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Anatomy of a metabentonite: Nucleation and growth of illite crystals and their coalescence into mixed-layer illite/smectite

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Published/Copyright: April 2, 2015
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American Mineralogist
From the journal American Mineralogist Volume 96 Issue 4

Abstract

The illite layer content of mixed-layer illite/smectite (I/S) in a 2.5 m thick, zoned, metabentonite bed from Montana decreases regularly from the edges to the center of the bed. Traditional X-ray diffraction (XRD) pattern modeling using Markovian statistics indicated that this zonation results from a mixing in different proportions of smectite-rich R0 I/S and illite-rich R1 I/S, with each phase having a relatively constant illite layer content. However, a new method for modeling XRD patterns of I/S indicates that R0 and R1 I/S in these samples are not separate phases (in the mineralogical sense of the word), but that the samples are composed of illite crystals that have continuous distributions of crystal thicknesses, and of 1 nm thick smectite crystals. The shapes of these distributions indicate that the crystals were formed by simultaneous nucleation and growth. XRD patterns for R0 and R1 I/S arise by interparticle diffraction from a random stacking of the crystals, with swelling interlayers formed at interfaces between crystals from water or glycol that is sorbed on crystal surfaces. It is the thickness distributions of smectite and illite crystals (also termed fundamental particles, or Nadeau particles), rather than XRD patterns for mixed-layer I/S, that are the more reliable indicators of geologic history, because such distributions are composed of well-defined crystals that are not affected by differences in surface sorption and particle arrangements, and because their thickness distribution shapes conform to the predictions of crystal growth theory, which describes their genesis.

Keywords : Illite; smectite; diagenesis; mixed-layer clay; bentonite; metabentonite; crystal growth
Received: 2010-8-31
Accepted: 2010-11-6
Published Online: 2015-4-2
Published in Print: 2011-4-1

© 2015 by Walter de Gruyter Berlin/Boston

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  1. Roebling Medal Lecture. The three partners of metamorphic petrology
  2. Relationship between structure, morphology, and carbon isotopic composition of graphite in marbles: Implications for calcite-graphite carbon isotope thermometry
  3. Crystal structure, mosaicity, and strain analysis of Hawaiian olivines using in situ X-ray diffraction
  4. Characterization of deep weathering and nanoporosity development in shale—A neutron study
  5. Structural water in ferrihydrite and constraints this provides on possible structure models
  6. Critical evaluation of the revised akdalaite model for ferrihydrite
  7. Neutron diffraction study of hydrogen in birnessite structures
  8. Pressless split-sphere apparatus equipped with scaled-up Kawai-cell for mineralogical studies at 10–20 GPa
  9. Dislocation microstructures in majorite garnet experimentally deformed in the multi-anvil apparatus
  10. Density of carbonated peridotite magma at high pressure using an X-ray absorption method
  11. Stability and bulk modulus of Ni3S, a new nickel sulfur compound, and the melting relations of the system Ni-NiS up to 10 GPa
  12. Far-infrared spectra of synthetic [4][(Al2-xGax)(Si2–yGey)](OH,OD,F)2-kinoshitalite: Characterization and assignment of interlayer Ba-Oinner and Ba-Oouter stretching bands
  13. High-temperature elasticity of polycrystalline orthoenstatite (MgSiO3)
  14. Anatomy of a metabentonite: Nucleation and growth of illite crystals and their coalescence into mixed-layer illite/smectite
  15. Zn-O tetrahedral bond length variations in normal spinel oxides
  16. A new thermodynamic analysis of the intergrowth of hedenbergite and magnetite with Ca-Fe-rich olivine
  17. Raman spectroscopic investigations of some Tl-sulfosalt minerals containing pyramidal (As,Sb)S3 groups
  18. A first record of strong structural relaxation of TO4 tetrahedra in a spinel solid solution
  19. The high-pressure behavior of orthorhombic amphiboles
  20. XAS determination of the Fe local environment and oxidation state in phonolite glasses
  21. Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)
  22. Light-induced molecular change in HgI2·As4S4: Evidence by single-crystal X-ray diffraction and Raman spectroscopy
  23. Low-temperature electron paramagnetic resonance studies on natural calumetite from Khetri copper mine, Rajasthan, India
  24. Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert
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https://doi.org/10.2138/am.2011.3682
Keywords for this article
Illite; smectite; diagenesis; mixed-layer clay; bentonite; metabentonite; crystal growth

Articles in the same Issue

  1. Roebling Medal Lecture. The three partners of metamorphic petrology
  2. Relationship between structure, morphology, and carbon isotopic composition of graphite in marbles: Implications for calcite-graphite carbon isotope thermometry
  3. Crystal structure, mosaicity, and strain analysis of Hawaiian olivines using in situ X-ray diffraction
  4. Characterization of deep weathering and nanoporosity development in shale—A neutron study
  5. Structural water in ferrihydrite and constraints this provides on possible structure models
  6. Critical evaluation of the revised akdalaite model for ferrihydrite
  7. Neutron diffraction study of hydrogen in birnessite structures
  8. Pressless split-sphere apparatus equipped with scaled-up Kawai-cell for mineralogical studies at 10–20 GPa
  9. Dislocation microstructures in majorite garnet experimentally deformed in the multi-anvil apparatus
  10. Density of carbonated peridotite magma at high pressure using an X-ray absorption method
  11. Stability and bulk modulus of Ni3S, a new nickel sulfur compound, and the melting relations of the system Ni-NiS up to 10 GPa
  12. Far-infrared spectra of synthetic [4][(Al2-xGax)(Si2–yGey)](OH,OD,F)2-kinoshitalite: Characterization and assignment of interlayer Ba-Oinner and Ba-Oouter stretching bands
  13. High-temperature elasticity of polycrystalline orthoenstatite (MgSiO3)
  14. Anatomy of a metabentonite: Nucleation and growth of illite crystals and their coalescence into mixed-layer illite/smectite
  15. Zn-O tetrahedral bond length variations in normal spinel oxides
  16. A new thermodynamic analysis of the intergrowth of hedenbergite and magnetite with Ca-Fe-rich olivine
  17. Raman spectroscopic investigations of some Tl-sulfosalt minerals containing pyramidal (As,Sb)S3 groups
  18. A first record of strong structural relaxation of TO4 tetrahedra in a spinel solid solution
  19. The high-pressure behavior of orthorhombic amphiboles
  20. XAS determination of the Fe local environment and oxidation state in phonolite glasses
  21. Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)
  22. Light-induced molecular change in HgI2·As4S4: Evidence by single-crystal X-ray diffraction and Raman spectroscopy
  23. Low-temperature electron paramagnetic resonance studies on natural calumetite from Khetri copper mine, Rajasthan, India
  24. Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert
  25. Hazenite, KNaMg2(PO4)2⋅14H2O, a new biologically related phosphate mineral, from Mono Lake, California, U.S.A.
  26. The fractional latent heat of crystallizing magmas
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