Simultaneous inversion of gravity and heat flow data: constraints on thermal regime, rheology and evolution of the Canadian Shield crust

Heat flow and gravity are sensitive to crustal composition and thickness. In this paper, we show that heat flow and gravity data, combined with constraints from seismic refraction, can be inverted to obtain the gross composition of the crust. The inversion method is used to determine the crustal structure in different parts of the Canadian Shield. The long wavelength variations in heat flow imply a difference in thermal regime between and within provinces and subprovinces of the Canadian Shield. The crustal heat production determined by inversion is used to construct temperature and rheological profiles for the lithosphere in different parts of the Canadian Shield. Regions enriched in radioelements (the western part of the Abitibi subprovince and the Thompson Belt) had a weak rheology after they stabilized and could not withstand stresses for geologically long times. In contrast, subprovinces that are depleted in radioelements (the eastern part of the Abitibi and the Lynn Lake Belt) had a stronger rheology and might have preserved crustal roots after their formation.