X-RAY-MICROANALYSIS OF FROZEN FLUID INCLUSIONS

Identification of the electrolytes contained in fluid inclusions in amounts as low as 0.1 wt.% is possible by means of a liquid nitrogen-cooled stage placed in a scanning electron microscope equipped with an X-ray energy-dispersive system. Practical procedures for sample preparation, observation and analysis (freezing, breaking, coating) are described. Quantitative analysis in the system NaCl-CaCl2-KCl has been approached by means of reference solutions of known composition and using the peak-to-background ratio method for comparison. The volatility of the ice and of some electrolytes has appeared to be the main disadvantage, imposing serious constraints to the size of the fluid inclusions that can be analyzed. Despite this disadvantage and the difficulty in manipulation, the type of information obtained on the chemistry of the trapped fluids cannot be determined by other analytical techniques and justifies further development of the proposed method.