Plume-subduction interaction in southern Central America: Mantle upwelling and slab melting

► We report a migration of back-arc alkaline volcanism towards the north-northwest of 40 mm/yr., consistent with arc-parallel mantle flow models. ► In the opposite direction we report and age migration 35 mm/yr. in the adakites tracking the southwest migration of the triple junction where the Panama Fracture Zone intersects the Middle America Trench. ► The alkaline magmas are restricted to areas that have no seismic evidence of a subducting slab with a geochemistry controlled by mantle upwelling. ► Mantle potential temperatures (TP) of the alkaline basalt primary magmas increased from expected ambient mantle TP~ 1380-1410˚C in the Pliocene to TP's higher than ambient mantle (TP max = 1450˚C) in the younger units.