Plume-Ridge Interaction During Large Igneous Province Formation

Large Igneous Provinces (LIPs) and their mechanisms of formation play an important role in plate tectonics and life cycles of the planet. They represent the main magmatic pulse of a mantle plume when it impinges the lithosphere creating a massive outpouring of lavas in short periods of time (<5-10 Ma); these plumes are usually associated to large low shear-velocity provinces (LLSVPs) in the lower mantle. Global tomography and numerical models suggest a link between the margins of the LLSVPs and the occurrence of mantle plumes and LIPs. Moreover, kinematic and paleotectonic reconstructions also suggest that mid-ocean ridges play a role during the emplacement of oceanic LIPs. Here, we further explore the petrological evidence of this interaction, preserved in major and trace elements from oceanic LIP basalts. Using the FeO and MgO contents from calculated primary magmas determined for several oceanic LIPs, we estimated the initial and final pressures at which melting occurred. We found that the average final melting pressures for LIPs are between values of 2.5 and 1.5 GPa, overlapping with modern MORB data, which suggest that a shallow melting process took place in order to form the LIPs. Furthermore, the length of the melting column, as defined by P_initial-P_final, denotes both deep melting initiation, as well as, high melt productivity, due to the excess temperature of their mantle source. Our results are also in good agreement with geochemical and isotopic data which suggest a deep mantle component in the source of these lavas, perhaps related to the LLSVPs. In the light of these findings we conclude that Plume-Ridge interaction is a key process that allows material ascent and extensive melting during the formation of LIPs.