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Assessment of cation substitutions along the gallium and fluorine analogue of the tremolite-glaucophane join

  • Michael S. Pavlovich EMAIL logo
Published/Copyright: March 31, 2015
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American Mineralogist
From the journal American Mineralogist Volume 88 Issue 10

Abstract

Assessment of the glaucophane substitution, [M4]Ca + [VI]Mg ↔[M4]Na + [VI]Al, along the Ga and F analogue of the tremolite-glaucophane join, ⃞Ca2Mg5Si8O22F2-⃞Na2Mg3Ga2Si8O22F2 (= F-Ga-glauc), was conducted at 900 °C and 1.5 GPa in 10 mol% increments. Several chemical exchanges deviating from the glaucophane substitution were identified, namely the “edenite” substitution [A] ⃞ + [IV]Si ↔[A]Na + [IV]Ga toward F-Ga-nyböite, the [A] ⃞ + [M4]Na + [VI]Ga + [IV]Si ↔[A]Na + [M4]Mg + [VI]Mg + [IV]Ga exchange toward F-Ga-Na-magnesiokatophorite, and the [A] ⃞ + [VI]Ga ↔[A]Na + [VI]Mg exchange toward F-Ga-eckermannite. Minor displacements from the join due to the [M4]Na + [VI]Ga ↔ [M4]Mg + [VI]Mg exchange toward “cummingtonite” and the richterite exchange [A] ⃞ + [M4]Ca ↔ [A]Na + [M4]Na were also observed. Amphibole syntheses with low F-Ga-glauc contents (≤ 60 mol%) were primarily influenced by the “edenite” exchange, while those with high F-Ga-glauc contents (≈ 70 mol%) were dominated by the “glaucophane” substitution. Powder X-ray diffraction Rietveld refinements were obtained without restrictions for the amphiboles formed in the range 0-40 mol% FGa- glauc. Refinements for samples in the ranges of 50-70 and 100 mol% F-Ga-glauc were possible only after applying some restrictions to the A- and M4-site occupancies because of the appearance of a layered silicate and an unidentified Ga-rich phase that complicated the refinement. The successful refinements indicated that amphibole exhibits [VI]Ga ordering at the M2 site and [IV]Ga ordering at T1. The refinements also show a transition in A-site occupancy from A2 to Am with increasing FGa- glauc content. The inability to synthesize stoichiometric glaucophane and the types of chemical deviations that are observed in this analogue system are virtually identical to what has been observed in previous studies. Extrapolation of the results from this and previous studies suggests that ideal glaucophane would be obtained at approximately 3.85 GPa and 585 °C.

Received: 2002-8-5
Accepted: 2003-3-31
Published Online: 2015-3-31
Published in Print: 2003-10-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Structural systematics of hydrous ringwoodite and water in earth’s interior
  2. Compressibility of phase Egg AlSiO3OH: Equation of state and role of water at high pressure
  3. Synchrotron infrared spectroscopy of OH-chondrodite and OH-clinohumite at high pressure
  4. Structural deformation mechanisms of zeolites under pressure
  5. Variation of hydrogen bonded O···O distances in goethite at high pressure
  6. Pressure-controlled polytypism in hydrous layered materials
  7. OH– in synthetic and natural coesite
  8. Pressure-induced phase transformation of kalicinite (KHCO3) at 2.8 GPa and local structural changes around hydrogen atoms
  9. Potential docking sites and positions of hydrogen in high-pressure silicates
  10. Contrasting bonding behavior of two hydroxyl-bearing metamorphic minerals under pressure: Clinozoisite and topaz
  11. Experimental investigation of crystallization kinetics in a haplogranite system
  12. Assessment of cation substitutions along the gallium and fluorine analogue of the tremolite-glaucophane join
  13. Experimental hydrothermal alteration of partially metamict zircon
  14. On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion
  15. Ordering in spinels—A Monte Carlo study
  16. Single-crystal in situ high-temperature structural investigation of the I1̅ –I2/c phase transition in Ca0.2Sr0.8Al2Si2O8 feldspar
  17. New clinopyroxene-liquid thermobarometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho
  18. Fe and Ni impurities in synthetic diamond
  19. Phase transformations and reaction kinetics during the temperature-induced oxidation of natural olivine
  20. Thermal infrared spectroscopy and modeling of experimentally shocked plagioclase feldspars
  21. Oxygen isotopic composition of nano-scale uraninite at the Oklo-Okélobondo natural fission reactors, Gabon
  22. Clinopyroxenite from the Sulu ultrahigh-pressure terrane, eastern China: Origin and evolution of garnet exsolution in clinopyroxene
  23. Letters. An assessment of nuclear microprobe analyses of B in silicate minerals
  24. Incommensurate phase in the kosmochlor-diopside join: A new polymorph of clinopyroxene
  25. Elastic properties of hydrous ringwoodite
  26. Thermochemistry of guest-free melanophlogite
  27. A simple model for the pressure preservation index of inclusions in diamond
https://doi.org/10.2138/am-2003-1012

Articles in the same Issue

  1. Structural systematics of hydrous ringwoodite and water in earth’s interior
  2. Compressibility of phase Egg AlSiO3OH: Equation of state and role of water at high pressure
  3. Synchrotron infrared spectroscopy of OH-chondrodite and OH-clinohumite at high pressure
  4. Structural deformation mechanisms of zeolites under pressure
  5. Variation of hydrogen bonded O···O distances in goethite at high pressure
  6. Pressure-controlled polytypism in hydrous layered materials
  7. OH– in synthetic and natural coesite
  8. Pressure-induced phase transformation of kalicinite (KHCO3) at 2.8 GPa and local structural changes around hydrogen atoms
  9. Potential docking sites and positions of hydrogen in high-pressure silicates
  10. Contrasting bonding behavior of two hydroxyl-bearing metamorphic minerals under pressure: Clinozoisite and topaz
  11. Experimental investigation of crystallization kinetics in a haplogranite system
  12. Assessment of cation substitutions along the gallium and fluorine analogue of the tremolite-glaucophane join
  13. Experimental hydrothermal alteration of partially metamict zircon
  14. On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion
  15. Ordering in spinels—A Monte Carlo study
  16. Single-crystal in situ high-temperature structural investigation of the I1̅ –I2/c phase transition in Ca0.2Sr0.8Al2Si2O8 feldspar
  17. New clinopyroxene-liquid thermobarometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho
  18. Fe and Ni impurities in synthetic diamond
  19. Phase transformations and reaction kinetics during the temperature-induced oxidation of natural olivine
  20. Thermal infrared spectroscopy and modeling of experimentally shocked plagioclase feldspars
  21. Oxygen isotopic composition of nano-scale uraninite at the Oklo-Okélobondo natural fission reactors, Gabon
  22. Clinopyroxenite from the Sulu ultrahigh-pressure terrane, eastern China: Origin and evolution of garnet exsolution in clinopyroxene
  23. Letters. An assessment of nuclear microprobe analyses of B in silicate minerals
  24. Incommensurate phase in the kosmochlor-diopside join: A new polymorph of clinopyroxene
  25. Elastic properties of hydrous ringwoodite
  26. Thermochemistry of guest-free melanophlogite
  27. A simple model for the pressure preservation index of inclusions in diamond
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