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Crystal chemistry of Fe32+Cr2Si3O12–Fe32+Fe23+Si3O12 garnet solid solutions and related spinels

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Published/Copyright: April 1, 2015
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American Mineralogist
From the journal American Mineralogist Volume 94 Issue 2-3

Abstract

Garnet solid solutions have been synthesized across the skiagite-Fe-knorringite (Fe32+Fe23+Si3O12- Fe3Cr2Si3O12) binary join. Such compositions reflect a simple Cr-Fe3+ exchange on the octahedral sites, with Fe2+ occupying the adjacent dodecahedral sites. Solid solution is complete across the join and the correct stoichiometry was verified by Mössbauer spectroscopy. A symmetric fit to the molar volume data yields 119.77(2) cm3/mol [unit-cell parameter ao =11.6736(7) Å] for the Fe-knorringite end-member and a small negative excess volume, Wv = -0.76(15) cm3/mol. Combining this result with literature data reveals that binary joins involving octahedral site substitutions exhibit significantly different behavior than those where substitution occurs on the dodecahedral sites. In the former case, WV is usually negative, whereas the latter joins have positive deviations from ideal behavior. Therefore, we conclude that the garnet structure responds in a fundamentally different way when accommodating different cations on the dodecahedral or octahedral sites. Mössbauer spectra of skiagite-Fe-knorringite garnets do not exhibit any significant asymmetry in the [8]Fe2+ doublet. Fe3+/ΣFe values determined at room temperature and 80 K confirm the general applicability of the recoil-free fraction correction factors reported by Woodland and Ross (1994) for mixed-valence garnets. Coexisting spinels in some samples are either binary Fe3O4-Fe2SiO4 or Fe3O4-FeCr2O4 solid solutions. Very little mutual solubility is apparent suggesting a significant solvus may exist between the silicate and Cr-bearing spinel series.

Keywords : Fe-knorringite; Fe-Cr garnet; skiagite; molar volume; Mössbauer spectroscopy; excess thermodynamic properties; Fe-Cr spinel
Received: 2008-6-9
Accepted: 2008-10-30
Published Online: 2015-4-1
Published in Print: 2009-2-1

© 2015 by Walter de Gruyter Berlin/Boston

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  1. Determination of high-pressure phase equilibria of Fe2O3 using the Kawai-type apparatus equipped with sintered diamond anvils
  2. Suhailite, a new ammonium trioctahedral mica
  3. First record of K-cymrite in North Qaidam UHP eclogite, Western China
  4. Stability of uranium (VI) peroxide hydrates under ionizing radiation
  5. Heat capacities and thermodynamic functions of TiO2 anatase and rutile: Analysis of phase stability
  6. The behavior of Co and Ni in olivine in planetary basalts: An experimental investigation
  7. Partitioning of Ni between olivine and an iron-rich basalt: Experiments, partition models, and planetary implications
  8. The application of Lorentz transmission electron microscopy to the study of lamellar magnetism in hematite-ilmenite
  9. A Monte Carlo study of short- and long-range order of tetrahedral cations in sapphirine and khmaralite
  10. High-pressure ammonium-bearing silicates: Implications for nitrogen and hydrogen storage in the Earth’s mantle
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  12. U-Pb age, trace-element, and Hf-isotope compositions of zircon in a quartz vein from eclogite in the western Dabie Mountains: Constraints on fluid flow during early exhumation of ultrahigh-pressure rocks
  13. Interaction of phosphate-bearing solutions with gypsum: Epitaxy and induced twinning of brushite (CaHPO4·2H2O) on the gypsum cleavage surface
  14. Fukalite: An example of an OD structure with two-dimensional disorder
  15. Chemical control of 3T stacking order in a Li-poor biotite mica
  16. Site preference of U and Th in Cl, F, and Sr apatites
  17. High-pressure structural behavior of ingersonite, Ca3Mn2+Sb5+4O14: An in-situ single-crystal X-ray study
  18. Crystal chemistry of Fe32+Cr2Si3O12–Fe32+Fe23+Si3O12 garnet solid solutions and related spinels
  19. A method to synthesize large fluid inclusions in quartz at controlled times and under unfavorable growth conditions
  20. The stability of methane hydrate intercalates of montmorillonite and nontronite: Implications for carbon storage in ocean-floor environments
  21. Structure and carbonate orientation of vaterite (CaCO3)
  22. Qusongite (WC): A new mineral
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https://doi.org/10.2138/am.2009.3040
Keywords for this article
Fe-knorringite; Fe-Cr garnet; skiagite; molar volume; Mössbauer spectroscopy; excess thermodynamic properties; Fe-Cr spinel

Articles in the same Issue

  1. Determination of high-pressure phase equilibria of Fe2O3 using the Kawai-type apparatus equipped with sintered diamond anvils
  2. Suhailite, a new ammonium trioctahedral mica
  3. First record of K-cymrite in North Qaidam UHP eclogite, Western China
  4. Stability of uranium (VI) peroxide hydrates under ionizing radiation
  5. Heat capacities and thermodynamic functions of TiO2 anatase and rutile: Analysis of phase stability
  6. The behavior of Co and Ni in olivine in planetary basalts: An experimental investigation
  7. Partitioning of Ni between olivine and an iron-rich basalt: Experiments, partition models, and planetary implications
  8. The application of Lorentz transmission electron microscopy to the study of lamellar magnetism in hematite-ilmenite
  9. A Monte Carlo study of short- and long-range order of tetrahedral cations in sapphirine and khmaralite
  10. High-pressure ammonium-bearing silicates: Implications for nitrogen and hydrogen storage in the Earth’s mantle
  11. Formation of aragonite mesocrystals and implication for biomineralization
  12. U-Pb age, trace-element, and Hf-isotope compositions of zircon in a quartz vein from eclogite in the western Dabie Mountains: Constraints on fluid flow during early exhumation of ultrahigh-pressure rocks
  13. Interaction of phosphate-bearing solutions with gypsum: Epitaxy and induced twinning of brushite (CaHPO4·2H2O) on the gypsum cleavage surface
  14. Fukalite: An example of an OD structure with two-dimensional disorder
  15. Chemical control of 3T stacking order in a Li-poor biotite mica
  16. Site preference of U and Th in Cl, F, and Sr apatites
  17. High-pressure structural behavior of ingersonite, Ca3Mn2+Sb5+4O14: An in-situ single-crystal X-ray study
  18. Crystal chemistry of Fe32+Cr2Si3O12–Fe32+Fe23+Si3O12 garnet solid solutions and related spinels
  19. A method to synthesize large fluid inclusions in quartz at controlled times and under unfavorable growth conditions
  20. The stability of methane hydrate intercalates of montmorillonite and nontronite: Implications for carbon storage in ocean-floor environments
  21. Structure and carbonate orientation of vaterite (CaCO3)
  22. Qusongite (WC): A new mineral
  23. Nanoscale “liquid” inclusions of As-Fe-S in arsenian pyrite
  24. Water speciation in hydrous silicate and aluminosilicate glasses: Direct evidence from 29Si-1H and 27Al-1H double-resonance NMR
  25. Acid production by FeSO4·nH2O dissolution and implications for terrestrial and martian aquatic systems
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