Search results for " element"
showing 10 items of 2679 documents
Dynamics of particulate major and trace elements in the lower reaches of the Daugava River and adjacent area of the Gulf of Riga (Baltic Sea).
2004
Suspended particulate matter (SPM) was collected in the freshwater-seawater mixing zone in the lower reaches of the Daugava River (Latvia) and adjacent marine area, during five cruises in 1998-2001. The study focused on biogeochemical phase exchange processes. SPM in the freshwater was found to be mainly allochthonous with a high content of organic matter, Mn and sorbed phosphate. Property-salinity plots suggested flocculation of humic-Fe complexes across the salinity gradient. The variability of sorbed phosphate was related to particulate Fe, although no dependence on pH and ionic strength was observed. The Mn contents of SPM mainly follow conservative mixing, but there are also indication…
Ultra-conserved elements provide insights to the biogeographic patterns of three benthic macroinvertebrate species in the Baltic Sea
2022
The Baltic Sea, with its steep salinity gradient, high water retention time, and relatively young age, represents a marginal ecosystem between marine and freshwater extremes. Due to differing invasion history and dispersal capabilities of Baltic species, there are large differences in species distributions, species-specific genetic structure and variation, and edge populations that may represent both a subset of the original population, as well as unique genetic lineages. We used a phylogenomic approach to investigate relationships between populations of three benthic macroinvertebrate species: Pygospio elegans, Corophium volutator, and Mya arenaria, providing new insight into evolutionary …
Baltijas valstu un Somijas tūrisma galamērķa tēla elementi Krievijas auditorijā
2022
Tēlam ir ļoti liela nozīme ceļojuma galamērķa veiksmīgā attīstībā, jo pozitīvs tēls palielina galamērķa atpazīstamību un ietekmē tūristu vēlmi apmeklēt šo galamērķi. Šī pētījuma mērķis ir izpētīt galamērķa tēlu veidojošos elementus, ko Krievijas ceļotāji veido un izplata par Baltijas valstīm (Igauniju, Latviju un Lietuvu) un Somiju. Šajā darbā tēls, tostarp tēla elementi tiek pētīti, izmantojot krievu tūristu atsauksmju, kas publicētas ar ceļošanu saistītās tīmekļa vietnēs, satura analīzi. Darbā tiek atklāti nozīmīgākie galamērķa tēla atribūti, tādi kā, kultūras un dabas resursi, atmosfēra, infrastruktūra, gastronomiskais piedāvājums un nakts dzīve, tīrība, drošība, vietējo iedzīvotāju vies…
Numerical modelling of the tensile behaviour of BFRCM strips
2019
This paper aims at investigating the tensile behaviour of basalt fibres on cementitious matrix for the strengthening of masonry structures. The use of Basalt Fibre Reinforced Cementitious Matrix (BFRCM) is favourably considered by the scientific community because it represents a natural composite material with high compatibility with stone and masonry substrate. The study is developed through the generation of Finite Element (FE) models capable of reproducing the tensile behaviour of BFRCM strips with different number of layers of grid. For the scope, the micro-modelling approach is adopted assuming different levels of detail for the simulation of the interface constitutive behaviour. Fibre…
Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa)
2019
A well-preserved sequence, by Archean standards, of mantle-derived metabasalts and metakomatiites forms large parts of the lower Onverwacht Group of the Barberton Greenstone Belt (South Africa). To elucidate the origin of mafic and ultramafic rocks from this 3.55 to 3.45 Ga sequence, we present a comprehensive geochemical dataset including major and trace elements as well as Lu-Hf and Sm-Nd isotope compositions for a variety of metavolcanic rocks. These include metabasalts of the amphibolite-facies Sandspruit and Theespruit Formations as well as metabasalts and metakomatiites of the lower greenschist-facies Komati Formation. Based on their incompatible trace element patterns, the basalts of…
GEOCHEMICAL CONSTRAINTS ON THE ORIGIN OF CALCALKALINE AND ALKALINE MAGMAS OF THE EASTERN TRANS-MEXICAN VOLCANIC BELT
1988
Se presentan datos de elementos mayores, elementos trazas y tierras raras de rocas calco-alcalinas y alcalinas de la parte este del cinturón volcánico transmexicano (TMVB), así como conclusiones acerca de su origen y de su significado tectónico. Las andesitas y dacitas muestran características geoquímicas que descartan su derivación de los magmas basálticos por el proceso de cristalización fraccionada. Las distribuciones gráficas de los elementos LIL y HFS son interpretadas como indicadoras de la formación de magmas en el manto superior modificado por procesos de subducción. Las riolitas se interpretan como resultado de la fusión parcial de la corteza continental.
