1,721,083 research outputs found
REE and Nd-isotope evidence for the origin of siderite from the Jebel Awam deposit (Central Morocco)
No full textREE contents and Nd-isotope ratios were determined in siderite ores from the "Filon du Signal" and the "Filon Sud" of the Pb-Zn-Ag mineralization of the Jebel Awam deposit, central Morocco. The deposit was formed by the intrusion of granites into the Lower Paleozoic metasedimentary basement probably by 280 Ma. The REE contents in the siderites allow for discrimination between the two veins, likely reflecting different concentrations in the mineralizing fluids. All siderites display positive Eu anomalies, indicating that the parent fluids were meta morphogenic. Assuming a common origin of the fluids, the higher REE contents and higher LREE/HREE ratios of FS siderites compared to FdS siderites suggest that the FS fluids were hotter and more acidic. The epsilon(Nd) and the Sm-147/Nd-144 ratios of the siderites range from -5.97 to -7.74, and from 0.172 to 0.183, respectively, and are statistically irrespective of sample provenance. The homogeneous isotopic data prevent use of the data forage-determination purposes, but they support the common origin of the mineralizing fluids. Moreover, since the siderites exhibit epsilon(Nd) (280 Ma) comprised between the values of the basement schists and the granites, this supports a hydrothermal origin for the mineralizing fluids. which acquired Sm and Nd by leaching both lithotypes. These conclusions, corroborating earlier information provided by Sr isotopes, demonstrate the potential of Nd isotopes and REE as geochemical tracers in the study of hydrothermal deposits. C) 2008 Elsevier B.V. All rights reserved
Contributo degli isotopi radiogenici allo studio dei suoli
No full textGli isotopi dello Sr e del Nd sono stati applicati allo studio di 4 differenti suoli della zona di Ravenna: un suolo naturale della Pineta di san Vitale, due suoli agricoli e il suolo del Giardino pubblico della città. Lo studio di questi profili è stato condotto analizzando gli estratti in aqua regia dei campioni dei vari orizzonti. I risultati ottenuti indicano che per il suolo pinetale si osserva una diminuzione dei valori di 87Sr con la profondità, mentre per tutti gli altri suoli questa caratteristica non è apparente, probabilmente perchè sono perturbati dalle attività agricole e di giardinaggio che rivoltano continuamente gli orizzonti omogeneizzandoli. I rapporti isotopici dello Sr sono stati misurati anche su alcune piante orticole e un frutto arboreo, raccolti a fine ciclo vegetativo. I 87Sr delle orticole sono più alti dei valori dell’orizzonte superficiale del suolo di riferimento, suggerendo che lo Sr preso dalle piante derivi dalle acque d’irrigazione e dalle deposizioni atmosferiche. Al contrario per il frutto arboreo è rilevabile il contributo anche del suolo, in accordo con la maggiore profondità dell’apparato radicale. Al contrario degli isotopi dello Sr, quelli del Nd non distinguono tra i vari suoli e mostrano scarsa variabilità dei valori di εNd con la profondità, probabilmente perché le sorgenti dell’elemento sono rappresentate da minerali poco alterabili (silicati) e poco abbondanti (apatite). Per quanto riguarda le potenziali fonti d’inquinamento, principalmente quello da ricaduta di particolato da fumi industriali, la sovrapposizione dei campi di 87Sr e εNd di sorgenti naturali e antropiche non permette di distinguere tra i due gruppi di contributi. Nel complesso l’applicazione congiunta degli isotopi dello Sr e del Nd allo studio dei suoli può fornire utili informazioni sui processi pedogenetici e sulla eventuale presenza di alcuni inquinanti.Sr and Nd isotopes have been applied to the study of 4 different soils from the Ravenna area: a natural profile from the san Vitale Pinewood, two cultivated profiles and a profile from the urban public Park of Ravenna. Their study has been conducted analyzing the aqua regia extracts of samples from the different horizon. The results show that the Pinewood soil
displays decreasing 87Sr with depth, while the other profiles exhibit no typical trends, probably because these soils are, to variable extent, perturbed by agricultural activity and gardening, making the horizons homogenized by relentless upturning. The Sr isotopic ratios have also been measured in the tissues of horticultural plants and a tree fruit sample, all taken at the end or their vegetal cycles. The 87Sr of horticultural plants are higher than the value of the surface horizon of the soil, suggesting that the Sr taken up by the plants derives from irrigation waters and atmospheric depositions. In contrast, it is recognized tthe contribution from the soil in the fruit sample, likely because of deeper location of the tree roots. Unlikc Sr isotopes, Nd isotopes do not distinguish among the different profiles, and show scarce variability of εNd with depth, probably because the sources of Nd are represented by minerals that are little weathered (silicates) and little abundant (apatite). As concerns potential sources of pollution, mainly from atmospheric particulates of industries, the overlap of 87Sr and εNd ranges of natural and anthropic sources does not allow for distinguishing between the two group of contributions. As a whole, the joint application of Sr and Nd isotopes to the study of soils, can provide useful information on the pedogenic processes and the potential presence of pollutants
