Search results for "MINERALOGY"
showing 10 items of 1516 documents
Determination of Diffusion Parameters by a Computer Code (FDP) Based on Mathematica 6.0
2010
A computer code named Fitting for Diffusion Parameters (FDP) based on Mathematica 6.0 has been developed for modeling through- and out-diffusion experiments. FDP was used to determine the diffusion coefficients (De ) and the rock capacity factors (α) for tritiated water (HTO) and 22 Na+ and the distribution coefficient (Kd ) of 22 Na+ in Opalinus Clay (OPA). The values for De and α were obtained by fitting the results of experimental data of both transient and steady-state phases to the analytical solution of accumulated activity. The quality of the parameters De and α was tested by using them as input parameters in the equation of flux. Moreover, the diffusion parameters of HTO and 22 Na+ …
Chemical weathering of volcanic rocks at the island of Pantelleria, Italy: Information from soil profile and soil solution investigations
2007
Abstract Concentrations of major, minor and trace elements were determined in soil profiles and soil solutions from the island of Pantelleria, Sicily Channel, to evaluate the weathering extent of soils evolved on trachytic and pantelleritic rocks and the aqueous transport of elements by their soil solutions. The chemical index of alteration (CIA) indicates a low-to-moderate degree of weathering; consistently, the mineralogical and geochemical imprints of the parent rocks are generally preserved. The chemical weathering appears to be incongruent, owing to primary minerals and glass dissolving to a variable degree while secondary minerals have formed. Based on the calculated saturation state …
Clay minerals, oxyhydroxide formation, element leaching and humus development in volcanic soils
2008
Aweathering sequence with soils developing on volcanic, trachy-basaltic parent materials with ages ranging from 100–115,000 years in the Etna region served as the basis to analyse and calculate the accumulation and stabilisation mechanisms of soil organic matter (SOM), the transformation of pedogenic Fe and Al, the formation and transformation of clay minerals, the weathering indices and, by means of mass-balance calculations, net losses of the main elements. Although the soils were influenced by ash depositions during their development and the soil on the oldest lava flow developed to a great extent under a different climate, leaching of elements and mineral formation and transformation co…
Age and mineralogy of supergene uranium minerals — Tools to unravel geomorphological and palaeohydrological processes in granitic terrains (Bohemian …
2010
Abstract Uranyl phosphates (torbernite, autunite, uranocircite, saleeite) and hydrated uranyl silicates (normal and beta-uranophane) found in various erosion levels and structures in the Late Variscan granites at the western edge of the Bohemian Massif, Germany, were the target of mineralogical investigations and age dating, using conventional and more advanced techniques such as Laser-Ablation-Inductive-Coupled-Plasma Mass Spectrometry (LA-ICP-MS). Supergene U minerals have an edge over other rock-forming minerals for such studies, because of their inherent ‘clock’ and their swift response to chemical and physical environmental changes on different scales. Uraniferous phoscretes and silcre…
Two-Stage Origin of K-Enrichment in Ultrapotassic Magmatism Simulated by Melting of Experimentally Metasomatized Mantle
2019
The generation of strongly potassic melts in the mantle requires the presence of phlogopite in the melting assemblage, while isotopic and trace element analyses of ultrapotassic rocks frequently indicate the involvement of subducted crustal lithologies in the source. However, phlogopite-free experiments that focus on melting of sedimentary rocks and subsequent hybridization with mantle rocks at pressures of 1&ndash
Analytical study by SEM/EDX and metallographic techniques of materials used in the iron production process during the iberian period
2002
Abstract This work is the archaeometric study of different types of materials used in iron production in the Iberian Period (6th–2nd century b.c.). The materials were recovered in several archaeological digs (which makes it possible to date the archaeological remains) on different sites in the Levante area of the Iberian Peninsula. The samples selected for this study belong to different materials used in the ancient iron production process such as ores, slags, finished objects, etc. The use of scanning electron microscopy (SEM) is proposed to observe surface images of the samples to determine their morphological, microstructural and topographic characteristics to obtain valuable information…
Determination of the Porosity, Permeability and Diffusivity of Rock in the Excavation-Disturbed Zone Around Full-Scale Deposition Holes Using the He-…
1999
AbstractIn a nuclear waste repository, rock in the excavation-disturbed zone adjacent to the walls of deposition holes for waste canisters is a potential pathway for the transport of corrosive agents and radionuclides. Three experimental holes the size of deposition holes in a KBS-3 type repository (depth 7.5 m and diameter 1.5 m) were bored in hard granitic rock in the Research Tunnel at Olkiluoto and the porosities, effective diffusivities and permeabilities of rock in the excavation-disturbed zone were determined in a direction parallel to the disturbed surface using He-gas methods. Permeability and diffusivity in a direction parallel to the rock schistosity was found to be clearly large…
Dielectric characterization and ionic conductivity of α-LiIO3 crystals related to the growth conditions
2000
Abstract The dielectric response of α-LiIO3 has been studied at room temperature between 20 Hz and 1 MHz with various types of electrodes and compared to the results in the literature. By changing the sample thickness, a relaxation of space charges is clearly identified and the bulk ionic conductivity is deduced from the admittance diagram. Finally a comparison is carried out between chromium doped and undoped crystals obtained from acid and neutral growth solutions.
Non-linear dielectric behaviour and glass phase in Sr1-xCaxTiO3(x= 0.002 andx= 0.003)
1999
This work reports a study of the temperature and electric field dependence of the dielectric constant of strontium calcium titanate. The first part of the paper is focused on the analysis of a mean-field model for the polar clusters generated by the random impurities of calcium. It is shown that the dipolar moments within each cluster can be represented by an equivalent quantum two-level system. General expressions for the temperature and field dependence of the Edward-Anderson order parameter and of the electrical polarization are given. Analytical solutions are also obtained in the limit of high temperatures and in the limit of high tunnelling frequencies. The second part of the work repo…
Tuning the dielectric properties of hafnium silicate films
2007
The influence of Si concentration in hafnium silicate dielectrics on thermal stability and dielectric permittivity was analyzed. A phase diagram was developed using GIXRD and FTIR measurement. The stabilization of the ''higher-k'' cubic/tetragonal phase for annealing temperatures up to 1000^oC with a steady increase in capacitance was demonstrated for Hf"0"."9"4Si"0"."0"6O"2 films. It was also shown that the stabilization of nano-crystalline Hf"0"."8"0Si"0"."2"0O"2 films can be realized for annealing temperatures up to 900^oC. The influence of TiN electrodes on the dielectric constant and the leakage current characteristic was also investigated. A permittivity increase for annealing tempera…