HR: 10:50h
AN: T22B-03    [Abstracts]
TI: Thermal Isostasy – a new Constraint for Heat Generation Models of Continental Lithosphere
AU: * Chapman, D S
EM: chapman@earth.utah.edu
AF: Dept of Geology & Geophysics University of Utah, 135 S, 1460 E, Salt Lake City, UT 84112, United States
AU: Hasterok, D
EM: hasterok@earth.utah.edu
AF: Dept of Geology & Geophysics University of Utah, 135 S, 1460 E, Salt Lake City, UT 84112, United States
AB: A general thermal isostasy model for continental provinces provides a new constraint for continental geotherms and therefore for the vertical distribution of heat generation throughout the lithosphere. Continental elevation results primarily from a combination of compositional and thermal buoyancy. The thermal component of elevation is isolated by using seismic velocity data and a velocity-density transform to remove crustal thickness and local crustal density effects. The remaining "adjusted" elevation of continental provinces for 73 global tectonic provinces shows an approximate 3000 m variation between hot rift zones and cold shield regions, not unlike the elevation difference between hot mid ocean ridges and cool abyssal plains in the oceanic case. Both amplitude and trends of thermal elevation are well predicted from a set of continental geotherms for which we assume a standard vertical distribution of heat production. A diagnostic plot of adjusted elevation versus heat flow allows us to identify regions of anomalous heat generation. For example the low thermal/adjusted elevation (84 m) of the Precambrian Wopmay Orogen in northern Canada is consistent with a surface heat flow of 43 mW- m^-2 rather than the observed heat flow of 75 mW-m^-2. The excess 32 mW-m^-2 heat flow most likely arises from anomalous heat generation, the vertical distribution of which is tightly constrained because it must produce a geotherm equivalent to the standard geotherm consistent with a surface heat flow of 43 mW- m^-2. Further examples are drawn from north and south Australian cratons.
DE: 8103 Continental cratons
DE: 8110 Continental tectonics: general (0905)
DE: 8130 Heat generation and transport
SC: Tectonophysics [T]
MN: 2007 Fall Meeting