Abstract
The slope year tslope for the U-Pb dating method is given as , where λ238 and λ235 are the decay constants for 238U and 235U, respectively, and k is the slope of the tangent line at a point on either the Concordia or Discordia line. These two lines are determined by the initial 206(7)Pbi concentrations in minerals. If , the line is the Concordia. However, if (∧ is the logical operator “and”, also known as the logical conjunction), or , the line is Discordia. The Concordia line is of the form (where p stands for the present), while the Discordia line has the form (where k and b are the slope and intercept of the straight line, respectively).
Highlights
In nature, uranium has three radioactive isotopes: 238U(99.2743%), 235U(0.7200%) and 234U(0.0057%) [1] [2]
238U and 235U are λ238 = (1.55125 ± 0.00672) ×10−10 (1σ ) a−1 and λ235 =(9.8485 ± 0.00083) ×10−10 (1σ ) a−1, respectively [2]-[4]. These nuclear reactions occur in host minerals, such as zircon (ZrSiO4), and are the basis of the U-Pb dating method in geology [5]-[8]
It was found that if no 206(7)Pb isotopes are initially present in minerals, the Pb/U ratios plot on the Concordia line
Summary
Uranium has three radioactive isotopes: 238U(99.2743%), 235U(0.7200%) and 234U(0.0057%) [1] [2]. 238U and 235U are λ238 = (1.55125 ± 0.00672) ×10−10 (1σ ) a−1 and λ235 =(9.8485 ± 0.00083) ×10−10 (1σ ) a−1, respectively [2]-[4] These nuclear reactions occur in host minerals, such as zircon (ZrSiO4), and are the basis of the U-Pb dating method in geology [5]-[8]. In Zheng et al (2012) (Figure 1), all zircons in YX1 from Yingxian lamproites were found to be discordant and yielded a lower intercept age of −370 ± 690 Ma. According to conventional theories, this age indicates that the samples will experience a metamorphic process in a distant age. The slope years tslopes for the U-Pb dating method for the Concordia and Discordia lines are presented, and a method for estimating values for tslope from the experimental data is proposed. Four examples are presented to illustrate the application of the proposed method
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