A 3.85 Ga record of heat production and its geodynamic response

<div> <div> <div> <div> <p>Radiogenic heat production is perhaps the largest contributor to uncertainties when extrapolating the surface ther- mal regime to greater depths. Despite its reputation as a notoriously difficult to predict quantity, there are several geodynamic processes that may lead to systematic variations in heat production in igneous rocks. In this presenta- tion, we discuss the influence of some of these processes including fractionation in volcanic arc settings, thermal stability in the early Earth, and the impact of supercontinents. Within volcanic arc settings, the concentration of heat producing elements is controlled by height of the crustal column as are many trace elements. Three arcs, Banda, Calabrian and Aeolian, are clear outliers, which is likely due to the subduction of continental crust and/or thick pack- ages of continental sediments. A similar pattern to volcanic arcs is observed in the continental crust through time, which may be recording the growth of continental crustal thickness, with low heat production in Archean terranes and increasing to approximately 2 Ga. At 2 Ga, heat production rapidly increases before remaining relatively stable until the present day. An alternative hypothesis for the gradual increase in heat production in the Archean suggests heat production is limited by crustal stability. If heat production exceeds a stability threshold then the crust will likely be reworked or remelted, resetting high temperature geochronometers. The crust becomes stable once heat production decays below the threshold. Evidence for such a threshold is inferred from the near constant ‘original’ heat production of terranes—accounting for decay since formation. Knowledge of these controls and/or variations on heat production will help produce more accurate geotherms for the continental crust and can improve regional prospectively for many trace elements.</p> </div> </div> </div> </div>