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1 Dipartimento Scienze della Terra, Università degli Studi di Milano, Via Botticelli 23- 20133 Milano, Italy
2 National Research Council, IDPA, Section of Milan, Via Botticelli 23-20133 Milano, Italy
3 Dipartimento di Scienze Mineralogiche e Petrologiche, Università degli Studi di Torino, Via Valperga Caluso 37-10125 Torino, Italy
4 Dipartimento di Scienze Chimiche, Università di Padova, Via Marzolo 1-35131 Padova, Italy
Correspondence: * E-mail: alessandro.pavese{at}unimi.it
The P-V and T-V equations of state of a natural biotite sample (Mg/Fe ratio
1) have been studied using in-situ high-pressure (0.000111 GPa) synchrotron radiation powder diffraction at the European Synchrotron Radiation Facilities (ESRF) in Grenoble, France, and in-situ high-temperature (298610 K) laboratory X-ray powder diffraction. A third-order Birch-Murnaghan model [V0 = 498.7(1) Å3, measured value] provides the following elastic parameters: K0 = 49(1) GPa, K = 8.1(5). The volume thermal expansion is satisfactorily described by a constant value resulting in 37(2) 106 K1. Mössbauer spectroscopy proves that REDOX reactions have occurred upon heating, presumably 2(OH + Fe2+)
2O2 + 2Fe3+ + H2
and/or 4Fe2+ + 2OH + O2
4Fe3+ + 3O2 + H2O. On the basis of the elastic and thermal parameters measured we have modeled the deformation contribution (Gdeform) to the Gibbs energy. The third-order Birch-Murnaghan model with V0 fixed at its experimental value and the model with refined V0 do not significantly differ from one another in terms of Gdeform. A comparison based on Gdeform between biotite and phlogopite shows a better compliance to P of the former, though balanced in mineral reactions by a difference of molar volume, i.e., V0(biotite) > V0(phlogopite).
Key Words: High-pressure studies high-temperature studies biotite P-T stability
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G. Ventruti, D. Levy, A. Pavese, F. Scordari, and E. Suard High-temperature treatment, hydrogen behaviour and cation partitioning of a Fe-Ti bearing volcanic phlogopite by in situ neutron powder diffraction and FTIR spectroscopy European Journal of Mineralogy, April 1, 2009; 21(2): 385 - 396. [Abstract] [Full Text] [PDF] |
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