HR: 14:25h
AN: GP13A-03    [Abstracts]
TI: Conductivity Structure Associated with the Yellowstone-Snake River Hotspot Track
AU: * de Groot-Hedlin, c
EM: chedlin@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 gilman drive, La Jolla, 92093-0225 United States
AU: Constable, S
EM: sconstable@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 gilman drive, La Jolla, 92093-0225 United States
AU: Weitemeyer, K
EM: kweitemeyer@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 gilman drive, La Jolla, 92093-0225 United States
AU: Terzi, L
EM: lucreziaterzi@hotmail.com
AF: Dipartimento di Geologia, Universita Statale di Milano, Milan, 20121 Italy
AB: The Snake River Plain (SRP) in Idaho marks the path of an active hotspot with a terminus under Yellowstone National Park in Wyoming. In the 2003 and 2004 field seasons we collected magnetotelluric (MT) data at 36 sites in the Snake River Plain (SRP) region to map the conductivity structure of this region. Our objective is to detect conductive anomalies associated with the Yellowstone hotspot, and ultimately, to place limits on the temperature and melt fraction of these features. To this end, we collected long period electrical and magnetic data at 28 sites along a northwest-southeast line stretching from near Challis to the southeast corner of Idaho, at an average spacing of 13 km, and 8 more sites along a perpendicular transect along the SRP, at an average spacing of 30km. We used long period MT equipment from the ElectroMagnetic Study Of the Continents (EMSOC) instrument pool, and broadband field data at 2 sites using SIO's MT equipment. Parkinson vectors for this area point in the direction of the Snake River Plain but in a direction slightly to the southwest of the transect, and not to the northeast where the Yellowstone hotspot currently lies. Initial results of inversions of these data suggest that the mantle in this region is unusually conductive, suggesting that it is anomalously warm, or has a high melt fraction in this region. Detailed mantle structure in this region is, however, partially masked by the presence of highly conductive features at depths from approximately 10-35km. Our preliminary interpretation is that the shallow, conductive features correlate with the subsurface dikes that trend across the SRP and are associated with the extension of the Snake River Plain; deeper conductive features correspond to melt associated with the passage of the Yellowstone hotspot. A better understanding of the complex interaction between the Yellowstone hotspot track and the dynamics of crustal extension at the surface will require a full 3D analysis of MT data, thus we are proposing to collect data at 1 or 2 more transects across the Plain.
DE: 8010 Fractures and faults
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 3210 Modeling
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting