Vanadium Occurrence and Enrichment Mechanisms in Lower-Middle Carboniferous Black Shales of the Central Taurus Belt, Turkiye: Insights into Critical Element Potential

Vanadium(V) is considered a critical metal due to its increasing use in low-carbon energy technologies, particularly V redox-flow batteries. Black shale-hosted deposits represent an important unconventional V resource, where enrichment is closely linked to depositional redox conditions, organic matter accumulation, and postdepositional processes. This study investigates Lower-Middle Carboniferous black shales from the Çavuşlar-Kırtıl (Mersin) regions in the Central Taurus Belt of Türkiye, which represent a notable occurrence of V enrichment. Using an integrated geochemical and mineralogical approach, this study constrains V sources, reconstructs paleo-redox conditions, determines host phases, and identifies the key controls on V enrichment. The studied black shales are composed mainly of quartz, calcite, feldspar, and Illite-dominated clay minerals, representing mixed mudstone lithofacies. TOC contents range from 1.72 to 2.79 wt %, whereas V concentrations vary between 411 and 615 ppm. EFs indicate moderate-strong enrichment of redox-sensitive elements (V–Mo–U). Multiple reliable paleoredox proxies (UEF, MoEF, VEF, and NiEF, Fe/Al, Th/U, and Corg/P) consistently indicate deposition under predominantly suboxic to anoxic conditions with intermittent euxinic episodes. Trace element source assessment based on Fe/Ti, Al/(Al+Fe), Eu/Eu*, and elemental relationships indicates predominantly nonhydrothermal and authigenic signatures, supporting a trustworthy interpretation of the paleodepositional environment. EPMA and SEM–EDS analyses reveal that V is heterogeneously distributed within the shale matrix and associated with both organic matter and illitic clay minerals. Positive TOC-redox-sensitive element correlations suggest that organic matter might be the control on V enrichment, while measurable V in Illite indicates partial diagenetic redistribution into clay minerals under oxygen-deficient conditions. Overall, the results provide new insights into shale-hosted V enrichment mechanisms and their regional metallogenic significance.