The Nd-isotope composition of siderite and its bearing for ore genesis : the case study of the Jebel Awam polymetallic deposit (central Morocco)
No full textextended abstrac
REY and Sr-Nd isotopic ratios of aqua regia extracts to assess pedogenic processes and pollution in soils from Ravenna (north Italy)
No full textSr, Ca and REY (REE+Y) concentrations along with Sr-Nd isotopic ratios have been determined in 17 aqua regia extracts from three soils of different land use, located in the area near the industrial town of Ravenna, in northern Italy, to test what information can be obtained about the pedogenesis, Sr and REY provenance and soil pollution. 6 samples of selected parts of horticultural plants from the agricultural soil, have also been analyzed for Sr isotopic composition. The Sr and Ca concentrations in the extracts generally increase with depth in each soil profile, reflecting selective mineral weathering in upper horizons and removal of the two elements by the soil solution. In this context, the decrease of the Sr/Ca ratios with depth in each profile suggests preferential removal of Ca, due to resistance of non-carbonate Sr-bearing minerals to weathering and preferential Ca uptake by plants as a nutrient. The PAAS-normalized REY patterns of the extracts from two out of the three studied soils, are similar, displaying middle REE enrichment with a Gd peak and, generally, a positive Y anomaly. These characteristics suggest the contribution of marine carbonates and phosphates. The aqua regia extracts of the two soils perturbated by plowing and gardening practices, exhibit narrower ranges of delta Sr-87 (from -0.49 to -0.97) than the natural soil (from -1.03 to +0.37). However, excluding decarbonated upper horizons, the natural soil displays a delta Sr-87 range (from -0.47 to -1.03) similar to the other two soils. These overlapping ranges indicate that labile Sr mainly derives from a common source, represented by marine carbonates and phosphates of the bedrocks. In the geological context of the study area, Miocene sedimentary formations of Romagna's Apennines may be the likely sources of those phases. In contrast, the more positive delta Sr-87 (from -0.21 to +0.37) of decarbonated upper horizons of the natural soil, likely reflect the contribution of radiogenic Sr from silicates of old crustal rocks from either the bedrock and/or atmospheric deposition (Saharan dust). The three soils display overlapping and relatively narrow ranges of epsilon(Nd) (from -6.5 to -9.4), indicating a common source of Nd, mainly represented by phosphates. The contribution from silicates of old crustal rocks appears to be very subordinate. The Sr-Nd isotopic overlap of the soil extracts with the corresponding ranges of anthropogenic (i.e. industry, traffic) sources, prevents from ascertaining potential pollution from the study area. Compared with the isotopic values of the soil extracts, the higher delta Sr-87 (from -0.32 to -0.07) of selected parts of horticultural plants grown on the agricultural soil, indicate the soil solution from which the plants uptake Sr, contains more radiogenic Sr. The comparison with the delta Sr-87 of the ammonium acetate extracts from the same soil samples, indicates that the milder extraction than that carried out with aqua regia, leaves non-radiogenic Sr-bearing phosphates undissolved and, thus, more radiogenic Sr in the solution. As a whole, the aqua regia extraction of soil samples can provide significant information on the behavior of Sr and REY in the pedogenesis as well as in recognizing the sources of these elements with respect to the soluble soil phases and their possible references in the geological context of the study area. In contrast, the aqua regia extraction is not a suitable procedure for studying the soil-plant relationship, providing less information than the ammonium acetate extraction
Sr-Nd isotopes of mosses (Hypnum cupressiforme Hdw.) as a tool for studying the atmospheric pollution in north-central Italy
No full textRare earth elements and Sr–Nd isotopes in mosses from Romagna (Italy) and their environmental significance.
