Method for uranium lead dating of baddeleyite by using secondary ion mass spectroscopy

A technology of secondary ion mass spectrometry and baddeleyite uranium, which is applied in the field of baddeleyite uranium-lead dating by secondary ion mass spectrometry, can solve the problems of discrete uranium-lead ratio distribution and unsuitability for practical applications, and achieve the goal of improving analysis accuracy Effect

Inactive Publication Date: 2011-08-03
INST OF GEOLOGY & GEOPHYSICS CHINESE ACAD OF SCI
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Problems solved by technology

For baddeleyite, due to its extremely small particles, it is impossible to ensure that the optical axes of all particles have the same orientation during sample preparation, that is, the direction of the SIMS primary ion ...

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  • Method for uranium lead dating of baddeleyite by using secondary ion mass spectroscopy
  • Method for uranium lead dating of baddeleyite by using secondary ion mass spectroscopy
  • Method for uranium lead dating of baddeleyite by using secondary ion mass spectroscopy

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Embodiment Construction

[0031] The technical solution involved in the present invention will be further described below in conjunction with specific samples, but it is not intended to limit the content of the present invention.

[0032] Taking six baddeleyite samples: Phalaborwa, FC-4b, 05-JX02, Kovdor, LGXL-01 and SK10-2 as examples, the specific implementation of the technical method of the present invention is introduced. Among them, Phalaborwa is the international standard baddeleyite age sample, with an age of 2059.6±3.5Ma. The age of each of the remaining samples has been determined by other methods or can be precisely defined based on the known ages of other minerals formed at the same time. Except for the standard sample Phalaborwa, the ages of the other five samples or the mineral ages of the same period are 1098.2±1.5Ma, 810±6Ma, 377.52±0.94Ma, 195±1Ma and 32.1±0.49Ma, respectively. These known reference ages are used as a standard for validation in this method to test the accuracy of this...

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Abstract

The invention discloses a method for determining uranium lead age of baddeleyite by using secondary ion mass spectroscopy, which belongs to the field of secondary ion mass spectroscopy dating method in geochronology and particularly relates to a method applied to a large secondary ion mass spectrometer having oxygen blowing conditions. In the measurement method described by the invention, the degree of vacuum in a sample cavity of the spectrometer is enabled to reach 1E-8Torr at first, and an oxygen leak valve is then opened to blow the oxygen with the purity of 99.99% to the surface of the sample so that the oxygen partial pressure of the sample cavity reaches 1E-5Torr. The method of the invention can reduce the optical axis effect, which is exhibited by secondary ion mass spectroscopy during the uranium-lead dating of baddeleyite, to be below 2%, thus the accuracy of uranium-lead age when the baddeleyite is subjected to secondary ion mass chromatographic analysis is significantly improved. After uranium-lead measurement ratio is obtained, uranium-lead fractionation correction is performed by adopting a linear relation between ln(Pb+/U+) and ln(UO2+/U+) in order to obtain accurate age.

Description

technical field [0001] The invention relates to a method for determining the age of baddeleyite uranium-lead by using a secondary ion mass spectrometer (SIMS), and belongs to the category of secondary ion mass spectrometry mineral dating methods in geochronology. Background technique [0002] Secondary ion mass spectrometry is an advanced method for micro-area in situ analysis, which has the advantages of high sensitivity, high spatial resolution and high precision. The accelerated primary ion beam is used to focus and bombard the surface of the sample to be tested, the surface components of the sample are sputtered, and some of the sputtered atoms, molecules and atomic groups are ionized to form secondary ions. After the secondary ions are accelerated by high pressure on the surface of the sample, they enter the mass spectrometer for mass analysis, and the element and isotope information of the sample in the micro area is obtained. When using SIMS analysis, the yields of d...

Claims

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Application Information

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IPC IPC(8): G01N27/62
Inventor 刘宇李秋立唐国强李献华郭春华
Owner INST OF GEOLOGY & GEOPHYSICS CHINESE ACAD OF SCI
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