Resolve discrepancies in UCC-normalized Zn, Sb, and W abundances for “BeLaU” spherules

Determine the cause of the discrepancies in Upper Continental Crust (UCC)–normalized concentrations of Zn, Sb, and W for the “BeLaU” spherules between the values computed in this study—which indicate Zn enrichment relative to UCC and higher enrichments for Sb and W—and the values reported by Loeb et al. (2024) in their Figure 20. Ascertain whether these differences arise from data selection, normalization choices, computational methodology, or measurement inconsistencies, to ensure a consistent geochemical comparison framework.

Background

In comparing element concentrations of the “BeLaU” spherules to terrestrial reference compositions, the paper reproduces a UCC-normalized spider diagram similar to Loeb et al. (2024). During this reproduction, specific differences emerged between the two presentations for several trace elements, notably Zn, Sb, and W.

The paper explicitly acknowledges an inability to account for why its UCC-normalized plot shows Zn enrichment (rather than depletion) and stronger enrichments of Sb and W, relative to Loeb et al.’s presentation. Clarifying the source of these discrepancies would strengthen the comparability of datasets and the robustness of conclusions regarding the terrestrial origin of the spherules.

References

We note some differences between this plot and Figure 1 of Loeb et al. (2024): relative to UCC, we find that Zn is enriched, not depleted, and that Sb and W are more enriched than they found. We cannot explain the differences.

— Be,La,U-rich spherules as microtektites of terrestrial laterites: What goes up must come down  (2403.05161 - Desch, 2024) in Section “Compositions Indicate an Origin on Earth,” paragraph discussing Figure 2 (immediately preceding Figure 2)