Title page for ETD etd-02072000-12380020

Type of Document Master's Thesis
Author Baldassaro, Paige Marie
Author's Email Address pmbalda@vt.edu
URN etd-02072000-12380020
Title Low Temperature Phase Relations in the System H2O-NaCl-FeCl2
Degree Master of Science
Department Geological Sciences
Advisory Committee
Advisor Name Title
Bodnar, Robert J. Committee Chair
Rimstidt, james Donald Committee Member
Tracy, Robert J. Committee Member
  • sodium chloride
  • low temperature aqueous geochemistry
  • synthetic fluid inclusions
  • iron chloride
Date of Defense 1998-05-08
Availability unrestricted

The low temperature phase behavior of the system H2O-NaCl-FeCl2 was

examined using synthetic fluid inclusions. Experiments were conducted along the 5 wt%

NaCl (relative to the total solution) pseudobinary, with FeCl2 concentrations varying from

2 to 33 wt%, and along the pseudobinary defined by mixing known amounts of

FeCl2-4H2O with a 5 wt% NaCl solution, with final FeCl2 concentrations varying from 0 to

29 wt%. Synthetic fluid inclusions in quartz were prepared in cold-seal pressure vessels

at 500 degrees C - 800 degrees C and 2 or 3 kilobars. The fO2 conditions were controlled

by the Ni-NiO equilibrium curve. The liquid released from the capsule upon opening was

initially colorless, but turned yellow-orange after contact with atmospheric O2. The clear

color is characteristic of ferrous iron solutions, whereas the yellow-orange color is consistent

with the presence of Fe3+ in solution. This color change suggested that the unopened

capsules initially contained ferrous iron in solution, which oxidized to ferric iron when

exposed to the atmosphere.

Borisenko (1977) reported a eutectic temperature of -37 degrees C for the system

H2O-NaCl-FeCl2. In this study, it was not possible to verify this temperature due to the

persistence of a metastable liquid down to liquid N2 temperatures (~-196 degrees C).

Final ice melting temperatures were obtained for concentrations less than 24 wt%

FeCl2 and show a decrease in temperature with increase in FeCl2 concentration.

For more concentrated solutions, final melting temperatures could not be obtained

because the samples could not be frozen.

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