New Data on the Chemical Composition of Lithium Micas from Granitic Pegmatites of the Murzinka Pluton, Central Urals, Ru
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Data on the Chemical Composition of Lithium Micas from Granitic Pegmatites of the Murzinka Pluton, Central Urals, Russia T. A. Gvozdenkoa, b, *, I. A. Baksheeva, **, E. I. Gerasimovab, ***, D. A. Khaninc, ****, M. V. Chervyakovskaya d, *****, and V. O. Yapaskurta, ****** aDepartment
of Geology, Moscow State University, Moscow, 119991 Russia State Geological Museum, Russian Academy of Sciences, Moscow, 125009 Russia c Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow Oblast, 142432 Russia d Institute of Geology and Geochemistry, Urals Branch, Russian Academy of Sciences, Ekaterinburg, 620016 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: [email protected] *****email: [email protected] ******e-mail: [email protected] b
Received November 11, 2019; revised January 15, 2020; accepted January 15, 2020
Abstract—Micas from granitic pegmatites of the Mokrusha and Ministerskaya mines within the Murzinka Pluton in the Central Urals are polylithionite, sokolovaite, trilithionite, Li-bearing muscovite, and annite– phlogopite in solid solution. Chromium and magnesium, which are uncommon elements for light mica that were detected in micas from both mines indicate pegmatite contamination by the material of the host rocks. The low K/Rb and Ta/Nb ratios testify to a very high degree of pegmatite differentiation of both mines. Keywords: Li-bearing micas, granitic pegmatite, Murzinka granitic pluton, Central Urals DOI: 10.3103/S0145875220040079
INRODUCTION Micas are typical rock-forming constituents of granitic pegmatites. Variations in the Cs, Rb, Li, Ta, Nb, and F concentrations in them are crucial indicators of the physicochemical formation conditions and the evolution of pegmatites. A K/Rb ratio in micas that gradually decreases during pegmatite crystallization is very informative during the evaluation of pegmatite differentiation; the Ta/Nb ratio in these minerals is also important, because Ta predominates at the final formation stage, indicating pegmatite differentiation (Černý et al., 1985; Van Lichtervelde et al., 2008; Roda-Robles et al., 2006; Rosing-Schow et al., 2018). The Murzinka mines, which have been known since the 17th century, comprise more than 250 pegmatite bodies with rare metal and gem (tourmaline, topaz, beryl, amethyst) mineralization. The latest mineralogical data for these mines were published at the end of the 20th century. Some papers concern the Mokrusha mine (Fershtater et al., 2018; Gurkov, 2000; Kanonerov et al., 2000; Popov et al., 1999; Smertenko et al., 1980). Other mines, including Ministerskaya, are poorly documented (Kanonerov et al., 2000; Popov et al., 1999; Talantsev, 1988).
Annite, siderophyllite, phlogopite, trilithionite, masutomilite, muscovite, and vermiculite were observed in the Murzinka pegmatites (Kanonerov et al., 2000). However, no detailed information about the chemical composition of micas was obtained. This study aims to understand the evolution of the pegmatite system on
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