Abstract
AbstractEarth's heat budget is strongly influenced by spatial and temporal variations in surface heat flow caused by plate tectonic cycles. Here, we use a novel set of paleo‐seafloor age grids extending back to the mid‐Paleozoic to infer spatiotemporal variations in surface heat loss. The time‐averaged oceanic heat flow is 36.6 TW, or ∼25% greater than at present‐day. Our thermal budget for the mantle indicates that 149 K/Gyr of cooling occurred over this period, consistent with geochemical estimates of mantle cooling for the past 1 Gyr. Our analysis also suggests sustained rapid cooling of the Pacific mantle hemisphere, which may have cooled ∼50 K more than its African counterpart since 400 Ma. The extra heat released from the Pacific mantle may have been trapped there by the earlier long‐lived supercontinent Rodinia (∼1.1–0.7 Ga), and the Pacific mantle may still be hotter than the African mantle today.
Highlights
Earth's thermal evolution is largely controlled by the rate of heat loss through the oceanic lithosphere
Earth's heat budget is strongly influenced by spatial and temporal variations in surface heat flow caused by plate tectonic cycles
The extra heat released from the Pacific mantle may have been trapped there by the earlier long-lived supercontinent Rodinia (∼1.1–0.7 Ga), and the Pacific mantle may still be hotter than the African mantle today
Summary
Earth's thermal evolution is largely controlled by the rate of heat loss through the oceanic lithosphere. For the present-day, Brandl et al (2013) present thermometric evidence (temperature of average zero-age mid-ocean ridge basalts (MORBs)) that the Pacific mantle domain is 25–30 K hotter than the African domain (the Atlantic and Indian ridges). This finding agrees with Dalton et al.'s. (2014) combined analysis of geophysical and geochemical data, which indicates a higher mantle potential temperature in the Pacific Such hemispheric variability in mantle temperature should be linked to spatial variations in the mantle's cooling rate. We use models for Earth's surface heat flow during the past 400 Myr to estimate individual cooling histories for the Pacific and African mantle domains, and briefly entertain some simple scenarios that could explain their potentially distinct thermal evolution
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