Experimental determination of rare earth element partitioning between hydrous silicate melt,amphibole and garnet peridotite minerals at upper mantle pressures and temperatures |
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| Authors: | Bjørn O Mysen |
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| Institution: | Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20008, U.S.A. |
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| Abstract: | Partition coefficients of Ce, Sm and Tm involving garnet peridotite minerals, amphibole and hydrous silicate melt have been determined experimentally in the temperature and pressure ranges 950–1075°C and 10–25 kbar.Only several parts per million to several tens of parts per million of rare earth element (REE) can dissolve in the minerals before the crystal-liquid partition coefficients begin to vary as a function of REE content. The concentration ranges of constant partition coefficient increase with increasing temperature and are also positively correlated with the magnitude of the crystal-liquid partition coefficients. The upper concentration limits of constant partition coefficient and the value of the crystal-liquid partition coefficient for REE decrease in the order garnet > clinopyroxene > amphibole > orthopyroxene > olivine.Partition coefficients may vary by at least an order of magnitude as a function of bulk composition of the liquid phase (e.g. changing from basaltic to andesitic). The approximate ranges of the values of the partition coefficients as a function of bulk liquid composition are as follows: where the values increase with increasing acidity of the melt. |
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