^1,2,3,4Ke Zhu 朱柯, ⁵Peng Ni, ⁶Qi Chen, ⁷Mahesh Anand, ²Meng-Hua Zhu, ⁴Tim Elliott
Earth and Planetary Science Letters 683, 119974 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2026.119974]
¹State Key Laboratory of Geological Processes and Mineral Resources, Hubei Key Laboratory of Planetary Geology and Deep-Space Exploration, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
³School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC 3800, Australia
⁴Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, United Kingdom
⁵Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095, USA
⁶Department of Earth Science & Environmental Change, University of Illinois at Urbana Champaign, Urbana, IL, USA
⁷School of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, United Kingdom
Copyright Elsevier

Although the Moon is thought to have formed through a giant impact between proto-Earth and a Mars-sized body, the processes responsible for the chemical and mass-dependent isotopic differences between Earth and Moon remain debated. We report high-precision mass-dependent Ni isotope data for 19 Apollo samples, including one dunite (72415), fifteen low-Ti basalts, and three high-Ti basalts, analyzed by double-spike technique using a multi-collector plasma-sourced mass spectrometer. The dunite 72415 shows an extremely high δ60/58Ni value of +1.80 ± 0.01‰, which we attribute to kinetic isotope fractionation from Ni diffusion during re-equilibration between olivine and a later melt. Diffusion modeling of Ni–Fe–Mg systematics reproduces the observed heavy Ni enrichment. In contrast, low-Ti basalts display a mean δ60/58Ni of 0.23 ± 0.20‰ (2SD), unaffected by cosmic-ray exposure, while high-Ti basalts are slightly isotopically lighter (0.06 ± 0.22‰, 2SD). Petrological modeling using pMELTS with recently constrained silicate mineral-melt fractionation factors suggests limited Ni isotope fractionation (<0.05‰) during lunar magma ocean crystallization and partial melting, yielding an estimated bulk silicate Moon (BSM) δ60/58Ni = 0.18 ± 0.20‰ (2SD). This overlaps with the bulk silicate Earth (BSE: 0.11 ± 0.07‰), indicating that Ni depletion in the lunar mantle, by a factor of ∼4 relative to Earth, can be caused by core formation (that does not fractionate Ni isotopes). However, our modelling shows evaporative loss of Ni can elevate δ60/58Ni value of < 0.23‰, which remains consistent with those of BSM within uncertainty. Hence, the mechanism of Ni evaporation cannot be ruled out.

¹Toni Schulz,¹Christian Koeberl,^1,2Olivier Heldwein,³Bo-Magnus Elfers,⁴Jonas Tusch,⁵Stefan T. M. Peters,⁶Andreas Pack,⁴Carsten Münker
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70124]
¹Department of Lithospheric Research, University of Vienna, Vienna, Austria
²Institute of Social Ecology, University of Natural Resources and Life Sciences, Vienna, Austria
³Technische Universität Hamburg, Zentrallabor Chemische Analytik, Hamburg, Germany
⁴Institut für Geologie und Mineralogie, Universität zu Köln, Köln, Germany
⁵Zentrum für Biodiversitätsmonitoring, Leibniz-Institut zur Analyse des Biodiversitätswandels, Hamburg, Germany
⁵Geowissenschaftliches Zentrum, Georg-August-Universität Göttingen, Göttingen, Germany
Published by arrangement with John Wiley & Sons

Archean impact spherule layers represent exceptional archives of extraterrestrial (ET) material, containing large amounts of ET highly siderophile elements (HSE) that dominate the bulk content of these elements. This enrichment makes them prime targets for testing additional impact tracers, such as ε182W and triple oxygen isotopes. We investigated samples from the Paleoarchean BARB5 drill core (Barberton Mountain Land, South Africa), which preserves four spherule layers with chondritic HSE contents and 187Os/188Os signatures. Tungsten isotope data from bulk spherule layer samples yield ε182W values indistinguishable from the bulk silicate Earth, most likely reflecting the limited sensitivity of the ε182W composition to detect meteoritic admixture. If present, such a component must lie within analytical uncertainties, limiting contributions to ≤6% for a chondritic endmember or ≤3% for an iron-meteorite endmember, unless a larger signal was erased by postimpact hydrothermal overprint. In addition, bulk triple oxygen data fall within Archean shale fields and do not show resolvable ET signatures, consistent with a chondritic contribution of at most ~5% given analytical uncertainties; elevated 18O values most likely reflect seawater alteration of glass spherules. Thus, despite clear HSE–Os isotope evidence for admixture of ET components, ε182W and oxygen isotopes yield no such information. This can be explained by plume condensation models predicting temporally separated fallout of refractory and volatile element carriers. To test this, we separated spherules, matrix, and mixed fractions from one of the four BARB5 beds. While the matrix hosts the highest HSE contents and least radiogenic 187Os/188Os, spherules have the lowest HSE contents and slightly more radiogenic 187Os/188Os signatures, with mixed fractions being intermediate. Together with highly siderophile interelement trends, these results most likely highlight stepwise condensation followed by early syn-depositional to diagenetic alteration, establishing Archean spherule beds as unique probes of early plume dynamics and impact processes.