Hotspot magmas can form by fractionation and contamination of mid-ocean ridge basalts

Melts ascending from deep reservoirs and trapped beneath thick lithosphere exchange heat with and partially melt the shallow mantle as they crystallize. Basalts erupting through thick lithosphere are more likely to have experienced deep crystal fractionation and contamination than those at mature spreading centres. Geochemical data for ocean island and other hotspot magmas do not require a primitive or lower mantle source.