Mantle dynamics beneath the Pacific Northwest and the generation of voluminous back-arc volcanism

Maureen D. Long, Christy Till, Kelsey A. Druken, Richard W. Carlson, Lara S. Wagner, Matthew J. Fouch, David E. James, Timothy L. Grove, Nicholas Schmerr, Chris Kincaid

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

The Pacific Northwest (PNW) has a complex tectonic history and over the past ∼17Ma 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-20Ma 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 ∼20Ma. 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.

Original languageEnglish (US)
Article numberQ0AN01
JournalGeochemistry, Geophysics, Geosystems
Volume13
Issue number1
DOIs
StatePublished - 2012
Externally publishedYes

Fingerprint

Pacific Northwest (US)
plains
upwelling water
volcanism
Earth mantle
arcs
Rivers
rivers
lava
Geodynamics
mantle
flood basalt
alluvial plain
Columbia (Orbiter)
geodynamics
slab
upwelling
Melting
subduction
melting

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Mantle dynamics beneath the Pacific Northwest and the generation of voluminous back-arc volcanism. / Long, Maureen D.; Till, Christy; Druken, Kelsey A.; Carlson, Richard W.; Wagner, Lara S.; Fouch, Matthew J.; James, David E.; Grove, Timothy L.; Schmerr, Nicholas; Kincaid, Chris.

In: Geochemistry, Geophysics, Geosystems, Vol. 13, No. 1, Q0AN01, 2012.

Research output: Contribution to journalArticle

Long, MD, Till, C, Druken, KA, Carlson, RW, Wagner, LS, Fouch, MJ, James, DE, Grove, TL, Schmerr, N & Kincaid, C 2012, 'Mantle dynamics beneath the Pacific Northwest and the generation of voluminous back-arc volcanism' Geochemistry, Geophysics, Geosystems, vol. 13, no. 1, Q0AN01. https://doi.org/10.1029/2012GC004189
Long, Maureen D. ; Till, Christy ; Druken, Kelsey A. ; Carlson, Richard W. ; Wagner, Lara S. ; Fouch, Matthew J. ; James, David E. ; Grove, Timothy L. ; Schmerr, Nicholas ; Kincaid, Chris. / Mantle dynamics beneath the Pacific Northwest and the generation of voluminous back-arc volcanism. In: Geochemistry, Geophysics, Geosystems. 2012 ; Vol. 13, No. 1.
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