Equilibrium cerium isotope fractionations in cerium-bearing minerals and aqueous species are estimated using electronic structure calculations that include both nuclear volume and mass dependent effects. As with europium and uranium, the nuclear volume effect in redox reactions goes in the opposite direction from equilibrium massdependent fractionation for 142 Ce/ 140 Ce because of the larger nuclear charge radius of the 142 Ce nucleus. Massdependent effects dominate 136 Ce/ 140 Ce and 138 Ce/ 140 Ce fractionations because 136 Ce, 138 Ce, and 140 Ce share very similar nuclear charge radii. 142 Ce/ 140 Ce is predicted to be lower in most Ce(IV)-bearing species than in coexisting Ce(III)-bearing species, particularly at high temperatures. However, species with Ce:Zr substitution, such as zirconium-rich compositions along the stetindite-zircon (CeSiO 4 -ZrSiO 4 ) solid solution series and a model Cesubsituted baddeleyite (CeZr 3 O 8 ), may show higher 142 Ce/ 140 Ce at ambient to low-T metamorphic temperatures because of higher effective force constants acting on the smaller, more snug substitution sites. Ce(III)P(V) chargecoupled substitution into zircon is likewise associated with high 142 Ce/ 140 Ce relative to other Ce(III) species. 136 Ce/ 140 Ce and 138 Ce/ 140 Ce fractionations will tend to favor more massive isotopes in Ce(IV)-bearing species, by 0.1-1.0‰ at 25°C and 0.01-0.1‰ at 727°C depending on the species present. The models predict ~0.3‰ higher 142 Ce/ 140 Ce in Ce(III)-bearing solution than coexisting Ce(IV)-solids at ambient temperatures, roughly agreeing with measurements. Zircon in equilibrium with typical silicate melts is predicted to be slightly enriched in 140 Ce relative to 142 Ce, 138 Ce, and 136 Ce. Supplementary calculations based on 141 Pr-Mössbauer spectroscopy literature suggest somewhat (~1/3) smaller nuclear volume fractionation effects than the electronic structure models.

Edwin A. Schauble

GEOCHEMICAL JOURNAL

《地球化学杂志》是一本致力于发表地球化学和宇宙化学原创研究论文的国际期刊。它是日本地球化学会的主要期刊。研究领域如下：宇宙化学；矿物和岩石化学；火山学和水热化学；同位素地球化学和地球年代学；大气化学；水文和海洋化学；有机地球化学；环境化学。

The Geochemical Journal is an international journal dedicated to publishing original research papers in the fields of geochemistry and cosmochemistry. It is the main journal of the Geochemical Society of Japan, covering research areas such as cosmochemistry, mineral and rock chemistry, volcanology and hydrochemistry, isotope geochemistry and geochronology, atmospheric chemistry, hydrology and marine chemistry, organic geochemistry, and environmental chemistry.

《Geochemical Journal》是一本国际期刊，专注于发表地球化学和宇宙化学领域的原创研究论文。它是日本地球化学会的主要期刊，涵盖的研究领域包括：宇宙化学、矿物和岩石化学、火山学与水热化学、同位素地球化学与地球年代学、大气化学、水文与海洋化学、有机地球化学以及环境化学。

Category	Quartile
地球科学	4
地球科学, 地球化学与地球物理	4

Nuclear volume and mass dependent fractionation of cerium isotopes

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Journal Info

Category	Quartile
GEOCHEMISTRY & GEOPHYSICS	3