Calcian dravite from metacarbonate rocks of the Mutnik magnesite-talc deposit, Hnust'a, Slovakia
Uher, Pavel; Janá k, Marian; Ozdí n, Daniel
published: Feb 8, 2002
Dark-grey and brown columnar dravite (0.5-2cm crystals in size) in the calcite-diopside marble and dolomite-tremolite schist from the MÃºtnik magnesite-talc deposit near HnÃºÅ¡t'a (central Slovakia) was investigated. Electron microprobe and BSE analyses reveal the calcian dravite composition of investigated tourmaline. Dravite forms the poikiloblasts with numerous inclusions of diopside, calcite, rarely quartz, titanite, apatite, galena and Bi-phase in the calcite-diopside marble, or tremolite-actinolite, dolomite, phlogopite, clinochlore, quartz, titanite, apatite and zircon in the dolomite-amphibole schist. Calcian dravite is relatively homogeneous, locally with Ca and Mg enriched rims. Atomic Ca/(Ca+Na) ratios of dravite vary from 0.33-0.44 in the marble, and 0.05-0.46 in the schist, respectively. The Fe/(Fe+Mg) = 0.09-0.11 in the marble and 0.12-0.21 in the schist, X-site vacations x□â¤0.15apfu are low in the both dravite-bearing rocks. Calculated P-T-X conditions suggest the origin of calcian dravite and the metacarbonate assemblages in the amphibolite facies conditions (550-600 Â°C; 7-9 kbar; XCO2 = 0.4- 0.5), during the Alpine (Cretaceous) orogeny.