Lithium isotope composition of ordinary and carbonaceous chondrites, and differentiated planetary bodies

Bulk solar system and solar reservoirs

authored by

Hans Michael Seitz, Gerhard P. Brey, Jutta Zipfel, Ulrich Ott, Stefan Weyer, Soodabeh Durali, Stephan Weinbruch

Abstract

In order to better constrain the Li isotope composition of the bulk solar system and Li isotope fractionation during accretion and parent body processes, Li isotope compositions and concentrations were determined on a number of meteorite falls and finds. This is the first comprehensive study that systematically investigates a representative set of samples from carbonaceous chondrites (CI, CM2, CO3, CV3, CK4 and one ungrouped member), enstatite chondrites (EH, EL), ordinary chondrites (H, L, LL), and achondrites (one eucrite, diogenites, one pallasite, and a silicate inclusion from a IAB iron). Carbonaceous chondrites have an average isotope composition of δ⁷Li = + 3.2‰ ± 1.9 (2σ) which agrees with the average composition of relatively pristine olivines (representative for the bulk composition) from the Earth primitive upper mantle (PUM). This is lighter than the average δ⁷Li of the basaltic differentiates of the Earth, Moon and Mars and the achondrites. It is an important observation, however, that the lighter end of the isotopic range of the differentiates always coincides with the averages of the mantle olivines and the carbonaceous chondrites. From this we conclude that the bulk of the inner solar system consists mostly of material from carbonaceous chondrites and that the variation seen in the differentiates is due to planetary body processes. Ordinary chondrites are significantly lighter than carbonaceous chondrites. No significant differences in δ⁷Li exist between enstatite chondrites (n = 3) and carbonaceous or ordinary chondrites. The difference between carbonaceous and ordinary chondrites and the variability within the chondrites could indicate the existence of distinct Li isotope reservoirs in the early solar nebula.

External Organisation(s)

Goethe University Frankfurt
Max Planck Institute for Chemistry (Otto Hahn Institute)
Senckenberg Research
Technische Universität Darmstadt

Type

Article

Journal

Earth and Planetary Science Letters

Volume

260

Pages

582-596

No. of pages

15

ISSN

0012-821X

Publication date

30.08.2007

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Geophysics, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Space and Planetary Science

Electronic version(s)

https://doi.org/10.1016/j.epsl.2007.06.019 (Access: Unknown)