Mössbauerite and trebeurdenite from bottom sediments of the Bol'shoy Tatkul' Lake (Ilmen Mountains, the South Urals)

Nikandrova N. K., Shcherbakova E. P., Valizer P. M., Nikandrov A. 5., Nikandrox S. N.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 4. P. 75-83

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Language: Russian

Abstract

Mössbauerite O₄(OH)₈(CO₃) · 3H₂O and trebeurdenite O₂(OH)₁₀(CO₃) · 3H₂O have been found in the lacustrine marls composing the lowest horizons of bottom sediments in the freshwater lake Bol’shoy Tatkul’ at the South Urals (Ilmen Mountains). These minerals belong to the fougerite group O₁₂H_2(7-3x)CO₃ · 3H₂O(CO₃) · 3H₂O, which belongs to the hydrotalcite supergroup (or family). Synthetic analogues of the fougerite group minerals correspond to the so-called «green rusts» formed in result of iron corrosion under oxygen deficient conditions. For the first time, fougerite group minerals have been discovered in the gleysoils of France. Lacustrine marls of the Bol’shoy Tatkul’ lake are similar to the fougerite-bearing soils by a number of signs, such as mode of occurrence, peculiarities of chemical and mineral composition. This similarity allowed using for research of lacustrine marls the same complex of methods (X-ray diffractometry and Mössbauer spectroscopy) which had been used in France. Presence of fougerite group minerals in diffractograms is determined by characteristic line in the range 7.32—7.45 Å. The precise diagnostic, up to the certain mineral species. is made by parameters of Mössbauer spectra. In Russia, mössbauerite and trebeurdenite have been established for the first time.

Key words: mössbauerite, trebeurdenite, minerals of fougerite group, bottom sediments, lacustrine marls, Mössbauer spectroscopy, X-ray diffractometry, Bol’shoy Tatkul’ Lake, the South Urals.