TY - JOUR

T1 - Identification of Earth's late accretion by large impactors through mass independent Cr isotopes

AU - Kadlag, Yogita

AU - Anand, Aryavart

AU - Fischer-Gödde, Mario

AU - Mezger, Klaus

AU - Szilas, Kristoffer

AU - Goderis, Steven

AU - Leya, Ingo

N1 - Funding Information: We would like to thank Dr. Tanja Mohr-Westheide for providing impact spherule samples. We are grateful to Associate Editor Dr. Paolo Sossi, Dr. Craig Walton, and an anonymous reviewer for constructive reviews. Y.K. would like to acknowledge NCCR PlanetS ( Swiss National Science Foundation , Switzerland Grand Nr. 51NF40-141881 ) for providing financial support during the experimental work and Physical Research Laboratory, India for support during writing and completion of this study. Funding Information: We would like to thank Dr. Tanja Mohr-Westheide for providing impact spherule samples. We are grateful to Associate Editor Dr. Paolo Sossi, Dr. Craig Walton, and an anonymous reviewer for constructive reviews. S.G. acknowledges the support by the Belgian Science Policy (BELSPO), the Research Foundation - Flanders (FWO-Vlaanderen), and the VUB strategic research. Y.K. would like to acknowledge NCCR PlanetS (Swiss National Science Foundation, Switzerland Grand Nr. 51NF40-141881) for providing financial support during the experimental work and Physical Research Laboratory, India for support during writing and completion of this study. Publisher Copyright: © 2024 Elsevier Inc.

PY - 2024

Y1 - 2024

N2 - The late addition of extra-terrestrial material may represent an important source of Earth's volatiles. The composition of impactors can be reconstructed using 54Cr abundances in impact related rocks preserved in the terrestrial record. The average ε53Cr and ε54Cr of Earth's mantle determined from mantle rocks of 3.8 Ga to present are 0.03 ± 0.02 and 0.08 ± 0.04, respectively. Impact melt rocks and spherule beds linked to impact structures larger than 50 km that formed between 3.4 Ga and 66 Ma have ε53Cr ranging from −0.04 to 0.17, and ε54Cr ranging from −0.64 to 1.41. A carbonaceous chondrite-like impactor contribution dominated the Meso- to Paleoarchean spherule layers (> 3.0 Ga), whereas a mixed chondrite flux composed of carbonaceous and non‑carbonaceous chondrites, with a possible contribution of differentiated meteorites is observed in the younger spherule layers (2.5 Ga to 66 Ma). This likely reflects the break-up of distinct asteroid families through time. Although available impact materials are limited, the Cr isotope signatures of materials related to large impacts suggest a change in the composition of crater-forming impactors on Earth, from predominantly carbonaceous chondrite-like more oxidized material during the Archean to predominantly non‑carbonaceous -like more reduced and volatile poor material in recent times. Chromium isotopes suggest that not more than 0.01 wt% of CC-like material added to the Earth's mantle after the Archean. Thus, it is inferred that the mass accreted after 3.0 Ga contributed insignificantly to the water and other volatile element budget of the Earth.

AB - The late addition of extra-terrestrial material may represent an important source of Earth's volatiles. The composition of impactors can be reconstructed using 54Cr abundances in impact related rocks preserved in the terrestrial record. The average ε53Cr and ε54Cr of Earth's mantle determined from mantle rocks of 3.8 Ga to present are 0.03 ± 0.02 and 0.08 ± 0.04, respectively. Impact melt rocks and spherule beds linked to impact structures larger than 50 km that formed between 3.4 Ga and 66 Ma have ε53Cr ranging from −0.04 to 0.17, and ε54Cr ranging from −0.64 to 1.41. A carbonaceous chondrite-like impactor contribution dominated the Meso- to Paleoarchean spherule layers (> 3.0 Ga), whereas a mixed chondrite flux composed of carbonaceous and non‑carbonaceous chondrites, with a possible contribution of differentiated meteorites is observed in the younger spherule layers (2.5 Ga to 66 Ma). This likely reflects the break-up of distinct asteroid families through time. Although available impact materials are limited, the Cr isotope signatures of materials related to large impacts suggest a change in the composition of crater-forming impactors on Earth, from predominantly carbonaceous chondrite-like more oxidized material during the Archean to predominantly non‑carbonaceous -like more reduced and volatile poor material in recent times. Chromium isotopes suggest that not more than 0.01 wt% of CC-like material added to the Earth's mantle after the Archean. Thus, it is inferred that the mass accreted after 3.0 Ga contributed insignificantly to the water and other volatile element budget of the Earth.

KW - Archean

KW - Chromium isotopes

KW - Impacts

KW - Late accretion

U2 - 10.1016/j.icarus.2024.116143

DO - 10.1016/j.icarus.2024.116143

M3 - Journal article

AN - SCOPUS:85195192678

VL - 418

JO - Icarus

JF - Icarus

SN - 0019-1035

M1 - 116143

ER -