No full textSr and Nd isotopes were applied to the study of a large number of moss samples from Romagna, northern Italy, to investigate whether these isotopes can provide useful information on environmental quality. Sr, Ca, and rare earth elements plus Y, i.e. REY, were also determined in selected samples. The REY contents (0.014–2.65 mg/kg) likely correlate with the different age of the samples. The REY patterns normalized to Post-Archean Australian Shale show a middle REY enrichment suggestive of phosphate assimilation by the mosses, whereas the Gd and Y positive anomalies along with the Ce negative anomaly envisage carbonate assimilation and, lastly, the Nd negative anomaly may refer to either Nd retention onto soil clay or Nd substitution for Ca under Ca deficiency. The 87Sr values of the samples (from -1.4 to 0.2) collected from tree canopy-protected areas support the hypothesis of Sr provenance from marine carbonates. In contrast, the uppermost of the samples from open spaces display 87Sr values (0.1–3.6) suggestive of a significant Sr contribution from crustal silicates. The Nd range (from -10.9 to - 4.1) supports the hypothesis of a Nd crustal source for all the mosses. As a whole, there is no evidence of contribution of Sr and Nd from pollution sources. Lastly, this paper yields the largest data base ever carried out about the Sr–Nd isotopic composition of a moss species
The Fe isotopic composition of soils and waters from the Ravenna area (Northern Italy) and its significance for environmental studies
No full textStable Fe-isotope ratios have been measured by TIMS in samples of natural and cultivated soils as well as surface waters from a sector of the Ravenna area located next to the industrial zone that host particularly iron mills, and contoured by fields exploited by intensively agriculture. The soils, that can be classified as entisols in interdune lowlands and are composed of quartz, feldspars, calcite, muscovite, chlorite and dolomite, were analyzed following a three-step sequential chemical procedure, to obtain different extractable fractions and, thus, determine the potential sources of Fe in poorly-crystalline Fe oxides, crystalline Fe oxides and silicate-bound Fe (Wiederhold et al., 2007). Iron isotope ratios of bulk soil digests were compared with those of the different Fe fractions. In particular, the δ56Fe of the hydrochloric extracts of the soils, that can represent the metal fraction available to the plants and, thus, provide information on health of the vegetal ecosystem, range narrowly, increasing from slightly negative values in upper horizons to slightly positive values downward each profile. This trend suggests the Fe isotopes are little fractionated biologically during the pedogenesis. Preliminary analyses of waters from the irrigation network related to both natural and cultivated soils, display slightly negative δ56Fe. As a whole, the isotopic signatures of both soils and waters suggest the natural cycle of Fe in these materials is unaffected by significant anthropogenic contributions, despite the location of the study area just in front of major pollution sources. This conclusion is consistent with what has been acknowledged by a study on the distribution of potentially toxic metals and stable/radiogenic isotopes, carried out on the same materials from the Ravenna area. Lastly, the results corroborate previous information on fractionation mechanisms of Fe isotopes and help in the development of these isotopes as tracers for biogeochemical Fe cycling in nature
Sr isotopic evidence for studyng the salinization of soils : an example from the San Vitale Pinewood (Ravenna)
No full textIn the frame of a multidisciplinary project of research on the San Vitale Pinewood ecosystem, north of Ravenna, the Sr isotope study of a soil profile developed on an old coastal dune aiming at detecting the effect of salinization is presented. The Sr isotope ratios of the bulk soil samples decreased significantly from upper (0.717) to lower (0.712) horizons because of the abundant marine salts deposited by the brackish water present in the deep soil. While the main source of Sr in the upper horizons is the silicates, especially the feldspaths contained in the old dune sediments; in contrast, Sr in the lower horizons is significantly also of evaporitic origin (0.707-0.709). This latter is dominantly the strontium bio-available to the plants
The Sr-isotope composition of soils: A case study from Muravera (Se Sardinia, Italy)
No full textThis paper presents a case study of applying Sr-isotope geochemistry to a soil, located near the coast in the island of Sardinia, Italy. Therefore, we have measured the Sr-isotope ratios of bulk samples from the three soil horizons as well as correlated acid extracts and insoluble residue obtained by sequential attack of bulk samples. The results indicate that the Sr isotopic compositions of acid extracts vary with depth (“vertical” isotopic trend) as well as within each horizon (“chemical” isotopic trend). Both trends can be explained assuming that bulk Sr in the soil proceeds from two reservoirs: one internal represented mainly by plagioclase of the parent rock, and the other external represented by minerals and salts carried by rainwater and winds. Calculations may provide a quantitative approach to the case study here presented
- …
