Trivalent titanium in high-titanium lunar ilmenite

Vira, Advik D. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000308694951); Burgess, Katherine D. [US Naval Research Lab. (NRL), Washington, DC (United States)] (ORCID:000000032028447X); First, Emily C. [Macalester College, Saint Paul, MN (United States)] (ORCID:0000000267951228); Tian, Mengkun [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000327907799); Eames, Keyes M. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0009000854797330); Trivedi, Roshan S. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0009000229753340); Dotson, Gabriella K. [Georgia Institute of Technology, Atlanta, GA (United States)]; Kim, Dean M. [Georgia Institute of Technology, Atlanta, GA (United States)]; Farr, Tyler P. [Georgia Institute of Technology, Atlanta, GA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)]; Lisabeth, Harrison [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:000000034491013X); Tamura, Nobumichi [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000236982611); Livernois, Emma R. [Georgia Institute of Technology, Atlanta, GA (United States)]; Jones, Brant M. [Georgia Institute of Technology, Atlanta, GA (United States)]; Orlando, Thomas M. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000224224506); Jiang, Zhigang [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000198843337); First, Phillip N. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000308199598)

doi:10.1038/s41467-026-69770-w

DOE OSTI · 3363743

Trivalent titanium in high-titanium lunar ilmenite

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Abstract

Lunar mare basalts are often rich in titanium, hosted predominantly within the mineral ilmenite (Fe 2+ Ti 4+ O 3 ). Here, we examine ilmenite in a ~3.8 billion-year-old mare basalt (Apollo rock 75035) using high-resolution electron microscopy and electron energy loss spectroscopy. A key finding is that 75035 ilmenite is itself enriched in Ti, beyond the end member of the conventional solid solution series. Using energy loss near-edge spectroscopy, we determine that the excess Ti is trivalent, with Ti 3+ accounting for 13% of the total Ti content. This discovery confirms the presence of trivalent Ti in lunar ilmenite, long hypothesized based on the Moon’s reducing environment. Accounting for the change in implied stoichiometry, a review of literature data suggests that Ti 3+ may be present in ilmenite across a wide range of lunar samples. We extrapolate known relationships from the literature to connect Ti 3+ to redox conditions, estimating the oxygen fugacity during crystallization of 75035 to be below the iron-wüstite buffer, ΔIW≤ − 1.6. Further quantifying the relationship between Ti valence state and oxygen fugacity would allow Ti 3+ -bearing ilmenite to serve as an oxybarometer able to access the reducing conditions found on many planetary bodies.

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Vira, Advik D. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000308694951), Burgess, Katherine D. [US Naval Research Lab. (NRL), Washington, DC (United States)] (ORCID:000000032028447X), First, Emily C. [Macalester College, Saint Paul, MN (United States)] (ORCID:0000000267951228), Tian, Mengkun [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000327907799), Eames, Keyes M. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0009000854797330), Trivedi, Roshan S. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0009000229753340), Dotson, Gabriella K. [Georgia Institute of Technology, Atlanta, GA (United States)], Kim, Dean M. [Georgia Institute of Technology, Atlanta, GA (United States)], Farr, Tyler P. [Georgia Institute of Technology, Atlanta, GA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Lisabeth, Harrison [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:000000034491013X), Tamura, Nobumichi [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000236982611), Livernois, Emma R. [Georgia Institute of Technology, Atlanta, GA (United States)], Jones, Brant M. [Georgia Institute of Technology, Atlanta, GA (United States)], Orlando, Thomas M. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000224224506), Jiang, Zhigang [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000198843337), First, Phillip N. [Georgia Institute of Technology, Atlanta, GA (United States)] (ORCID:0000000308199598). 2026-03-27. Trivalent titanium in high-titanium lunar ilmenite. https://doi.org/10.1038/s41467-026-69770-w

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