Acta Musei Moraviae

Mineral assemblage of Sn-W ores from Ovesná Lhota near Světlá nad Sázavou, Czech Republic

Quartz veins from the Ovesná Lhota contain muscovite, scheelite, cassiterite, tourmaline and wolframite. Intimate aggregates of cassiterite and wolframite suggest possible unusual coprecipitation of both minerals. Wolframites are dominated by ferberite end member with average chemical composition (Fe_0.754Mn_0.204Mg_0.016)_Σ0.974(W_1.003Zr_0.002Ti_0.001)_Σ1.006O₄ with huanzalaite content up to 2.9 %. Cassiterites are slightly zonal but with low chemical variability. Average cassiterite composition is (Sn_0.984Ti_0.011Ta_0.002)_Σ0.997O₂. Scheelite forms small grains together with quartz included in cassiterite or rarely bigger individual grains. It’s chemical composition is close to ideal formula. Phengitic muscovite has increased content of Na, Mg, Fe and especially F (up to 1.48 wt. %). Observed mineral assemblage and mineral chemistry suggest hydrothermal fluids of plutonic origin with acidic and saline characteristics. Estimated crystallization temperature was 300–400 °C.