Pressure Effect on Hydrogen Isotope Fractionation Between Brucite and Water at Elevated Temperatures
Juske Horita,
*
Thomas Driesner,
David R. Cole
Experimental evidence for a pressure effect on isotopic
partitioning at elevated temperatures demonstrates that equilibrium deuterium-protium fractionation between the mineral brucite
[Mg(OH)2] and pure water systematically increases by 12.4 per mil as pressure increases from 15 to 800 megapascals at 380°C. A
linear relation is observed between the measured fractionation factor
and the density of water (0.070 to 1.035 grams per cubic centimeter). The trend of the isotope pressure effect is the same as that of recent
theoretical studies, but the magnitude is smaller. The pressure effect
must be accounted for in the interpretation of isotopic data of
geologic systems involving water (paleotemperature, source of fluids).
Chemical and Analytical Sciences Division, Oak Ridge National
Laboratory, Post Office Box 2008, MS 6110, Oak Ridge, TN 37831-6110,
USA.
*
To whom correspondence should be addressed. E-mail:
horitaj{at}ornl.gov
Present address: Eidgenössische Technische
Hochschule Zürich, Isotope Geochemistry and Mineral Resources,
ETH Zentrum NO, CH-8092 Zurich, Switzerland.
