SATPAYEV INSTITUTE OF GEOLOGICAL SCIENCES Mineralogical laboratory Satpaev Institute of Geological Sciences SATPAYEV INSTITUTE OF GEOLOGICAL SCIENCES Rare earth minerals from the Verkhnee Espe rare element deposit (East Kazakhstan) PhD student Baisalova A. baisalova73@mail.ru

Geology of the Verkhnee Espe deposit Mineralogical laboratory Satpaev Institute of Geological Sciences Geology of the Verkhnee Espe deposit The rare metal mineralization at the Verkhnee Espe deposit is related to altered alkaline granitic rocks of the Greater and Lesser cupolas and to the exo-contact altered host rocks. The host rocks are represented by the thin-bedded grey sandstone, siltstone, tuffite and carbonaceous materials. The host rocks are cut by pre-granitic dikes of diorite and diabase porphyry. The outcrops are composed of the following granitic rocks; - porphyritic biotite granite developed in the south-western part of the Greater Cupola; the medium-coarse- grained riebeckite and pegmatoid granite composed about 70-80% of both outcrops; the fine-grained riebeckite granite, which forms minor intrusions in inner parts of the Creater and Lesser Cupolas. Geological structure of the Verkhnee Espe deposit Biotite granite coarse- grained riebeckite Pegmatoid granite fine-grained riebeckite granite

Rocks of Verkhnee Espe deposit Mineralogical laboratory Satpaev Institute of Geological Sciences Rocks of Verkhnee Espe deposit The rare pegmatite veins are concentrated mostly within the Greater Cupola. The microcline-astrophyllite and albite-pegmatite facies are recognized. These facies are enriched in zircon minerals, more minerals of REE and Nb. The specific feature of the Verkhnee Espe deposit consists in the alkaline metamorphic alteration that has affected both granitic and host rocks and gave rise to the increased Li2O contents in micas, amphibole and to the enrichment of granite in Li, Rb, REE, Y, Nb, Zr. Pegmatite veins microcline-astrophyllite rock Albitized granite Metacrystalls of narsarsukite in fenitized slate Metasomatic alteration slate of exo-contact riebeckite-albite apogranite Phenocryst crystals of Narsarsukite in fenitized siltstone.

Classification of rare metal minerals Mineralogical laboratory Satpaev Institute of Geological Sciences Classification of rare metal minerals Mineral composition of deposit characterized by great diversity and include of 120 minerals. Among them are rare, very rare and re-discovered mineral types and species. The minerals are distributed by classes as follows; fluorides: gagarinite, fluorite-(Y), fluocerite; phosphates: xenotime, monazite, fluorapatite; fluorocarbonates: bastnesite - (Ce), bastnaesite - (Y), synchusite – (Y) niobates: pyrochlor group minerals and fergusonite; silicates: natrotitanite, gadolinite, yftisite, rowlandite

Group of fluorides Gagarinite NaCaYF6 Fluorite-(Y) (Ca,Y)(F,O,OH)2 Mineralogical laboratory Satpaev Institute of Geological Sciences Group of fluorides Gagarinite NaCaYF6 Fluorite-(Y) (Ca,Y)(F,O,OH)2 An aggregate of gagarinite in phenite rocks BEI (compo) of an aggregate of gagarinite (grey), zircon (dark grey), quartz (black). BEI (compo) of an aggregate of bastnaesite-(Ce) (white) and fluorite-(Y) (black). The chemical composition of fluorite-(Y) The chemical composition of gagarinite Constituent (1) F 43.14 Na 2.17 Si 0.64 K 0.30 Ca 19.32 Fe 0.18 Co 0.13 Y 28.44 Ce 0.96 Nd 0.67 Sm 0.24 Gd 1.01 Dy 1.43 Er 0.81 Yb 0.93 Σ 100.36 Constituent Wt.% (1) (2) F 42.13 41.85 Na 6.16 4.51 Ca 10.97 10.85 Y 18.21 17.92 La 1.43 1.92 Ce 6.03 6.69 Pr 0.74 1.24 Nd 4.41 4.66 Sm 2.15 2.55 Eu 0.00 0.52 Gd 2.72 2.86 Tb 0.70 0.87 Dy 3.27 Ho 0.27 Er 1.73 1.53  100.66 101.50 Constituent Wt.% (1) (2) (3) Mean F 30.33 30.50 30.90 30.58 Y 0.96 1.50 1.08 1.18 La 11.15 11.89 9.39 10.81 Ce 36.95 35.53 35.81 36.10 Pr 4.25 3.94 4.27 4.15 Nd 14.93 14.14 15.30 14.79 Sm 2.18 2.03 2.27 2.16  100.75 99.53 99.02 99.77 The empirical formula, calculated on the basis of REEs+Ca+Na=3 apfu: 1. (Y0.68Ce0.14Nd0.10Dy0.07Gd0.06Sm0.05La0.03Er0.03Pr0.02Tb0.01)1.19Ca0.91Na0.89F6.28 2. (Y0.71Ce0.17Nd0.11Dy0.07Gd0.06Sm0.06La0.05Er0.03Pr0.03Tb0.02Eu0.01Ho0.01)1.33Ca0.96Na0.70F6.61.

