Abstract

New hornblende/groundmass partition coefficients for rare earths in a sodic, high-Al2 O3 dacite range from 0.9 for Ce to 4.5 to 6.2 for heavy rare earths, and the pattern is concave down with a distinct negative Eu anomaly. These coefficients indicate that hornblende may have been an important residual phase in the generation of high-Al2 O3, heavy-rare-earth-depleted trondhjemites, tonalites, and equivalent dacites, implying that the magmas formed at a depth of less than 60 k.

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