Naoya Sakamoto

Naoya Sakamoto
Hokkaido University | Hokudai · Creative Research Institution

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137
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Introduction
Skills and Expertise

Publications

Publications (137)
Preprint
We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anoma...
Article
Full-text available
We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXAʼs Hayabusa2 mission. We report the detection of all major presolar grain types with O-and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomal...
Article
Background: A persistently high methylation level in gastric mucosa after Helicobacter pylori (H. pylori) eradication is presumed to be a risk for metachronous gastric cancer (MGC); however, long-term changes in aberrant DNA methylation and histological gastritis have been unclear. Our aim was to examine changes in DNA methylation and histological...
Article
Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measure the mineralogy, bulk chemical and isotopic compositions of Ryugu samples. They are mainly composed of materials similar to carbonaceous chondrite meteorites, par...
Article
Full-text available
Background Endocytoscopy (ECS) enables microscopic observation in vivo for the gastrointestinal mucosa; however, there has been no prospective study in which the diagnostic accuracy of ECS for lesions that have not yet undergone histological diagnosis was evaluated. We conducted a surveillance study for patients in a high-risk group of esophageal s...
Article
Impact is a fundamental process shaping the formation and evolution of planets and asteroids. It is inevitable that some materials on the surface of planets and asteroids have been impacted for many times. However, unambiguous petrological records for multiple post-formation impact events are rarely described. Here, we report that the thin shock me...
Article
Magma differentiation in arc settings has usually been attributed to an interplay of processes (fractional crystallization, assimilation, and magma mixing). Homogeneous fractional crystallization has been widely used to model the magmatic evolution of volcanic systems in arc settings due to its simplicity, even though boundary layer fractionation (...
Preprint
Full-text available
Background A persistently high methylation level in gastric mucosa after Helicobacter pylori (H. pylori) eradication is presumed to be a risk for metachronous gastric cancer (MGC); however, long-term changes in aberrant DNA methylation and histological gastritis have been unclear. Our aim was to examine changes in DNA methylation and histological g...
Article
Full-text available
Background Therapy for eradication of Helicobacter pylori (H. pylori) improves symptoms of H. pylori-associated dyspepsia (HPD), but the effects of eradication in elderly patients are unclear. The aim of our study was to investigate dyspepsia symptoms and long-term effects of eradication in elderly patients. Methods This retrospective study includ...
Preprint
Full-text available
Background Endocytoscopy (ECS) enables microscopic observation in vivo for the gastrointestinal mucosa; however, there has been no prospective study in which the diagnostic accuracy of ECS for lesions that have not yet undergone histological diagnosis was evaluated. We conducted a surveillance study for patients in a high-risk group of esophageal s...
Article
Full-text available
Arc magmas typically contain phenocrysts with complex zoning and diverse growth histories. Microlites highlight the same level of intracrystalline variations but require nanoscale resolution which is globally less available. The southern Taupo Volcanic Zone (TVZ), New Zealand, has produced a wide range of explosive eruptions yielding glassy microli...
Article
The sources and processes involved in the genesis of the voluminous rhyolitic magmas of cataclysmic caldera-forming eruptions, and the intervening lower-volume intra-caldera extrusions, have been subject to much debate. To better understand generation of high-volume and low-volume silicic eruptions within a single volcanic centre, and how they may...
Article
Coarse-grained, igneous Ca-Al-rich inclusions (CAIs) in CV chondrites formed through multiple melting events. We conducted in situ O-isotope analysis and Al-Mg systematics by secondary ion mass spectrometry of relict and overgrown minerals from a partial melting event in an Allende Type B CAI, Golfball. Golfball has a Type B CAI bulk composition an...
Article
Classical view has interpreted deuterons in nominally anhydrous minerals (NAMs) diffuse slightly slower than protons by the Knudsen limit of 2, whereas here we report deuteron diffusion is about 3∼7 times faster than proton one in Mg2SiO4 wadsleyite based on the H-D interdiffusion couple experiments using a pair of wadsleyite single crystal at 16 G...
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Full-text available
Shock-lithification is a fundamental process of making rocks from fine-grained and porous regoliths on the surface of the Moon. Previous investigations have constrained potential shock pressures during shock-lithification based on experimental and numerical simulations. However, pressure and temperature conditions during shock-lithification have no...
Article
Full-text available
Olivine-hosted melt inclusions (MIs) are widely used as a tool to study the early stages of magmatic evolution. There are a series of processes that affect MI compositions after trapping, including post-entrapment crystallization (PEC) of the host mineral at the MI boundaries, exsolution of volatile phases into a “shrinkage bubble” and diffusive ex...
