Abstract:

Since nearly two decades ago, many temporary arrays have been deployed in the Archean Wyoming province and its neighboring areas. Due to the small station spacing (up to 2 km) of these array deployments, it is now possible to image the seismic structure in the Wyoming crust and upper mantle with a resolution scale comparable to active source profiling studies. Remarkable agreements between the passive and active source studies are found in the crust and shallow upper mantle. A high velocity dipping structure down to >150 km is revealed from tomography at the southern craton edge. Supported by other lines of evidence, a frozenin fossil subduction slab model at the craton margin is preferred, which indicates that lateral slab accretion may be an important mechanism during the early craton assembly. High velocity lower crust magmatic underplates are present in the northern and central craton, but are perhaps inexistent in the south, indicating that they are related to possible different cratonization processes among the craton subprovinces. The spatial coincidence of these relict seismic structures with the surface sutures suggests the early lithospheric responses to various mantle deformation processes have been well preserved. Young tectonisms, for example the Yellowstone hotspot, have significantly altered the crust and lithosphere in the western side of the craton.

Key words: Wyoming, craton, lithosphere, seismic imaging, mantle plume, wedge