High Lava Plains ProjectHigh Lava Plains Project

Matt FouchMatt FouchArizona State UniversityArizona State University

School of Earth and Space ExplorationSchool of Earth and Space Exploration

2007 EarthScope National Meeting, Monterey, CA2007 EarthScope National Meeting, Monterey, CA

MARGINS/GeoSwath WorkshopMARGINS/GeoSwath Workshop

High Lava Plains Project:High Lava Plains Project:Understanding the Causes of Continental Understanding the Causes of Continental

Intraplate Tectonomagmatism Intraplate Tectonomagmatism

Arizona State University - Matt FouchArizona State University - Matt Fouch

Carnegie Institution of Washington - Rick Carlson, David Carnegie Institution of Washington - Rick Carlson, David JamesJames

Miami University - Bill HartMiami University - Bill Hart

Massachusetts Institute of Technology - Tim GroveMassachusetts Institute of Technology - Tim Grove

Oregon State University - Anita Grunder, Bob DuncanOregon State University - Anita Grunder, Bob Duncan

University of Oklahoma - Randy KellerUniversity of Oklahoma - Randy Keller

University of Rhode Island - Chris KincaidUniversity of Rhode Island - Chris Kincaid

University of Texas, El Paso - Steve HarderUniversity of Texas, El Paso - Steve Harder

Funded byFunded by

NSF-ContinentalNSF-Continental

DynamicsDynamics

OR

ID

MT

WY

NV

CA

UT

WA

OWL

VFZ

BFZEDFZ

MFZ

ESRP

SAFZ

14

1210

86

42

0

0

2

46

810

NNR

North American Plate14-26 km/Ma

JdFPlate

NB

Post 10 Ma Volcanism in the Western US (After Smith and Luedke, 1984)

87Sr/86Sr > 0.706

Observations on Post-12 Ma VolcanismObservations on Post-12 Ma Volcanism

• Two migrating Two migrating volcanic tracesvolcanic traces

• Migrating volcanism Migrating volcanism defined by rhyolitesdefined by rhyolites

• Basaltic activity Basaltic activity continuous along continuous along both tracesboth traces

• Volcanism in HLP Volcanism in HLP associated with associated with right-lateral S-S right-lateral S-S faulting as B&R faulting as B&R extension dies out extension dies out to Nto N

0.704

0.705

0.706

0.707

115 116 117 118 119 120 121Longitude

87Sr/86Sr4

5

6

7

8

9

10

5 10 15 20Age (Ma)

MgO (wt%)

Strong Temporal and Spatial Strong Temporal and Spatial Relationships with Basalt CompositionRelationships with Basalt Composition

• HLP basalts become HLP basalts become more primitive with timemore primitive with time

• Composition shifts Composition shifts towards a high-Al tholeiite towards a high-Al tholeiite consistent with a very consistent with a very shallow mantle sourceshallow mantle source

• Primitive basalts across Primitive basalts across HLP show limited isotopic HLP show limited isotopic variationvariation

• Changes dramatically at Changes dramatically at border with Precambrian border with Precambrian North AmericaNorth America

Isostatic GravityIsostatic Gravity• Eastern OR/WA Eastern OR/WA

show no gravity show no gravity signal of signal of underplated underplated basalt, unlike basalt, unlike SRPSRP

• Where are the Where are the fractionation fractionation products of products of 250,000 km250,000 km33 of of flood basalts and flood basalts and underplating underplating expected with expected with HLP volcanism?HLP volcanism?

LOGISTICS:LOGISTICS:Local Contacts Local Contacts

EssentialEssential

• 2-pager2-pager(Jenda Johnson)(Jenda Johnson)

• Town meetings / Town meetings / school visitsschool visits

• ““Kicking dirt”Kicking dirt”

Local Contacts EssentialLocal Contacts Essential

January, 2006 InstallationsJanuary, 2006 Installations

Timeline: Seismic ComponentTimeline: Seismic Component

October 2005October 2005 ReconnaissanceReconnaissance

January 2006January 2006 Install Phase Ia (4 instruments)Install Phase Ia (4 instruments)June 2006June 2006 Install Phase Ib (12 instruments)Install Phase Ib (12 instruments)October 2006October 2006 Recon (19 sites; vaults constructed)Recon (19 sites; vaults constructed)

April 2007April 2007 Recon (~60 sites)Recon (~60 sites)June 2007June 2007 Complete Phase I (102 stations)Complete Phase I (102 stations)September 2008September 2008 Phase II (relocate ~70)Phase II (relocate ~70)

Active source experimentActive source experiment

Fall 2009Fall 2009 DemobilizationDemobilization

Summers: Summers: “Friends of HLP” meetings“Friends of HLP” meetings

Shear Wave Shear Wave Splitting Across Splitting Across

the PNWthe PNW• Very simple across Very simple across

most of regionmost of region• Local complexity near Local complexity near

Cascades and Cascades and accreted terranesaccreted terranes

N=439

Roth and Fouch, this meeting

Opportunities Opportunities from Dense from Dense

Seismic Coverage Seismic Coverage Across the Pacific Across the Pacific

NorthwestNorthwest

• Over 250 BB Over 250 BB sites in addition sites in addition to ~75 USArray to ~75 USArray and permanent and permanent stationsstations

Opportunities Opportunities from Dense from Dense

Seismic Coverage Seismic Coverage Across the Across the

Western U.S.Western U.S.

• Over 400 BB Over 400 BB sites in addition sites in addition to USArray and to USArray and permanent permanent stationsstations

Observations on Neogene VolcanismObservations on Neogene Volcanism

• B&R and volcanism does not B&R and volcanism does not notice pC continental notice pC continental boundaryboundary

• Volcanism concentrated at Volcanism concentrated at B&R margins, particularly B&R margins, particularly Northern boundaryNorthern boundary

• Volcanism does not obviously Volcanism does not obviously correlate with extension correlate with extension amountamount

• Largest volume of basalt Largest volume of basalt erupted well N of SRP; no erupted well N of SRP; no associated silicic volcanismassociated silicic volcanism

• Bimodal volcanism Bimodal volcanism characteristic of HLP, SRP characteristic of HLP, SRP and B&Rand B&R

• ~4 Myr hiatus between flood ~4 Myr hiatus between flood basalts and beginning of basalts and beginning of rhyolite migrationsrhyolite migrations

Oregon

Idaho

Wyoming

Nevada

California

Utah

Arizona

Basalt

Andesite

Rhyolite

< 5 5-10 10-17 Ma

87Sr/86Sr > 0.706

Post 17 Ma Volcanism in the Western US (after Luedke and Smith, 1984)

Great Basin

January, 2006 InstallationsJanuary, 2006 Installations

January, 2006 InstallationsJanuary, 2006 Installations

Shear Wave Shear Wave Splitting Across Splitting Across

the PNWthe PNW• Very simple across Very simple across

most of regionmost of region• Larger splitting times Larger splitting times

in southern Cascadiain southern Cascadia

N=439