Title page for ETD etd-566232139711101

Type of Document Dissertation
Author Schmidt, Christian
Author's Email Address schmidtc@vtml.cc.vt.edu
URN etd-566232139711101
Title Experimental Study of the PVTX Properties in Part of the Ternary System H2O-NaCl-CO2
Degree PhD
Department Geological Sciences
Advisory Committee
Advisor Name Title
Chou, I. M.
Craig, James R.
Roedder, E.
Tracy, Robert J.
Bodnar, Robert J. Committee Chair
  • raman spectroscopy
  • synthetic fluid inclusions
  • PVTX properties
  • water - sodium chloride - carbon dioxide
  • hydrothermal diamond-anvil cell
Date of Defense 1997-03-21
Availability unrestricted
Phase equilibria and volumetric properties in the system water-sodium chloride-carbon dioxide were determined experimentally for pressures between about 1 to 6 kbar, temperatures of 300° to 800°C, and fluid compositions up to 40 wt% NaCl and 20 mol% carbon dioxide, both relative to water. This was accomplished by using the synthetic fluid inclusion technique in conjunction with conventional microthermometry, a hydrothermal diamond-anvil cell and Raman spectroscopy.

At constant salinity, the high-pressure portion of the solvus migrates to higher pressures and temperatures with increasing carbon dioxide concentration. Immiscibility is possible in this ternary system over almost the entire range of crustal P-T conditions at salinities equal to or in excess of 20 wt% NaCl and carbon dioxide concentrations between about 30 and 70 mol% carbon dioxide. The dP/dT slopes of lines of equal homogenization temperature decrease nonlinearly with increasing homogenization temperature; at constant homogenization temperature, these slopes become steeper (higher) along pseudobinaries with addition of carbon dioxide and particularly with addition of sodium chloride. Up to concentrations of 20 wt% NaCl and 20 mol% carbon dioxide, a sharp rise in the critical temperature was observed with increasing salinity at a fixed water/carbon dioxide ratio. The critical point shifts rapidly towards higher pressures with increasing carbon dioxide concentration. Addition of carbon dioxide to an aqueous 40 wt% NaCl solution results in a slight elevation of the halite dissolution temperature under vapor-saturated conditions.

A significant error can be associated with the calculation of molar volumes from measured densities of the carbonic phase of water-sodium chloride-carbon dioxide inclusions. To avoid such errors, phase diagrams were constructed based on the obtained lines of equal homogenization temperature for salinities between 6 and 40 wt% NaCl and carbon dioxide concentrations between 5 and 20 mol% relative to water. These diagrams are of direct applicability to the interpretation of natural fluid inclusions from a wide variety of geologic environments.

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