The manganese occurrences in southern Sabzevar are historically attributed to hydrothermal exhalative, Besshi-type volcanogenic massive sulfide (VMS) systems; however, the precise timing of volcanosedimentary accumulation and its geodynamic driver have remained poorly constrained. Here, we present in situ zircon U–Pb geochronology and trace-element geochemistry from tuffaceous units interbedded with these Mn-bearing successions. Zircons exhibit clear oscillatory zoning and high Th/U ratios (0.28–1.03), indicative of a primary magmatic origin. Weighted mean 206Pb/238U ages from four key localities, Landaran (102 ± 0.6 Ma), Bardashkand (104.2 ± 0.9 Ma), Kuhsakht (100.2 ± 0.8 Ma), and Siabkuh (99.6 ± 1.6 Ma), define a coherent mid-Cretaceous (ca. 104–100 Ma; Albian–Cenomanian boundary) maximum depositional age for the host volcaniclastic sequences and contemporaneous hydrothermal exhalative Mn mineralization. Subordinate inherited zircons yielding older ages (up to ~140 Ma) record the assimilation of earlier Mesozoic basement lithologies. Trace-element discrimination diagrams demonstrate that parental melts were predominantly generated within an oceanic island-arc regime, with subordinate within-plate components and localized continental crustal input in the Bardashkand sector. Combined with adjacent crustal evidence of fossil hydrothermal chimneys, spilitic alteration, and pervasive base-metal mineralizations, our findings demonstrate that ore genesis took place within an evolving accretionary wedge–forearc–arc system rather than an isolated back-arc basin. Extensional rifting in this dynamic subduction-related realm promoted elevated geothermal gradients and seawater convection through permeable oceanic crust, culminating in the exhalative precipitation of stratiform Mn deposits on the paleo-seafloor.