- Webb 1100
Forrest Horton, PhD Candidate (UCSB), “Did mantle-derived phosphorus fertilize the Neoproterozoic ocean?”
Abstract: The bioavailability of phosphorus on Earth over time may be linked to the supercontinent cycle, as well as the progressive cooling of crustal subduction zones. Large igneous province (LIP) magmatism associated with the breakup of supercontinent Rodinia led to the erosion of large volumes of mafic rock into the Neoproterozoic ocean. Based on the phosphorus contents and the areal extent of mafic dike swarms associated with the LIPs, models suggest that the erosion of LIPs sustained an elevated phosphorus flux to the ocean for >100 Myr. Thus, the erosion of LIPs may explain elevated marine phosphate levels that led to an increase in biologic activity in the Cryogenian. LIP magmas with especially high phosphorus concentrations were likely sourced from phosphorus-rich zones in the mantle that resulted from CO2 metasomatism. Prior to the Neoproterozoic, hotter-than-present subduction zones probably inhibited the efficient transport of CO2 into the deep mantle. Therefore, widespread CO2 metasomatism of mantle lithosphere—the principle cause of phosphorus-rich flood basalts—may be a primarily Neoproterozoic and Phanerozoic phenomenon.