The styles of ore deposit have changed over time due to secular change in an ever-cooling Earth. Prior to this study, no intrusive magmatic Ni-Cu-(Co) deposits were confidently known to exist before 2930 Ma, begging the question whether this is a function of preservation bias or geological consequence. Here, we use zircon U-Pb and sulfide Re-Os geochronology of the mineralizing gabbro at the Andover Deposit in the Pilbara Craton, WA, to show that it formed at 3015.6 ± 1.5 Ma, ~85 m.y. older than the next oldest deposit, through mantle-melting induced by slab breakoff. Complementary zircon Hf, stable S and initial Os isotopes reveal assimilation of continental crust, an interaction that is crucial to cause S immiscibility and yield economic Ni-Cu deposits. At ca. 3.2–3.0 Ga, a global extraction of mantle material occurred to produce major, buoyant continental crust as part of the transition of dominantly stagnant-lid to plate tectonics on Earth. Prior to this time, the lack of preservation potential of buoyant felsic continental crust meant that Ni-Cu deposits are unlikely to have formed in economic quantities, nor be preserved. Ultimately, we posit that the secular change of Earth’s tectonic regime led to the rise of magmatic Ni-Cu deposits in the Mesoarchean.