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Electron Microprobe Analysis (electron + microprobe_analysis)
Selected AbstractsA comparative electron microprobe study of "Aeginetan" wares with potential raw material sources from Aegina, Methana, and Poros, GreeceGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2002Michael J. Dorais Qualitative stylistic evidence from ceramic vessels and limited petrographic analysis suggested that a distinctive group of ceramics with visible inclusions of biotite (Gold Mica Fabric) was produced on the island of Aegina, Greece, during the Middle Helladic and Late Helladic I periods. To quantitatively evaluate this provenance, we sampled all potential source rocks on Aegina, Methana, and Poros. Electron microprobe analysis of amphibole in these samples revealed that each of these volcanic centers has its own unique mineralogical signature. Comparative analyses of amphibole in Zerner's original stylistic "Gold Mica Fabric" type sample with the reference samples reveal that two sherds are Aeginetan. Three additional sherds from this sample may have a non-Aeginetan provenance, probably from a back-arc setting outside the Saronic Gulf. These results suggest that the hypothesis of a single source production site for Aeginetan Ware should be reexamined. © 2002 Wiley Periodicals, Inc. [source] Metamorphic diogenite Grosvenor Mountains 95555: Mineral chemistry of orthopyroxene and spinel and comparisons to the diogenite suiteMETEORITICS & PLANETARY SCIENCE, Issue 4 2000J. J. PAPIKE It does not show the usual brecciated appearance of other diogenites or wide compositional variability of orthopyroxene or spinel. Electron microprobe analysis (EMPA) and secondary ion mass spectrometer (SIMS) analysis of orthopyroxene and EMPA of spinel show limited compositional variability. Compositions for orthopyroxene for Fe/(Fe + Mg) atomic, Al, Zr, Y, and Yb fall in the middle of the compositional ranges of the diogenite suite. Apparently, GRO 95555 formed at sufficient depth or location to escape brecciation by meteorite bombardment and in a thermal regime that led to high-grade metamorphism resulting in homogeneous mineral compositions. [source] Diffusion couple studies of the Ti-Bi-Zn systemCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2004G. P. Vassilev Abstract The system Ti-Bi-Zn has been investigated using diffusion couples consisting of solid Ti and liquid (Bi+Zn) phase. The diffusion paths at 400, 500, 700 and 800 °C have been traced by means of electron microprobe analyses. The growth constants of the diffusion layers are roughly assessed. The phase diagram data obtained in this investigation are compared with previous studies of equilibrated alloys. The existence of the ternary compound TiBiZn has been confirmed. The formation of another phase with approximate formulae Ti4Bi3Zn to Ti9Bi7Zn4 has been observed at high temperatures. The latter compound as well as the ternary extension of the TiXBiY (X , 5, Y , 6) phase react easily with air. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystallization of Highly Supercooled Silicate MeltsADVANCED ENGINEERING MATERIALS, Issue 12 2006M. Roskosz Crystallization of liquids in the system CaO-MgO-Al2O3 -SiO2 at one atmosphere has been studied at temperatures between the glass transition (Tg) and the solidus. To determine the textures, compositions and unit-cell parameters of the crystalline phases, the authors have characterized the experimental charges over a wide range of length scales by scanning and transmission electron microscopy, electron microprobe analyses, X-ray diffraction, and Raman spectroscopy. With increasing temperature, crystals tend to reach the equilibrium composition, but the relative importance of thermodynamic and kinetic factors is a single function of T - Tg, regardless of liquid composition. This feature is of considerable practical interest as it provides the possibility, not only to predict, but also to control the composition of the crystallizing phases. [source] Late Cretaceous-Cenozoic exhumation of the Yanji area, northeast China: Constraints from fission-track thermochronologyISLAND ARC, Issue 1 2010Xiaoming Li Abstract The Yanji area, located at the border of China, Russia, and Korea, where the Phanerozoic granitoids have