MANTLE STRUCTURE BENEATH THE ROCKY MOUNTAINS: CD-ROM PASSIVE EXPERIMENT
The Continental Dynamics - Rocky Mountains (CD-ROM) experiment seeks to constrain the evolution, stabilization and modification of the continental lithosphere. We present the detailed results of images of the mantle constructed using broadband teleseismic receiver functions beneath the interior western United States, with focus on the southern Rocky Mountains. The targets of this experiment were the Cheyenne suture, an Archean continent Proterozoic arc terrane boundary, and the Jemez suture/volcanic lineament, which separates the Proterozoic Mazatzal and Yavapai provinces. The main features observed underneath the Cheyenne belt are: 1) a Proterozoic oceanic slab most plausibly tectonically emplaced beneath the rifted Archean margin; 2) Structurally separate, old and thick (>150 km) lithosphere as evidenced by changes in mantle layering across the Cheyenne Suture. Below the Jemez volcanic lineament two strong sub-crustal layers are imaged down to 100 km depth that correlate well with a low velocity zone. This layering is interpreted to map the extent of the lithosphere and most plausibly results from changes in lithospheres chemical makeup. The mantle transition zone in this region shows 30 km of topography. This would suggest significant thermal heterogeneities possibly originating from mass transport across the transition zone, supplying the upper mantle with the observed heterogeneities.