Fluid inclusion

If minute crystals, such as halite, sylvite, hematite or sulfides, are present in the inclusion, they provide direct clues as to the composition of the original fluid.

FIS analysis takes the spectrometric reading of a fluid inclusion's volatile species; these are indicative of a natural gas or oil deposit nearby.

[10] CO2-rich fluid inclusions were also recorded from a number of ultra high temperature granulite facies terranes, suggesting the involvement of CO2 in extreme crustal metamorphism.

[10] Some recent studies speculate that CO2 derived by sub-solidus decarbonation reactions during extreme metamorphism has contributed to the deglaciation of the snowball Earth.

[12] Trapped bubbles of air and water within fossil amber can be analyzed to provide direct evidence of the climate conditions existing when the resin or tree sap formed.

The data indicate that the oxygen content of the atmosphere reached a high of nearly 35% during the Cretaceous Period and then plummeted to near present levels during the early Tertiary.

The abrupt decline corresponds to or closely follows the Cretaceous–Paleogene extinction event and may be the result of a major meteorite impact that created the Chicxulub Crater.

Trapped in a time capsule the same size as the diameter of a human hair, the ore-forming liquid in this inclusion was so hot and contained so much dissolved solids that when it cooled, crystals of halite, sylvite, gypsum, and hematite formed. As the samples cooled, the fluid shrank more than the surrounding mineral, and created a vapor bubble. Source: USGS
Photomicrographs from Pea Ridge, MO, USA of secondary fluid inclusions in apatite (image A) and quartz (images B–H).
This 84-million-year-old air bubble lies trapped in amber (fossilized tree sap). Using a quadrupole mass spectrometer, scientists can learn what the atmosphere was like when the dinosaurs roamed the earth. Source: USGS