Chemical composition of Late Cenozoic volcanic and volcaniclastic deposits from the western Woodlark Basin area, SW Pacific

Tephra fallout layers and volcaniclastic deposits, derived from volcanic sources around and on the Papuan Peninsula, form a substantial part of the Woodlark Basin marine sedimentary succession. Sampling by the Ocean Drilling Program Leg 180 in the western Woodlark Basin provides the opportunity to document the distribution of the volcanically-derived components as well as to evaluate their chronology, chemistry, and isotope compositions in order to gain information on the volcanic sources and original magmatic systems. Glass shards selected from 57 volcanogenic layers within the sampled Pliocene-Pleistocene sedimentary sequence show predominantly rhyolitic compositions, with subordinate basaltic andesites, basaltic trachy-andesites, andesites, trachy-andesites, dacites, and phonolites. It was possible to correlate only a few of the volcanogenic layers between sites using geochemical and age information apparently because of the formation of strongly compartmentalised sedimentary realms on this actively rifting margin. In many cases it was possible to correlate Leg 180 volcanic components with their eruption source areas based on chemical and isotope compositions. Likely sources for a considerable number of the volcanogenic deposits are Moresby and Dawson Strait volcanoes (D'Entrecasteaux Islands region) for high-K calc-alkaline glasses. The Dawson Strait volcanoes appear to represent the source for five peralkaline tephra layers. One basaltic andesitic volcaniclastic layer shows affinities to basaltic andesites from the Woodlark spreading tip and Cheshire Seamount. For other layers, a clear identification of the sources proved impossible, although their isotope and chemical signatures suggest similarities to south-west Pacific subduction volcanism, e.g. New Britain and Tonga- Kermadec island arcs. Volcanic islands in the Trobriand Arc (for example, Woodlark Island Amphlett Islands and/or Egum Atoll) are probable sources for several volcaniclastic layers with ages between 1.5 to 3 Ma. The Lusancay Islands can be excluded as a source for the volcanogenic layers found during Leg 180. Generally, the volcanogenic layers indicate much calc-alkaline rhyolitic volcanism in eastern Papua since 3.8 Ma. Starting at 135 ka, however, peralkaline tephra layers appear. This geochemical change in source characteristics might reflect the onset of a change in geotectonic regime, from crustal subduction to spreading, affecting the D'Entrecasteaux Islands region. Initial 143Nd/144Nd ratios as low as 0.5121 and 0.5127 for two of the tephra layers are interpreted as indicating that D'Entrecasteaux Islands volcanism younger than 2.9 Ma occasionally interacted with the Late Archean basement, possibly reflecting the mobilisation of the deep continental crust during active rift propagation.

Geochemistry and radiogenic isotope ratios of the volcanic sequences from Izu-Bonin Arc, Japan

New radiogenic isotope and trace element data are presented for the volcanic sequences along 600 km of the active Izu-Bonin arc, the Oligocene Izu arc, and their associated rift basins. As with many intra-oceanic island arcs, the Pliocene-Recent Izu-Bonin frontal-arc lavas are highly depleted in Zr, Nb and the rare-earth elements relative to typical mid-ocean ridge basalt (MORB), indicating that the mantle wedge source has undergone a previous episode of melting. Ratios between these elements (such as Nb/Zr and La/Sm), as well as 143Nd/144Nd, do not vary significantly along the length of the frontal-arc. These parameters suggest that each of the arc volcanoes is derived from similar melt fractions of the mantle wedge. However, Ba/Zr, Ba/Rb and 87Sr/86Sr increase along the frontal-arc to the north. This leads us to propose that a variable enrichment in Ba and radiogenic Sr is superimposed on the mantle wedge. Sr-Nd and Pb-Nd isotope variation indicate that both Sr and Pb become more radiogenic after fluid addition. However, Pb isotope ratios do not correlate with increases in Pb concentration or ratios such as Ba/Zr and Nb/Pb. In other words, the Pb isotopic composition of the arc lavas appears to be independent of the amount of Pb introduced by subduction fluids into the mantle source. This buffering of Pb isotopes along the frontal-arc means that the isotopic composition of the lavas is indistinguishable from that of the fluid. Isotopic mixing models presented for the arc are only illustrative of the many plausible combinations of components and quantities. Despite this, we are able to determine that the mantle wedge has isotopic characteristics similar to Indian Ocean MORB, and that the subduction-fluid solute is primarily derived from subducted oceanic basalt with a <2% contribution from subducted sediment. Lavas in the Oligocene Izu arc and fore-arc basin were derived from a mantle wedge of similar composition to the active arc. Despite levels of Pb enrichment comparable to those of the modern arc, the Pb isotopes of the Oligocene volcanics indicate a lower sediment input into the melting region.

