Formation of baotite in alcaline rocks of a moraine of Dara-i-Pioz glacier, Tadjikistan

Authors: Karpenko, Vladimir; Pautov, Leonid

Source: Neues Jahrbuch für Mineralogie - Monatshefte, Volume 2002, Number 10, 1 October 2002 , pp. 459-467(9)

Publisher: E. Schweizerbart'sche Verlagsbuchhandlung

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Abstract:

Unusual baotite aggregates were found among boulders, bearing alcaline mineralization at a moraine of the Dara-i-Pioz glacier, Tadjikistan. Baotite forms intergrowths with barylite and berezanskite (association #1) and with quartz in tienshanite (Tn), as well as radial needle splitted crystals in tienshanite voids (association #2). Electron microprobe analysis gives (wt %, assoc. #1/assoc. #2): SiO₂ 15.65/15.80, TiO₂ 41.05/36.97, Nb₂O₅ 0.72/2.70, Fe₂O₃ 0.33/1.21, Al₂O₃ 0.14/1.21, PbO 1.39/-, BaO 37.96/38.14, Cl 2.46/2.29, MnO, CaO, Na₂O, K₂O - traces, total 99.24/98.17. Optically uniaxial, positive, omega

= 1.940(5), epsi

> 2.00. Six strongest lines in the X-ray powder diffraction pattern are (d_obs., I): 3.73(6), 3.52(6), 3.32(8), 2.92(5), 2.236(10), 1.334(4). The origin of the baotite (Baot), associated with tienshanite (Tn) appears to result from the hydrothermal alteration. A possible reaction is:

8Tn + Cl^- = 1Baot + 44Qv + 8(2Na⁺, Mn⁺², 2B⁺³, 5.5O^-2).

Keywords: BAOTITE; TIENSHANITE; BEREZANSKITE; ALCALINE MASSIF; DARA-I-PIOZ; TADJIKISTAN

Document Type: Regular paper

DOI: http://dx.doi.org/10.1127/0028-3649/2002/2002-0459

Publication date: 2002-10-01