Basaltic Cannibalism at Thrihnukagigur Volcano, Iceland

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Project Name:Basaltic Cannibalism at Thrihnukagigur Volcano, Iceland

Location: 
Thrihnukagigur Volcano, Iceland
Collaborators: 
Dr. Freysteinn Sigmundsson (NORDVULK), Inside the Volcano
Project Description:

Thrihnukagigur volcano (pronounced: three-nuke-a-gig-ur) is the main vent of a fissure eruption on the Reykjanes Peninsula, southwest, Iceland. Despite being relatively small in size, it has been developed into a popular tourist attraction. The uppermost conduit of Thrihnukagigur remained evacuated following an eruption ~3,500 Ka and a crater allows visitors to drop 120 meters straight down into the “heart of the volcano.” The cave gives us a unique opportunity to observe pristine outcrops and relationships between different units at depth in a volcanic system. Three main units are of interest to my project: 1) a vertical dike that rips 180° across the ceiling of the cave, 2) the lava flows that are the surface expression of the magma in the dike, and 3) a cinder cone exposed in the wall of the cave.

I hypothesize based on preliminary mineralogical and geochemical observations that the magma digested or “cannibalized” the cinder cone to create the cave. I will be looking at small crystals of a mineral called plagioclase in all three units to determine if crystals from the cinder cone have a distinct shape, size, and chemistry and to see if they may have been incorporated into the magma in the dike and surface lavas. This will require a lot of time at the microscope and in the ICP-MS lab (short for inductively coupled plasma mass spectrometer) where I’ll be using a laser to vaporize and analyze microscopic spots of these crystals to determine their chemical composition.

If we can confirm this hypothesis, it will suggest that there is recycling of crustal material in Iceland. Basaltic crust is not considered to be readily recycled, so a positive result would add another complexity to the evolution of magma in an already complex volcanic and tectonic region. It also has potential implications for the source of dangerous volcanic gases produced by Icelandic volcanoes that are hereto poorly understood and that I hope to pursue for my doctoral work.