The weathering of voluminous large igneous provinces

The weathering of voluminous large igneous provinces (LIPs) fertilized the Neoproterozoic ocean with P. The massive Franklin LIP was formed 720 Ma as a result of the supercontinent Rodinia breaking apart. Preceding eruption, LIP magmas became variably enriched in P by entraining metasomatised parts of the lithosphere and during crystal fractionation. The mafic dike swarms covered 3.7 × 106 km2, and the flood basalts could have covered twice that area, i.e. 8% of the Neoproterozoic land surface. Basalt chemical weathering would have liberated a bioavailable LIP-derived P flux of 1-5 × 109 mol/yr, which may have been sustained for millions of years (Horton 2015). This could have doubled the global flux of dissolved P to the ocean, and this fertilisation would have increased the burial of organic C and thus the rate of O2 production in the ocean. Further, the CO2 removal by photosynthesis and basalt weathering could have triggered the Sturtian glaciation. These tectonically driven events provided the conditions for the evolution of complex multicellular life (Horton 2015).