Proceedings of the Japan Academy, Series B
Online ISSN : 1349-2896
Print ISSN : 0386-2208
Diffusivities of Rare Earth Elements and Ba in Magmatic Silicate Melts at High Pressures
Eizo NAKAMURAIkuo KUSHIRO
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1997 Volume 73 Issue 3 Pages 44-47

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Abstract

Diffusivities of 11 rare earth elements (REE) and Ba in jadeite (NaAlSi2O6) and diopside (CaMgSi2O6) melts have been measured at pressures between 10 and 20kbar. In jadeite melt, diffusivities of REE increase regularly with increasing their ionic radii, light REE (e.g., La and Ce) diffuse faster than heavy REE (e.g., Yb and Lu) by about 30%, Eu diffuses faster by factor of 8 to 12 than other REE under reducing conditions, and diffusivities of REE increase with increasing pressure at constant temperature. In diopside melt, diffusivities of REE are nearly the same as that of Ca and decrease with increasing pressure. The present study demonstrates that diffusion process in magma should change the relative abundances of REE and also generate Eu anomalies without involvement of plagioclase feldspar. This diffusion-induced process is a newly recognized mechanism of changing the relative REE abundances in magmas and generating Eu anomalies, and it must be taken into account in interpreting the REE abundance patterns of igneous rocks.

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