Acta Musei Moraviae

Tourmaline from the mica schist of the Svratka Crystalline Complex

Tourmaline is a typical accessory mineral for most of micaschists in the Svratka Crystalline Complex. Based on petrographic and chemical data, two main generations of tourmaline have been distinguished. The first generation (tourmaline cores) corresponds to the prograde metamorphic event characterised by mineral assemblage Ms+Bt+Tu±Ky±St. The second generation of tourmaline (tourmaline rims) formed during exhumation of the Svratka Crystalline Complex, simultaneously with decompression breakdown of staurolite. Microprobe analyses of tourmalines reveal a compositional variation between Al-rich schorldravite to dravite (X_Fe 0.22–0.61; Al 5.88–6.77 apfu; Na 0.45–0.91 apfu). Tourmaline rims are typically enriched in Fe, usually enriched in Al and depleted in Mg, Na, Si relative to tourmaline cores.