FIG. 7. ¹⁸⁷Re/¹⁸⁸Os vs. ¹⁸⁷Os/¹⁸⁸Os isochron diagram for samples from the Thompson nickel belt. The line represents model 3 least squares regression (Ludwig, 1999) of those samples (n = 23) shown with solid symbols. Errors for the age and initial ¹⁸⁷Os/¹⁸⁸Os are given at the 95 percent confidence level. The MSWD of this regression line is 80, using the 2 errors given in Table 3. Four data shown in open symbols were omitted from the regression line and are discussed in the text.