Quick Search:       Advanced Search
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,(3):451-459
View Full Text   View/Add Comment   EndNote   BibTeX   Download reader
Determination of Experimental Parameters during Measurement of 40Ar Content in K-Ar Dilution Method
Received:December 04, 2020  Revised:April 27, 2021
DOI:10.15898/j.cnki.11-2131/td.202012040158
Key words: K-Ar dilution dating  40Ar content  heating release time  absorption time  melting temperature
Author NameAffiliation
ZHANG Jia Beijing Research Institute of Uranium Geology, Beijing 100029, China 
LIU Han-bin Beijing Research Institute of Uranium Geology, Beijing 100029, China 
LI Jun-jie Beijing Research Institute of Uranium Geology, Beijing 100029, China 
JIN Gui-shan Beijing Research Institute of Uranium Geology, Beijing 100029, China 
HAN Juan Beijing Research Institute of Uranium Geology, Beijing 100029, China 
ZHANG Jian-feng Beijing Research Institute of Uranium Geology, Beijing 100029, China 
SHI Xiao Beijing Research Institute of Uranium Geology, Beijing 100029, China 
Hits: 47
Download times: 112
Abstract:
      BACKGROUND: The 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.
OBJECTIVES: To determine the parameters by conditional experiments and establish a complete measurement method of 40Ar content in K-Ar dilution method.
METHODS: Parameters 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.
RESULTS: The 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.
CONCLUSIONS: The obtained condition parameters meet the accurate measurement of 40Ar content using the K-Ar dilution method.