Fig. A1. Chondrite-normalized concentrations of REEs (rare earth elements) in geostandards. Historically, "chondrite-normalized" concentrations have been based on averages or composites of data for ordinary chondrites (20, 21, 30). However, the most precise set of REE concentrations in meteorites is that of the compilation of Anders and Grevesse (31) for C1 chondrites. C1 (carbonaceous) and ordinary chondrites have similar relative concentrations of REEs, but absolute concentrations are greater in ordinary chondrites because they are depleted in volatile elements compared to C1 chondrites. Thus for this plot, REE concentrations of the geostandards are divided by the factor f C_C1, where C_C1 is the concentration "Mean C1 Chondr." from Table 1 of Anders and Grevesse (31) and f = 1.36. The factor f yields concentrations of all REE similar in absolute magnitude to those of the ordinary chondrites of Haskin et al. (20, 21) and Nakamura (30), but the resulting values are more precise (i.e., they generate smoother patterns).