A method for standard-free argon-argon dating of minerals

Abstract

The invention discloses a mineral stantardless argon-argon dating method. The mineral stantardless argon-argon dating method comprises wrapping a mineral sample into a sample piece through aluminum foil, pasting high-purity nickel pieces on the front side and the rear side of the ample piece respectively and placing the sample piece into an accelerator neutron source for neutron irradiation; detecting the nickel pieces after the irradiation, determining a value of a neutron reaction section sigma and calculating the neutron flux N of the accelerator neutron source; loading the mineral sample after the irradiation to a rare gas measurement system, heating and melting the sample, determining the argon isotope content of the mineral sample through a rare gas mass spectrometer and obtaining the required formula through data calculation; substituting the neutron flux N of the accelerator neutron source, the reaction section sigma and the formula into the formula to calculate the argon-argon age of the mineral sample. According to the mineral stantardless argon-argon dating method, the problem that a J value which is related to the neutron flux of a 235 U fission reactor needs to be corrected through a known age standard sample in the traditional argon-argon dating is solved, the argon-argon dating can be implemented without any geological standard sample, and the accuracy of an argon-argon dating method is improved.

Description

technical field [0001] The invention relates to the technical field of argon-argon dating, in particular to a method for standard-free argon-argon dating of minerals. Background technique [0002] The basic principle of argon-argon dating is as follows: according to the law of radioactive decay, as long as the content of radioactive parent and radioactive factor body is measured, the mineral age can be calculated according to the following formula 1: [0003] Formula 1 [0004] Among them, t is the mineral age, λ is 40 The total decay constant of K, λ=5.543(±0.010)×10 -10 a -1 ,λ e , λ' e respectively 40 K decays to 40 The decay constants of the two branches of Ar, λ e =0.572(±0.004)×10 -10 a -1 ,λ′ e =0.0088(±0.0017)×10 -10 a -1 , 40 K is the content of the radioactive parent, 40 Ar* is the content of the radioactive factor. [0005] Transforming formula 1 can get: [0006] Formula 2 [0007] According to the nuclear reaction 39 K(n,p) 39 Ar, [0...

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Problems solved by technology

[0021] In view of this, the main purpose of the present invention is to provide a method for carrying out argon-argon dating without standard samples to minerals, to solve the problem that traditional argon-argon dating must use standard samples of known age to correct and 235 The neutron flux of U fission reactor and other related J value issues can achieve the purpose of argon-argon dating without using any geological standard samples, and improve the accuracy of argon-argon dating method

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