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How it works:
Small, mm-scale
chips of crystalline minerals are mounted between thin glass plates in an area of the stage that contains a sensitive
thermocouple and is surrounded by insulating material. Fluid inclusions, which are tiny bits of fluid trapped during
crystal growth, are observed through the glass plates in the stage using a high-powered microscope. Samples are chilled
or heated by passing heated or chilled gas, usually nitrogen, over them.
Crystals that grow in fluid-rich environments often trap a bit of the surrounding fluid in small inclusions within the grain. As the mineral cools, the liquid in the inclusion shrinks in volume and a vapor bubble appears. By heating the sample on a fluid inclusion stage until the bubble is reabsorbed, the "homogenization temperature" of the fluid inclusion is found. This temperature represents the minimum temperature at which the inclusion was trapped and therefore can be used to estimate the minimum temperature of mineral crystallization. Freezing and melting temperatures can be determined by chilling fluid inclusions. Because the freezing and melting temperatures of the fluid are controlled by its salt content, the composition of fluids in the inclusion that were involved in crystal growth can be constrained. Last updated 11/10 |
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