Transient mobilization of subcrustal carbon coincident with Palaeocene–Eocene Thermal Maximum

Plume magmatism and continental breakup led to the opening of northeast Atlantic Ocean during globally warm early Cenozoic. This warmth culminated in a transient (170 thousand year, kyr) hyperthermal event associated with large, if poorly constrained, emission carbon called Palaeocene–Eocene Thermal Maximum (PETM) 56 million years ago (Ma). Methane from hydrothermal vents coeval North Igneous Province (NAIP) has been proposed as trigger, though isotopic constraints deep sea sediments have instead implicated direct volcanic dioxide (CO2) emissions. Here we calculate that background levels outgassing mid-ocean ridges large igneous provinces yield only one-fifth required trigger hyperthermal. However, geochemical analyses sequences spanning rift-to-drift phase NAIP indicate sudden ~220 kyr-long intensification magmatic activity coincident PETM. was likely driven by thinning enhanced decompression melting sub-continental lithospheric mantle, which critically contained high proportion carbon-rich metasomatic carbonates. Melting models coupled tectonic–geochemical simulations >104 gigatons subcrustal mobilized into ocean atmosphere sufficiently rapidly explain scale pace A change style rifting fluxes helped Maximum, according well tectonic modelling.