HR: 0830h
AN: T31D-0868    [PDF]
TI: Cool Cratons and Thermal Blankets: How Continents Affect Mantle Convection
AU: * Trubitsyn, V P
AF: Institute of Physics of the Earth, B Gruzinskaya 10, Moscow, 123810 Russian Federation
AU: * Trubitsyn, V P
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Abbott, D H
EM: dallas@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964 United States
AB: Mantle convection models with moving continents show that continents profoundly affect the form of mantle convection. If the continents are wider than the wavelength of convection cells (about 3000 km), they cause neighboring thermal upwelling zones to coalesce into a single focused upwelling. This focused upwelling zone will have a potential temperature anomaly of about 200 degrees C, much higher than the 100 degree C temperature anomaly of upwelling zones generated beneath typical oceanic lithosphere. This excess temperature anomaly persists for about 100 Ma after supercontinent breakup. In contrast, small continental blocks ($<$3000 km diameter) do not induce focused upwelling zones. Instead small continental blocks are dragged to mantle downwelling zones. As a result of emplacement over relatively cold mantle (downwellings), small continental blocks develop thick, cold thermal boundary layers (cratonic roots), and are geologically favored to keep these roots and to have low geothermal gradients.
DE: 7218 Lithosphere and upper mantle
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8125 Evolution of the Earth
SC: Tectonophysics [T]
MN: 2003 Fall Meeting