Slope Year for the U-Pb Dating Method and Its Applications

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).