Extended Data Fig. 8: Raman spectroscopic spectra and zircon δ18O (‰), U (ppm), Th/U ratio, and discordance percentage.
From: Onset of the Earth’s hydrological cycle four billion years ago or earlier

(a) Raman spectra for representative grains including the zircon standards. (b-e) FWHM values (cm–1) versus δ18O (‰), U contents, Th/U ratios, and discordance percentage show no correlation and support a primary origin for the signatures of these zircons.