Thermal equation of state of lawsonite up to 10 GPa and 973 K

Access this Article

Author(s)

    • CAI Nao
    • Geodynamics Research Center, Ehime University

Abstract

Thermal equation of state (EoS) of synthetic lawsonite [CaAl<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>(OH)<sub>2</sub>·H<sub>2</sub>O] has been established using in–situ X–ray diffraction methods under high pressure and high temperature. Sodium chloride NaCl was used as the pressure standard in the experiments. The unit–cell volumes were measured up to 10 GPa and 973 K after the deviatric stress was released at high temperature. The <i>P–V–T</i> dataset was analyzed using a Birch–Murnaghan equation of state, yielding the room pressure volume <i>V</i><sub>0</sub> = 674.2(2) Å<sup>3</sup> and the isothermal bulk modulus at room temperature <i>K</i><sub>0</sub> = 129(2) GPa (K′ set to 4). These values are comparable with the previous studies. When fitting the high temperature data, a second order temperature derivative of the bulk modulus was considered. Unlike Daneil et al. (1999) who reported a minimum value of bulk modulus at ~500 K, the bulk modulus decreases with increasing temperature at least up to 973 K. The dataset yields: <i>V</i><sub>0</sub> = 674.3(4) Å<sup>3</sup>, <i>K</i><sub>0</sub> = 128.7(15) GPa, (∂<i>K<sub>T</sub></i>/∂<i>T</i>)<i><sub>P</sub></i> = −0.047(8) GPa K<sup>−1</sup>, (∂<sup>2</sup><i>K<sub>T</sub></i>/∂<i>T</i><sup>2</sup>)<i><sub>P</sub></i> = 0.028(6) × 10<sup>−3</sup> GPa K<sup>−1</sup>, <i>α</i> = 3.13(25) × 10<sup>−5</sup> K<sup>−1</sup>, assuming <i>K</i>′ = 4. These data can be used to calculate the density and the stability of lawsonite under high pressure and high temperature conditions.

Journal

  • Journal of Mineralogical and Petrological Sciences

    Journal of Mineralogical and Petrological Sciences 110(5), 235-240, 2015

    Japan Association of Mineralogical Sciences

Codes

  • NII Article ID (NAID)
    130005108540
  • Text Lang
    ENG
  • ISSN
    1345-6296
  • Data Source
    J-STAGE 
Page Top