<p>Fluctuations in marine redox conditions on the Yangtze Block, recorded by widespread black shales, critically influenced local biological habitability during the early Cambrian. However, the relation between redox conditions and precipitation of massive barite and witherite hosted within these black shales remains poorly constrained. Here, we integrate barium and sulfur isotope data to elucidate metallogenesis of these deposits within its paleoceanographic environment. Systematic δ¹³⁸Ba variations reveal water-column barium enrichment under sulfate-depleted conditions, modulated by primary productivity. Offshore decreasing δ³⁴S values of barite indicate that open-ocean incursions were the primary source of sulfate. Mixing of this sulfate with dissolved barium induced barite precipitation. Within the marginal basins, organic carbon export and sulfate replenishment fueled sulfate reduction, generating hydrogen sulfide that promoted euxinia expansion from deep- to shallow-waters. Our findings bear on the early Cambrian marine redox evolution on the Yangtze Block and demonstrate that massive barite and witherite precipitation was directly coupled with euxinia expansion.</p>