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Single-crystal thermometric calibration of Fe-Mg order-disorder in pigeonites

  • Daria Pasqual , Gianmario Molin EMAIL logo and Mario Tribaudino
Published/Copyright: March 26, 2015
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American Mineralogist
From the journal American Mineralogist Volume 85 Issue 7-8

Abstract

The single-crystal X-ray technique was used to calibrate a new intracrystalline geothermometer based on equilibrium Mg-Fe* fractionation (Fe* = Fe2+ + Mn2+) between M1 and M2 sites of natural P21/c pigeonite. Suitable crystals free of exsolution textures and sharp diffraction maxima were selected by careful TEM and XRD investigations from a large number of samples. Two single crystals, PCA82506-3 (Wo6En76Fs18) from the Pecora Escarpment 82506 Antarctic ureilite, and BTS308- 2 (Wo10En47Fs43) from the BTS308 Paranà rhyodacite, were annealed at temperatures ranging from 600 to 1000 °C. The TEM investigation, carried out on fragments of selected single crystals both before and after thermal treatment, shows heating-induced texture modifications preliminary to spinodal decomposition in both crystals and a size increase in antiphase domains in BTS308-2. The two geothermometric equations calculated by linear regression of ln KD* vs. 1/T are:

ln KD* = -3291(± 269)/T(K) + 0.971(±0.253); (r2 = 0.974)

ln KD* = -2816(± 83)/T(K) + 0.542(±0.083); (r2 = 0.995)

respectively for PCA82506-3 (XFe* = 0.20) and BTS308-2 (XFe* = 0.49) [XFe* = Fe*/(Fe* + Mg)]. These results imply negligible compositional effects on Mg-Fe* site partitioning within the range of compositions encompassed by the samples. Comparison of the intracrystalline fractionation data of pigeonites with those of Pbca orthopyroxenes shows a similar degree of ordering for both at a given temperature. This result suggests only a small effect of Ca on Fe*-Mg ordering in pyroxene with Ca content up to Wo10-.

Received: 1999-6-29
Accepted: 2000-1-23
Published Online: 2015-3-26
Published in Print: 2000-7-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Application of new experimental and garnet Margules data to the garnet-biotite geothermometer
  2. Volumes of mixing in aluminosilicate garnets: Solid solution and strain behavior
  3. Cerium anomaly and Th/U fractionation in the 1.85 Ga Flin Flon Paleosol: Clues from REE- and U-rich accessory minerals and implications for paleoatmospheric reconstruction
  4. Os solubility in silicate melts: New efforts and results
  5. Enstatite-forsterite-water equilibria at elevated temperatures and pressures
  6. The OH-F substitution in synthetic pargasite at 1.5 kbar, 850 °C
  7. Uptake of aqueous Pb by Cl-, F–, and OH– apatites: Mineralogic evidence for nucleation mechanisms
  8. Temperature dependence of the hyperfine parameters of synthetic P21/c Mg-Fe clinopyroxenes along the MgSiO3-FeSiO3 join
  9. Single-crystal thermometric calibration of Fe-Mg order-disorder in pigeonites
  10. TEM observations on the P1̄ -I1̄ phase transition in feldspars along the join CaAl2Si2O8-SrAl2Si2O8
  11. Phase transitions induced by solid solution in stuffed derivatives of quartz: A powder synchrotron XRD study of the LiAlSiO4-SiO2 join
  12. The transformation of andalusite to mullite and silica: Part I. Transformation mechanism in [001]A direction
  13. The transformation of andalusite to mullite and silica: Part II. Transformation mechanisms in [100]A and [010]A directions
  14. Structure and twinning of tetragonal Ca3Mn2Ge3O12 garnet
  15. The equation of state of lawsonite to 7 GPa and 873 K, and calculation of its high pressure stability
  16. Boron K-edge XANES of borate and borosilicate minerals
  17. 113Cd double-resonance NMR as a probe of clay mineral cation exchange sites
  18. Solid state NMR study of oxygen site exchange and Al-O-Al site concentration in analcime
  19. Isomorphous substitution effect on the vibration frequencies of hydroxyl groups in molecular cluster models of the clay octahedral sheet
  20. Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel’s salt)
  21. VIII(Mg,Fe)0.85VI(Mg,Fe)4IV(Fe,Ge)3O12: A new tetragonal phase and its comparison with garnet
  22. Rietveld analysis of dicalcium aluminate (Ca2Al2O5) – A new high pressure phase with the Brownmillerite-type structure
  23. Suredaite, PbSnS3, a new mineral species, from the Pirquitas Ag-Sn deposit, NW-Argentina: mineralogy and crystal structure
  24. Kozoite-(Nd), Nd(CO3)(OH), a new mineral in an alkali olivine basalt from Hizen-cho, Saga Prefecture, Japan
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  26. Letters. Computer simulation of high-temperature, forsterite-melt partitioning
https://doi.org/10.2138/am-2000-0709

