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Mass-independent fractionation of titanium isotopes and its cosmochemical implications


Isotopes of heavy elements are produced in various amounts by nuclear processes in stars1,2. Consequently, the presence of isotopic anomalies in the Solar System is considered to reflect the presence of presolar grains condensed in previous generations of stars3 and not a (proto-) Solar System process. However, for oxygen, the major rock-forming element, it has been shown that physico-chemical reactions applicable to the presolar cloud or the protoplanetary disk were a possible source of isotopic variations due to mass-independent isotopic fractionation (MIF)4,5. Here we show that MIF effects are not restricted to oxygen, but can also be produced for titanium. Titanium-rich grains experimentally condensed from a TiCl4(g)/C5H12(g) plasma exhibit MIF effects from −25% to +120% for all Ti isotopic ratios. These large Ti isotopic variations follow the model developed for oxygen MIF6 and mimic the Ti isotopic anomalies observed in some presolar grains. This effect is ascribed to the reactions between chemically indistinguishable isotopes6 and could contribute to the complexity of isotopic anomalies observed in Solar System materials1,7,8,9,10,11,12,13,14.

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Fig. 1: Ti isotope ratios in OM deposited from a TiCl4/C5H12 plasma.
Fig. 2: Ti isotopic variations in OM deposited from a TiCl4/C5H12 plasma.
Fig. 3: Ti isotopic compositions.
Fig. 4

Data availability

The data that support the plots within this paper and other findings of this study are available in the Supplementary Information or from the corresponding author upon reasonable request.


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F.R. acknowledges support (Overheads) of ERC Advanced Grant PaleoNanoLife (PI: F.R.; grant. no. 161764). R.T. acknowledges support from the UK Science and Technology Facilities Council (grant no. ST/P005225/1). At The University of Manchester, the NanoSIMS was funded by UK Research Partnership Investment Funding (UKRPIF) Manchester RPIF Round 2, and the installation of a Hyperion RF plasma ion source was supported by the Henry Royce Institute for Advanced Materials, funded through EPSRC grant nos EP/R00661X/1, EP/P025021/1 and EP/P025498/1. M.C. acknowledges support from ANR Cradle (grant no. ANR-15-CE31-0004-01).

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Authors and Affiliations



F.R. designed the project and provided samples for this study. R.T. collected and analysed the NanoSIMS data. F.R., R.T., Z.D. and M.C. interpreted the cosmochemistry results and wrote the paper. G.L. interpreted the plasma physics results. B.D. and M.R. obtained and interpreted the microscopic images. P.R. participated in the interpretation of the Ti-MIF effects in terms of theoretical physics.

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Correspondence to François Robert.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Andrew Davis, Justin Simon and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–6, Table 1, discussion and references.

Supplementary Data

Excel version of Supplementary Table 1.

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Robert, F., Tartèse, R., Lombardi, G. et al. Mass-independent fractionation of titanium isotopes and its cosmochemical implications. Nat Astron 4, 762–768 (2020).

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