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High Lava Plains Project

High Lava Plains Project. Matt Fouch Arizona State University School of Earth and Space Exploration 2007 EarthScope National Meeting, Monterey, CA MARGINS/GeoSwath Workshop. High Lava Plains Project: Understanding the Causes of Continental Intraplate Tectonomagmatism.

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High Lava Plains Project

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  1. High Lava Plains Project Matt Fouch Arizona State University School of Earth and Space Exploration 2007 EarthScope National Meeting, Monterey, CA MARGINS/GeoSwath Workshop

  2. High Lava Plains Project:Understanding the Causes of Continental Intraplate Tectonomagmatism Arizona State University - Matt Fouch Carnegie Institution of Washington - Rick Carlson, David James Miami University - Bill Hart Massachusetts Institute of Technology - Tim Grove Oregon State University - Anita Grunder, Bob Duncan University of Oklahoma - Randy Keller University of Rhode Island - Chris Kincaid University of Texas, El Paso - Steve Harder Funded by NSF-Continental Dynamics

  3. Observations on Post-12 Ma Volcanism • Two migrating volcanic traces • Migrating volcanism defined by rhyolites • Basaltic activity continuous along both traces • Volcanism in HLP associated with right-lateral S-S faulting as B&R extension dies out to N

  4. Strong Temporal and Spatial Relationships with Basalt Composition • HLP basalts become more primitive with time • Composition shifts towards a high-Al tholeiite consistent with a very shallow mantle source • Primitive basalts across HLP show limited isotopic variation • Changes dramatically at border with Precambrian North America

  5. Isostatic Gravity • Eastern OR/WA show no gravity signal of underplated basalt, unlike SRP • Where are the fractionation products of 250,000 km3 of flood basalts and underplating expected with HLP volcanism?

  6. LOGISTICS:Local Contacts Essential • 2-pager (Jenda Johnson) • Town meetings / school visits • “Kicking dirt”

  7. Local Contacts Essential

  8. January, 2006 Installations

  9. Timeline: Seismic Component October 2005 Reconnaissance January 2006 Install Phase Ia (4 instruments) June 2006 Install Phase Ib (12 instruments) October 2006 Recon (19 sites; vaults constructed) April 2007 Recon (~60 sites) June 2007 Complete Phase I (102 stations) September 2008 Phase II (relocate ~70) Active source experiment Fall 2009 Demobilization Summers: “Friends of HLP” meetings

  10. Shear Wave Splitting Across the PNW • Very simple across most of region • Local complexity near Cascades and accreted terranes N=439

  11. Roth and Fouch, this meeting

  12. Opportunities from Dense Seismic Coverage Across the Pacific Northwest • Over 250 BB sites in addition to ~75 USArray and permanent stations

  13. Opportunities from Dense Seismic Coverage Across the Western U.S. • Over 400 BB sites in addition to USArray and permanent stations

  14. Observations on Neogene Volcanism • B&R and volcanism does not notice pC continental boundary • Volcanism concentrated at B&R margins, particularly Northern boundary • Volcanism does not obviously correlate with extension amount • Largest volume of basalt erupted well N of SRP; no associated silicic volcanism • Bimodal volcanism characteristic of HLP, SRP and B&R • ~4 Myr hiatus between flood basalts and beginning of rhyolite migrations

  15. January, 2006 Installations

  16. January, 2006 Installations

  17. Shear Wave Splitting Across the PNW • Very simple across most of region • Larger splitting times in southern Cascadia N=439

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