TY - JOUR

T1 - Chondritic osmium isotope composition of early Earth mantle

AU - Waterton, P.

AU - Serre, S. H.

AU - Pearson, G.

AU - Woodland, S.

AU - DuFrane, S. A.

AU - Morishita, T.

AU - Szilas, K.

N1 - Funding Information: This study was supported by the Carlsberg Foundation through grant CF18-0090 to Kristoffer Szilas. We thank Richard Walker and an anonymous reviewer for constructive reviews, and Helen Williams for editorial handling. Publisher Copyright: © 2024 The Authors Published by the European Association of Geochemistry.

PY - 2024

Y1 - 2024

N2 - The Ujaragssuit Intrusion, North Atlantic Craton (NAC), Greenland, is thought to host the oldest chromitites (>3.8 Ga) on Earth, showing evidence of both Hadean mantle depletion events and nucleosynthetic isotopic heterogeneities. We set out to verify the age of the intrusion and identify the Os isotope composition of the Ujaragssuit mantle source. Here, we show that the only minimum age constraint is 2970 ± 8 Ma, provided by cross-cutting leucogranites. Concordant Re-Pt-Os isotope ages are consistent with formation of the intrusion from a chondritic primitive mantle source at 3246 ± 120 Ma; mean Pt-depletion ages of 3437 ± 587 Ma offer no direct evidence for Hadean mantle depletion. No nucleosynthetic Os isotopic anomalies could be identified, consistent with large scale Os homogeneity in the presolar nebular. The new ‘young’ age for Ujaragssuit means that nucleosynthetic anomalies occur repeatedly between ∼3.8 and >3.0 Ga in the NAC, suggesting its unique mantle source was repeatedly tapped over ∼600 Myr without significant mixing with the rest of Earth’s mantle.

AB - The Ujaragssuit Intrusion, North Atlantic Craton (NAC), Greenland, is thought to host the oldest chromitites (>3.8 Ga) on Earth, showing evidence of both Hadean mantle depletion events and nucleosynthetic isotopic heterogeneities. We set out to verify the age of the intrusion and identify the Os isotope composition of the Ujaragssuit mantle source. Here, we show that the only minimum age constraint is 2970 ± 8 Ma, provided by cross-cutting leucogranites. Concordant Re-Pt-Os isotope ages are consistent with formation of the intrusion from a chondritic primitive mantle source at 3246 ± 120 Ma; mean Pt-depletion ages of 3437 ± 587 Ma offer no direct evidence for Hadean mantle depletion. No nucleosynthetic Os isotopic anomalies could be identified, consistent with large scale Os homogeneity in the presolar nebular. The new ‘young’ age for Ujaragssuit means that nucleosynthetic anomalies occur repeatedly between ∼3.8 and >3.0 Ga in the NAC, suggesting its unique mantle source was repeatedly tapped over ∼600 Myr without significant mixing with the rest of Earth’s mantle.

U2 - 10.7185/geochemlet.2424

DO - 10.7185/geochemlet.2424

M3 - Journal article

AN - SCOPUS:85196732338

VL - 31

SP - 1

EP - 6

JO - Geochemical Perspectives Letters

JF - Geochemical Perspectives Letters

SN - 2410-3403

ER -