Deciphering the Origin of Intra-Plate Volcanism in the Pacific Northwest Using Geodynamic Models with Data Assimilation

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

We propose to investigate the origin of the intra-plate volcanic province in Pacific Northwest, with features including the mid-Miocene Steens-Columbia River flood basalt and subsequent Yellowstone and Newberry hotspot tracks. Possible mechanisms we will test include a mantle plume originating from the core-mantle boundary, and volcanism from shallow mantle processes such as slab-driven upwelling flow. Besides geological observations, we emphasize on better constraining deep mantle dynamics including the pattern of mantle flow and the nature of slow seismic anomalies beneath the Pacific Northwest. Our approach is 4-D geodynamic modeling with data assimilation, which involves both high-resolution forward subduction simulations and adjoint convection calculations reconstructing past mantle states. Important model constraints come from the much improved mantle structure revealed by USArray and the well understood Cenozoic subduction history beneath western North America. This proposal attempts to solve for a long-debated issue in the scientific community: formation of volcanisms far away from active tectonic plate boundaries. The Pacific Northwest represents an ideal study region due to the existence of such volcanisms as the voluminous eruption of Columbia River flood basalt ~16 million years ago and the ongoing Yellowstone-Newberry hotspot volcanoes. Origin of these volcanic events has remained elusive because of our poor understanding on the configuration of deep mantle where these volcanisms originate. Now with the USArray seismic experiment finally delineating a 3-dimentional picture of the sub-continental mantle, a better understanding on the formation the Pacific Northwest volcanism becomes possible. To solve this apparently complex problem, we will rely on sophisticated numerical models based on powerful supercomputers. These models will take into account not only surface geologic records, but also the mantle structures underneath, and most importantly the time-evolution of the system since the remote past. Scientifically, the proposed work has impacts on almost every field of solid Earth research. Another important implication of this research is to improve knowledge on the formation of natural hazards and their effects on climate and environment.