Geochemistry in the mid Atlantic Ocean ridge basalts

The main objective of Leg 82 of the Glomar Challenger was to document mantle heterogeneity in the vicinity of, and away from, a so-called hot spot: the Azores Triple Junction. One of the geochemical tools that permits, at least in part, the recognition of mantle heterogeneities uses hygromagmaphile elements, those elements that have an affinity for the liquid. This tool is presented in terms of an extended Coryell-Masuda plot, which incorporates within the rare earth elements the hygromagmaphile transition elements Th, Ta, Zr, Hf, Ti, Y, and V. The extended Coryell-Masuda plot is used to summarize our knowledge of mantle heterogeneity along the ridge axis at zero-age. It is also used by choosing those hygromagmaphile elements that can be analyzed on board by X-ray fluorescence spectrometry to give preliminary information on the enriched or depleted character of recovered samples. Shore-based results, which include analyses of most of the hygromagmaphile elements measured either by X-ray spectrometry or neutron activation analysis, confirm the shipboard data. From the point of view of comparative geochemistry, the variety of basalts recovered during Leg 82 provides a good opportunity to test and verify the classification of the hygromagmaphile elements. Analyses from Leg 82 provide new data about the relationship between extended rare earth patterns (enriched or depleted) that can be estimated either by La/Sm ratio or Nb/Zr (or Ta/Hf) ratios: samples from Hole 556 are depleted (low Nb/Zr ratio) but have a high 206Pb/ 204Pb (19.5) ratio; in Hole 558 a moderately enriched basalt unit with a La/Sm (= Nb/Zr) ratio (chondrite normalized) of 2 has a high 206Pb/204Pb (20) ratio. One of the most interesting results of Leg 82 lies in the crossing patterns of extended Coryell-Masuda plots for basalts from the same hole. This result enhances the notion of local mantle heterogeneity versus regional mantle heterogeneity and is confirmed by isotope data; it also favors a model of short-lived, discrete magma chambers. The data tend to confirm the Hayes Fracture Zone as a southern limit for the influence of Azores-type mantle. Nevertheless, north of the Hayes Fracture Zone, the influence of a plumelike mantle source is not simple and probably requires an explanation more complex than a contribution from a single fixed hot spot.

Geochemistry of lower sheeted dike complex samples of ODP Holes 137-504B and 140-504B

Rocks of the lower sheeted dike complex of Hole 504B sampled during Leg 140 were analyzed for major and trace element compositions to investigate the effects of igneous processes and hydrothermal alteration on the compositions of the rocks. The rocks are relatively uniform in composition and similar to the shallower dikes. They are moderately evolved mid-ocean-ridge basalts (MORB) with relatively high MgO (7.9-10 wt%) and Mg# (0.60-0.70), and have unusually low incompatible element contents (TiO2 = 0.42-1.1 wt%, Zr = 23-62 ppm). Discrete compositional intervals in the hole reflect varying degrees of differentiation, and olivine and plagioclase accumulation in the rocks, and may be related to injection of packets of dikes having similar compositions. Systematic depletions of total REE, Zr, Y, TiO2, and P2O5 in centimeter-size patches are most likely attributed to exclusion of highly differentiated, late-stage interstitial liquids from small portions of the rocks. The rocks exhibit increased H2O+ reflecting hydrothermal alteration. Replacement of primary plagioclase by albite and oligoclase led to local gains of Na2O, losses of CaO, and slightly positive Eu anomalies. Some mobility of P2O5 led to minor increases and decreases in P2O5 contents, and some local mobility of Ti may have occurred during alteration of titanomagnetite to titanite. Higher temperatures of alteration in the lower sheeted dikes led to breakdown of pyroxene and sulfide minerals and losses of Zn, Cu, and S to hydrothermal fluids. Later addition of anhydrite to the rocks in microfractures and replacing plagioclase caused local increases in sulfur contents. The lower sheeted dikes are a major source of metals to hydrothermal fluids for the formation of metal sulfide deposits on and within the seafloor.

