The influence of Al (sub 2) O (sub 3) on the H (sub 2) O content in periclase and ferropericlase at 25 GPa
The influence of Al (sub 2) O (sub 3) on the H (sub 2) O content in periclase and ferropericlase at 25 GPa
Russian Geology and Geophysics (June 2010) 51 (6): 644-649
- aluminum
- chemical reactions
- color
- electron probe data
- experimental studies
- ferric iron
- ferropericlase
- fluid inclusions
- FTIR spectra
- glasses
- high pressure
- igneous rocks
- inclusions
- infrared spectra
- iron
- laboratory studies
- lower mantle
- mantle
- melts
- metals
- oxides
- periclase
- peridotites
- plutonic rocks
- point defects
- pressure
- reduction
- solubility
- spectra
- substitution
- synthetic materials
- temperature
- ultramafics
- volatiles
- water content
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 degrees C. The IR spectra of their crystals show narrow absorption peaks at 3299, 3308, and 3474 cm (super -1) . The calculated H (sub 2) O contents are 11-25 ppm in periclase (Al (sub 2) O (sub 3) = 0.9-1.2 wt.%) and 14-79 ppm in ferropericlase (Al (sub 2) O (sub 3) = 0.9-2.9 wt.%). Ferropericlase contains more H (sub 2) O and Al (sub 2) O (sub 3) than periclase at 1800-2000 degrees C. I suggest that addition of Al (sub 2) O (sub 3) does not influence the solubility of water in ferropericlase but can favor the additional incorporation of Fe (sub 2) O (sub 3) into the structure. The incorporation of Fe (super 3+) into ferropericlase increases water solubility as a result of iron reduction to Fe (super 2+) . 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.