A5035350706- Astro and Planetary Science
- Geological and Geochemical Analysis
- Planetary Science and Exploration
- High-pressure geophysics and materials
- earthquake and tectonic studies
- Isotope Analysis in Ecology
- Geology and Paleoclimatology Research
- Geomagnetism and Paleomagnetism Studies
- Geochemistry and Geologic Mapping
- Geochemistry and Elemental Analysis
- Solar and Space Plasma Dynamics
- Paleontology and Stratigraphy of Fossils
- Ionosphere and magnetosphere dynamics
- Radioactive element chemistry and processing
- Space Exploration and Technology
- Nuclear Physics and Applications
- Stellar, planetary, and galactic studies
- Magnetic confinement fusion research
- Analytical chemistry methods development
- Astronomical and nuclear sciences
- Groundwater and Isotope Geochemistry
- Hydrocarbon exploration and reservoir analysis
- Mineralogy and Gemology Studies
- Geological Studies and Exploration
- Radioactive contamination and transfer
University of Maryland, College Park
2015-2024
Reitaku University
2018-2020
Tokyo Institute of Technology
2010
Planetary Science Institute
1980-2008
University of California, Los Angeles
1981-2008
University of North Carolina at Chapel Hill
2002
University of California, Berkeley
2002
University of London
2001
United States Geological Survey
1989-2000
University of Maryland, Baltimore
2000
Rhenium and osmium concentrations isotopic ratios of group IIA, IIIA, IVA, IVB iron meteorites were determined by negative thermal ionization mass spectrometry with modified digestion equilibration techniques. Precise isochrons are defined for all four groups. An absolute age 4558 million years is assumed IIIA irons, leading to closure ages 4537 ± 8, 4456 25, 4527 29 the respectively. The initial osmium-187/osmium-188 IVA groups, as a function crystallization age, suggest that rhenium/osmium...
▪ Abstract The Re-Os isotope sytem, based on the long-lived β − transition of 187 Re to Os, has matured wide use in cosmochemistry and high-temperature geochemistry. siderophilic/chalcophilic behavior Os is different from that elements comprise most other radiogenic systems. Magmatic iron meteorites (IIIAB, IIAB, IVA, IVB) have isochrons indicate asteroidal core crystallization within first 10–40 million years Solar System evolution. Rocks Earth's convecting mantle show generally chondritic...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarius Tube Digestion for Low-Blank Rhenium-Osmium AnalysisSteven B. Shirey and Richard J. WalkerCite this: Anal. Chem. 1995, 67, 13, 2136–2141Publication Date (Print):July 1, 1995Publication History Published online1 May 2002Published inissue 1 July 1995https://pubs.acs.org/doi/10.1021/ac00109a036https://doi.org/10.1021/ac00109a036research-articleACS PublicationsRequest reuse permissionsArticle Views1281Altmetric-Citations730LEARN ABOUT THESE...
The North China Craton (NCC) was originally formed by the amalgamation of eastern and western blocks along an orogenic belt at ∼1.9 Ga. After cratonization, NCC essentially stable until Mesozoic, when intense felsic magmatism related mineralization, deformation, pull-apart basins, exhumation deep crust widely occurred, indicative destruction or decratonization. Accompanying this significant removal cratonic keel lithospheric transformation, whereby thick (∼200 km) refractory Archean...
Understanding core formation in meteorite parent bodies is critical for constraining the fundamental processes of protoplanet accretion and differentiation within solar protoplanetary disk. We report variations 5 to 20 parts per million (182)W, resulting from decay now-extinct (182)Hf, among five magmatic iron groups. These (182)W indicate that occurred over an interval ~1 years may have involved early segregation Fe-FeS a later Fe melts. Despite this protracted formation, probably accreted...
Late accretion, early mantle differentiation, and core-mantle interaction are processes that could have created subtle (182)W isotopic heterogeneities within Earth's mantle. Tungsten data for Kostomuksha komatiites dated at 2.8 billion years ago show a well-resolved excess relative to modern terrestrial samples, whereas Komati 3.5 no such excess. Combined (182)W, (186,187)Os, (142,143)Nd indicate the source of included material from primordial reservoir represents either deep region...
A mantle story told with metal and gas Differences in isotopic compositions of trace elements can help identify how regions Earth's have evolved over time. Mundl et al. identified several ancient domains that been isolated from homogenization thus contain signatures primordial material. Tungsten helium isotope values indicate fractionation isolation these just after formation. The findings constrain processes such as core formation, but also provide insight into unexplained structures the...
Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples the asteroid (162173) Ryugu were retrieved by Hayabusa2 spacecraft. We measured mineralogy and bulk chemical isotopic compositions samples. The samples mainly composed materials similar those carbonaceous chondrite meteorites, particularly CI (Ivuna-type) group. consist predominantly minerals formed in aqueous fluid on a parent planetesimal. primary altered fluids at temperature 37° ± 10°C, about...
We report measurements of the isotopic composition lithium in basalts using a multicollector magnetic sector plasma-source mass spectrometer (MC-ICP-MS). This is first application this analytical technique to Li isotope determination. External precision multiple replicate and duplicate for variety sample types averages ±1.1‰ (2σ population). The method allows rapid (∼8 min/sample) analysis small samples (∼40 ng Li) relative commonly used thermal ionization methods. has been applied suite...
The notion of magnetic field line resonance has been very effective in explaining many features long‐period geomagnetic pulsations. To date the decoupled transverse wave equations have solved a dipole field, whereas only WKB approximate solutions used more general geometries. We developed solution that includes both geometry and effects density mass composition. aim this paper is to isolate examine effect on eigenfrequencies by keeping constant along all lines. review diurnal variations...
It is now well established that lithospheric thinning of the eastern North China Craton (NCC) occurred during Phanerozoic. The cause and extent thinning, however, remains highly debated. In this study, mantle xenoliths from Paleozoic Mengyin kimberlites, along with Cenozoic Penglai Shanwang basalts in Shandong Province, are investigated via traditional petrographic elemental, Sr–Nd–Hf–Os isotopic platinum-group element (PGE) analyses. Late Archean Os model ages c. 2·5 Ga for peridotites...
Osmium isotopic analyses of picritic lavas from Hawaii show enrichments in the osmium-186/osmium-188 ratio (186Os/188Os) 0. 008 to 0.018%, relative a chondritic upper mantle, that are positively correlated with 187Os/188Os 5.4 9.0%. The most viable mechanism produce these coupled 186Os and 187Os is by addition 0.5 1 weight percent outer core metal portion D" layer subsequent upwelling mixture. These data suggest some plumes originate at core-mantle boundary Os isotopes may be used...
Films of single-walled carbon nanotubes have been obtained by simple evaporation suspended on a glass substrate. The technique has also used to create patterned structures (see Figure) treating the substrate before and thus creating hydrophobic hydrophilic areas. films showed orientational ordering, which could be useful for optical applications.