No consensus has yet been reached on which slope of the reference line should be chosen. We choose a reference line with a slope of 0.528 in order to have a consistent terminology across disciplines (see discussion, e.g., in Miller & Pack, 2021, Pack & Herwartz, 2014, or Sharp & Wostbrock, 2021). However, any of the definitions of Δ' 17 O used in the literature, does not change the interpretation of triple oxygen isotope data. Modern tropospheric O 2 has a composition of δ 18 O = 24‰ (i.e., the 18 O/ 16 O ratio is 2.4% higher than in ocean water) and Δ′ 17 O = −0.432 ± 0.010‰ (

Oxygen isotopes provide a unique possibility to study Earth's late accretion phase from a lithophile element perspective, because most carbonaceous chondritesmeteorites that likely resemble the composition of the terrestrial late veneerhave markedly different Δ 0 17 O values than the silicate Earth. Ultramafic rocks in the early Archean assemblage of southwest Greenland have not incorporated the full amount of late accreted materials, and therefore possibly record the Δ 0 17 O of the mantle before late accretion. We measured 17 O/ 16 O and 18 O/ 16 O ratios of olivine from these ultramafic rocks and compared them with olivine from post-Archean mantle peridotite. A missing late veneer component was not resolved. The missing component from the early Archean mantle is therefore restricted to ≤0.12 % of Earth's mass (M ⊕ ) for most carbonaceous chondrite-like materials, unless the missing component resembles CI chondritesthe only carbonaceous chondrites with Δ 0 17 O values similar to those of the silicate Earth. If the early Archean mantle had incorporated 60 % late veneer, the overall late accreted mass would be restricted to ≤0.3 % M ⊕ for most types of carbonaceous chondrites, with a more massive late veneer only possible for CI-like chondrites.