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Charge contrast imaging of fine-scale microstructure and compositional variation in garnet using the environmental scanning electron microscope

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Published/Copyright: March 28, 2015
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American Mineralogist
From the journal American Mineralogist Volume 90 Issue 4

Abstract

Gaseous secondary electron (GSE) imaging of eclogite garnets under the environmental scanning electron microscope (ESEM) at low chamber gas pressures reveals detailed image contrast patterns (charge-contrast images, CCI) that are not present in back-scattered or secondary electron images. Image intensity is a function of the amount of surface charge accumulation. Successful acquisition of CCI depends on frame size and beam scan rate at a given chamber gas pressure and beam current. Images are obtained in a few seconds, and are stable and reproducible. CCI patterns do not correlate with cracks or grain boundaries, but do correspond closely to variations in major-element composition, both in the form of concentric (growth) zoning, and branching, linear features interpreted as cracks that have been healed by new garnet growth. Causes of CCI are not yet well understood, but may be related to variations in lattice defect density and their influence on charge-trapping and dissipation. These in turn influence the rate of charge build-up at or very close to the specimen surface. One interesting possibility is that CCI images detect vacancies related to non-homovalent coupled substitutions involving, for example, REE and hydroxyl, so the method offers a way of imaging the distribution of these trace species in garnets. The CCI images are rich in microstructural detail and offer the potential for rapid, high-resolution, low-noise reconnaissance mapping of intragranular microstructure and compositional variation in both natural and synthetic garnets.

Received: 2004-12-5
Accepted: 2004-11-30
Published Online: 2015-3-28
Published in Print: 2005-4-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Analytical perils (and progress) in electron microprobe trace element analysis applied to geochronology: Background acquisition, interferences, and beam irradiation effects
  2. Contributions to precision and accuracy of monazite microprobe ages
  3. Electron-microprobe age mapping of monazite
  4. Isotopic age constraints from electron microprobe U-Th-Pb dates, using a three-dimensional concordia diagram
  5. Monazite ages in the Chesham Pond Nappe, SW New Hampshire, U.S.A.: Implications for assembly of central New England thrust sheets
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  8. Re-examination of the hydrogarnet structure at high pressure using neutron powder diffraction and infrared spectroscopy
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  10. Crystal chemistry of the hydrothermally synthesized Na2(Mn1-xFex 2+)2Fe3+(PO4)3 alluaudite-type solid solution
  11. Thermodynamic properties of uvarovite garnet (Ca3Cr2Si3O12)
  12. Post-aragonite phase transformation in CaCO3 at 40 GPa
  13. Direct formation of the γ-CaSO4 phase in dehydration process of gypsum: In situ FTIR study
  14. The order-disorder character of FeOHSO4 obtained from the thermal decomposition of metahohmannite, Fe3+2(H2O)4[O(SO4)2]
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  16. Low-T neutron powder-diffraction and synchrotron-radiation IR study of synthetic amphibole Na(NaMg)Mg5Si8O22(OH)2
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  18. Piston-cylinder experiments on H2O undersaturated Fe-bearing systems: An experimental setup approaching fO₂ conditions of natural calc-alkaline magmas
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  20. The true structure of wonesite, an interlayer-deficient trioctahedral sodium mica
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  22. XRMapAnal: A program for analysis of quantitative X-ray maps
  23. Letter. Growth zoning and strain patterns inside diamond crystals as revealed by Raman maps
  24. Letter. Differentiation of commercial vermiculite based on statistical analysis of bulk chemical data: Fingerprinting vermiculite from Libby, Montana U.S.A.
  25. Letter. Crystal structure of single-crystal CaGeO3 tetragonal garnet synthesized at 3 GPa and 1000 °C
  26. Letter. Iron isotope exchange kinetics at the nanoparticulate ferrihydrite surface
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https://doi.org/10.2138/am.2005.1572

Articles in the same Issue

  1. Analytical perils (and progress) in electron microprobe trace element analysis applied to geochronology: Background acquisition, interferences, and beam irradiation effects
  2. Contributions to precision and accuracy of monazite microprobe ages
  3. Electron-microprobe age mapping of monazite
  4. Isotopic age constraints from electron microprobe U-Th-Pb dates, using a three-dimensional concordia diagram
  5. Monazite ages in the Chesham Pond Nappe, SW New Hampshire, U.S.A.: Implications for assembly of central New England thrust sheets
  6. Electron-microprobe dating as a tool for determining the closure of Th-U-Pb systems in migmatitic monazites
  7. Comparative isotopic and chemical geochronometry of monazite, with implications for U-Th-Pb dating by electron microprobe: An example from metamorphic rocks of the eastern Wyoming Craton (U.S.A.)
  8. Re-examination of the hydrogarnet structure at high pressure using neutron powder diffraction and infrared spectroscopy
  9. Anomalous elastic behavior and high-pressure structural evolution of zeolite levyne
  10. Crystal chemistry of the hydrothermally synthesized Na2(Mn1-xFex 2+)2Fe3+(PO4)3 alluaudite-type solid solution
  11. Thermodynamic properties of uvarovite garnet (Ca3Cr2Si3O12)
  12. Post-aragonite phase transformation in CaCO3 at 40 GPa
  13. Direct formation of the γ-CaSO4 phase in dehydration process of gypsum: In situ FTIR study
  14. The order-disorder character of FeOHSO4 obtained from the thermal decomposition of metahohmannite, Fe3+2(H2O)4[O(SO4)2]
  15. Temperature and composition dependence of structural phase transitions in Ca(TixZr1-x)OGeO4
  16. Low-T neutron powder-diffraction and synchrotron-radiation IR study of synthetic amphibole Na(NaMg)Mg5Si8O22(OH)2
  17. Charge contrast imaging of fine-scale microstructure and compositional variation in garnet using the environmental scanning electron microscope
  18. Piston-cylinder experiments on H2O undersaturated Fe-bearing systems: An experimental setup approaching fO₂ conditions of natural calc-alkaline magmas
  19. Environmentally important, poorly crystalline Fe/Mn hydrous oxides: Ferrihydrite and a possibly new vernadite-like mineral from the Clark Fork River Superfund Complex
  20. The true structure of wonesite, an interlayer-deficient trioctahedral sodium mica
  21. Clinoholmquistite discredited: The new amphibole end-member fluoro-sodic-pedrizite
  22. XRMapAnal: A program for analysis of quantitative X-ray maps
  23. Letter. Growth zoning and strain patterns inside diamond crystals as revealed by Raman maps
  24. Letter. Differentiation of commercial vermiculite based on statistical analysis of bulk chemical data: Fingerprinting vermiculite from Libby, Montana U.S.A.
  25. Letter. Crystal structure of single-crystal CaGeO3 tetragonal garnet synthesized at 3 GPa and 1000 °C
  26. Letter. Iron isotope exchange kinetics at the nanoparticulate ferrihydrite surface
  27. Letter. Cation distribution in MgFe2O4 vs. pressure and temperature: Experiments in a piston-cylinder apparatus
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