Anisotropy of hydrogen diffusion in tourmaline

作者：De**ois Guillaume; Ingrin Jannick^*

来源：Geochimica et Cosmochimica Acta, 2007, 71(21): 5233-5243.

DOI：10.1016/j.gca.2007.08.027

Hydrogen-deuterium exchange in tourmaline single crystals of elbaite composition from Nepal has been studied at I atm and at temperatures between 973 and 1073 K. H/D ratios were determined after each annealing experiment using micro FTIR-spectroscopy. Diffusion coefficients (10(-16)-10(-15) M-2 s(-1)) were determined by fitting the data using a 3D numerical simulation. The rate of diffusion is two to three times faster along the c direction than along directions parallel to the basal plane. The diffusion laws are, respectively:
[Graphics]
and
[Graphics]
with D in m(2) s(-1), Tin Kelvin and the activation energy in kJ mol(-1). The diffusion rates are one order of magnitude faster, and have slightly lower activation energies, than those found by previous authors for schorlite (125 kJ mo(l-1)). The closure temperature of hydrogen isotope exchange in the tourmaline-water system is lower for elbaite than for schorlite.

• 出版日期2007-11-1