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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