Partitioning behaviour of Hf and Zr between amphibole, clinopyroxene, garnet and silicate melts at high pressure
Partitioning behaviour of Hf and Zr between amphibole, clinopyroxene, garnet and silicate melts at high pressure (in EMPG-VI; Experimental mineralogy, petrology and geochemistry, E. A. J. Burke (editor), C. Chopin (editor), W. V. Maresch (editor), L. Ungaretti (editor) and C. Willaime (editor))
European Journal of Mineralogy (April 1997) 9 (2): 379-391
Partition coefficients (D) have been determined for Hf and Zr for amphibole, clinopyroxene and garnet crystallizing from Zr- and Hf-enriched basanite and andesite compositions at 0.5-3.0 GPa and 1000-1050 degrees C (basanite) or 900-950 degrees C (andesite). D (sub Hf) and D (sub Zr) for amphibole and clinopyroxene decrease with increasing P, and D (sub Hf) is consistently >><$I> D (sub Zr) ; for garnet, however, D (sub Zr) >><$I> D (sub Hf) . The effect of P is most noteworthy between 0.5 and 1.5 GPa ( approximately a threefold decrease from 0.61 to 0.20 in D (sub Hf) for amphibole). This should be taken into account when modelling the behaviour of Zr and Hf in magmas, especially at crustal depths. The partitioning results for Hf are linked with established patterns for REE in clinopyroxene and garnet crystallizing from a similar basanite, and confirm that the depth of initiation of melting for oceanic basalts may be shallower than originally believed. The near-chondritic constancy of Sm/Hf in mantle derived melts cannot be attributed to a combined role of residual garnet and clinopuyroxene.