Rare earth element measurements and mapping of minerals in the Allende CAI, 7R19‐1, by NanoSIMS ion microprobe          下载免费PDF全文

Motoo Ito  Scott Messenger 《Meteoritics & planetary science》2016,51(4):818-832

We have established analytical procedures for quantitative rare earth element (REE) measurements by NanoSIMS 50L ion microprobe with 2–10 μm spatial resolution. Measurements are performed by multidetection using energy filtering under several static magnetic field settings. Relative sensitivity factors and REE oxide/REE element secondary ion ratios that we determined for the NanoSIMS match values previously determined for other ion microprobes. REE measurements of 100 ppm REE glass standards yielded reproducibility and accuracy of 0.5–2.5% and 5–15%, respectively. REE measurements of minerals of an Allende type‐A CAI, 7R19‐1, were performed using three different methods: spot analysis, line profile, and imaging. These data are in excellent agreement with previous REE measurements of this inclusion by IMS‐3f ion microprobe. The higher spatial resolution NanoSIMS measurements provide additional insight into the formation process of this CAI and offer a promising new tool for analysis of fine‐grained and complexly zoned materials.  相似文献   

Transformation dynamics and reactivity of dissolved and colloidal iron in coastal waters     

Manabu Fujii  Hiroaki Ito  Andrew L. Rose  T. David Waite  Tatsuo Omura 《Marine Chemistry》2008,110(3-4):165-175

We have investigated the chemical forms, reactivities and transformation kinetics of Fe(III) species present in coastal water with ion exchange and filtration methods. To simulate coastal water system, a mixture of ferric iron and fulvic acid was added to filtered seawater and incubated for a minute to a week. At each incubation time, the seawater sample was acidified with hydrochloric acid and then applied to anion exchange resin (AER) to separate negatively charged species (such as fulvic acid, its complexes with iron and iron oxyhydroxide coated with fulvic acid) from positively charged inorganic ferric iron (Fe(III)′). By monitoring the acid-induced Fe(III)′ over an hour, it was found that iron complexed by fulvic acid dissociated rapidly to a large extent (86–92% at pH 2), whereas amorphous ferric oxyhydroxide particles associated with fulvic acid (AFO-L) dissociated very slowly with the first-order dissociation rate constants ranging from 6.1 × 10^− 5 for pH 3 to 2.7 × 10^− 4 s^− 1 for pH 2. Therefore, a brief acidification followed by the AER treatment (acidification/AER method) was likely to be able to determine fulvic acid complexes and thus differentiate the complexes from the AFO-L particles (the dissolution of AFO-L was insignificant during the brief acidification). The acidification/AER method coupled with a simple filtration technique suggested that the iron–fulvic acid complexes exist in both the < 0.02 μm and 0.02–0.45 μm size fractions in our coastal water system. The truly dissolved iron (< 0.02 μm) was relatively long-lived with a life-time of 14 days, probably due to the complexation by strong ligands. Such an acid-labile iron may be an important source of bioavailable iron in coastal environments, as a significant relationship between the chemical lability and bioavailability of iron has been well recognised.  相似文献   

Tropospheric delay correction with dense GPS network in L1-SAIF augmentation   总被引：2，自引：0，他引：2  

Noboru Takeichi  Takeyasu Sakai  Sounosuke Fukushima  Ken Ito 《GPS Solutions》2010,14(2):185-192

The L1-SAIF (L1 Submeter-class Augmentation with Integrity Function) signal is one of the Quasi-Zenith Satellite System (QZSS) navigation signals, which provides an augmentation function for mobile users in Japan. The tropospheric delay correction in the L1-SAIF augmentation is discussed in detail. Because the topographical features in Japan are complicated, the correction information is generated from GPS observation data collected at 200 GPS stations which are densely distributed over Japan. A total of 210 Tropospheric Grid Points (TGPs) are arranged to fully cover Japan. The TGPs that provide the correction information are selected adaptively to achieve the expected correction accuracy. This selection of TGPs is provided by the TGP mask message. Mobile users acquire the zenith tropospheric delay (ZTD) value at neighboring TGPs from the correction messages, and can estimate the local ZTD value accurately by using a suitable ZTD model. Only up to seven L1-SAIF messages are sufficient to provide the full correction information. Accuracy evaluations have proven that it is possible to achieve a correction accuracy of 13.4 mm RMS. The strategy presented here has been implemented into the augmentation system using the L1-SAIF signal, and its application guidance is presented in the QZSS interface specification.  相似文献   

On the high energy proton spectrum measurements     

R. W. Ellsworth  A. Ito  J. Macfall  F. Siohan  R. E. Streitmatter  S. C. Tonwar  P. R. Vishwanath  G. B. Yodh  V. K. Balasubrahmanyan 《Astrophysics and Space Science》1977,52(2):415-427

The steepening of the proton spectrum beyond 1000 GeV and the rise in inelastic cross sections between 20 and 600 GeV observed by the PROTON 1-2-3 satellite experiments may be explained by systematic effects of energy dependent albedo (back-scatter) from the calorimeter.

---

Résumé L'accroissement avec l'énergie de l'albedo dû au calorimètre peut expliquer l'augmentation de la pente du spectre primaire de protons au-delà de 1000 GeV et la croissance des sections efficaces inélastiques entre 20 et 600 GeV observés lors des expériences en satellite PROTON 1, 2 et 3.

