Copper isotopes track the Neoproterozoic oxidation of cratonic mantle roots
The oxygen fugacity (fO 2 ) of the lower cratonic lithosphere influences diamond formation, melting mechanisms, and lithospheric evolution, but its redox evolution over time is unclear. We apply Cu isotopes (δ 65 Cu) of ~ 1.4 Ga lamproites and < 0.59 Ga silica-undersaturated alkaline rocks from t...
| Published in: | Nature Communications |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://researchers.mq.edu.au/en/publications/54b12234-058a-4ea1-97fb-c2f6bd73de1f https://doi.org/10.1038/s41467-024-48304-2 https://research-management.mq.edu.au/ws/files/351615315/350920709.pdf http://www.scopus.com/inward/record.url?scp=85193940481&partnerID=8YFLogxK |
| Summary: | The oxygen fugacity (fO 2 ) of the lower cratonic lithosphere influences diamond formation, melting mechanisms, and lithospheric evolution, but its redox evolution over time is unclear. We apply Cu isotopes (δ 65 Cu) of ~ 1.4 Ga lamproites and < 0.59 Ga silica-undersaturated alkaline rocks from the lithosphere-asthenosphere boundary (LAB) of the North Atlantic Craton to characterize fO 2 and volatile speciation in their sources. The lamproites’ low δ 65 Cu (−0.19 to −0.12‰) show that the LAB was metal-saturated with CH 4 + H 2 O as the dominant volatiles during the Mesoproterozoic. The mantle-like δ 65 Cu of the < 0.59 Ga alkaline rocks (0.03 to 0.15‰) indicate that the LAB was more oxidized, stabilizing CO 2 + H 2 O and destabilizing metals. The Neoproterozoic oxidation resulted in an increase of at least 2.5 log units in fO 2 at the LAB. Combined with previously reported high fO 2 in peridotites from the Slave, Kaapvaal, and Siberia cratonic roots, this oxidation might occur in cratonic roots globally. |
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