Lithium-containing Na-Fe-amphibole from cryolite rocks of the Katugin rare-metal deposit (Transbaikalia, Russia): chemical features and crystal structure

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• 作者：V.V. Sharygin^a ; ^b ; ^{sharygin@igm.nsc.ru" class="auth_mail" title="E-mail the corresponding author} ; N.V. Zubkova^c ; I.V. Pekov^c ; V.S. Rusakov^d ; D.A. Ksenofontov^c ; E.N. Nigmatulina^a ; N.V. Vladykin^e ; D.Yu. Pushcharovsky^c
• 关键词：Na-amphibole subgroup ; ferro-ferri-fluoro-leakeite ; ferro-ferri-fluoro-nyb0ite ; fluoro-riebeckite ; fluoro-arfvedsonite ; cryolite ; alkali granites ; Katugin deposit ; Transbaikalia
• 刊名：Russian Geology and Geophysics
• 出版年：2016
• 出版时间：August 2016
• 年：2016
• 卷：57
• 期：8
• 页码：1191-1203
• 全文大小：1573 K

文摘

Detailed chemical and structural studies were carried out for Li-Na-Fe-amphibole from cryolite rocks of the Katugin deposit, Transbaikalia. The rocks contain 30-70 vol.% cryolite, mafic minerals as Fe-silicates (Li-Na-Fe-amphibole, Li-containing fluorannite, and bafertisite), oxides (magnetite, ilmenite, pyrochlore, cassiterite, and others), and sulfides (sphalerite, pyrite, and chalcopyrite). Quartz, K-feldspar, polylithionite, REE-fluorides, and albite occur as minor or accessory phases. The chemical composition of amphibole (wt.%) varies as follows: SiO₂, 48.5-48.9; TiO2, 0.4-0.8; M2O3, 1.6-2.2; Fe2O3, 15.9-17.1; FeO, 17.6-18.4; MnO, 0.8-0.9; ZnO, 0.3-1.1; MgO, 0.2-0.3; CaO, < 0.1; Na2O, 8.4-8.7; K₂O, 1.4-1.5; Li₂O, 0.6-0.8; H₂O, 0.7-0.8; and F, 2.2-2.5. The amphibole has a specific composition intermediate among the F-Fe members of the Na-amphibole subgroup: 40-45 mol.% ferro-ferri-fluoro-nyb0ite, 40-45 mol.% ferro-ferri-fluoro-leakeite, and 10-20 mol.% fluoro-riebeckite ± fluoro-arfvedsonite. The mineral is monoclinic, space group C2/m, a = 9.7978(2), b = 17.9993(3), c = 5.33232(13) A, P = 103.748(2)°, V = 913.43(3) A³, and Z = 2. The structural formula of Li-Na-Fe-amphibole is (Nao.₄6Ko.₂₄do.₃o)Na₂.oo(Fea95Mgo.o5)₂- (Fe0⁺ 95Ti0.025Mg0.025)2(Li0.37Fea48Mn0.10Zn0.05)[(Si0.91Al <).09)4Si4O22](F0.58(OH)0.42)2. R^amaⁿ and Mossbauer spectroscopy data are given for this amphibole.