---

---

On sabbatical leave at Goddard Space Flight Center, Greenbelt, Md.  相似文献   

Palaeomagnetic record of a late Tertiary field reversal     

R. Dodson  J. R. Dunn  M. Fuller  I. Williams  H. Ito  V. A. Schmidt  Yee-Ming Wu 《Geophysical Journal International》1978,53(2):373-412

  相似文献   

Kimberlites and their ultramafic xenoliths from western Kenya     

Dr. M. Ito 《Mineralogy and Petrology》1986,35(3):193-216

  相似文献   

Crustal structure in the Mizuho Plateau, East Antarctica, by a two-dimensional ray approximation     

Akira Ikami  Kiyoshi Ito 《Journal of Geodynamics》1986,6(1-4)

Studies on the crustal and upper-mantle structure in Antarctica have been one of the major contributions to Antarctic research since the International Geophysical Year of 1957–1958. Many refraction surveys with small charge size have been conducted in Antarctica, but long-range experiments were also made in 5 regions on the margin of the Antarctic continent.In 1979–1981, the scientific program of the Japanese Antarctic Research Expedition was focused on the earth sciences, and in particular, an explosion seismic experiment along a long survey line was the major item during these years. An experiment along a 300 km-long line with three shots and 27 observation stations was successfully made in the northern Mizuho Plateau, East Antarctica.From the analysis of travel times and the amplitude study of synthetic seismograms, the crustal structure of the northern Mizuho Plateau was determined. The depths of the Conrad and the Moho discontinuties were determined as 31 km and 42 km, respectively. The P-wave velocity and depth relation was determined as 6.0 km/s on the surface of the bedrock, 6.3 km/s at a depth of 2 km, 6.8 km/s at the Conrad and 7.9 km/s at the Moho. The velocity in the crust increases gradually. The crustal structure obtained is representative of East Antarctica.  相似文献   

Submarine metamorphism of gabbros from the Mid-Cayman rise: An oxygen isotopic study     

Emi Ito  Robert N. Clayton 《Geochimica et cosmochimica acta》1983,47(3):535-546

Oxygen isotopic compositions of minerals in 22 samples of submarine gabbros were determined. The gabbros were collected using the submersible Alvin from the 700 m vertical section of the rift-valley wall of the Mid-Cayman spreading center. Our study indicates that in the Mid-Cayman Rise seawater barely reached the bottom of the plutonic layer. Abundant seawater penetration (water/rock mass ratio > 1) was limited to the upper part of the plutonic layer. From the observed oxygen isotopic compositions of coexisting minerals, and from the experimental and empirical determinations of equilibrium fractionation of oxygen isotopes for mineral-water, and mineral-mineral pairs, we show the following: (1) pyroxene and olivine did not exchange oxygen with seawater, (2) plagioclase is in isotopic disequilibrium with pyroxene; (3) the rate of oxygen exchange in plagioclase was not slowed by the absence of cation exchange; (4) plagioclase and amphibole have exchanged oxygen with seawater or isotopically modified seawater (δ¹⁸O ≤ 3%.); and (5) amphibole has exchanged or acquired (during formation) hydrogen from seawater at 380°C ≤ T ≤ 600°C. The decrease in extent of isotopic exchange of plagioclase and the decrease in amphibole abundance with depth indicate that seawater flux decreased rapidly with depth (water/rock mass ratio falling from 1.7 to 0.2 over a 300 m interval).  相似文献   

The effect of ferric iron on the electrical conductivity of olivine     

Al Duba  Jun Ito  John C. Jamieson 《Earth and Planetary Science Letters》1973,18(2):279-284

  相似文献   

Trace-element and isotopic constraints on the source of magmas in the active volcano and Mariana island arcs, Western Pacific     

Robert James Stern  Emi Ito   《Journal of Volcanology and Geothermal Research》1983,18(1-4)

Analytical results of the relative and absolute abundance of LIL-incompatible trace elements (K, Rb, Cs, Sr, and Ba) and isotopic compositions ( , , and ) are summarized for fresh samples from active and dormant volcanoes of the Volcano and Mariana island arcs. The presence of thickened oceanic crust (T 15–20 km) beneath the arc indicates that while hybridization processes resulting in the modification of primitive magmas by anatectic mixing at shallow crustal levels cannot be neglected, the extent and effects of these processes on this arc's magmas are minimized. All components of the subducted plate disappear at the trench. This observation is used to reconstruct the composition of the crust in the Wadati-Benioff zone by estimating proportions of various lithologies in the crust of the subducted plate coupled with analyses from DSDP sites. Over 90% of the mass of the subducted crust consists of basaltic Layers II and III. Sediments and seamounts, containing the bulk of the incompatible elements, make up the rest. Bulk Western Pacific seafloor has , δ ¹⁸O +7.2, K/Rb 510, K/Ba 46, and K/Cs 13,500. Consideration of trace-element data and combined systematics limits the participation of sediments in magmagenesis to less than 1%, in accord with the earlier results of Pb-isotopic studies. Combined data indicate little, if any, involvement of altered basaltic seafloor in magmagenesis. Perhaps more important than mean isotopic and LIL-element ratios is the restricted range for lavas from along over 1000 km of this arc. Mixtures of mantle with either the subducted crust or derivative fluids should result in strong heterogeneities in the sources of individual volcanoes along the arc. Such heterogeneities would be due to: (1) gross variations of crustal materials supplied to the subduction zone; and (2) lesser efficiency of mixing processes accompanying induced convection between arc segments (parallel to the arc) as compared to that perpendicular to the arc. The absence of these heterogeneities indicates that either some process exists for the efficient mixing of mantle and subducted material parallel to the arc or that subducted materials play a negligible role in the generation of Mariana-Volcano arc melts.Consideration of plausible sources in the mantle indicates that (1) an unmodified MORB-like mantle cannot have generated the observed trace-element and isotopic composition of this arc's magmas, while (2) a mantle similar to that which has produced alkali-olivine basalts (AOB) of north Pacific “hot spot” chains is indistinguishable in many respects spects from the source of these arc lavas.  相似文献