HR: 0830h
AN: T31E-0883    [PDF]
TI: Gravity Modeling of a Batholith and Low-Velocity Mantle Zone Beneath the Colorado Mineral Belt
AU: * McCoy, A M
EM: amccoy@shomaker.com
AF: John Shomaker and Associates, Inc., 2703 Broadbent Parkway NE, Suite B, Albuquerque, NM 87107 United States
AU: Roy, M
EM: mroy@unm.edu
AF: Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, NM 87131 United States
AU: Trevino, L
EM: trevino@geo.utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968-0555 United States
AU: Keller, R
EM: keller@geo.utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968-0555 United States
AB: The Colorado Mineral Belt (CMB) is delineated as a belt of mostly Laramide mineralization within a broader zone of Laramide and older magmatism in central Colorado. One of North America's largest Bouguer gravity anomalies coincides with this broad NE-trending zone of protracted magmatic activity. Seismic studies suggest that parts of the CMB region are underlain by anomalously low-density crust and that the CMB lies within a broad zone of low seismic velocities in the uppermost mantle. Our gravity modeling explores simple distributions of subsurface mass deficits that can explain the CMB negative Bouguer gravity anomaly, and are constrained by geologic estimates of the extent of crustal plutonic bodies and by seismically-inferred crustal and upper mantle velocity anomalies. Specifically, our forward models include (1) a low-density batholithic body in a 20-km thick upper crust with a density contrast of 150 kg/m3, (2) a 25-km thick lower crust with a potential low-density body of density contrast 150 kg/m3, and (3) an upper mantle with a low-density body of variable density contrast placed at variable depth. The viability of the crust and mantle low-density bodies in our first-order forward models is tied to their consistency with seismic observations, and we work toward refinement of the models using empirical density/velocity relationships and the upper crustal structure established by the CDROM seismic refraction line.
DE: 8102 Continental contractional orogenic belts
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8122 Dynamics, gravity and tectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting