Absolute isotopic abundances of Ti in meteorites

doi:10.1016/0016-7037(85)90176-0

Geochimica et Cosmochimica Acta

Volume 49, Issue 3, March 1985, Pages 835-851

https://doi.org/10.1016/0016-7037(85)90176-0 Get rights and content

Abstract

The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using $^{46} Ti^{48} Ti$ . Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. We provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components. The absolute Ti and Ca isotopic compositions still support the correlation of ⁵⁰Ti and ⁴⁸Ca effects in the FUN inclusions and imply contributions from neutron-rich equilibrium or quasi-equilibrium nucleosynthesis. The present identification of endemic effects at ⁴⁶Ti, for the absolute composition, implies a shortfall of an explosive-oxygen component or reflects significant isotope fractionation. Additional nucleosynthetic components are required by ⁴⁷Ti and ⁴⁹Ti effects. Components are also defined in which ⁴⁸Ti is enhanced.

Bulk samples of carbonaceous meteorites (C2 and C3 types) show distinct excesses at ⁵⁰Ti but no nonlinear effects at the other Ti isotopes. Other chondrites, including Orgueil (Cl), show no nonlinear effects. Relative to terrestrial Ti, a small isotope fractionation is found for only an enstatite chondrite. The Ti absolute compositions in Ca-Al-rich inclusions show significant isotope fractionation effects corresponding to an enhancement in the heavier isotopes relative to the lighter isotopes as compared to Ti in a TiO₂ standard and in chondrites. The absence of a correlation of Ti isotope fractionation effects with those for Ca and Mg is indicative of multiple processes of condensation, volatilization and recondensation; however, the mechanisms causing the isotope fractionation are not well understood.

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^∗: Division Contribution No. 4010 (459).

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Absolute isotopic abundances of Ti in meteorites

Abstract

Geochim. Cosmochim. Acta

Icarus

Geochim. Cosmochim. Acta

Geochim. Cosmochim Acta

Geochim. Cosmochim Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Chromium isotopic anomalies in Allende refractory inclusions

Geophys. Res. Lett.

Nuclear quasi-equilibrium during silicon burning

Astrophys. J. Suppl.

The neutronrich silicon-burning and equilibrium processes of nucleosynthesis

Astrophys. J. Lett.

Correlated O and Mg isotope anomalies in Allende inclusions: I

Oxygen. Geophys. Res. Lett.

A component of primitive nuclear composition in carbonaceous meteorites

Science

Isotopic fractionation of Si in Allende inclusions

New “FUN” inclusions from Allende

Lunar Planet. Sci. XIV

A new type of white inclusion in Allende: Petrography, mineral chemistry, 40Ar-39Ar ages and genetic implications

Isotopic analysis of barium in meteorites and in terrestrial samples

J. Geophys. Res.

Neutrino processes and pair formation in massive stars and supernovae

Astrophys. J. Suppl.

Refractory inclusions in the Allende meteorite

Ann. Rev. Earth Planet. Sci.

On the e-process: its components and their neutron excesses

Astrophys. J.

The sp-process and Allende isotope anomalies in calcium and titanium

Astrophys J.

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Astrophys. J.

Evidence of a new isotopic anomaly from Ti isotope ratios in meteoric materials

Nature

Nucleosynthesis of rare nuclei from seed nuclei in explosive carbon burning

Astrophys. J.

A new type of white inclusion in Allende: Petrography, mineral chemistry, $^{40} Ar-^{39} Ar$ ages and genetic implications