Ascending Heat and Mass Flow in Continental Crust: on the Problem of Driving Forces of Tectogenesis

Abstract

The geophysical and geochemical indicators of the ascending heat and mass flow in the continental crust—conductive heat flow through the surface of the crust and the isotopic composition of helium in freely circulating underground fluids—are considered. The tectonic ordering of the heat flow and the factors responsible for the dispersion in its density (q) are discussed. The sources and reservoirs of terrestrial helium are characterized; the stability of 3Не/4Не ratio in the geological section along the depth and in time is demonstrated; linear and areal variations in this ratio on different scales are revealed and their similarity with heat flow distribution is established. The correlations of helium isotopic composition in freely circulating underground fluids with the conductive heat flow density and helium composition in gases in the regions of recent volcanism as well as with strontium composition in young lavas indicate helium transport from the mantle to the crust by the magmatic melts.