Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting... more Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting the viscosity of magmas and inducing bubble nucleation. We present detailed microscopic and nanoscopic petrographic analyses of nanolite-bearing and nanolite-free pumice from the 2021 eruption of Fukutoku-Oka-no-Ba, Japan. The nanolite mineral assemblage includes biotite, which is absent from the phenocryst mineral assemblage, and magnetite and clinopyroxene, which are observed as phenocrysts. The boundary between the nanolite-bearing brown glass and nanolite-free colorless glass is either sharp or gradational, and the sharp boundaries also appear sharp under the transmitted electron microscope. X-ray absorption fine structure (XAFS) analysis of the volcanic glass revealed that the nanolite-free colorless glass records an oxygen fugacity of QFM + 0.98 (log units), whereas the nanolite-bearing brown glass records a higher oxygen fugacity (~ QFM + 2). Thermodynamic modelling using MELTS i...
The magnitude and spatial distribution of hydration of the oceanic plate is a key to understand w... more The magnitude and spatial distribution of hydration of the oceanic plate is a key to understand water-carbon circulation at subduction zone, and also trigger earthquakes and arc magmatism. Hydration of oceanic plate at the outer rise region due to bending and faulting before subduction has been conceptually proposed (e.g., Peacock, 2001 Geolgy) and has been recently supported by seismic observations (e.g., Ranero et al., 2003 Nature; Worzewski et al., 2010 Nature Geosci.). It is, however, not clear yet, how, how deep and how much water can infiltrate into the bending oceanic plate. Dredging and submersible studies cannot provide the deep and spatial information of oceanic plate. We are going to propose a drilling project to obtain the spatial information of altered oceanic plate along bending-induced faults in off-Tohoku incoming plate, which is an old and cold end member of the oceanic plate. Although trenchward-dipping seismic reflections have not been observed in the studied regi...
The room-temperature bulk modulus of rhenium (Re) was measured in the pressure range 0 to 115 GPa... more The room-temperature bulk modulus of rhenium (Re) was measured in the pressure range 0 to 115 GPa using a laser-annealing diamond anvil cell and the synchrotron X-ray diffraction method. Thermal properties of Re were investigated up to 4000 K based on first-principles molecular dynamics calculations, and the equation of state for Re was determined using experimental and calculated data. A Vinet equation of state fitted to the 300 K data yielded a bulk modulus of KT0 = 384 GPa and a pressure derivative of K T 0 ′ = 3.26. The contribution of thermal pressure was determined to have the form ΔPth = [αKT(Va) + (∂KT/∂T)Vln(Va/V)]ΔT. When αKT(Va) was assumed to be constant, the fit to the data yielded αKT(Va) = 0.0056 GPa/K. In contrast, the volume dependence of the thermal pressure was very small, and fitting yielded a value of (∂KT/∂T)V = −0.00042.
Abstract Crystalline phases coexisting with H2O fluids in a Bassett type externally heated diamon... more Abstract Crystalline phases coexisting with H2O fluids in a Bassett type externally heated diamond anvil cell are identified at 800-1000 C and 0.5-5.2 GPa using synchrotron X-ray diffraction at SPring-8. Up to 3.3 GPa, forsterite (Mg2SiO4) crystallizes in enstatite ( ...
In situ observations of the phase transition in Fe2O3 were carried out in a multianvil and in a d... more In situ observations of the phase transition in Fe2O3 were carried out in a multianvil and in a diamond anvil cell high-pressure apparatus using synchrotron radiation. The phase transition of haematite was observed at high pressures and high temperatures. The phase boundary between the haematite and high-pressure phase in the temperature range of 800–2500K was determined to be P(GPa) =
The 2021 eruption of Fukutoku-Oka-no-Ba (FOB) in the northwest Pacific on 13 August 2021 produced... more The 2021 eruption of Fukutoku-Oka-no-Ba (FOB) in the northwest Pacific on 13 August 2021 produced a large volume of pumice that drifted westward for ~1300 km to the Nansei Islands, Japan, and some extent. In February 2022, pumice with similar characteristics to the FOB pumice was deposited along along the Gulf of Thailand. The pumice clasts deposited in Songkhla Province, Thailand, were <4 cm in length and rounded. Most of the clasts consisted of clinopyroxene, plagioclase (andesine), and olivine phenocrysts in a vesiculated grey groundmass, with black-coloured spots exhibiting signatures of a basaltic magma. The whole-rock compositions of the pumice are trachytic, with 61 mass% SiO2 and 9 mass% total alkali (Na2O + K2O). The overall characteristics in the pumice from Thailand are similar to those in FOB pumice. These pumice in Thailand were from the 2021 FOB eruption, and drifted >2800 km south-westward across the South China Sea.
The physical properties of argon (Ar) are investigated to 382 GPa and 3000 K using diamond anvil ... more The physical properties of argon (Ar) are investigated to 382 GPa and 3000 K using diamond anvil cell experiments and first-principles molecular dynamics. The estimated density of Ar is smaller that of the Preliminary reference Earth model (PREM) mantle, which indicates that the density crossover does not occur at the bottom of the lower mantle. A large volume dependence of the thermal pressure of Ar is revealed at pressures higher than 200 GPa, and a significant temperature dependence of the calculated effective Grüneisen parameters is confirmed at high pressures. A melting temperature of Ar is estimated from the calculation data and a significant pressure dependence is confirmed. If the pressure-temperature path of the subducted slab is lower than the critical condition, ~750 K and ~7.5 GPa, solid Ar can be carried down into the deep mantle. Melting of solid Ar in the upwelling mantle plume occurs at the bottom of the transition zone. Thus, solid Ar plays an important role in Ar r...
Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting... more Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting the viscosity of magmas and inducing bubble nucleation. We present detailed microscopic and nanoscopic petrographic analyses of nanolite-bearing and nanolite-free pumice from the 2021 eruption of Fukutoku-Oka-no-Ba, Japan. The nanolite mineral assemblage includes biotite, which is absent from the phenocryst mineral assemblage, and magnetite and clinopyroxene, which are observed as phenocrysts. The boundary between the nanolite-bearing brown glass and nanolite-free colorless glass is either sharp or gradational, and the sharp boundaries also appear sharp under the transmitted electron microscope. X-ray absorption fine structure (XAFS) analysis of the volcanic glass revealed that the nanolite-free colorless glass records an oxygen fugacity of QFM + 0.98 (log units), whereas the nanolite-bearing brown glass records a higher oxygen fugacity (~ QFM + 2). Thermodynamic modelling using MELTS i...
The magnitude and spatial distribution of hydration of the oceanic plate is a key to understand w... more The magnitude and spatial distribution of hydration of the oceanic plate is a key to understand water-carbon circulation at subduction zone, and also trigger earthquakes and arc magmatism. Hydration of oceanic plate at the outer rise region due to bending and faulting before subduction has been conceptually proposed (e.g., Peacock, 2001 Geolgy) and has been recently supported by seismic observations (e.g., Ranero et al., 2003 Nature; Worzewski et al., 2010 Nature Geosci.). It is, however, not clear yet, how, how deep and how much water can infiltrate into the bending oceanic plate. Dredging and submersible studies cannot provide the deep and spatial information of oceanic plate. We are going to propose a drilling project to obtain the spatial information of altered oceanic plate along bending-induced faults in off-Tohoku incoming plate, which is an old and cold end member of the oceanic plate. Although trenchward-dipping seismic reflections have not been observed in the studied regi...
The room-temperature bulk modulus of rhenium (Re) was measured in the pressure range 0 to 115 GPa... more The room-temperature bulk modulus of rhenium (Re) was measured in the pressure range 0 to 115 GPa using a laser-annealing diamond anvil cell and the synchrotron X-ray diffraction method. Thermal properties of Re were investigated up to 4000 K based on first-principles molecular dynamics calculations, and the equation of state for Re was determined using experimental and calculated data. A Vinet equation of state fitted to the 300 K data yielded a bulk modulus of KT0 = 384 GPa and a pressure derivative of K T 0 ′ = 3.26. The contribution of thermal pressure was determined to have the form ΔPth = [αKT(Va) + (∂KT/∂T)Vln(Va/V)]ΔT. When αKT(Va) was assumed to be constant, the fit to the data yielded αKT(Va) = 0.0056 GPa/K. In contrast, the volume dependence of the thermal pressure was very small, and fitting yielded a value of (∂KT/∂T)V = −0.00042.
Abstract Crystalline phases coexisting with H2O fluids in a Bassett type externally heated diamon... more Abstract Crystalline phases coexisting with H2O fluids in a Bassett type externally heated diamond anvil cell are identified at 800-1000 C and 0.5-5.2 GPa using synchrotron X-ray diffraction at SPring-8. Up to 3.3 GPa, forsterite (Mg2SiO4) crystallizes in enstatite ( ...
In situ observations of the phase transition in Fe2O3 were carried out in a multianvil and in a d... more In situ observations of the phase transition in Fe2O3 were carried out in a multianvil and in a diamond anvil cell high-pressure apparatus using synchrotron radiation. The phase transition of haematite was observed at high pressures and high temperatures. The phase boundary between the haematite and high-pressure phase in the temperature range of 800–2500K was determined to be P(GPa) =
The 2021 eruption of Fukutoku-Oka-no-Ba (FOB) in the northwest Pacific on 13 August 2021 produced... more The 2021 eruption of Fukutoku-Oka-no-Ba (FOB) in the northwest Pacific on 13 August 2021 produced a large volume of pumice that drifted westward for ~1300 km to the Nansei Islands, Japan, and some extent. In February 2022, pumice with similar characteristics to the FOB pumice was deposited along along the Gulf of Thailand. The pumice clasts deposited in Songkhla Province, Thailand, were <4 cm in length and rounded. Most of the clasts consisted of clinopyroxene, plagioclase (andesine), and olivine phenocrysts in a vesiculated grey groundmass, with black-coloured spots exhibiting signatures of a basaltic magma. The whole-rock compositions of the pumice are trachytic, with 61 mass% SiO2 and 9 mass% total alkali (Na2O + K2O). The overall characteristics in the pumice from Thailand are similar to those in FOB pumice. These pumice in Thailand were from the 2021 FOB eruption, and drifted >2800 km south-westward across the South China Sea.
The physical properties of argon (Ar) are investigated to 382 GPa and 3000 K using diamond anvil ... more The physical properties of argon (Ar) are investigated to 382 GPa and 3000 K using diamond anvil cell experiments and first-principles molecular dynamics. The estimated density of Ar is smaller that of the Preliminary reference Earth model (PREM) mantle, which indicates that the density crossover does not occur at the bottom of the lower mantle. A large volume dependence of the thermal pressure of Ar is revealed at pressures higher than 200 GPa, and a significant temperature dependence of the calculated effective Grüneisen parameters is confirmed at high pressures. A melting temperature of Ar is estimated from the calculation data and a significant pressure dependence is confirmed. If the pressure-temperature path of the subducted slab is lower than the critical condition, ~750 K and ~7.5 GPa, solid Ar can be carried down into the deep mantle. Melting of solid Ar in the upwelling mantle plume occurs at the bottom of the transition zone. Thus, solid Ar plays an important role in Ar r...
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Papers by Shigeaki Ono