Experimental crystallization of chevkinite/perrierite from REE- enriched silicate liquids at high pressure and temperature

The synthetic crystallization of chevkinite/perrierite is reported from a series of REE-enriched compositions ranging from basalt to andesite and rhyolite, at 7.5-20 kbar and 900-1050oC. The Al₂O₃ content increased with increasing P, but no other consistent variation with P and T was observed. The REE partition consistently favoured light over heavy REE, with a regular decrease in partition coefficient (D) from La to Lu; D values increase with decreasing T and decreasing REE content but appear unaffected by P and fO₂. Chevkinite/perrierite may be a significant fractionating phase in evolving silicic magmas, or as a residual phase from low degrees of partial melting of granulites. In both cases it will exert a major control on the REE content of derivative liquids. -R.A.H.