Original Paper
Magnesian tourmalines from plagioclase-muscovite-scapolite metaevaporite layers in dolomite marble near Prosetín (Olešnice Unit, Moravicum, Czech Republic)
Journal of Geosciences, volume 57 (2012), issue 3, 143 - 153
DOI: http://doi.org/10.3190/jgeosci.120
Radial aggregates of blue-grey tourmaline were found in plagioclase-muscovite-scapolite metaevaporite layers in dolomite marble near Prosetín (Olešnice Unit, Moravicum, Czech Republic). It occurs in association with plagioclase (An15-37), muscovite, scapolite, phlogopite, vermiculite, pumpellyite-(Al), and clinozoisite. Electron-microprobe analyses of tourmaline show dravitic composition with very high content of Mg (1.92 to 2.77 apfu), Al (up to 6.71 apfu), low content of Fe (up to 0.39 apfu) and variable amounts of vacancies (0.09 to 0.47) and Ca (0.03 to 0.29 apfu) in the X-site. Some analyses correspond to “oxy-dravite” and some others almost attain magnesio-foitite compositions. The proportion of X-site vacancy decreases from the crystal cores to their rims while Ca content increases. Generally, charge excess due to the high Al-contents is balanced either by an increasing X-site vacancy or by deprotonization of WOH; the WO2- content calculated from charge-balanced formula attains 0.71 apfu. Lattice parameters [a = 15.9116(6) Å; c = 7.1987(4) Å] and calculated average bond lengths (
IF (WoS, 2022): 1.4
5 YEAR IF (WoS, 2022): 1.8
Policy: Open Access
ISSN: 1802-6222
E-ISSN: 1803-1943