An Evaluation of Dating of Diagenetic Xenotime by Electron Microprobe.

Xenotime is an igneous mineral commonly present in pegmatite and fractionated granite. Recent studies reveal that it also forms as a diagenetic mineral. Minute (0.1-5 μm) xenotime overgrowths typically crystallise on the surfaces of detrital zircon shortly after sedimentation, in a wide range of siliciclastic sedimentary units. For example, in backscattered electron (BSE) imaging using a scanning electron microscope (SEM), two minute, euhedral, pyramidal, xenotime overgrowths on an oscillatory-zoned detrital Ambergate zircon are evident (figure 1).Electron microprobe analysis (EMPA) geochronology is a chemical dating method that uses precisely measured concentrations of U, Th, and Pb, and the decay rates of U238, U235, and Th232, to calculate an age for a mineral. The EMPA dating method used in this study to date igneous xenotime and igneous-metamorphic monazite is the chemical isochron method (CHIME). EMPA geochronology is not a widely used technique because of the higher precision of isotopic geochronology.

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Improved X-ray Spectrum Simulation for Electron Microprobe Analysis

Microscopy and Microanalysis ◽

10.1007/s10005-001-0010-6 ◽

2001 ◽

Vol 7 (4) ◽

pp. 341-355 ◽

Cited By ~ 2

Author(s):

Peter Duncumb ◽

Ian R. Barkshire ◽

Peter J. Statham

Keyword(s):

Electron Microprobe ◽

Microprobe Analysis ◽

Electron Microprobe Analysis ◽

Background Radiation ◽

Collection Efficiency ◽

Fast Method ◽

X Ray ◽

Peak Intensity ◽

Spectrum Simulation ◽

Wide Range

AbstractThe accurate calculation of characteristic peak intensity is essential for interpreting X-ray spectra in electron microprobe analysis. Conventionally, the measured intensity from a standard of known composition is used as a reference to simplify the calculation. However, if no such standard is available, then all factors influencing X-ray generation and X-ray detection efficiency must be included. If the intensity and energy distribution of the background radiation can also be calculated, the investigator can simulate an entire spectrum from an assumed composition, gaining powerful benefits in setting up an experiment and in confirming the results. The study presented here demonstrates a fast method of spectrum simulation, suitable for energydispersive spectroscopy (EDS), and assesses the accuracy using 309 spectra from samples of known composition. These include K, L, and M lines from elements of atomic number 6–92, excited by beam energies in the range of 5–30 keV. The RMS error between 360 measured and calculated peak intensities was found to be 7.1%. Central to the method is the use of the ratio of peak intensity/total background intensity, which allows spectra to be compared from instruments of differing collection efficiency, thereby easing the collection of data over a wide range of conditions.

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Silver mineralization at Sark's Hope mine, Sark, Channel Islands

Mineralogical Magazine ◽

10.1180/minmag.1983.047.345.15 ◽

1983 ◽

Vol 47 (345) ◽

pp. 539-545 ◽

Cited By ~ 5

Author(s):

R. A. Ixer ◽

C. J. Stanley

Keyword(s):

Electron Microprobe ◽

Manganese Oxides ◽

Microprobe Analysis ◽

Electron Microprobe Analysis ◽

Late Precambrian ◽

Wide Range ◽

Ore Minerals ◽

Growth Zoning ◽

Silver Mineralization ◽

Iron And Manganese

AbstractSark's Hope silver-lead lode, which was mined during the 1830s and 1840s cuts a Late Precambrian granite at the southernmost point of the island of Sark. The primary ore assemblage is pyrite, galena, chalcopyrite, tennantite, tetrahedrite, sphalerite, marcasite, arsenopyrite, pyrrhotine, bravoite, enargite, and the silver minerals pyrargyrite, pearceite, polybasite, and acanthite. Gangue minerals are hematitic quartz, calcite, and illite. Alteration products include chalcosine, covelline, blaubleibender covelline, limonite, malachite, azurite, cerussite, and anglesite. The generalized paragenesis is of early Fe, Co, Ni, As, and S species and later minerals of Pb, Cu, Ag, Zn, Fe, As, Sb, and S. The earliest alteration products are copper sulphides; these are followed by lead and copper carbonates and sulphates, and hydrated iron and manganese oxides. Growth zoning is a common feature of many of the ore minerals, and electron microprobe analysis shows that this is sometimes related to compositional differences. Tetrahedrite and tennantite, particularly, exhibit a wide range of compositions.

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Scanning Electron Microscopy and Electron Microprobe Analysis of Malignant Cell Cultures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100561 ◽

1968 ◽

Vol 26 ◽

pp. 164-165

Author(s):

R. I. Johnsson-Hegyeli ◽

A. F. Hegyeli ◽

D. K. Landstrom ◽

W. C. Lane

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Cell Cultures ◽

Electron Microprobe ◽

Microprobe Analysis ◽

Electron Microprobe Analysis ◽

Three Dimensional ◽

Malignant Cell ◽

Interference Microscopy ◽

Scanning Electron

Last year we reported on the use of reflected light interference microscopy (RLIM) for the direct color photography of the surfaces of living normal and malignant cell cultures without the use of replicas, fixatives, or stains. The surface topography of living cells was found to follow underlying cellular structures such as nuceloli, nuclear membranes, and cytoplasmic organelles, making possible the study of their three-dimensional relationships in time. The technique makes possible the direct examination of cells grown on opaque as well as transparent surfaces. The successful in situ electron microprobe analysis of the elemental composition and distribution within single tissue culture cells was also reported.This paper deals with the parallel and combined use of scanning electron microscopy (SEM) and the two previous techniques in a study of living and fixed cancer cells. All three studies can be carried out consecutively on the same experimental specimens without disturbing the cells or their structural relationships to each other and the surface on which they are grown. KB carcinoma cells were grown on glass coverslips in closed Leighto tubes as previously described. The cultures were photographed alive by means of RLIM, then fixed with a fixative modified from Sabatini, et al (1963).

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