Search results for "Rare-earth element"

Combined thermodynamic and rare earth element modelling of garnet growth during subduction: Examples from ultrahigh-pressure eclogite of the Western …

2008

Abstract Major and trace element zonation patterns were determined in ultrahigh-pressure eclogite garnets from the Western Gneiss Region (Norway). All investigated garnets show multiple growth zones and preserve complex growth zonation patterns with respect to both major and rare earth elements (REE). Due to chemical differences of the host rocks two types of major element compositional zonation patterns occur: (1) abrupt, step-like compositional changes corresponding with the growth zones and (2) compositionally homogeneous interiors, independent of growth zones, followed by abrupt chemical changes towards the rims. Despite differences in major element zonation, the REE patterns are almost…

Radiation hardening of Rare-Earth doped fiber amplifiers

2012

We investigated the radiation hardening of optical fiber amplifiers operating in space environments. Through a real-time analysis in active configuration, we evaluated the role of Ce in the improvement of the amplifier performance against ionizing radiations. Ce-codoping is an efficient hardening solution, acting both in the limitation of defects in the host glass matrix of RE-doped optical fibers and in the stabilization of lasing properties of the Er3+-ions. On the one hand, in the nearinfrared region, radiation induced attenuation measurements show the absence of radiation induced P-related defect species in host glass matrix of the Ce-codoped active fibers; on the other hand, in the Ce-…

Comment on: Application of Raman Spectroscopy to Distinguish Metamorphic and Igneous Zircon (Xian et al., Anal. Lett. 2004, v. 37, p. 119)

2005

Abstract We critically discuss a recently proposed technique ((Xian et al. 2004)) used to distinguish igneous (i.e., magmatic) from metamorphic growth of the mineral zircon according to the intensity of the 1461 cm−1 band observed in those author's Raman spectra. The band evaluated by Xian et al. (2004) is actually due to laser‐induced photoluminescence of trace amounts of the trivalent rare earth element Er, which, as an analytical artefact, overlays the Raman spectrum when green Ar+ laser excitation is used. We demonstrate that this band is not a Raman band, and discuss why the intensity of Er3+ luminescence is not uniquely indicative of the geologic origin of a zircon crystal. The techni…

Finite amplitude method applied to giant dipole resonance in heavy rare-earth nuclei

2015

Background: The quasiparticle random phase approximation (QRPA), within the framework of the nuclear density functional theory (DFT), has been a standard tool to access the collective excitations of the atomic nuclei. Recently, finite amplitude method (FAM) has been developed, in order to perform the QRPA calculations efficiently without any truncation on the two-quasiparticle model space. Purpose: We discuss the nuclear giant dipole resonance (GDR) in heavy rare-earth isotopes, for which the conventional matrix diagonalization of the QRPA is numerically demanding. A role of the Thomas-Reiche-Kuhn (TRK) sum rule enhancement factor, connected to the isovector effective mass, is also investig…

Radiation responses of Yb/Er-doped phosphosilicate optical fibers: hardening mechanisms related to Ce-codoping

2012

International audience; In this paper, we investigated the origins of the Ce positive influence on the radiation response of Yb/Er-doped phosphosilicate optical fibers. To this purpose, we carried out during γ-irradiations an online characterization on active optical fiber prototypes, made with different Ce concentrations and integrated in optical amplifiers. The hardening effect of Ce-codoping is highlighted, as well as some aspects related to the radiation response of the phosphosilicate host glass of the active optical fibers.

Zirconium–hafnium and rare earth element signatures discriminating the effect of atmospheric fallout from hydrothermal input in volcanic lake water

2016

The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidicwaters are sulphate dominatedwith different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr a nd Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters. Y-Ho and Zr-Hf (twin pairs) have a…

ChemInform Abstract: Rare Earth Element Catalysts

2010

Microanalytical methods for in-situ high-resolution analysis of rock varnish at the micrometer to nanometer scale

2015

Abstract A wide range of analytical techniques were used to investigate rock varnish from different locations (Negev, Israel; Knersvlakte, South Africa; Death Valley and Mojave Desert, California): a 200 nm-femtosecond laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS), an electron probe microanalyzer (EPMA), focused ion beam (FIB) slicing, and scanning transmission X-ray microscopy–near edge X-ray absorption fine structure spectroscopy (STXM–NEXAFS). This combination enables comprehensive high-spatial-resolution analysis of rock varnish. Femtosecond LA-ICP-MS and EPMA were used for quantitative determination of element concentrations. In-situ measurements were conducte…

Rare earth element contents of Jurassic fish and reptile teeth and their potential relation to seawater composition (Anglo-Paris Basin, France and En…

2002

The rare earth element (REE) chemistry of Jurassic shelf seawater from western Europe (Anglo-Paris Basin) was investigated by analyzing the fish and reptile teeth deposited in shallow to deeper water (<200 m) environments. REE patterns in apatites are controlled by the host sediments. Vertebrate teeth sampled from the siliciclastic sediments (calcareous sandstones and shales) show flat shale-normalized REE patterns that reflect the dominant influence of the continental source from which the REE were derived. Carbonate deposits, protected from the clastic sources, contain fish and reptile teeth whose REE patterns reflect more accurately the REE composition of the overlying water column. The …

The behaviour of REEs in Thailand's Mae Klong estuary: Suggestions from the Y/Ho ratios and lanthanide tetrad effects

2007

Abstract The concentrations of Rare Earth Elements and yttrium (REY) were measured in dissolved phase, in suspended particulate matter (SPM) and in sediments in seven sampling stations in the Mae Klong estuarine system (Inner Thailand Gulf) in order to study their behaviour and distribution pattern. The analysed samples generally show high Rare Earth Element (REE) content in the dissolved phase, with high Medium Rare Earth Elements (MREEs) and Y enrichments in the shale-normalized pattern (versus PAAS). These chemical features are interpreted in terms of direct influences of weathering processes of REE-rich minerals (e.g., phosphates), which abundantly out-crop in the Mae Klong watershed. T…