Article
Instrumental mass fractionation of Mg-isotopes and the relative sensitivity factor (RSF) for ²⁷Al/²⁴Mg ratios for in situ analysis by secondary ion mass spectrometry were investigated for minerals in Ca-Al-rich inclusions (CAIs) of meteorites, to verify systematic errors in Al-Mg chronological systematics of CAIs. We synthesized seventeen glasses w...
Article
Tough double network (DN) hydrogels are promising substitutes of soft supporting tissues such as cartilage and ligaments. For such applications, it is indispensable to robustly fix the hydrogels to bones with medically feasible methods. Recently, robustly bonding the DN hydrogels to defected bones of rabbits in vivo has been proved successful. The...
Article
The diversity of lithologies is an important proxy of internal evolution in differentiated planets and asteroids. The major lithologies in Vesta, based on the howardite-eucrite-diogenite clan meteorites, include basalt, gabbro, noritic orthopyroxenite, orthopyroxenite, dunite, harzburgite, and dacite. No other lithology has been reported up to date...
Article
Calcium‐aluminum‐rich inclusions (CAIs) are the first solid materials formed in the solar nebula. Among them, ultrarefractory inclusions are very rare. In this study, we report on the mineralogical features and oxygen isotopic compositions of minerals in a new ultrarefractory inclusion CAI 007 from the CV3 chondrite Northwest Africa (NWA) 3118. The...
Article
Full-text available
To assess whether magma ascent rates control the style of volcanic eruption, we have studied the petrography, geochemistry and size distribution of microlites of plagioclase and pyroxene from historical eruptions from Tongariro, Ruapehu and Ngauruhoe volcanoes located in the southern Taupo Volcanic Zone, New Zealand. The studied deposits represent...
Article
Full-text available
“Cr-Zr-Ca armalcolite” is a mineral originally found in Apollo samples five decades ago. However, no structural information has been obtained for this mineral. In this study, we report a new occurrence of “Cr-Zr-Ca armalcolite” and its associated mineral assemblage in an Mg-suite lithic clast (Clast-20) from the brecciated lunar meteorite Northwest...
Article
Fine-grained Ca-Al-rich inclusions (FGIs) in CV chondrites are suggested to be condensates formed directly from the solar nebular gas. Al−Mg mineral isochrons of seven FGIs from reduced CV chondrites Efremovka, Vigarano, Thiel Mountains 07007, and Northwest Africa 8613 were obtained via in situ Al–Mg isotope measurements using secondary ion mass sp...
Article
Full-text available
Diogenites are a group of meteorites that are derived from the interior of the largest protoplanet Vesta. They provide a unique opportunity to understanding together the internal structure and dynamic evolution of this protoplanet. Northwest Africa (NWA) 8321 was suggested to be an unbrecciated noritic diogenite meteorite, which is confirmed by our...
Article
Most meteorites are believed to be chips from planetesimals and can provide clues to constrain the chemical evolution and dynamic history of the early Solar System. In this study, we report two unique fragments (ALF-1 and ALF-2) enclosed in the CH3 carbonaceous chondrite Sayh al Uhaymir 290. These two fragments are dominated by Ca,Fe-rich olivine w...
Conference Paper
The Tongariro Volcanic Centre (TgVC), located at the southern end of the Taupo Volcanic Zone in New Zealand, has produced historical explosive eruptions of different eruptive styles. To understand magma ascent processes and their associated timescales, the textures and compositions of microlites and micro-phenocrysts from glass shards (c. 12 ka BP...
Article
Due to their common occurrence in various types of chondrites, igneous rims formed on pre-existing chondrules throughout chondrule-forming regions of the solar nebula. Although the peak temperatures are thought to reach similar values to those achieved during chondrule formation events, the heating duration in chondrule rim formation has not been w...
Conference Paper
Full-text available
To assess how magma ascent rates control the style of volcanic eruption, we have studied microlites from historical eruptions from the Tongariro Volcanic Centre, New Zealand, ranging in age from 11,000 years BP to 1996, and covering a range of eruption styles from Strombolian to Plinian. Petrographic analysis shows that larger microlites display co...
Article
Full-text available
Knowledge of water content and distribution in the Earth's mantle is critical to understanding the geochemical evolution and geodynamic processes of the Earth, since water can incorporate into nominally anhydrous minerals at high pressure and dramatically affect the chemical and physical properties of mantle minerals. Hydrogen diffusion controls th...
