Comparison of the NanoSIMS data on OR7 (filled red circles) and the IF7 mixing lines derived from the mixing model. Columns 1, 2 and 3 show the ¹⁵N/¹⁴N vs, ¹³C/¹²C, ¹⁵N/¹⁴N vs D/H and ¹³C/¹²C vs D/H compositions, respectively. Row a, b and c: mixing lines for α_N = α_C = α_H = α. Row a: the abundance of ¹⁵N₂ is fixed and the abundances of CD₄ and ¹³CO are varying. Row b: the abundance of CD₄ is fixed and the abundances of ¹⁵N₂ and ¹³CO are varying. Row c: the abundance of ¹³CO is fixed and the abundances of ¹⁵N₂ and CD₄ are varying. The value of α is indicated by the blue to red color contours. IF mixing lines with varying labeled layer compositions are displayed with dashed lines. The composition of the unlabeled ice is indicated in gray. Row d: the composition of IF7 is fixed and the mixing factors α_N, α_C, α_H are set as free parameters. The value of the mixing factors are given by the gray scale on the top and right axes. The nominal mixing lines are plotted with bold dotted lines.