Contributions to Mineralogy and Petrology

, Volume 146, Issue 4, pp 506–512 | Cite as

Equations of state of Plagioclase Feldspars

  • R. J. AngelEmail author
Original Paper


The volume variation with pressure of seven intermediate plagioclase feldspars has been determined by high-pressure single-crystal X-ray diffraction. The bulk moduli of plagioclases for a 3rd-order Birch-Murnaghan EoS can be described by the following pair of equations:
$$ K_{{T0}} = 54.1{\left( 3 \right)} + 0.39{\left( 1 \right)}X_{{An}} {\text{ for }}X_{{An}} < {\text{50}} $$
$$ K_{{T0}} = 59.5{\left( {3.1} \right)} + 0.23{\left( 4 \right)}X_{{An}} {\text{ for }}X_{{An}} > {\text{50}} $$
with \({K}'_{0} = 5.8\) for plagioclase with X An <20 and \({K}'_{0} = 3.2\) for X An >35. These parameters can also be used in a Murnaghan EoS to describe the volume variation of plagioclase feldspars up to pressures of 3 GPa. For a Murnaghan EoS with \({K}'_{0} = 4\), the values of the bulk moduli can be described by a single equation, \( K_{{T0}} = 57.7{\left( 6 \right)} + 0.24{\left( 1 \right)}X_{{An}} \), with a small loss in the accuracy of the predicted volumes up to pressures of 3 GPa.


Bulk Modulus Finite Strain Thermodynamic Database Bulk Modulo Plagioclase Feldspar 
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Michael Carpenter generously donated the samples and provided details of some unpublished electron microprobe and TEM analyses, and Patrick O’Brien analyzed sample 67783. The X-ray diffraction data was collected while the author was a member of the Bayerisches Geoinstitut in Bayreuth. Data analysis was supported by NSF grant EAR-0105864 to NL Ross and RJ Angel at Virginia Tech.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Crystallography Laboratory, Dept. GeoSciencesVirginia Polytechnic Institute and State UniversityBlacksburgUSA

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