Propriedade fotoluminescente da ZrO2: Tb+3, Eu+3, Tm+3 obtida pelo método de polimerização de complexos

Recent studies are investigating a new class of inorganic materials which arise as a promising option for high performance applications in the field of photoluminescence. Highlight for rare earth (TR +3 ) doped, which have a high luminous efficiency, long decay time and being able to emit radiation in the visible range, specific to each element. In this study, we synthesized ZrO2: Tb +3 , Eu +3 , Tm +3 nanoparticles complex polymerization method (CPM). We investigated the influences caused by the heat treatment temperature and the content of dopants in zirconia photoluminescent behavior. The particles were calcined at temperature of 400, 500 and 600 ° C for two hours and ranged in concentration of dopants 1, 2, 4 and 8 mol% TR +3 . The samples were characterized by thermal analysis, X-ray diffraction, photoluminescence of measurements and uv-visible of spectroscopies. The results of X-ray diffraction confirmed the formation of the tetragonal and cubic phases in accordance with the content of dopants. The photoluminescence spectra show emission in the region corresponding simultaneous to blue (450 nm), green (550 nm) and red (615 nm). According to the results, ZrO2 particles co-doped with rare earth ions is a promising material white emission with a potential application in the field of photoluminescence

Princípios fundamentais e modelos de transferência de energia inter e intramolecular

This work outlines the historic development of the concept and main theories of energy transfer, as well as the principal experiments carried out to confirm or refute the proposed theories. Energy transfer in coordination compounds is also discussed with a focus on rare earth systems.

Técnica de bombeio e prova para medidas de absorção de estado excitado e de emissão estimulada, em materiais sólidos dopados com íons terras raras

Rare earth ion doped solid state materials are the most important active media of near-infrared and visible lasers and other photonic devices. In these ions, the occurrence of Excited State Absorptions (ESA), from long lived electronic levels, is commonplace. Since ESA can deeply affect the efficiencies of the rare earth emissions, evaluation of these transitions cross sections is of greatest importance in predicting the potential applications of a given material. In this paper a detailed description of the pump-probe technique for ESA measurements is presented, with a review of several examples of applications in Nd3+, Tm3+ and Er3+ doped materials.

Influence of metallic nanoparticles on electric-dipole and magnetic-dipole transitions of Eu(3+) doped germanate glasses

Luminescence properties of Eu(3+) doped germanate glasses containing either silver or gold nanoparticles (NPs) were investigated for excitation at 405 nm. Enhanced emissions and luminescence quenching of the Eu(3+) transitions in the range from 570 to 720 nm were observed for samples having various concentrations of metallic NPs. Electric-dipole and magnetic-dipole transitions that originate from the Eu(3+) level (5)D(0) exhibit large enhancement due to the presence of the metallic NPs. The results suggest that the magnetic response of rare-earth doped metal-dielectric composites at optical frequencies can be as strong as their electric response due to the confinement of the optical magnetic field. (C) 2010 American Institute of Physics. [doi:10.1063/1.3431347]

Metal-insulator transition in Nd(1-x) Eu(x) NiO(3) probed by specific heat and anelastic measurements

Oxides RNiO(3) (R - rare-earth, R not equal La) exhibit a metal-insulator (MI) transition at a temperature T(MI) and an antiferromagnetic (AF) transition at T(N). Specific heat (C(P)) and anelastic spectroscopy measurements were performed in samples of Nd(1-x)Eu(x)NiO(3), 0 <= x <= 0.35. For x - 0, a peak in C(P) is observed upon cooling and warming at essentially the same temperature T(MI) - T(N) similar to 195 K, although the cooling peak is much smaller. For x >= 0.25, differences between the cooling and warming curves are negligible, and two well defined peaks are clearly observed: one at lower temperatures that define T(N), and the other one at T(MI). An external magnetic field of 9 T had no significant effect on these results. The elastic compliance (s) and the reciprocal of the mechanical quality factor (Q(-1)) of NdNiO(3), measured upon warming, showed a very sharp peak at essentially the same temperature obtained from C(P), and no peak is observed upon cooling. The elastic modulus hardens below T(MI) much more sharply upon warming, while the cooling and warming curves are reproducible above T(MI). Conversely, for the sample with x - 0.35, s and Q(-1) curves are very similar upon warming and cooling. The results presented here give credence to the proposition that the MI phase transition changes from first to second order with increasing Eu doping. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3549615]

