Evolution of magma storage conditions along the track of Yellowstone Hotspot: investigation of the volcanic rocks from Snake River Plain

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The planed ICDP drilling in the Snake River Plain volcanic province (western United States) is aimed to trace the Snake River Plain – Yellowstone (SRPY) hotspot and its interaction with the lithosphere. This province represents one of the best examples of a thermal anomaly related to hotspot volcanism within the continental lithosphere. Over the last 15 Ma, the SRPY-hotspot migrated ca. 600 km eastwards resulting in a bimodal (rhyolitic-basaltic) magmatism. Understanding the interaction of the SRPY-hotspot with the lithosphere requires information on the evolution of chemistry, sources, differentiation and storage conditions of both the rhyolitic and basaltic magmas with time and space. The proposed project aims at understanding the evolution of the magma storage conditions in the SRPY-province in the last 12 Ma. This information will be gained (1) from the chemical analysis of natural minerals and glasses combined with (2) high pressure experimental studies to determine phase equilibria and (3) thermodynamic modeling. Particular attention will be given to trace the evolution of the depth and temperature of the rhyolitic magma chambers using the Bruneau-Jarbidge and Heise volcanic centers (12.5-8.0 Ma and 6.5-4.3 Ma, respectively) as reference materials. Concomitantly, the storage conditions of basaltic lavas of different ages will be explored. The results will also be useful to understand the interactions between basaltic and rhyolitic magma chambers at depth, to constrain the conditions prevailing during partial melting processes in the crust, and to discuss the vertical migration distance of rhyolitic melts (magmas) from the source to the magma chamber. This work will benefit from the cooperation with petrologists and geochemists from USA (e.g., E. Christiansen, B. Nash, J. Shervais).