Figure 3.

Measurements of the ratio of ⁸⁶Sr to the sum of (⁸⁶Sr + ⁸⁸Sr) in the Duluth Gabbro (black diamonds) and the GSD‐1G standard (gray squares). The IUPAC value for this ratio is 0.1067,47 although our instrumental fractionation generally favors the detection of ⁸⁶Sr over ⁸⁸Sr. The error‐weighted mean ratio for GSD‐1G (gray line) is ~1% higher than for the Duluth Gabbro (black line). These data illustrate that our instrumental fractionation is matrix‐dependent, and we correct our raw signals for this effect. Error bars on each symbol and dashed intervals around each weighted mean represent 1σ confidence intervals.