Constraints on the Genesis of Potassium-rich Italian Volcanic Rocks from U/Th Disequilibrium     

Avanzinelli  Riccardo; Elliott  Tim; Tommasini  Simone; Conticelli  Sandro 《Journal of Petrology》2008,49(2):195-223

We present new U-series isotope, ⁸⁷Sr/ ⁸⁶Sr, ¹⁴³Nd/ ¹⁴⁴Nd andtrace element data for a set of mafic, K-rich rocks from volcanoesin Central–Southern Italy. These shoshonitic to ultrapotassiclavas display strongly depleted high field strength element(HSFE) abundances with respect to other incompatible trace elementstogether with high but variable ⁸⁷Sr/ ⁸⁶Sr and low but variable¹⁴³Nd/ ¹⁴⁴Nd values. Such characteristics are thought to bedue to addition of subducted crust of variable amount and compositionto their mantle sources prior to magma genesis. Rocks from thenorthernmost region (i.e. Tuscan Magmatic Province and NorthernRoman Magmatic Province) display (²³⁰Th/ ²³⁸U) activity ratiosclose to radioactive equilibrium, suggesting that metasomatismof their sources occurred before 400 ka and recent melting tookplace at shallow depths, in the absence of garnet. A ²³⁸U excessof up to 27% has been measured in rocks from the NeapolitanDistrict. The occurrence of significant U excesses is a featureof arc magmas, but is typically seen in depleted lavas ratherthan in highly enriched rocks such as these (20 ppm Th). Thissignature requires a recent addition of a U-rich component tothe already strongly enriched mantle wedge beneath this regionof Italy. We suggest that a supercritical liquid, from deeplysubducted carbonate-rich sediments of the still-active Ionianslab, is responsible for generating a high-U, low-Th component,which produces the observed disequilibria. A 30% ²³⁰Th excessmeasured in a single unaltered sample from the Lucanian MagmaticProvince, along with a less marked negative HFSE anomaly, suggeststhe contribution of a deeper, garnet-bearing component in thegenesis of these magmas, plausibly related to the upwellingof asthenospheric mantle around the corner of the Ionian slab. KEY WORDS: U/Th disequilibria; potassic and ultrapotassic rocks; subduction: metasomatism; mantle melting; Central and Southern Italy  相似文献   

ICP-MS DETERMINATION OF 45 TRACE ELEMENTS IN WHOLE COAL USING MICROWAVE OVEN ACID DIGESTION FOR SAMPLE PREPARATION     

Sandro FADDA  Alessandro RIVOLDINI  Ignazio CAU 《Geostandards and Geoanalytical Research》1995,19(1):41-54

The microwave oven acid digestion technique has been routinely applied to the ICP-MS multielement analysis of whole powdered coal. Samples were treated with a mixture of HF/aqua regia/HClO₄ in closed Teflon PFA vessels without any pre-treatment. Complete dissolution of the coal matrix is not required, but only one that results in quantitative and reproducible recovery of more than 40 trace elements with minimum digestion time, minimum use of reagents and minimal operator attendance. The precision of the analysis as well as the repeatability of the sample preparation procedure and precision of instrumental measurements have been evaluated. Eight coal standards, including NBS SRM 1632b, 3 South Africa Reference Materials (SARMs) 18 to 20 and 4 USA ARs 1800 to 1803 were analysed in this manner providing data for all the 14 rare earth elements along with others of geochemical interest, technological relevance as well as environmental and health concern. The results, from the ppb level to several ppm, are discussed for all the elements including detection and quantification limits, precision and accuracy. In general, good agreement was achieved with the certified and/or available published values.  相似文献   

Interactive effects of cadmium and zinc pollution on PGI and PGM polymorphisms in Idotea baltica     

Marina De Nicola  Carmela Gambardella  Sandro M. Guarino 《Marine pollution bulletin》1992,24(12):619-621

Separate and interactive pollution effects of Cd and Zn on electrophoretically-detected allozyme frequencies of the different genotypes at PGI and PGM loci were studied in Idotea baltica.

Differential survivorship of PGM genotypes was detected in the presence of the single or combined pollutants, while no effect was observed for PGI. Cadmium decreased heterozygosity while zinc or Cd + Zn increased it, suggesting an antithetic action of the two metals and the prevalence of zinc.  相似文献   

Some expansions of the elliptic motion to high eccentricities     

Sandro Da Silva Fernandes 《Celestial Mechanics and Dynamical Astronomy》1995,62(4):305-321

Some classic expansions of the elliptic motion — cosmE and sinmE — in powers of the eccentricity are extended to highly eccentric orbits, 0.6627...<e<1. The new expansions are developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients are given in terms of the derivatives of Bessel functions with respect to the eccentricity. The expansions have the same radius of convergence (e*) of the extended solution of Kepler's equation, previously derived by the author. Some other simple expansions — (a/r), (r/a), (r/a) sinv, ..., — derived straightforward from the expansions ofE, cosE and sinE are also presented.  相似文献   

The Kleiner Feldberg Cloud Experiment 1990: Introduction     

Sandro Fuzzi 《Journal of Atmospheric Chemistry》1994,19(1-2):1-2

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Occurrence of selected estrogens in mangrove sediments   总被引：1，自引：0，他引：1  

Froehner S  Machado KS  Stefan E  Bleninger T  da Rosa EC  Martins Cde C 《Marine pollution bulletin》2012,64(1):75-79

