Tracing the origin and P-T metamorphic history of the VMS Besshi-type Tisová deposit, Czech Republic: Evidence for Co, As and Sb mobility

• Metamorphosed VMS deposit – lower blueschist-facies. • Bohemian Massif, Erzgebirge area, Variscan orogeny. • Sulfides, sulfoarsenides and sulfoantimonides. • Arsenopyrite thermometry and sphalerite-pyrrhotite thermobarometry. • Mobility of cobalt and antimony under metamorphic overprint. The Tisová deposit, a Besshi-type Cu-(Co) VMS deposit, is situated in the Bohemian Massif near the Czech-German border. It experienced blueschist facies metamorphism (∼13 kbar, ∼530 °C) during Variscan subduction (∼360–335 Ma). Hosted by Cambrian volcanic-sedimentary rocks, the deposit includes three stratiform ore horizons: pyrite-rich (upper), pyrrhotite-rich (middle and lower), with chalcopyrite distributed throughout. In addition to the major sulfides, the following minor phases (arsenopyrite, galena, sphalerite ≫ cobaltite > ullmanite > costibite ≫ gersdorffite) and trace phases (native bismuth, bismuthinite, Pb-Sb sulfosalts, cassiterite) occur. Very rare phases are Au-Ag-Hg alloy, electrum, canfieldite, and Ag-rich tetrahedrite. Metamorphic overprinting produced intense foliation, the formation of siderite impregnations and veinlets, and the recrystallization of the ore. Mining (1970–1989) yielded 561 kt of ore (0.6 % Cu). Supplementary data indicate 0.12–4.32 g/t Au, 4–20 g/t Ag, with Co as a potential by-product. Detailed mineralogical studies reveal seven arsenopyrite generations, indicating complex metamorphic recrystallization (from ∼13 kbar, ∼500 °C down to 2–3 kbar, 300–400 °C), wide variations in arsenic content (∼27.3 to ∼37.3 at% As) and admixture (up to 6.9 wt% Co, 3.7 wt% Ni, 9.3 wt% Sb). Four pyrite generations were identified, showing evidence of Co mobilization and late-stage crystallization of Bi- and Sb-bearing phases during retrograde metamorphism. Sphalerite-pyrrhotite-pyrite thermobarometry indicates ∼5 kbar, 530 °C, differing from barren-rock estimates of (∼13 kbar, potentially due to fluid-mediated resetting. These findings enhance understanding of the deposit’s tectonothermal evolution and its implications for Co mobility under metamorphic processes.