Thermo-optical characteristics and concentration quenching effects in Nd(3+)doped yttrium calcium borate glasses

In this work we present a comprehensive study of the spectroscopic and thermo-optical properties of a set of samples with composition xNd(2)O(3)-(5-x)Y(2)O(3-)40CaO-55B(2)O(3) (0 <= x <= 1.0 mol%). Their fluorescence quantum efficiency (eta) values were determined using the thermal lens technique and the dependence on the ionic concentration was analyzed in terms of energy transfer processes, based on the Forster-Dexter model of multipolar ion-ion interactions. A maximum eta = 0.54 was found to be substantially higher than for yttrium aluminoborate crystals and glasses with comparable Nd(3+) content. As for the thermo-optical properties of yttrium calcium borate, they are comparable to other well-known laser glasses. The obtained energy transfer microparameters and the weak dependence of. on the Nd(3+) concentration with a high optimum Nd(3+) concentration put this system as a strong candidate for photonics applications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3567091]

Structural models for yttrium aluminium borate laser glasses: NMR and EPR studies of the system (Y(2)O(3))(0.2)-(Al(2)O(3))(x)-(B(2)O(3))(0.8-x)

The structure of laser glasses in the system (Y(2)O(3))(0.2){(Al(2)O(3))(x))(B(2)O(3))(0.8-x)} (0.15 <= x <= 0.40) has been investigated by means of (11)B, (27)Al, and (89)Y solid state NMR as well as electron spin echo envelope modulation (ESEEM) of Yb-doped samples. The latter technique has been applied for the first time to an aluminoborate glass system. (11)B magic-angle spinning (MAS)-NMR spectra reveal that, while the majority of the boron atoms are three-coordinated over the entire composition region, the fraction of three-coordinated boron atoms increases significantly with increasing x. Charge balance considerations as well as (11)B NMR lineshape analyses suggest that the dominant borate species are predominantly singly charged metaborate (BO(2/2)O(-)), doubly charged pyroborate (BO(1/2)(O(-))(2)), and (at x = 0.40) triply charged orthoborate groups. As x increases along this series, the average anionic charge per trigonal borate group increases from 1.38 to 2.91. (27)Al MAS-NMR spectra show that the alumina species are present in the coordination states four, five and six, and the fraction of four-coordinated Al increases markedly with increasing x. All of the Al coordination states are in intimate contact with both the three-and the four-coordinate boron species and vice versa, as indicated by (11)B/(27)Al rotational echo double resonance (REDOR) data. These results are consistent with the formation of a homogeneous, non-segregated glass structure. (89)Y solid state NMR spectra show a significant chemical shift trend, reflecting that the second coordination sphere becomes increasingly ""aluminate-like'' with increasing x. This conclusion is supported by electron spin echo envelope modulation (ESEEM) data of Yb-doped glasses, which indicate that both borate and aluminate species participate in the medium range structure of the rare-earth ions, consistent with a random spatial distribution of the glass components.

Luminescent and thermo-optical properties of Nd(3+)-doped yttrium aluminoborate laser glasses

