Resonances of the fluid core for a tidally decelerating Earth: cause of increased plume activity and tectonothermal reworking events?

摘要: Abstract In the geological past when Earth's decelerating rotation passed through critical length of day ∼ 22.2 h, free nutation or ‘tipping’ fluid core (for a shape in hydrostatic equilibrium) would have resonated precisely with retrograde annual forced caused by solar torques. This resonance may orders-of-magnitude amplification and velocity motions, leading to temperature increase heat release near core-mantle boundary, instability D″ thermal boundary layer at base mantle, upwelling deep mantle plumes. Neoproterozoic palaeotidal data indicate 21.9 ± 0.4 h/day 620 Ma, thus placing h 530 100 Ma. A departing ±5% from its equilibrium value places interval 250 The one distinctive, major tectonothermal event Ma was that ‘late Pan-African’ age, which affected much Gondwana during late Neoproterozoic-early Palaeozoic. activity, peaked between 570 500 marked high temperatures mid-crustal levels elevated flow, widespread granulite facies metamorphism crustal reworking anatexis, commonly absence obvious pervasive deformation, extensive epeirogenic uplift extrusion flood basalts; such features an intense heating be ascribed plumes hotspots. Furthermore, volcanism rifting Laurentia Palaeozoic suggest coeval led continental breakup including opening Iapetus Ocean. apparent global peak plume activity reflect flux D″, equilibrium). evidently underwent stronger resonances semi-annual 1/3-annual nutations widely spaced times Archaean, approximately 17.7 15.4 respectively; these two probably greater increases amplitude motions than occurred resonance. Proterozoic palaeorotational very strong correlate worldwide 2700 Ma; this is granitoid intrusion basalts komatiites, has been high-temperature boundary. hypothesis events resulted generated response for tidally Earth tested acquisition quality early Palaeoproterozoic Archaean.