Considerable advances in our understanding of physicochemical properties of geological fluids and their roles in many geo logical processes have been achieved by the u se of synthetic fluid inclusions. We have developed a new method to synthesize fluid inclusions containing organic and inorganic materials in fused silica capillary tubing. We have used both round and square cross-section tubing.
For microthermometric measurements in a Linkam CAP500-type heating-cooling stag. The square-sectioned capsules have the advantage of providing images without optical distortion. However, the maximum internal pressure (P; about 100 MPa at 22 C) and temperature (T; about 500 C) maintaind by the square-sectioned
capsules are less than those held by the round-sectioned capsules (about 300 MPa at room T, and T up to 650 C).
The fused silica capsules can be applied to a wide range of problems of interest in fluid inclusion and hydrothermal research , such as creating standards for the calibration of thermocouples in heating-cooling stages and frequency shifts in Raman spectrometers. The fused silica capsules can also be used as containers for hydrothermal reactions, especially for organic samples, including individual hydrocarbons, crude oils, and gases, such as cracking of C18H38 between 350 and 400 C, isotopic exchanges between C18H38 and D20 and between C19D40 and H20 at similar temperatures. Results of these types of studies provide information on the kinetics of oil cracking and the changes of oil composition under thermal stress.
When compared with synthesis of fluid inclusions formed by healing fractures in quartz or other minerals or by overgrowth of quartz at elevated P-T conditions, the new fused -silica method has the following advantages: (I ) it is simple; (2) fluid inclusions without the presence of water can be formed; (3) synthesized inclusions are large and uniform, and they are able to tolerate high internal P; (4) it is suitable for the study of organic material; and (5) redox control is possible due to high permeability of the fused silica to hydrogen. Following figure is the picture of instruments for making synthesizing fluid inclusions in fused silica capillary tube.