Large Igneous Provinces are a Direct Consequence of the Early Global Magma Ocean

The large igneous provinces (LIPs) resulted from giant intraplate magmatic events mobilizing volumes of magma up to several 106 km3. They induced mass extinctions of life, break-up of continents and great regional uprisings. The production of LIPs implies high rates of mantle melting, suggesting similar melting processes for LIPs and Komatiites. Based on previous experimental works, the depth of the mantle source decreases from 600-700 km for the oldest komatiites to 100-300 km for picrites in phanerozoic flood basalt and recent oceanic islands. Globally, the rates of mantle melting range from 10 to 50%.

We develop a geodynamical model that explains the origin of the hot mantle plumes capable of generating the appropriated pressure-temperature for such mantle melting conditions. We show the major role of a largely super-adiabatic temperature gradient that was established in the deep mantle after the solidification of the magma ocean. Ascent of hot mantle plumes from high depths creates excess temperatures up to 250-300 K in the shallow mantle, which explains well the composition of ancient lavas. Secular mantle cooling induces a progressive flattening of the mantle temperature gradient toward an adiabatic profile and a temporal evolution of the lava types and compositions.