Article
Full-text available
Chondrites are fragments of asteroids that avoided melting and, thus, provide a record of the material that accreted to form protoplanets. The dominant constituent of chondrites are millimeter-sized chondrules formed by transient heating events in the protoplanetary disk. Some chondritic components, including chondrules, contain evidence of the ext...
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Full-text available
Ultrarefractory (UR) phases in CAIs could have formed at higher T compared to common CAI minerals and thus they potentially provide constraints on very high-T processes in the solar nebula. We report a detailed characterization of an UR phase davisite bearing CAI from a reduced type CV chondrite. Davisite occur only in one lithological unit that co...
Article
We investigated the potential of multi-collector secondary ion mass spectrometry (MC-SIMS) as a tool for obtaining Sr isotopic compositions in plagioclase, a ubiquitous mineral in igneous rocks that serves as a recorder of crystallization history. MC-SIMS allows for high spatial resolution analysis (~12 μm in this study) of isotopes, and therefore...
Article
Diffusion experiments of ² H 2 O at 900-750 °C and water vapor pressure of 50 bar found diffusion of water in SiO 2 glass more than one order of magnitude faster than that reported previously. The fast diffusion profile of water was observed as an extended tail of the normal water diffusion profile by a line scan analysis with SIMS, and it can be f...
Preprint
Full-text available
Ultrarefractory (UR) phases in CAIs could have formed at higher T compared to common CAI minerals and thus they potentially provide constraints on very high-T processes in the solar nebula. We report a detailed characterization of an UR phase davisite bearing CAI from a reduced type CV chondrite. Davisite occur only in one lithological unit that co...
Article
Crystallization is one of the most fundamental processes for both solid inorganic and organic materials in nature. The classical crystallization model mainly involves the monomer-by-monomer addition of simple chemical species. Recently, nanoparticle attachment has been realized as an important mechanism of crystallization in comparatively low-tempe...
Article
Full-text available
Crystals within volcanic rocks record geochemical and textural signatures during magmatic evolution before eruption. Clues to this magmatic history can be examined using crystal size distribution (CSD) studies. The analysis of CSDs is a standard petrological tool, but laborious due to manual hand-drawing of crystal margins. The trainable Weka segme...
Article
Full-text available
Meteoritic evidence suggests that oxygen isotopic exchange between ¹⁶O-rich amorphous silicate dust and ¹⁶O-poor water vapor occurred in the early solar system. In this study, we experimentally investigated the kinetics of oxygen isotopic exchange between submicron-sized amorphous forsterite grains and water vapor at protoplanetary disk-like low pr...
Article
The Mg grain boundary diffusion coefficients were measured in forsterite aggregates as a function of pressure (1 atm and 13 GPa), temperature (1100-1300 K), water content (<1-350 wt. ppm bulk water), and oxygen fugacity (10⁻¹⁸-10-0.7 bar) using a multi-anvil apparatus and a gas-mixing furnace. The diffusion profiles were analyzed by secondary ion m...
Conference Paper
Full-text available
Crystals within erupted volcanic rocks record geochemical and textural signatures during magmatic evolution prior to the onset of eruptions. Growth times of microlites can be derived through Crystal Size Distribution (CSD) analysis combined with well-constrained microlite growth rates, yielding petrologically-determined magma ascent timescales. Our...
Article
We determined the stability and chemical composition of Al-bearing superhydrous phase B at 20-24 GPa and 1400-2000 °C to discuss the mechanism of water transport in the mantle transition zone and uppermost lower mantle at temperatures close to the mantle geotherm. Superhydrous phase B contained significant amounts of Al2O3, from 14 to 32 wt%, and A...
Conference Paper
Full-text available
Introduction: Calcium-aluminum-rich inclusions (CAIs) are the oldest dated solar system solids [1] that can provide us a key to understand physicochemical processes which occurred in the early solar system. Their mineralogy , isotopic compositions and occurrence in carbonaceous chondrites and cometary samples indicate that they have formed near the...
Article
Water diffusion in silicate melts is a fundamental process controlling physical and chemical consequences for magmatism, but mechanisms of diffusion in silicate glasses and melts are not fully understood. In this study, water diffusion experiments in silica glass were performed at temperatures of 650-850 °C and water vapor pressure of 50 bar, with...
Article
Full-text available
We have developed an internal-resistive heated diamond-anvil cell (IHDAC) with a new resistance heater – boron-doped diamond (BDD) – along with an optimized design of the cell assembly, including a composite gasket. Our proposed technique is capable of heating a silicate/oxide material with (1) long-term stability (>1 h at 2500 K) and (2) uniform r...
