A High Core Heat Flow Solution to Earth’s Thermal and Magnetic Paradoxes

Abstract:

Recent discoveries relating to the thermal and magnetic history of the Earth have revealed that a clement surface and a dynamo generated magnetic field have persisted over almost all of Earth history. However, the preferred mantle radioactivity and heat loss efficiency predict wide spread mantle melting, or “thermal catastrophe”, only 2−3 Ga. Similarly, paleomagnetic observations that indicate a geodynamo as old as 3.4 Gyr are at odds with the “new core paradox”, which claims insufficient energy to drive the ancient geodynamo prior to inner core nucleation ~ 1 Ga in light of recent revisions to the thermal conductivity of the core. We demonstrate that to avoid both the mantle and core paradoxes restricts the present core heat flow to 13 − 17 TW, radiogenic core heat production to 1.5 − 2.0 TW, and inner core age to 0.4 − 0.5 Ga. This solution accommodates the geochemically preferred mantle radiogenic heat production of 13 TW, while maintaining a mostly solid mantle and core generated magnetic field over the geological history of the planet. Inner core nucleation should be accompanied by a boost in magnetic energy in the core and latent heat released at the inner-core boundary, which may be imprinted in the surface paleomagnetic and hot-spot record at that time.