Melt inclusions (the round circles in the video below) are little pockets of melt that are trapped in growing crystals during cooling of magma. If magma was erupted and cooled quickly, melt inclusions preserve the composition of the melt in which their host crystal formed. However, slow cooling will cause these melt inclusions to form daughter crystals (shown as the dark grains in the round circles) which change their original composition. In order to restore the pre-eruptive melt composition, I reheated these quartz-hosted crystallized melt inclusions (diameter=50 micrometers) at the USGS in Menlo Park, using a reheating stage and the assistance of Dr. Jake Lowenstern, scientist-in-Charge of the Yellowstone Volcano Observatory. These quartz crystals were taken from the upper portions of the Huckleberry Ridge Tuff fall deposit (2.1 Ma, 2,500km3), the oldest and largest of the three volcanic cycles that form the Yellowstone Volcanic Field. The bottom part of the deposit contains beautifully glassy, and bubble-free melt inclusions, however the upper portion had the unfortunate experience of being reheated after emplacement when the larger, and much hotter, ignimbrite was deposited.
In order to continue our evaluation of the composition of the magma that was being erupted at the onset of the Huckleberry Ridge Tuff eruption, I reheated around 10 quartz grains (each takes 1-2 hours, with the process violently halted if the quartz grain explodes due to it's initial experience at the alpha/beta transition) and videoed the process. Enjoy...
Ph.D candidate at the Department of Geological Sciences, University of Oregon.
PS I want to thank Madison for sharing her awesome research on my blog. I hope that there will be more of collaborative effort in exposing our research experience to the web-based audience.