Abstract by Patricia Ascanio-Pellon
Do Yellowstone basalts have a wet, subduction-zone signature? Evidence from plagioclase and olivine compositions.
Recent studies have suggested that the basalts of the Yellowstone hotspot track were heavily influenced by the subduction of the Farallon plate. Evidence for this theory arises from high concentrations of water (up to 4 wt. %) allegedly found within olivine-hosted melt inclusions in basalts from the Snake River Plain and the Columbia River Plateau. The hypothesis of wet volcanism can be tested using the compositions of plagioclase and olivine in the basalts. Experiments have shown that wet, arc-type basalts show high plagioclase An values (An85-100) for a given olivine composition of Fo60-80. Basalts from the Kimama drill core of the central Snake River Plain, however, have plagioclase ranging from An65-75 in apparent equilibrium with olivine ranging from Fo70-85. The Kimama basalt plagioclase An values are therefore inconsistent with wet magmas and arc-type volcanism, strongly arguing against a subduction-zone influence.