REE abundance patterns for lanthanite-(Nd) and kimuraite-(Y) regressed successfully by Jørgensen-Kawabe equation for the lanthanide tetrad effectg

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The REE abundance patterns for lanthanite-(Nd) [(La, Nd)z(CO3)3·8H2O] and kimuraite-(Y)[CaY2(CO3)4·6(H2O)], have been examined by Jørgensen-Kawabe equation for the lanthanide tetrad effect. The reported REE data for lanthanite-(Nd) samples from the Whitianga quarry, New Zealand (Graham et at., 2007) and Hizen, Higashi Mastuura, Japan (Akagi et al., 1996), give their chondrite-normalized REE patterns which can be regressed successfully by the theoretical equation, except for their Ce anomalies. When the lanthanite-(Nd) from Whitianga is normalized by the Hizen Ianthanite, their strong trends of light REE enrichment are cancelled mutually, leaving a small convex tetrad effect in the REE pattern. Two kimuraite-(Y) samples coexisting with the Hizen lanthanite-(Nd) show similar W-type tetrad effects (Akagi et al. 1993). One kimuraite-(Y) sample, in fact, exhibits a typical tetrad effect, but the other kimuraite-(Y) shows a less symmetrical one. The REE pattern for the former kimuraite, when normalized by chondrite or by the Hizen lanthanite, is immediately regressed by the theoretical equation, but the REE pattern for the latter kimuraite cannot be fitted to the equation without correcting for light REEs. The excesses of light REEs in the latter kimuraite are evaluated by the regular REE fractionation between kimuraite and lanthanite and the theoretical equation. The REE patterns for lanthanite-(Nd) and kimuraite-(Y) with the tetrad effects are certainly described quantitatively by Jørgensen-Kawabe equation, signifying its importance in considering the REE distributions in the representative rare earth minerals of lanthanite-(Nd) and kimuraite-(Y).

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