Alternation of magmatic and amagmatic seafloor along the slow and ultraslow spreading ridges is common. Yet, temporal variation is obscured by sediments blanketing oceanic basement away from spreading centers. Here we analyze aeromagnetic data covering zero age to ~35 Ma oceanic crust at the ultraslow-spreading Gakkel Ridge to characterize magmatic and amagmatic lithospheric domains and their links to melt supply. Amagmatic seafloor unexpectedly dominates ~68% of the Eurasian Basin, while only 32% of magmatic seafloor over the last 35 Ma. The melt supply exhibits cycles initiating over a short episode of robust magmatism followed by a longer intermediate magmatism, then starved magmatism. These observations suggest that strong lithosphere presumably characterizing this ultraslow spreading ridge may prevent a continuous melt supply, instead favoring episodic melt bursts. Our study indirectly constraints the extent and duration of melting events and lithospheric accretion through the Gakkel Ridge history, away from the present spreading axis.
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