THE INFLUENCE OF Al2O3 ON THE H2O CONTENT bearing IN PERICLASE AND FERROPERICLASE AT 25 GPA
K.D. Litasova
aV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Ferropericlase, periclase, lower mantle, water, IR spectroscopy
Pages: 644-649
Abstract
In this paper I present results of IR spectroscopic measurements of water solubility in Al-bearing periclase and ferropericlase (Mg# = 88) synthesized at 25 GPa and 1400-2000?C. The IR spectra of their crystals show narrow absorption peaks at 3299, 3308, and 3474 cm-1. The calculated H2O contents are 11-25 ppm in periclase (Al2O3 = 0.9-1.2 wt.%) and 14-79 ppm in ferropericlase (Al2O3 = 0.9-2.9 wt.%). Ferropericlase contains more H2O and Al2O3 than periclase at 1800-2000?C. I suggest that addition of Al2O3 does not influence the solubility of water in ferropericlase but can favor the additional incorporation of Fe2O3 into the structure. The incorporation of Fe3+ into ferropericlase increases water solubility as a result of iron reduction to Fe2+. It is shown that water has limited solubility in ferropericlase from mantle peridotite; therefore, ferropericlase cannot be considered an important hydrogen-bearing mineral in the lower mantle.
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