Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

摘要

Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep wells of the Canadian Arctic Archipelago. Corrected bottom hole temperature (BHT) data and drill stem test (DST) temperatures were used to determine the thermal gradients for sites for which the quality of data was sufficient. Thermal gradients evaluated for depths below the base of permafrost for the onshore wells and below sea bottom for the offshore wells were combined with the estimates of effective thermal conductivity to approximate heat flow for these sites. The present geothermal gradient is in the 15-50 mK/m range (mean = 31 +/- 7 mK/m). Present heat flow is mainly in the 35-90 mW/m(2) range (mean = 53 +/- 12 mW/m(2)). Maps of the present geothermal gradient and present heat flow have been constructed for the basin. The analysis of vitrinite reflectance profiles and the calculation of logarithmic coalification gradients for 101 boreholes in the Sverdrup Basin showed large variations related in many cases to regional variations of present terrestrial heat Bow. Paleo-geothermal gradients estimated from these data are mostly in the range of 15-50 mK/m (mean = 28 +/- 9 mK/m) and paleo-heat flow is in the 40-90 mW/m(2) range (mean = 57 +/- 18 mW/m(2)) related to the time of maximum burial in the Early Tertiary. Mean values of the present heat Bow and paleo-heat Bow for the Sverdrup Basin are almost identical considering the uncertainties of the methods used (53 +/- 12 versus 57 +/- 18 mW/m(2), respectively). Present geothermal gradients and paleo-geothermal gradients are also close when means are compared (31 +/- 7 versus 28 +/- 9 mK/m respectively). A zone of high present heat Bow and a paleo-heat flow zone coincide in places with the northeastem-southwestern incipient rift landward of the Arctic margin first described by Balkwill and Fox (1982). Correlation between present heat flow and paleo-heat flow for the time of maximum burial in the earliest Tertiary suggests that the high heat flow zone has prevailed since that time. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 45]