Influence of crustal thickening on arc magmatism:, Nevados de Payachata volcanic region, northern Chile
1993
Neogene through Pleistocene lava flows of the Nevados de Payachata region (lat 18°S) on the Altiplano of northern Chile fall into two discrete chemical groups defined by age and incompatible element concentrations. The Neogene suite (10.5-6.6 Ma) has trace element concentrations comparable to arc magmas erupted on thin crust in central Chile. Pleistocene lava flows (0.29-0 Ma) are enriched in incompatible elements relative to Neogene samples but have similar Sr, Nd, and Pb isotopic ratios. Incompatible element enrichment in mafic rocks reflects deep-crustal or subcrustal processes. Neogene volcanism in northern Chile immediately followed a period of intense crustal thickening. Uplift rates …
Trace element partitioning in lamproitic magmas—the Gaussberg olivine leucitite
2004
Abstract Partition coefficients for compatible and incompatible trace elements for use in modelling the origin and evolution of lamproitic and other potassic rocks are reported. These are based on values obtained by in situ determination using laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) on mineral/glass pairs in examples of the Gaussberg olivine leucitite, a classic leucite lamproite. Leucite/melt partition coefficients for 32 elements show values above 1 only for Cs and Rb, whereas values for Ni, Ga and Co are 0.4–0.1. DLc/Lq for most other elements are in the range 0.07–0.0005, and delineate a gently sloping pattern to lower values for elements gene…
Geochemical heterogeneities in magma beneath Mount Etna recorded by 2001-2006 melt inclusions
2015
We present a geochemical study on olivine and clinopyroxene-hosted melt inclusions (MIs) from 2001 to 2006 Etna basaltic lavas and pyroclastites. Three MI suites are distinguished on the basis of trace element fingerprinting. Type-1 MIs (from 2001 Upper South and 2002 Northeast vents) share their trace element signature with low-K lavas erupted before 1971. Critical trace element ratios (e.g., K/La, Ba/Nb), along with Pb isotope data of Type-1 MIs provide evidence for a heterogeneous mantle source resulting from mixing of three end-members with geochemical and isotopic characteristics of EM2, DMM, and HIMU components. Type-1 MIs composition does not support involvement of subduction-related…
MORB-type neon in an enriched mantle beneath Etna, Sicily
1997
Abstract Noble gas elemental and isotopic compositions were determined for five CO 2 –CH 4 samples collected around Etna, Sicily, to investigate the geochemical features of the mantle beneath the volcano. The samples contain mantle-derived noble gases. The measured helium isotopic ratios ( 3 He/ 4 He) vary between 5.9 and 6.4 times atmospheric ratio ( R a =1.4×10 −6 ), which are comparable to the ratios of olivines (6.1–8.2 R a ) in the lavas of the same volcano [1]. Neon in the samples is enriched in both 20 Ne and 21 Ne ( 20 Ne/ 22 Ne 9.95–10.7, 21 Ne/ 22 Ne 0.030–0.037), indicating derivation from the mantle. The δ ( 20 Ne/ 22 Ne)/ δ ( 21 Ne/ 22 Ne) values are identical with that of mid-…