Heat production and heat flow in the mantle lithosphere, Slave craton, Canada

Thermobarometric data for mantle xenoliths from a kimberlite pipe in the NWT Canada are used to constrain the thermal properties of the lithospheric mantle underlying the Slave craton. We derive an analytical expression for a steady-state conductive mantle geotherm that is independent of the geometry and thermal properties of the crust. The model has an upper boundary coincident with the MOHO at a depth Z(m), and has temperature T-m and heat flow q(m). The mantle is assumed to have constant radiogenic heat production (A) and we allow for a temperature-dependent thermal conductivity [K(T) = Ko(1 + B(T - T-m))]. Inverting the thermobarometric data through the model geotherm gives limiting values for mantle heat production (A) and bounds on the temperature dependence of K (e.g. B) that are consistent with the mantle P-T array. We characterize the Slave lithospheric mantle in terms of three critical parameters q(m) (mW m(-2)), A (muW m(-3)), T-m (degreesC). The optimal solution has values [15.1, 0.012, 455]. This characterization of thermal state of the Slave mantle is based mainly on petrological data and is not biased by assumptions about crustal thermal properties. Our analysis shows that a substantial range of parameter values can be used to describe the data accurately and the two bounding solutions are [24.2, 0.088, 296] and [12.3, 0, 534], respectively. However, model parameters are strongly correlated and this precludes the arbitrary selection of values of [q(m), A, T-m] from these ranges. (C) 2001 Elsevier Science B.V. All rights reserved.