Climax of Late Paleoproterozoic Rift‐Related Magmatism in the Columbia Supercontinent: Insights From a 1.77–1.76 Ga Large Igneous Province of the Dunhuang Block, Northwest China

Abstract Widespread mafic magmatism at ca. 1.8–1.7 Ga across fragments of the Columbia supercontinent records a transition in the Earth's supercontinent cycle. The paleogeographic position of the Dunhuang Block in northwestern China within Columbia, and its role in this tectonic reorganization, remain controversial. In this study, a potential fragment of a 1.77–1.76 Ga large igneous province (LIP), termed the Aksay LIP (ALIP), was identified that conformably overlies a coeval banded iron formation (BIF) in the northern Dunhuang Block. Field observations, zircon U–Pb dating, and whole‐rock geochemical and Sr–Nd–Fe isotopic data for the bimodal volcanic rocks and BIFs allow us to reconstruct the paleo‐position of the Dunhuang Block within Columbia and track the redox state at this time. The tholeiitic basalts were derived from an enriched mantle plume source in an extensional setting following the amalgamation of Columbia. The BIFs associated with the volcanic–sedimentary sequence were deposited in a sediment‐starved marine rift basin, where Fe was likely sourced from distal hydrothermal vents in under anoxic and ferruginous conditions. These findings combined with global LIP correlations suggest a late Paleoproterozoic tectonic link between the Dunhuang Block and the North China Craton within the Columbia supercontinent.