Pressures of Crystallization and Depth of Magma chambers beneath Hawai'ian Volcanoes

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Title: Pressures of Crystallization and Depth of Magma chambers beneath Hawai'ian Volcanoes
Creators: Ditkof, Julie
Advisor: Barton, Michael
Issue Date: 2010-12
Abstract: The Hawai’ian Emperor Seamount Chain was formed by a mantle plume beginning about 80 Ma. The crust is raised by the heat of the plume while continuous eruptions of magma formed by decompression melting of the plume form the islands. The Hawai’ian Emperor Seamount Chain formed as the Pacific plate moved to the north and northwest across the nearly stationary plume. As the islands begin to slide off the plume, they subside back to the sea floor, forming seamounts. There are currently more than 80 undersea volcanoes stretching from the Aleutian Trench to the newly formed Loi’hi Seamount. Eight major islands, all of volcanic origin, make up the state of Hawai’i. Seismic and other geophysical data have been used previously to determine the depth of magma chambers beneath Hawai’ian Volcanoes. Yang et al (1996) created a method in which three equations are used to calculate liquid compositions along the pressure-dependent olivine-plagioclase-clinopyroxene coetectic. I used chemical analyses of glasses, which represent quenched liquid compositions, to calculate the pressure and temperature at which these liquids crystallize the minerals olivine, plagioclase, and clinopyroxene. The depth of crystallization can be calculated from these pressures. I filtered the data, removing any glasses with anomalous chemical compositions or with compositions that yielded pressures associated with unacceptably large errors. Plots of CaO versus MgO, P versus MgO, T versus MgO, and depth versus MgO for the filtered results reveal similar trends for Mauna Loa, Mauna Kea, three localities associated with Kilauea, and Loi’hi. The pressures range from 0.1 to 526 MPa and average 78 MPa. These results agree with geophysical data, and show that the magma chambers lie at shallow depths, about 10km with average depths between 3.5 x 10-6 and 11.28 km. Knowledge of the depths of chambers and pressures of crystallization is important for a number of reasons including understanding magma evolution, magma plumbing systems, and predicting when an eruption will occur.
Embargo: A one-year embargo was granted for this item.
Series/Report no.: The Ohio State University. School of Earth Sciences Honors Theses; 2010
Keywords: Pressures of Crystallization
Depth of Magma Chambers
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