This paper presents results related to the occurrence and distribution of estrogens along the Brazilian coast. Three mangrove areas were chosen to evaluate the presence of estrogens in surface sediments of mangrove forests. The presence of estrogens was observed in all studied sites. 17-α-Ethinylestradiol (EE2), a synthetic estrogen, was the most common and has been found in higher concentration (0.45-129.78 ng/g) compared to 17-β-estradiol (E1) and estrone (E2) (both being natural estrogens). The concentrations of E1 and E2 ranged from 0.02 to 49.27 ng/g and 0.03 to 39.77 ng/g, respectively. Theoretically, under anaerobic conditions EE2 can be reduced to E1 even in environments such as sediments of mangrove forests, which are essentially anaerobic. Even if the concentrations of estrogens seem to be insignificant in some samples, the effects remain uncertain.  相似文献   

Isotope geochemistry (Sr–Nd–Pb) and petrogenesis of leucite-bearing volcanic rocks from “Colli Albani” volcano, Roman Magmatic Province, Central Italy: inferences on volcano evolution and magma genesis     

Elena Boari  Riccardo Avanzinelli  Leone Melluso  Guido Giordano  Massimo Mattei  Arnaldo A. De Benedetti  Vincenzo Morra  Sandro Conticelli 《Bulletin of Volcanology》2009,71(9):977-1005

The “Colli Albani” composite volcano is made up of strongly silica-undersaturated leucite-bearing rocks. Magmas were erupted during three main periods, but a complex plumbing system dominated by regional tectonics channelled magmas into different reservoirs. The most alkali-rich magmas, restricted to the caldera-forming period (pre-caldera), are extremely enriched in incompatible trace elements and display more radiogenic Sr (⁸⁷Sr/⁸⁶Sr?=?0.71057–0.71067), with slightly less radiogenic Pb with respect to those of the post-caldera period. Post-caldera volcanic activity was concentrated in three different volcanic environments: external to the caldera, along the caldera edge and within the caldera. The post-caldera magmas produced melilite- to leucitite-bearing, plagioclase-free leucitites. In contrast to the pre-caldera lavas, they are characterised by lower incompatible trace element abundances and less radiogenic Sr (⁸⁷Sr/⁸⁶Sr?=?0.71006–0.71039). Magmas evolved through crystal fractionation plus minor crustal assimilation in a large magma chamber during the pre-caldera period. The multiple caldera collapses dissected and partially obliterated the early magma chamber. During the post-caldera stage, magmas were channelled through several pathways and multiple shallow-level magma reservoirs were established. A lithospheric mantle wedge previously depleted in the basaltic component and subsequently enriched by metasomatic slab-derived component is suggested as the mantle source of Colli Albani parental magmas. Two different parental magmas are recognised for the pre- and post-caldera stages. The differences may be related to the interplay between smaller degrees of melting for the pre-caldera magmas and more carbonate-rich recycled subducted lithologies in the post-caldera magmas.  相似文献   

Static equivalent method for the kinematic interaction analysis of single piles     

Francesca Dezi  Sandro Carbonari  Graziano Leoni 《Soil Dynamics and Earthquake Engineering》2010

This paper presents a static equivalent approach to estimate the maximum kinematic interaction effects on piles subjected to lateral seismic excitation. Closed-form expressions are reported for the evaluation of the maximum free-field soil movements and for the computation of maximum pile shear force and bending moments. Firstly, modal analysis, combined with a suitable damped response spectrum, is used to evaluate the maximum free-field response. Secondly, the pile is schematised as a Winkler's beam subjected to equivalent static forces defined according to soil vibration modal shapes and amplitude. The method may be applied by using response spectra suggested by National Standards or those obtained with accelerograms. The procedure proposed may be conveniently implemented in simple spreadsheets or in commercial finite element programs and easily used by practicing engineers. Method accuracy is demonstrated by comparing the results with those obtained with a more rigorous model. Good results may be achieved by considering only the first soil vibration mode making the procedure straightforward for practical design purposes.  相似文献   

Long term spectral variability in the soft gamma-ray repeater SGR 1900+14     

Andrea Tiengo  Paolo Esposito  Sandro Mereghetti  Lara Sidoli  Diego Götz  Marco Feroci  Roberto Turolla  Silvia Zane  Gian Luca Israel  Luigi Stella  Peter Woods 《Astrophysics and Space Science》2007,308(1-4):33-37

We present a systematic analysis of all the BeppoSAX data of SGR1900+14. The observations spanning five years show that the source was brighter than usual on two occasions: ～20 days after the August 1998 giant flare and during the 10⁵?s long X-ray afterglow following the April 2001 intermediate flare. In the latter case, we explore the possibility of describing the observed short term spectral evolution only with a change of the temperature of the blackbody component. In the only BeppoSAX observation performed before the giant flare, the spectrum of the SGR1900+14 persistent emission was significantly harder and detected also above 10 keV with the PDS instrument. In the last BeppoSAX observation (April 2002) the flux was at least a factor 1.2 below the historical level, suggesting that the source was entering a quiescent period.  相似文献   

Thermohaline circulation sensitivity to intermediate-level anomalies     

Vincenzo Artale  Sandro Calmanti  Alfonso Sutera 《地球，A辑:动力气象学与海洋学》2002,54(2):159-174

Abstract A two-dimensional Boussinesq ocean model has been used to investigate the effect of intermediate-level thermal and saline anomalies on the known multiple equilibria structure of the thermohaline circulation. These anomalies are taken as a crude representation of the Mediterranean outflow in the Atlantic Ocean. The associated perturbation drives the system towards an overturning which resembles the present average Atlantic thermohaline circulation. The sensitivity to the depth at which the anomaly is placed is also investigated. We found that near-surface anomalies are more efficient in affecting the structure of the equilibria.  相似文献