Heat flow in kimberlite provinces of ancient platforms

Geothermal data on six kimberlite provinces of ancient platforms in Siberia , Africa, North America, and South America are considered. The intensity of heat flow there varies from 10-18 to 62-100 mW/m(2), averaging 46-54 mW/m( 2). These average values are in concordance with conductive geotherms obtai ned by thermobarometry of mineral associations from deep-seated xenoliths f rom kimberlite pipes. The only exclusion is the Yakutian kimberlite provinc e In the east of the Siberran Platform, where the intensity of measured hea t flows (20-30 mW/m(2)) is considerably lower than that calculated for the time of kimberlite formation (35-40 mW/m(2)). This anomaly may be related n ot to the climate cooling but to a decrease in the intensity of radiogenic heat generation in the Earth's crust and shielding of mantle heat now. This is suggested from the occurrence of kimberlite fields within the protrusio ns of the lower crust with minimum contents of radioactive elements in its rocks.