Email address:
schmidtc@vtvm1.cc.vt.edu

Title:
Experimental Study of the PVTX Properties in Part of the Ternary System H2O-NaCl-CO2

Date of defense:
March 21, 1997

Document Type:
PhD Dissertation

Degree:
Doctor of Philosophy

Department:
Geological Sciences

Abstract

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.

Keywords:
Water - Sodium Chloride - Carbon Dioxide, PVTX Properties, Synthetic Fluid Inclusions, Raman Spectroscopy, Hydrothermal Diamond-Anvil Cell

Availability:
In 3 months.

Public URL:
http://scholar.lib.vt.edu/theses/public/etd-566232139711101/etd-title.html

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List of attached files

File Name	Size (Bytes)
etd.pdf	610,699 Bytes

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Date item approved:
4/22/97

Fees:
Archiving fee received.

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