HEAT-FLOW VARIATIONS IN THE GRENVILLE PROVINCE, CANADA

Heat flow and heat production data provide strong constraints on the c omposition and evolution of the continental crust. Four new heat flow and heat production data from the Grenville Province in Canada are pre sented and included in local and regional analyses of heat flow variat ions. Thirty heat flow data are now available in the Late Proterozoic Grenville Province, where the mean heat flow (41+/-11 mW . m(-2)) does not differ from that in the Archean Superior Province (41+/-9 mW . m( -2)). It is shown that varying crustal heat production or heat refract ion effects account for most local heat flow variations. The average c rustal heat production is lower than in the other Late Proterozoic pro vinces because the tectonic evolution of the Grenville promoted the em placement of large mafic bodies. Statistical analyses of heat flow and heat production data in the Grenville Province, in the surrounding pr ovinces (Canadian Appalachians and Superior Province) and in the Norwe gian Shield indicate that, within each province, the range of heat flo w and heat production variations attains 40 mW . m(-2) and 2 mu W . m( -3) respectively. However, the patterns on the histograms are distinct ive and are shown to be regulated by the vertical distribution of heat production. Crustal structure and composition of the Grenville Provin ce and the Norwegian Shield account for similarities and differences i n the heat flow and heat production patterns of the two areas. Mantle heat flow in the Grenville Province lies between 9 and 16 mW . m(-2), as in the Superior Province and in the Norwegian Shield.