Structural systematics of hydrous ringwoodite and water in earth’s interior
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Joseph R. Smyth
,
Christopher M. Holl
Abstract
Seven separate samples of hydrous ringwoodite with compositions ranging from Fo100 to Fo89 and hydrogen contents from 0.2 to 1.1 wt% were synthesized in the 5000 ton multi-anvil press at the Bayerisches Geoinstitut. Synthesis conditions ranged from 18 to 22 GPa and 1400 to 1500 °C. The crystals were characterized by single-crystal X-ray diffraction, electron microprobe, IR and Mössbauer spectroscopy, and by analytical and high-resolution transmission electron microscopy. The crystals are optically isotropic, and the Fe-bearing samples are deep blue in color. Mössbauer spectroscopy and ELNE spectroscopy applied to the Fe-bearing samples indicates about 10% of the iron is in the ferric state. High-resolution TEM examination of one of the Fe-bearing samples indicates that the crystals are homogeneous and free of significant inclusions or exsolution features. Infrared spectra show a broad absorption band extending from about 2500 to 3600 cm-1 with maxima ranging from 3105 for the pure magnesian samples to 3150 cm-1 for the Fo89 samples. The crystal structures of the seven ringwoodite samples were refined by X-ray single-crystal diffraction. Refinement of cation site occupancies indicates full occupancy of the tetrahedral site for all samples, whereas the occupancy of the octahedral site appears to decrease systematically with H content. The principal hydration mechanism involves octahedral cation vacancies. The IR spectra are consistent with protonation of the short O-O approach on the tetrahedral edge, which would imply partial Mg-Si disorder.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Structural systematics of hydrous ringwoodite and water in earth’s interior
- Compressibility of phase Egg AlSiO3OH: Equation of state and role of water at high pressure
- Synchrotron infrared spectroscopy of OH-chondrodite and OH-clinohumite at high pressure
- Structural deformation mechanisms of zeolites under pressure
- Variation of hydrogen bonded O···O distances in goethite at high pressure
- Pressure-controlled polytypism in hydrous layered materials
- OH– in synthetic and natural coesite
- Pressure-induced phase transformation of kalicinite (KHCO3) at 2.8 GPa and local structural changes around hydrogen atoms
- Potential docking sites and positions of hydrogen in high-pressure silicates
- Contrasting bonding behavior of two hydroxyl-bearing metamorphic minerals under pressure: Clinozoisite and topaz
- Experimental investigation of crystallization kinetics in a haplogranite system
- Assessment of cation substitutions along the gallium and fluorine analogue of the tremolite-glaucophane join
- Experimental hydrothermal alteration of partially metamict zircon
- On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion
- Ordering in spinels—A Monte Carlo study
- Single-crystal in situ high-temperature structural investigation of the I1̅ –I2/c phase transition in Ca0.2Sr0.8Al2Si2O8 feldspar
- New clinopyroxene-liquid thermobarometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho
- Fe and Ni impurities in synthetic diamond
- Phase transformations and reaction kinetics during the temperature-induced oxidation of natural olivine
- Thermal infrared spectroscopy and modeling of experimentally shocked plagioclase feldspars
- Oxygen isotopic composition of nano-scale uraninite at the Oklo-Okélobondo natural fission reactors, Gabon
- Clinopyroxenite from the Sulu ultrahigh-pressure terrane, eastern China: Origin and evolution of garnet exsolution in clinopyroxene
- Letters. An assessment of nuclear microprobe analyses of B in silicate minerals
- Incommensurate phase in the kosmochlor-diopside join: A new polymorph of clinopyroxene
- Elastic properties of hydrous ringwoodite
- Thermochemistry of guest-free melanophlogite
- A simple model for the pressure preservation index of inclusions in diamond