Articles in the same Issue

  1. Application of new experimental and garnet Margules data to the garnet-biotite geothermometer
  2. Volumes of mixing in aluminosilicate garnets: Solid solution and strain behavior
  3. Cerium anomaly and Th/U fractionation in the 1.85 Ga Flin Flon Paleosol: Clues from REE- and U-rich accessory minerals and implications for paleoatmospheric reconstruction
  4. Os solubility in silicate melts: New efforts and results
  5. Enstatite-forsterite-water equilibria at elevated temperatures and pressures
  6. The OH-F substitution in synthetic pargasite at 1.5 kbar, 850 °C
  7. Uptake of aqueous Pb by Cl-, F–, and OH– apatites: Mineralogic evidence for nucleation mechanisms
  8. Temperature dependence of the hyperfine parameters of synthetic P21/c Mg-Fe clinopyroxenes along the MgSiO3-FeSiO3 join
  9. Single-crystal thermometric calibration of Fe-Mg order-disorder in pigeonites
  10. TEM observations on the P1̄ -I1̄ phase transition in feldspars along the join CaAl2Si2O8-SrAl2Si2O8
  11. Phase transitions induced by solid solution in stuffed derivatives of quartz: A powder synchrotron XRD study of the LiAlSiO4-SiO2 join
  12. The transformation of andalusite to mullite and silica: Part I. Transformation mechanism in [001]A direction
  13. The transformation of andalusite to mullite and silica: Part II. Transformation mechanisms in [100]A and [010]A directions
  14. Structure and twinning of tetragonal Ca3Mn2Ge3O12 garnet
  15. The equation of state of lawsonite to 7 GPa and 873 K, and calculation of its high pressure stability
  16. Boron K-edge XANES of borate and borosilicate minerals
  17. 113Cd double-resonance NMR as a probe of clay mineral cation exchange sites
  18. Solid state NMR study of oxygen site exchange and Al-O-Al site concentration in analcime
  19. Isomorphous substitution effect on the vibration frequencies of hydroxyl groups in molecular cluster models of the clay octahedral sheet
  20. Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel’s salt)
  21. VIII(Mg,Fe)0.85VI(Mg,Fe)4IV(Fe,Ge)3O12: A new tetragonal phase and its comparison with garnet
  22. Rietveld analysis of dicalcium aluminate (Ca2Al2O5) – A new high pressure phase with the Brownmillerite-type structure
  23. Suredaite, PbSnS3, a new mineral species, from the Pirquitas Ag-Sn deposit, NW-Argentina: mineralogy and crystal structure
  24. Kozoite-(Nd), Nd(CO3)(OH), a new mineral in an alkali olivine basalt from Hizen-cho, Saga Prefecture, Japan
  25. Florenskyite, FeTiP, a new phosphide from the Kaidun meteorite
  26. Letters. Computer simulation of high-temperature, forsterite-melt partitioning
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