Earth’s evolving geodynamic regime recorded by titanium isotopes

Zhengbin Deng (), Martin Schiller, Matthew G. Jackson, Marc-Alban Millet, Lu Pan, Katrine Nikolajsen, Nikitha S. Saji, Dongyang Huang and Martin Bizzarro
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Zhengbin Deng: University of Copenhagen
Martin Schiller: University of Copenhagen
Matthew G. Jackson: University of California, Santa Barbara
Marc-Alban Millet: Cardiff University
Lu Pan: University of Copenhagen
Katrine Nikolajsen: University of Copenhagen
Nikitha S. Saji: University of Copenhagen
Dongyang Huang: ETH Zürich
Martin Bizzarro: University of Copenhagen

Nature, 2023, vol. 621, issue 7977, 100-104

Abstract: Abstract Earth’s mantle has a two-layered structure, with the upper and lower mantle domains separated by a seismic discontinuity at about 660 km (refs. 1,2). The extent of mass transfer between these mantle domains throughout Earth’s history is, however, poorly understood. Continental crust extraction results in Ti-stable isotopic fractionation, producing isotopically light melting residues3–7. Mantle recycling of these components can impart Ti isotope variability that is trackable in deep time. We report ultrahigh-precision 49Ti/47Ti ratios for chondrites, ancient terrestrial mantle-derived lavas ranging from 3.8 to 2.0 billion years ago (Ga) and modern ocean island basalts (OIBs). Our new Ti bulk silicate Earth (BSE) estimate based on chondrites is 0.052 ± 0.006‰ heavier than the modern upper mantle sampled by normal mid-ocean ridge basalts (N-MORBs). The 49Ti/47Ti ratio of Earth’s upper mantle was chondritic before 3.5 Ga and evolved to a N-MORB-like composition between approximately 3.5 and 2.7 Ga, establishing that more continental crust was extracted during this epoch. The +0.052 ± 0.006‰ offset between BSE and N-MORBs requires that

Date: 2023
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DOI: 10.1038/s41586-023-06304-0

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