Contributions to Mineralogy and Petrology

, Volume 160, Issue 5, pp 743–759

TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz

  • Jay B. Thomas
  • E. Bruce Watson
  • Frank S. Spear
  • Philip T. Shemella
  • Saroj K. Nayak
  • Antonio Lanzirotti
Original Paper

DOI: 10.1007/s00410-010-0505-3

Cite this article as:
Thomas, J.B., Bruce Watson, E., Spear, F.S. et al. Contrib Mineral Petrol (2010) 160: 743. doi:10.1007/s00410-010-0505-3

Abstract

Quartz and rutile were synthesized from silica-saturated aqueous fluids between 5 and 20 kbar and from 700 to 940°C in a piston-cylinder apparatus to explore the potential pressure effect on Ti solubility in quartz. A systematic decrease in Ti-in-quartz solubility occurs between 5 and 20 kbar. Titanium K-edge X-ray absorption near-edge structure (XANES) measurements demonstrate that Ti4+ substitutes for Si4+ on fourfold tetrahedral sites in quartz at all conditions studied. Molecular dynamic simulations support XANES measurements and demonstrate that Ti incorporation onto fourfold sites is favored over interstitial solubility mechanisms. To account for the PT dependence of Ti-in-quartz solubility, a least-squares method was used to fit Ti concentrations in quartz from all experiments to the simple expression
$$ RT\ln X_{{{\text{TiO}}_{ 2} }}^{\text{quartz}} = - 60952 + 1.520 \cdot T(K) - 1741 \cdot P(kbar) + RT\ln a_{{{\text{TiO}}_{ 2} }} $$
where R is the gas constant 8.3145 J/K, T is temperature in Kelvin, \( X_{{{\text{TiO}}_{ 2} }}^{\text{quartz}} \) is the mole fraction of TiO2 in quartz and \( a_{{{\text{TiO}}_{ 2} }} \) is the activity of TiO2 in the system. The PT dependencies of Ti-in-quartz solubility can be used as a thermobarometer when used in combination with another thermobarometer in a coexisting mineral, an independent P or T estimate of quartz crystallization, or well-constrained phase equilibria. If temperature can be constrained within ±25°C, pressure can be constrained to approximately ±1.2 kbar. Alternatively, if pressure can be constrained to within ±1 kbar, then temperature can be constrained to approximately ±20°C.

Keywords

QuartzTitaniumSolubilityThermobarometryThermometryXANES

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Jay B. Thomas
    • 1
  • E. Bruce Watson
    • 1
  • Frank S. Spear
    • 1
  • Philip T. Shemella
    • 2
  • Saroj K. Nayak
    • 2
  • Antonio Lanzirotti
    • 3
  1. 1.Department of Earth and Environmental SciencesRensselaer Polytechnic InstituteTroyUSA
  2. 2.Department of Physics, Applied Physics, and AstronomyRensselaer Polytechnic InstituteTroyUSA
  3. 3.National Synchrotron Light Source, Brookhaven National LaboratoryThe University of Chicago—CARSUptonUSA