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