤,随着新型设计的双真空加热炉和气体纯化系统的应用,实验流程逐渐由人工操作向自动化程序控制转变。为建立完整的K-Ar稀释法中40Ar含量测量方法,相关参数还需多次条件实验得以确定。本文以空气标准为对象,通过活性炭冷指释放和吸附空气标准,确定活性炭冷指最佳加热释气时间为500s,液氮条件下最佳吸附时间为200s,在此条件下,加热炉熔融产生的40Ar气体可以完全转移和释放,避免发生同位素分馏;根据不同熔融温度下相同质量样品释放40Ar强度,确定黏土矿物、黑云母、白云母等类型样品加热炉熔融温度设置为1400℃,角闪石熔融温度为1500℃,基性岩熔融温度为1550℃,钾长石熔融温度为1600℃,不同类型样品采用对应熔融温度,保证样品完全熔融释气。对10组SK01透长石标准进行测量,得到K-Ar年龄结果与40Ar-39Ar定年标准值相一致,结果表明所得条件参数可满足K-Ar稀释法中40Ar含量的准确测量。

     

    Abstract:
    BACKGROUNDThe measurement of 40Ar content in K-Ar dilution method includes sample melting and releasing gas, gas purification and enrichment, mass spectrometry measurement. With the application of a newly designed double vacuum furnace and gas purification system, the experiment process gradually changes from manual operation to automatic program control, but the parameters are unclear.
    OBJECTIVESTo determine the parameters by conditional experiments and establish a complete measurement method of 40Ar content in K-Ar dilution method.
    METHODSParameters were determined by releasing and absorbing an air standard in activated carbon cold finger with different times, melting different types of samples with different temperatures of the double vacuum furnace. The method reliability was verified by K-Ar dating for SK01 sanidine standard.
    RESULTSThe optimal heating release time for activated carbon cold finger was 500s, and the adsorption time was 200s. Using these conditions, the gas produced by the melting in the furnace can be completely transferred and released to avoid isotope fractionation. The corresponding melting temperature was used for different types of samples to ensure that the samples were completely melted and outgassed, the melting temperature of the furnace for clay minerals, biotite, and muscovite should be set to 1400℃, and 1500℃ for amphibole, 1550℃ for basic rock, and 1600℃for potassium feldspar. The K-Ar dating of 10 sets of SK01 sanidine standards showed that the results were consistent with 40Ar-39Ar dating ages.
    CONCLUSIONSThe obtained condition parameters meet the accurate measurement of 40Ar content using the K-Ar dilution method.

     

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