Dataset Information

Extreme lithium isotopic fractionation in three zircon standards (Plesovice, Qinghu and Temora).

ABSTRACT: To understand the behavior of Li in zircon, we have analyzed the abundance and isotopic composition of Li in three zircon standards (Plešovice, Qinghu and Temora) widely used for microbeam analysis of U-Pb ages and O-Hf isotopes. We have mapped Li concentration ([Li]) on large grains, using a Cameca 1280HR Secondary Ion Mass Spectrometer (SIMS). All zircons have a rim 5-20??m wide in which [Li] is 5 to 20 times higher than in the core. Up to ~20‰ isotopic fractionation is observed on a small scale in the rims of a single zircon grain. The measured ?(7)Li values range from -14.3 to 3.7‰ for Plešovice, -22.8 to 1.4‰ for Qinghu and -4.7 to 16.1‰ for Temora zircon. The [Li] and ?(7)Li are highly variable at the rims, but relatively homogenous in the cores of the grains. From zircon rim to core, [Li] decreases rapidly, while ?(7)Li increases, suggesting that the large isotopic variation of Li in zircons could be caused by diffusion. Our data demonstrate that homogeneous ?(7)Li in the cores of zircon can retain the original isotopic signatures of the magmas, while the bulk analysis of Li isotopes in mineral separates and in bulk-rock samples may produce misleading data.

SUBMITTER: Gao YY

PROVIDER: S-EPMC4655365 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Extreme lithium isotopic fractionation in three zircon standards (Plešovice, Qinghu and Temora).

Gao Yu-Ya YY Li Xian-Hua XH Griffin William L WL Tang Yan-Jie YJ Pearson Norman J NJ Liu Yu Y Chu Mei-Fei MF Li Qiu-Li QL Tang Guo-Qiang GQ O'Reilly Suzanne Y SY

Scientific reports 20151123

To understand the behavior of Li in zircon, we have analyzed the abundance and isotopic composition of Li in three zircon standards (Plešovice, Qinghu and Temora) widely used for microbeam analysis of U-Pb ages and O-Hf isotopes. We have mapped Li concentration ([Li]) on large grains, using a Cameca 1280HR Secondary Ion Mass Spectrometer (SIMS). All zircons have a rim 5-20 μm wide in which [Li] is 5 to 20 times higher than in the core. Up to ~20‰ isotopic fractionation is observed on a small sca ...[more]

PMID: 26594042

Similar Datasets

Project description:The chemical and isotopic signatures of moderately volatile elements are useful for understanding processes of volatile depletion in planetary formation and differentiation. However, the fractionation factors between gas and melt phases during evaporation that are required to model these planetary volatile depletion processes are still sparse. In this study, twenty heating experiments were conducted in 1 atm gas-mixing furnaces to constrain the behavior of K, Cu, and Zn evaporation and isotopic fractionation from basaltic melts at high temperatures. The temperatures range from 1300 °C to 1400 °C, and durations are from 2 to 8 days. Oxygen fugacities (fO2) range from one log unit below to ten log units above that of the iron-wüstite buffer (IW-1 to IW+10, corresponding to logfO2 of -10.7 to -0.68 at 1400 °C). The conditions were selected to achieve an evaporation-dominated regime (where timescales of diffusion << evaporation for trace elements) in order to avoid diffusion-limited evaporation. Our results show during evaporation Zn behaved as the most volatile, followed by Cu and then K, regardless of temperature and oxygen fugacity. Partitioning of Zn into spinel layers within experimental capsules, however, has been observed, which has substantial effects on the Zn isotope fractionation factor. Therefore, Zn results are presented but further discussion is excluded. Element loss depends on both temperature and oxygen fugacity, where higher temperatures and lower oxygen fugacities promote evaporation. However, with varying temperature and oxygen fugacity, the kinetic isotopic fractionation factors, α (where, RR0=fα-1 ), for K and Cu remain constant, thus these factors can be applied to a wider range of conditions than those in this study. The experimentally determined fractionation factors for K, and Cu during evaporation from basaltic melts are 0.9944, and 0.9961, respectively. The fractionation factors for these elements with varying volatilities are all significantly larger than the "apparent observed fractionation factors," which approach one and are inferred from lunar basalts relative to the Bulk Silicate Earth. This observation suggests near-equilibrium conditions during volatile-element loss from the Moon as the "apparent observed fractionation factors" of lunar basalts are similar for all three elements.

Dataset Information

Extreme lithium isotopic fractionation in three zircon standards (Plesovice, Qinghu and Temora).

Publications

Extreme lithium isotopic fractionation in three zircon standards (Plešovice, Qinghu and Temora).

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets