Coupled strontium-calcium isotopes in Archean anorthosites reveal a late start for mantle depletion.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41173851.
- Also identified by DOI 10.1038/s41467-025-64641-2 and PMC identifier 12578967.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Voluminous felsic continental crust is, as far as we know, unique to Earth, yet the timescales of its earliest growth remain debated. Archean mantle evolution is complementary to crustal growth but is largely unconstrained for strontium isotopes due widespread Rb-Sr disturbance. Here, we perform high spatial resolution radiogenic Sr and Ca isotope measurements in magmatic plagioclase megacrysts from 3.7-2.8 Ga Archean anorthosites and leucogabbros. We report mantle-like Ca isotope signatures and the most unradiogenic terrestrial <sup>87</sup>Sr/<sup>86</sup>Sr ratio yet measured on Earth, in plagioclase (<sup>87</sup>Sr/<sup>86</sup>Sr<sub>initial</sub> = 0.700050 ± 0.000017, 95% confidence interval) from the 3.73 Ga Manfred Complex of the Narryer Terrane, Western Australia. These data are consistent with <sup>87</sup>Sr/<sup>86</sup>Sr homogenisation between the Earth and Moon (<sup>87</sup>Sr/<sup>86</sup>Sr<sub>initial</sub> ≈ 0.699061) at ca. 4.515 Ga during the Moon-forming giant impact. The appearance of a depleted mantle signature in the terrestrial strontium record post-3.5 Ga suggests that extensive continental growth began relatively late.