been widely exposed, was considered part of the orogenic collage between the North China Block in the south and the Jiamusi,Khanka Massifs in the northeast. In this study, the cooling and inferred uplift and denudation history since the late Mesozoic are intensively studied by carrying out apatite and zircon fission-track analyses, together with electron microprobe analyses (EMPA) of chemical compositions of apatite from the granitoid samples in the Yanji area. The results show that: (i) zircon and apatite fission-track ages range 91.7,99.6 Ma and 76.5,85.4 Ma, respectively; (ii) all apatite fission-track length distributions are unimodal and yield mean lengths of 12,13.2 µm, and the apatites are attributed to chlorine-bearing fluorapatite as revealed by EMPA results; and (iii) the thermal history modeling results based on apatite fission-track grain ages and length distributions indicate that the time,temperature paths display similar patterns and the cooling has been accelerated for each sample since ca 15 Ma. Thus, we conclude that sequential cooling, involving two rapid (95,80 Ma and ca 15,0 Ma) and one slow (80,15 Ma) cooling, has taken place through the exhumation of the Yanji area since the late Cretaceous. The maximum exhumation is more than 5 km under a steady-state geothermal gradient of 35°C/km. Combined with the tectonic setting, this exhumation is possibly related to the subduction of the Pacific Plate beneath the Eurasian Plate since the late Cretaceous. [source] Chemical characterization of ancient pottery from sudan by x-ray fluorescence spectrometry (xrf), electron microprobe analyses (empa) and inductively coupled plasma mass spectrometry (ICP,MS),ARCHAEOMETRY, Issue 3 2004M. Klein Sixty-four sherds and seven natural clays from prehistoric sites in northwestern Sudan have been submitted to petrological and chemical analysis using XRF spectrometry, EMPA and ICP,MS. According to their texture, the sherds form five different groups. The high contents of P2O5 (more than 0.5 wt%) discerned in 19 samples and the variation of the P2O5 content in two samples of the same vessel can be explained by post-depositional processes or by the ancient organic contents (e.g., milk) of the vessel. Chemical classification of the pottery bulk suggests that vessels were made locally, as only sherds from the same area show homogeneity of data. [source] A new piezoelectric single crystal obtained by Ge doping in the SiO2 structureCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2009M. Miclau Abstract The interest of Si1,xGexO2 single crystals with alpha-quartz structure is connected to improvement of electromechanical coefficients and rise of , , , phase transition of quartz one. Growth of an ,-SixGe1,xO2 crystal was realized by a hydrothermal method of temperature gradient in autoclaves, made from Cr,Ni alloys. Nutrient material was prepared from synthetic quartz as crashed rods and placed in the bottom of autoclaves. There was loaded GeO2 powder additive in proportions to quartz nutrient. Single crystals were investigated by electron microprobe analysis, X-ray diffraction and atomic force microscopy. The most important result, which was obtained during the investigations, is an experimental proof of growth of ,-SixGe1,xO2 single crystals under the hydrothermal conditions. The present results thus open the possibility to tune the piezoelectric properties of these materials by varying the chemical composition. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ultrahigh-pressure metamorphic records hidden in zircons from amphibolites in Sulu Terrane, eastern ChinaISLAND ARC, Issue 3 2003Fulai Liu Abstract The amphibolites occur sporadically as thin layers and blocks throughout the Sulu Terrane, eastern China. All analyzed amphibolite from outcrop and drill cores from prepilot drill hole CCSD-PP1 and CCSD-PP2, Chinese Continental Scientific Drilling Project in the Sulu Terrane, are retrograded eclogites overprinted by amphibolite-facies retrograde metamorphism, with characteristic mineral assemblages of amphibole + plagioclase + epidote ± quartz ± biotite ± ilmenite ± titanite. However, coesite and coesite-bearing ultrahigh-pressure (UHP) mineral assemblages are identified by Raman spectroscopy and electron microprobe analysis as inclusions