Article
Knowledge of the distribution of water in the Earth's mantle is key to understanding the mantle convection and geochemical evolution of the Earth. As wadsleyite and ringwoodite can incorporate large amounts of water in their crystal structures, proton conduction has been invoked to account for the widespread conductive anomalies observed in the man...
Article
Mg lattice diffusion coefficients in iron-free olivine aggregates were measured as a function of pressure from 1 to 13 GPa, temperature from 1100 to 1300 K, and bulk water content from less than 1 up to 350 wt. ppm using multi-anvil apparatus and secondary ion mass spectrometer in depth profiling mode. The water contents in the samples were analyze...
Article
Oxygen self-diffusion coefficients (DOx) were measured in single crystals of dry synthetic iron-free olivine (forsterite, Mg2SiO4) at a temperature of 1600 K and under pressures in the range 10⁻⁴ to 13 GPa, using a Kawai-type multi-anvil apparatus and an ambient pressure furnace. Diffusion profiles were obtained by secondary ion mass spectrometry o...
Article
Troilite-orthopyroxene intergrowths are present as a common material in the brecciated diogenite Northwest Africa (NWA) 7183. In this study, we report on the petrographic, mineralogical, and rare earth element abundances of the troilite-orthopyroxene intergrowths to constrain their origin and assess their implications for the diverse petrogenesis o...
Conference Paper
Full-text available
Submission 612 Pre-and syn-eruptive processes visualized through semi-automatic Crystal Size Distribution analysis of microlites from Tongariro Volcanic Centre tephras, New Zealand Microlite Crystal Size Distributions (CSDs) in volcanic rocks have become a useful tool to assess pre-and syn-eruptive processes such as nucleation and growth at the ons...
Article
A comprehensive study of the organic chemistry and mineralogy of an ultracarbonaceous micrometeorite (UCAMM D05IB80) collected from near the Dome Fuji Station, Antarctica, was carried out to understand the genetic relationship among organic materials, silicates, and water. The micrometeorite is composed of a dense aggregate of ∼5 µm-sized hollow el...
Conference Paper
Full-text available
Mineralogical, petrological and O-isotopic study of a CV CAI suggests that spinel framboids in the CAI were originally mini-CAIs that condensed separately under different conditions and subsequently aggregated to form the inclusion.
Article
Full-text available
TS34 is a Type B1 Ca-Al-rich inclusion (CAI) from the Allende CV3 chondrite, consisting of spinel, melilite, Ti-Al-rich clinopyroxene (fassaite) and minor anorthite in an igneous texture. Oxygen and magnesium isotopic compositions were measured by secondary ion mass spectrometry in spots of known chemical composition in all major minerals in TS34....
Article
Micrometeorites (MMs) recovered from surface snow near the Dome Fuji Station, Antarctica are almost free from terrestrial weathering and contain very primitive materials, and are suitable for investigation of the evolution and interaction of inorganic and organic materials in the early solar system. We carried out a comprehensive study on seven por...
Conference Paper
Full-text available
O-isotope imaging showed 16O-poor Sc-pyroxene is embedded in reversely-zoned 16O-poor melilite in a CV CAI, suggesting aggregation of 16O-poor and -rich phases.
Article
Diffusion of Si and O in single crystal stishovite was examined at pressures of 14.0–21.5 GPa and temperatures of 1673–2073 K. Self-diffusion coefficients of Si (DSi) and O ( ) were determined as DSi and , respectively, where P is pressure (in GPa), T is absolute temperature (in K) and R is the ideal gas constant. It was revealed that diffusion of...
Article
The last liquids of the lunar magma ocean, known as urKREEP, should be highly enriched in volatiles, such as water, fluorine, and chlorine. We find chlorine-rich glasses in two pristine KREEP basalts from the Moon and calculate the volatile contents of the urKREEP component, and use this to estimate the fluorine and chlorine content of the lunar ma...
Article
While it is now recognized that the Moon has indigenous water and volatiles, their total abundances are unclear, with current literature estimates ranging from nearly absent to Earth-like levels. Similarly unconstrained is the source of the Moon's water, which could be cometary, chondritic, or the primordial nebula. Here we measure H2O and D/H in o...
Article
We describe the petrographic occurrences, abundances, and compositional variations of symplectically intergrown Fe,Ni-sulfides and 17,18O-rich magnetite (Δ¹⁷O ∼ 90‰), named cosmic symplectites (COS; Sakamoto et al., 2007), from the Acfer 094 (C3.0) ungrouped carbonaceous chondrite. A total of 314 COS studied in two polished sections of this meteori...