In this work we performed a thorough spectroscopic and thermo-optical investigation of yttrium aluminoborate glasses doped with neodymium ions. A set of samples, prepared by the conventional melt-quenching technique and with Nd(2)O(3) concentrations varying from 0.1 to 0.75 mol %, were characterized by ground state absorption, photoluminescence, excited state lifetime measurements, and thermal lens technique. For the neodymium emission at 1064 nm ((4)F(3/2) -> (4)I(11/2) transition), no significant luminescence concentration quenching was observed and the experimental lifetime values ranged around 70 mu s. The obtained values of thermal conductivity and diffusivity of approximately 10.3 x 10(-3) W / cm K and 4.0 x 10(-3) cm(2) / s, respectively, are comparable to those of commercial laser glasses. Moreover, the fluorescence quantum efficiency of the glasses, calculated using the Judd-Ofelt formalism and luminescence decay, lies in the range from 0.28 to 0.32, larger than the typical values obtained for Nd(3+) doped YAl(3)(BO(3))(4) crystals. (c) 2009 American Institute of Physics. [DOI: 10.1063/1.3176503]

Polymer matrix sensitizing effect on photoluminescence properties of Eu(3+)-beta-diketonate complex doped into poly-beta-hydroxybutyrate (PHB) in film form

In this work is reported the sensitization effect by polymer matrices on the photoluminescence properties of diaquatris(thenoyltrifluoroacetonate)europium(III), [Eu(tta)(3)(H(2)O)(2)], doped into poly-beta-hydroxybutyrate (PHB) with doping percentage at 1, 3, 5, 7 and 10% (mass) in film form. TGA results indicated that the Eu(3+) complex precursor was immobilized in the polymer matrix by the interaction between the Eu(3+) complex and the oxygen atoms of the PHB polymer when the rare earth complex was incorporated in the polymeric host. The thermal behaviour of these luminescent systems is similar to that of the undoped polymer, however, the T(onset) temperature of decomposition decreases with increase of the complex doping concentration. The emission spectra of the Eu(3+) complex doped PHB films recorded at 298 K exhibited the five characteristic bands arising from the (5)D(0) -> (7)F(J) intraconfigurational transitions (J = 0-4). The fact that the quantum efficiencies eta of the doped film increased significantly revealed that the polymer matrix acts as an efficient co-sensitizer for Eu(3+) luminescent centres and therefore enhances the quantum efficiency of the emitter (5)D(0) level. The luminescence intensity decreases, however, with increasing precursor concentration in the doped polymer to greater than 5% where a saturation effect is observed at this specific doping percentage, indicating that changes in the polymeric matrix improve the absorption property of the film, consequently quenching the luminescent effect.

Elemental composition changes in citrus affected by the CVC disease

The citrus variegated chlorosis (CVC) disease results in serious economical losses for the Brazilian citriculture. The influence of CVC disease on the elemental composition of citrus plants was investigated. Leaves of sweet orange varieties Hamlin, Pera Rio and Valencia were collected from healthy and CVC-affected trees for chemical characterization by instrumental neutron activation analysis (INAA). Significant differences between healthy and CVC-affected leaves were identified for Ca, Ce, Co, Eu, Fe, K, La, Na, Nd, Rb, Sc and Sm. Rare earth elements presented consistently higher mass fractions in the healthy leaves.

Spontaneous infiltrations of compound systems of Y(2)O(3), Sm(2)O(3), RE(2)O(3), Al(2)O(3) and AIN in SiC ceramics

Silicon carbide ceramics (SiC) are used in different applications in the engineering area due to the excellent properties, mainly in high temperatures. They are usually obtained by liquid-phase sintering enabling to form volatile products and, consequently, defects. The present work aims at studying the obtention of SiC ceramics by spontaneous infiltration using a eutectic composition of the Al(2)O(3)/Y(2)O(3), AIN/Y(2)O(3), Al(2)O(3)/Sm(2)O(3), AlN/Sm(2)O(3), Al(2)O(3)/RE(2)O(3) and AlN/RE(2)O(3) Systems. RE(2)O(3) is the concentrate of the rare-earth oxide obtained from Xenotime ore. Infiltration tests were carried out in argon atmosphere, graphite crucibles, in several temperatures near the melting point of each system, varying from 2.5 to 60 min. It was observed that Al(2)O(3)/Y(2)O(3), Al(2)O(3)/SM(2)O(3), AlN/SM(2)O(3) and Al(2)O(3)/RE(2)O(3) systems do not infiltrate appropriately and the AlN/Y(2)O(3) and AlN/RE(2)O(3) systems infiltrated spontaneously more than 20 mm; however, the first one presented a higher degree of infiltration, approximately 97%. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.