LITHOSPHERE-SCALE MODELS OF THE 3D CONDUCTIVE THERMAL FIELD - PREDICTIONS AND LIMITATIONS IN THE BEAUFORT-MACKENZIE BASIN (ARCTIC CANADA)

The present-day temperature distribution of the Beaufort-Mackenzie Basin is characterised by large-scale anomalies that have proposed to be related to specific tectonic domains and heat transported by convection along major discontinuities (Chen et al., 2008). As a result of a poly-phase tectonostratigraphic history, the basin shows a complex stratigraphic architecture and density distribution (Sippel et al., submitted), arguing for a wide range of thermal conductivities which might additionally complicate the thermal structure. We calculate the 3D conductive thermal field for different lithosphere-scale models of the Beaufort-Mackenzie Basin, thus taking one step further towards a quantification and localization of heat transporting processes in this petroliferous region.

The base for our thermal calculations is provided by a crust-scale 3D finite-element model of the basin which is consistent with seismic and well data as well as the observed gravity field (Sippel et al., submitted). This model is composed of seven Mesozoic-Cenozoic tectonostratigraphic units which tend to be younger, less compacted, and thus less thermally conductive, towards the north. The crust below is mostly continental with an upper low-density part (2720 kg/m³) and a lower moderate-density part (2850 kg/m³). Only the northernmost parts of the basin are assumed be underlain by oceanic crust (2900 kg/m³).

For our thermal calculations, we extend the model down to the lithosphere-asthenosphere boundary which serves as the lower boundary condition of 1300 °C. The upper boundary condition is provided by the well-known depth distribution of the permafrost base (0 °C isotherm) in the region. For the calibration of the modelling results, we use temperature data from more than 230 wells and depths of up to 5000 m. We present different lithosphere-scale thermal models and comment on their (mis-)fits with the observed temperature distribution.

References:

Chen, Z., Osadetz, K.G., Issler, D.R., Grasby, S.E., 2008. Hydrocarbon migration detected by regional temperature field variations, Beaufort-Mackenzie Basin, Canada. AAPG Bulletin, 92(12): 1639-1653.

Sippel, J., Scheck-Wenderoth, M., Lewerenz, B., Kroeger, K.F., submitted. A crust-scale 3D structural model of the Beaufort-Mackenzie Basin (Arctic Canada). Submitted to Tectonophysics.