Acta Musei Moraviae

Characterization of tourmalines from albite unit of pegmatite dikes No. 5 and No. 8 at Dolní Bory – Hatě

Tourmaline crystals from albite units of pegmatite dikes No. 5 and No. 8 at Dolní Bory – Hatě were in vestigated by electron microprobe, LA-ICP-MS, and Mössbauer spectroscopy in order to get complete chemical characterization including Fe³⁺/Fe_tot, light, and trace elements contents. In transmitted light, tourmaline shows quite distinct core with a slight sector zoning which is overgrown by darker parts with oscillatory zoning and delta features. In some section of crystals, the core was not observed. The empirical formulae are characterized by 0.044–0.065 Fe³⁺/Fe_tot, high X-site vacancy (0.37–0.61 pfu), 1.57–1.64 apfu Fe_tot, low Mg (0.16–0.29 apfu) and elevated Al at the Y-site (0.69–1.01 apfu). Oxygen or the OH group dominates at W-site (0.44–0.69 and 0.20–0.42 apfu, respectively), whereas F is low (0.03–0.25 apfu). Based on these ionic ratios, the oxy-foitite>foitite>oxy-schorl are dominant endmembers in the tourmaline cores, whereas the oscilátory and delta features parts correspond to oxy-schorl to very rare schorl.