in zircons separated from these amphibolites. In general, coesite and other UHP mineral inclusions are preserved in the cores and mantles of zircons, whereas quartz inclusions occur in the rims of the same zircons. The UHP mineral assemblages consist mainly of coesite + garnet + omphacite + rutile, coesite + garnet + omphacite, coesite + garnet + omphacite + phengite + rutile + apatite, coesite + omphacite + rutile and coesite + magnesite. Compositions of analyzed mineral inclusions are very similar to those of matrix minerals from Sulu eclogites. These UHP mineral inclusion assemblages yield temperatures of 631,780°C and pressures of ,2.8 × 103 MPa, representing the P,T conditions of peak metamorphism of these rocks, which are consistent with those (T = 642,726°C; P , 2.8 × 103 MPa) deduced from adjacent eclogites. These data indicate that the amphibolites are the retrogressive products of UHP eclogites. [source] Tephrological implications of beam size,sample-size effects in electron microprobe analysis of glass shardsJOURNAL OF QUATERNARY SCIENCE, Issue 2 2001John B. Hunt Abstract This paper concerns the potential consequences of varying procedures for the determination of tephra geochemistry by electron microprobe. Application of electron probe microanalysis to tephrostratigraphical methods has increasingly facilitated the resolution and refinement of Quaternary chronology associated with records of proxy-environmental or proxy-climatic change. The geographical range over which tephras are recovered has expanded significantly with the identification and analysis of crypto (or hidden) tephras in areas far removed from tephra sources. These tephras are dominated by glass shards, which, in many distal environments, may be either small in size (,m) or may be highly pumiceous with low glass:void ratios and thin (<10 ,m) shard walls. We demonstrate that reducing the size of the electron beam used to analyse shard geochemistry cannot be used reliably to permit analysis of thin glass walls. This approach distorts the geochemical data, creating analytical differences that may generate inappropriate tephrogeochemical fingerprints. Additional distortion of the geochemical fingerprint in the form of hybrid analyses may be encountered in glass fragments containing micron-sized crystalline phases such as feldspar. Copyright © 2001 John Wiley & Sons, Ltd. [source] Grain-Boundary Diffusion of Cr in Pure and Y-Doped AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007K. Bedu-Amissah The diffusive transport of chromium in both pure and Y-doped fine-grained alumina has been investigated over the temperature range 1250°,1650°C. From a quantitative assessment of the chromium diffusion profile in alumina, as obtained from electron microprobe analysis, it was found that yttrium doping retards cation diffusion in the grain-boundary regime by over an order of magnitude. The Arrhenius equations for the undoped and Y-doped samples were determined to be: ,Db=(4.77±0.24) × 10,7 exp (,264.78±47.68 (kJ/mol)/RT)(cm3/s) and ,Db=(6.87±0.18) × 10,8 exp (,284.91±42.57 (kJ/mol)/RT)(cm3/s), respectively. Finally, to elucidate the mechanism for this retardation, the impact of yttrium doping on diffusion activation energies and prefactors was examined. [source] A STUDY OF GLASS TESSERAE FROM MOSAICS IN THE MONASTERIES OF DAPHNI AND HOSIOS LOUKAS (GREECE)ARCHAEOMETRY, Issue 5 2010R. ARLETTI In this work 51 glass mosaic tesserae from decorations of the two Greek monasteries of Daphni and Hosios Loukas were analysed by inductively coupled plasma optical emission spectroscopy, electron microprobe analysis and X-ray powder diffraction. On the basis of the chemical analyses, after discrimination between the tesserae of the original decorations and those from other periods, it was possible to outline the distinctive traits of Byzantine mosaic tesserae. In both the monasteries, the original mosaics were decorated with tesserae produced with plant ash based glass, either of the typical composition or a mixture with natron type glass. The samples from the Hosios Loukas decorations show a more homogeneous composition compared with those from Daphni. The major differences among the original samples are due to the presence of opacifiers and colourants. [source] | |||||||||||||||||||