REE, Ba, Sr and Na carbonates in miaskites of the Iilmenogorsky block (South Urals)
E.P. Makagonov, V.A. Kotlyarov
The REE, Ba, Sr and Na carbonates (ankilite-(Ce), barytocalcite, burbankite, dawsonite, stron-tianite and ewaldite) were identifed in miaskites of the Ilmenogorsky block (South Urals). Bary-tocalcite, burbankite, dawsonite and ewaldite were found for the frst time in the Ilmenogorsky miaskite block. The chemical composition of the minerals is as follows (wt. %): ankilite-(Ce) – SrO 18.1–19.7, CaO 1.24–2.52, REE oxides 47.41–50.53 (La/Ce ratio 0.40–1.00); barytocalcite – CaO 18.18–19.10, BaO 51.38–52.06; burbankite – Na2O 10.35–15.44, CaO 2.41–10.93, SrO 14.8–41.3, BaO 0–9.76, REE oxides 1.16–18.65 (La/Ce ratio 0.57–1.04), traces of Y, K, Fe; dawsonite – Al2O3 38.50, Na2O 19.76; strontianite (average of 11 analyzes) – SrO 66.79, CaO 2.92; ewaldite – BaO 36.10–36.84, SrO 8.55–8.88, Na2O 5.51–5.84, CaO 4.94–5.11, Y2O3 8.41–8.80, traces of Dy, Gd, Er, Th. The composition of carbonates is typical of those from alkaline carbonatite complexes. The morphology and assemblages of carbonates in miaskites indicate their formation at the fnal stages of evolution of the alkaline complex with participation of aqueous-carbonic fuid.
Figures 6. Tables 4. References 10.
Key words: ankilite-(Ce), barytocalcite, burbankite, dawsonite, strontianite, ewaldite, Ilmeno-gorsky miaskite massif.
МINERALOGY № 2 2017