Studies of fluid inclusions I: Low temperature application of a dual-purpose freezing and heating stage

Economic Geology



The design and operation of a microscope freezing stage developed for use at magnifications up to 500X are described. It makes possible studies of low-temperature phase changes such as the freezing of a saline water phase, and hence an estimate of the total salt concentration, in fluid inclusions as small as 10 microns (10-6 milligram in weight). The crystal or polished mineral plate containing the inclusions is viewed while immersed in a thermostated heat exchange medium (acetone) circulating rapidly in order to minimize thermal gradients. The stage permits easy operation at temperatures down to -35° C, with electrical control to ±0.05° C, and to much lower temperatures with manual control. With substitution of silicone oil for acetone, the same stage can be used for heating experiments up to +250° C. Calibration points in the low range indicate the accuracy of freezing temperature determinations on optimum material to be better than ±0.1° C. The low relief of ice crystals in water solution places considerable importance on sample selection, preparation, and lighting. As a result of almost ubiquitous and drastic supercooling (meta-stability), -35° C is inadequate to freeze most inclusions. Holding at -78.5° C (acetone + solid CO 2) for thirty minutes is generally adequate, although a few samples require extended immersion in liquid nitrogen at -196° C to cause freezing of even a part of their inclusions. Such extensive supercooling is not possible with most surface waters owing to the presence of abundant extraneous solid nuclei for the crystallization of ice. 

Publication type Article
Publication Subtype Journal Article
Title Studies of fluid inclusions I: Low temperature application of a dual-purpose freezing and heating stage
Series title Economic Geology
DOI 10.2113/gsecongeo.57.7.1045
Volume 57
Issue 1
Year Published 1962
Language English
Publisher Society of Economic Geologists
Description 17 p.
First page 1045
Last page 1061
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