Electrical conductivity, which depends on ionic fluids, metal or carbon content and temperature, provides complementary information to properties determined from seismic or potential field data. Our ability to image conductivity structure has recently undergone a revolution. These projects involve high resolution magnetotelluric (MT) profiling in the Trans-Hudson Orogen (THO) and the southeast Appalachians (SEA). The common element in the two experiments is illumination of processes in fossil zones of continental collision. The THO experiment will coincide with an 850 channel COCORP seismic reflection line across the Williston Basin and will be closely coordinated with the Canadian Lithoprobe transect of the THO. Its targets include the largest known conductivity anomaly in N. America, sutures between the orogen and adjacent Archean provinces and possibly anomalous mantle under the orogen. It is expected to provide a definitive demonstration of the resolving power of MT data in nearly ideal conditions. The SEA experiment will take advantage of the fact that the ocean edge can amplify MT response to certain structures. It is expected to settle the controversy about the location of the Alleghanian suture, map the sedimentary package under the thrust associated with this collision event, provide important insight into the preservation of retrograde metamorphic conditions in deep continental crust and estimate the volatile content in (and the presence of partial melt beneath) very old oceanic lithosphere.

Agency
National Science Foundation (NSF)
Institute
Division of Earth Sciences (EAR)
Application #
9121278
Program Officer
Leonard E. Johnson
Project Start
Project End
Budget Start
1991-09-01
Budget End
1995-08-31
Support Year
Fiscal Year
1991
Total Cost
$500,000
Indirect Cost
Name
Woods Hole Oceanographic Institution
Department
Type
DUNS #
City
Woods Hole
State
MA
Country
United States
Zip Code
02543