THERMAL STRUCTURE OF THE CONTINENTAL LITHOSPHERE - CONSTRAINTS FROM SEISMIC TOMOGRAPHY

Our ability to determine constrained estimates of the temperature structure of the continental lithosphere is hindered by the lack of independent observations of temperature within the crust. Presently used techniques for the estimation of crustal temperatures rely primarily on near-surface temperature and heat-flow observations coupled to estimates of crustal structure and associated distribution of thermal parameters within the crust. The achievements of seismic tomography in providing an image of the heterogeneous nature of the Earth's interior may provide an additional tool to help both constrain estimates of thermal structure within the crust and provide a means to evaluate assumptions of the spatial distribution of thermal parameters (thermal conductivity, heat production) within the crust. We have developed preliminary tools which help to exploit the information content of the seismic results as contained in the observed velocity anomalies. These techniques allow thermal-compositional (T-X) tomography of the lithosphere providing a means to separate the temperature from compositional effects in producing velocity anomalies. The resulting thermally dominated seismic structure can then be used (in conjunction with surface heat-flow observations) as an additional constraint on estimates of the temperature structure of the crust.