Interplay between dynamic oceanic conditions and unique nickel–molybdenum sedimentary mineralization during the Cambrian Explosion

Around 520 million-year-ago, the period of complex life diversification (i.e., Cambrian Explosion), unique nickel-molybdenum (Ni-Mo) sulfide-rich black shales deposited in South China, providing a new window for tracking the evolution of ancient marine chemistry and habitable Earth as well as the relationship between them. Here, we analyzed these Ni-Mo-rich shales and compared them with other rocks from the same interval. We find that the oceanic redox condition underwent a significant shift—from oxygen-rich to hydrogen sulfide-rich—in the early Cambrian. This change, alone with metals supplied by simultaneous deep hydrothermal inputs, triggered the formation of Ni-Mo sulfides. The formation and burial of organic matter and sulfide associated with hydrothermal activity likely boosted atmospheric oxygen levels, feeding back to the further biological diversification during the Cambrian Explosion. Our work highlights the interconnectedness of hydrothermal activity, redox evolution, and biological innovation during this pivotal interval in Earth’s history.