North Atlantic magmatism controlled by temperature, mantle composition and buoyancy

摘要

Large igneous provinces are characterized by anomalously high rates ofmagmaproduction~1. Such voluminous magmatism is commonly attributed to partial melting of hot, buoyantly upwelling mantle plume material~(2,3). However, compositional heterogeneity in the mantle, caused by the subduction of oceanic crust, can also enhancemagmaproduction, diminishing the need for elevated temperatures associated with upwelling plumes~(4,5). A plume origin for the North Atlantic large igneous province has been questioned because lava compositions correlate with crustal thickness, implying a link between magmaproductivity and mantle source composition~(4,6). Herewe use a numerical model that simulates upwelling and melting of compositionally heterogeneous mantle material to constrain the conditions that gave rise to magmatism in the North Atlantic. Using observations of lava compositions and volumes from the North Atlantic, we show that subducted crustal material represented less than 10% of the mantle source. We further showthat mantle temperatures have remained elevated by 85-210 oC and increased mantle upwelling up to 14 times the rate of plate separation has occurred over the past 56Myr. The enhanced temperatures and upwelling rates extended along more than 1,000 km of the Palaeogene rift, but are substantially more restricted along the modern Mid-Atlantic Ridge. These findings reflect the long-term manifestation of a mantle plume.