Mantle dynamics beneath the Pacific Northwest and the generation of voluminous back-arc volcanism
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Grove_Mantle dynamics.pdf
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Author(s)
Long, Maureen D.
Till, Christy B.
Druken, Kelsey A.
Carlson, Richard W.
Wagner, Lara S.
Fouch, Matthew J.
James, David E.
Grove, Timothy L.
Schmerr, Nicholas
Kincaid, Chris
Date Issued
August 2012
Journal
Geochemistry, Geophysics, Geosystems
Publisher
American Geophysical Union (AGU)
Citation
Long, Maureen D., Christy B. Till, Kelsey A. Druken, Richard W. Carlson, Lara S. Wagner, Matthew J. Fouch, David E. James, Timothy L. Grove, Nicholas Schmerr, and Chris Kincaid. “Mantle Dynamics Beneath the Pacific Northwest and the Generation of Voluminous Back-Arc Volcanism.” Geochem. Geophys. Geosyst. 13, no. 8 (August 2012): n/a–n/a. Copyright © 2012 American Geophysical Union
Version
Final published version
Abstract
The Pacific Northwest (PNW) has a complex tectonic history and over the past ~17 Ma has played host to several major episodes of intraplate volcanism. These events include the Steens/Columbia River flood basalts (CRB) and the striking spatiotemporal trends of the Yellowstone/Snake River Plain (Y/SRP) and High Lava Plains (HLP) regions. Several different models have been proposed to explain these features, which variously invoke the putative Yellowstone plume, rollback and steepening of the Cascadia slab, extensional processes in the lithosphere, or a combination of these. Here we integrate seismologic, geodynamic, geochemical, and petrologic results from the multidisciplinary HLP project and associated analyses of EarthScope USArray seismic data to propose a conceptual model for post-20 Ma mantle dynamics beneath the PNW and the relationships between mantle flow and surface tectonomagmatic activity. This model invokes rollback subduction as the main driver for mantle flow beneath the PNW beginning at ~20 Ma. A major pulse of upwelling due to slab rollback and upper plate extension and consequent melting produced the Steens/CRB volcanism, and continuing trench migration enabled mantle upwelling and hot, shallow melting beneath the HLP. An additional buoyant mantle upwelling is required to explain the Y/SRP volcanism, but subduction-related processes may well have played a primary role in controlling its timing and location, and this upwelling likely continues today in some form. This conceptual model makes predictions that are broadly consistent with seismic observations, geodynamic modeling experiments, and petrologic and geochemical constraints.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.1029/2012gc004189
