Oxides and silicates of rare and rare-earth elements in alkaline rocks of Ilmenogorsky block (Southern Urals)
E.P. Makagonov, V.A. Kotlyarov, V.A. Muftakhov
UDК 549.51(470.55)+549.6
A signifcant part of the REE and rare elements in the rocks of the Ilmenogorsky block forms its own minerals. Oxides and silicates of rare and rare-earth elements in alkaline rocks of Ilmenogorsky block (Southern Urals) include oxynatropyrochlore, oxycalciopyrochlore, hydroxycalciopyrochlo-re, hydroxynatropyrochlore, niobium rutile (ilmenorutile), fersmite, euxenite, zircon, allanite-(Ce), chevkinite-(Ce), catapleiite, mongolite.
Pyrochlore of fenites is distinct from that of miaskites be the higher content of trace elements (mean (maximum), wt.%): 3.08 (4.96) Ta2o5, 3.17 (4.01) ThO2, 4.07 (10.77) uo2, 1.79 (2.06) REE versus 1.11 (1.86) Ta2o5, 0.76 (2.07) ThO2, 0.34 (0.96) UO2, 1.87 (2.08) REE, respectively.
The Nb rutile contains (wt. %) 33.93–31.79 TiO2, 36.04–34.93 Nb2o5, 9.03–17.39 Fe2O3, 6.46– 7.67 Ta2O5, 0–0.77 La2O3, 0–1.54 Ce2O3, 0.77–2.9 ThO2, 0.95–1.06 UO2. The composition of eux-enite is as follows (wt. %): 21.87 TiO2, nb2o5, 43.49, FeO 1.31, 1.18 Ta2O5, Y2O3 9.5, CaO 3.73, REE 16.33. Fersmite contains 15.07–18.30 TiO2, 40.03–50.54 Nb2O5, 0.80–1.03 FeO, 0–3.52 Ta2O5, 0.63–7.36 Y2O3, 5.11–7.00 CaO, 22.98–23.46 UO2, 1.25–18.94 REE. The HfO2 average content of zircon in metamorphic rocks, fenites, and miaskites is 2.06, 1.58, and 1.30 wt. %, respectively. The REE contents of allanite-(Ce) and chevkinite-(Ce) are 18.28–27.05 and 44.55–45.35 wt. %, respectively. Catapleite contains (wt. %) 44.72–45.85 SiO2, 0.08–0.46 TiO2, 0.6–0.19 FeO, 0.04–0.23 CaO, 14.86–15.71 Na2O, 29.3–30.9 ZrO2, and 0.18–0.55 HfO2. Mongolic contains (wt. %) 12.84– 14.77 SiO2, 4.54–4.76 TiO2, 5.56–6.68 CaO, 34.81–38.58 Nb2O5, 3.27–3.47 Ta2O5, 3.09–3.83 ThO2, 2.95–7.68 UO3, 6.49–7.16 REE, and small amount of Pb, P, Ba, Sr, Na, Sc, Y, Mn, Fe, Al.
These minerals are unevenyl distributed by depth. The elevated contents are observed in feldspar rocks, biotite syenites (often with carbonates), and pegmatoid veins. Most minerals are characterized by several generations. Their crystallization was simultaneous with other minerals. Сatapleiite and mongolite are identifed for the frst time in the Ilmenogorsky block.
Figures 6. Tables 6. References 20.
Key words: oxynatropyrochlore, oxycalciopyrochlore, hydroxycalciopyrochlore, hydroxynatro-pyrochlore, niobium rutile (ilmenorutile), fersmite, euxenite, zircon, allanite-(Ce), chevkinite, cata-pleiite, mongolite, Ilmenogorsky miaskite block.
E.P. Makagonov, Institute of Mineralogy UB RAS, Miass; mak@mineralogy.ru; Faculty of Geology, National Research South Ural State University, Miass Branch;
V.A. Kotlyarov, Institute of Mineralogy UB RAS, Miass;
V.A. Muftakhov, Institute of Mineralogy UB RAS, Miass; Faculty of Geology, National Research South Ural State University, Miass Branch
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МINERALOGY № 3 2017