Experimental study on rare-earth element partitioning in olivine and clinopyroxene formed at 10 and 20kb for basaltic systems

Abstract

Partition coefficients of rare-earth elements (REE), Ba and Sr were precisely determined for crystal-glass pairs prepared by partial melting and partial solidification of alkali olivine basalt at 10kb and of picrite basalt at 10 and 20kb. Mutually unfractionated REE partition patterns were observed for olivine-glass pairs prepared by partial melting and partial solidification experiments on alkali olivine basalt. A similar unfractionated REE pattern was observed for (clinopyroxene + olivine)/glass formed by 10 kb partial melting of picrite basalt. On the other hand, clinopyroxene was produced in 10kb partial solidification of the same picrite basalt and the clinopyroxene showed fractionated, terrace-shaped REE partition pattern. Partial solidification experiments on picrite basalt produced only clinopyroxene as a mineral coexisting with melt, and the resultant REE partition pattern was a guyot-shaped one. It should be noted that the REE partition pattern (terrace-shaped or guyot-shaped) of clinopyroxene bears on the mutual relationship concerning the relative magnitudes of partition values of Fe and heavy REE. Finally, it is worth while to note that clinopyroxene is prevailingly formed in partial solidification process. © 1982, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.