New titanium isotope data for allende and efremovka CAIs

Maria Schonbachler, Ingo Leya, Maria Schönbächler, Urs Krähenbühl, Alex N. Halliday

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We measured the titanium (Ti) isotope composition, i.e., 50Ti/47Ti, 48Ti/47Ti, and 46Ti/47Ti, in five calcium-rich-aluminum-rich refractory inclusions (CAIs) from the oxidized CV3 chondrite Allende and in two CAIs from the reduced CV3 chondrite Efremovka. Our data indicate that CAIs are enriched in 50Ti/47Ti and 46Ti/47Ti and are slightly depleted in 48Ti/47Ti compared to normal Ti defined by ordinary chondrites, eucrites, ureilites, mesosiderites, Earth, Moon, and Mars. Some CAIs have an additional 50Ti excess of 8ε relative to bulk carbonaceous chondrites, which are enriched in 50Ti by 2ε relative to terrestrial values, leading to a total excess of 10ε. This additional 50Ti excess is correlated with nucleosynthetic anomalies found in 62Ni and 96Zr, all indicating an origin from a neutron-rich stellar source. Bulk carbonaceous chondrites show a similar trend, however, the extent of the anomalies is either less than or similar to the smallest anomalies seen in CAIs. Mass balance calculations suggest that bulk Allende Ti possibly consists of a mixture of at least two Ti components, anomalous Ti located in CAIs and a normal component possibly for matrix and chondrules. This argues for a heterogeneous distribution of Ti isotopes in the solar system. The finding that anomalous Ti is concentrated in CAIs suggests that CAIs formed in a specific region of the solar system and were, after their formation, not homogeneously redistributed within the solar system. Combining the CAI data with improved model predictions for early solar system irradiation effects indicates that a local production scenario for the relatively short lived radionuclides can be excluded, because the production of, e.g., 10Be, 26Al, and 41Ca, would result in a significant collateral shift in Ti isotopes, which is not seen in the measured data. © 2009. The American Astronomical Society. All rights reserved.
    Original languageEnglish
    Pages (from-to)1118-1126
    Number of pages8
    JournalAstrophysical Journal
    Volume702
    Issue number2
    DOIs
    Publication statusPublished - 2009

    Keywords

    • Abundances
    • Formation
    • Meteoroids
    • Meteors
    • Nuclear reactions
    • Nucleosynthesis
    • Solar system

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