Figure 5.

Zagami isochron diagrams for the four data runs described in the text. Dots represent individual spot analyses, with ellipses denoting their respective 1σ uncertainty intervals. The best-fitting line for the data from each run is shown, along with its 1σ uncertainty interval (dashed). The age is calculated from the slope of the best-fitting line, using the ⁸⁷Rb half-life determined by Rotenberg et al.⁵⁷ The only criterion used to reject a spot analysis from an isochron is failure to unambiguously detect one or more isotopes.