Group of phosphates Xenotime YPO4 Monazite CePO4 Mineralogical laboratory Satpayev Institute of Geological Sciences Group of phosphates Xenotime YPO4 SEI of an aggregate of xenotime (dark grey) and Y-bearing fluorite (grey). SEI of xenotime. The chemical composition (wt.) of xenotime BEI (compo) of an aggregate of aegirine with inclusions: K- feldspar (black) and REEs-bearing fluorapatite. N O P Y Gd Dy Ho Er Yb Lu Ta  (1) 30.87 15.26 25.00 0.70 5.13 1.25 7.15 12.51 1.41 0.84 100.13 (2) 31.26 15.86 23.78 0.76 4.93 1.17 7.67 12.49 1.72 0.80 100.45 (3) 30.48 15.50 23.70 0.74 5.03 1.33 7.14 12.32 1.53 0.36 98.13 Average of 3 analyses the empirical formula, calculated on the basis of P=1 apfu: (Y0.54Yb0.14Er0.09Dy0.06Ho0.02Lu0.02Gd0.01Ta0.01)0.89 ( P 1.00O3.85) . Monazite CePO4 The chemical composition (wt.) of monazite N SiO2 P2O5 La2O3 Ce2O3 Pr2O3 Nd2O3 ThO2  (1) 1.16 30.28 19.43 34.78 2.33 6.26 5.85 100.08 (2) 1.00 30.16 19.67 34.92 1.42 6.24 6.50 99.91 (3) 0.88 30.43 21.16 35.81 1.31 5.34 3.51 98.43 M 1.02 30.29 20.09 35.17 1.69 5.95 5.28 99.48 The average of 3 analyses the empirical formula, was calculated on the basis of REEs+Th+Si=1 apfu: (Ce0.53La0.31Nd0.09Pr0.03Th0.05)1.00(P1.06Si0.04)1.10O4.25. BEI (compo) of mineral-host monazite (white) with inclusions - crystals of zircon (grey).

Group of fluorocarbonates Mineralogical laboratory Satpaev Institute of Geological Sciences Group of fluorocarbonates Bastnesite - (Ce) Bastnaesite-(Y) (Y,Сe)(CO3)F·nH2O The empirical formula of bastnaesite-(Y) was calculated on the basis of REEs+Co+Ca = 1 (formula number corresponds to the number of analysis): (Y0.21Ce0.18Nd0.16Dy0.09Gd0.08Sm0.08La0.04Pr0.04Er0.02Yb0.02Ho0.01Co0.01Ca0.03Si0.02)0.99(CO3)F0.98; BEI (compo) of an aggregate of bastnaesite-(Ce) (grey) and bastnaesite-(Ce) with high Ca content (dark grey). BEI (compo) of an aggregate of bastnaesite-(Y) (white) and rowlandite-(Y) (grey). The chemical composition of bastnaesite-(Ce) Synchusite-(Y) СаY(CO3)2F Constituent Wt.% (1) (2) (3) Mean F 7.27 7.21 6.83 7.10 CaO 0.12 0.22 0.23 0.19 La2O3 20.20 17.89 17.63 18.57 Ce2O3 37.52 37.19 37.30 Pr2O3 1.92 2.04 2.33 2.10 Nd2O3 5.87 7.59 7.74 7.07 Sm2O3 1.13 0.80 1.46 ThO2 1.29 1.47 1.39 1.38  75.32 74.41 74.80 74.84 The empirical formula of synchusite-(Y) was calculated on the basis (Ca0.82Y0.83Dy0.12Er0.08Yb0.04Gd0.03Ho0.02Sm0.01Si0.05)2.00(CO3)2(O0.23OH0.40F0.36Cl0.01)1.00; BEI (compo) of an aggregate of synchusite-(Y) (white) and quartz (black) in the rim of mineral “porridge”. Average of 3 analyses the empirical formula of Bastnaesite (Ce) was calculated on the basis of REEs+Th+Ca = 1: (Ce0.55La0.28Nd0.10Pr0.03Sm0.02Th0.01Ca0.01)1.00(CO3)(F1.91OH0.09).

Group of silicates Natrotitanite Rowlandite-(Y) Gadolinite-(Y) Mineralogical laboratory Satpayev Institute of Geological Sciences Group of silicates Natrotitanite (Na0.5Y0.5)Ti(SiO4)O Gadolinite-(Y) Y2Fe[BeSiO4]2(O,OH)2 Rowlandite-(Y) Y4Fe2+Si4O14F2 BEI (compo) of rowlandite with variation of chemical composition. BEI (compo) of zones of gadolinite-(Y) with different Y content. BEI (compo) of an aggregate of wedge-shaped crystals of (Na,Y,REE)-bearing titanite (dark grey) and natrotitanite (grey). The polished section is approximately parallel to the direction of elongation of the crystals. BEI (compo) of an aggregate of rowlandite-(Y) (light grey) and fluorothalenite-(Y) with microinclusions of bastnaesite (white) and fluorite-(Y) (black). BEI (compo) of gadolinite-(Y) (grey) and gadolinite-(Y) with lower Y content (dark grey), in which inclusions of albite are black. Average of 8 analyses the empirical formula of gadolinite-(Y) was calculated on the basis of REEs+Y+Si = 4: (Y1.07Yb0.18Er0.16Dy0.15Ce0.06Ho0.04Gd0.03Tm0.03Nd0.03La0.02Sm0.02Lu0.02Tb0.02Eu0.01 Pr0.01Th0.01Si0.14)2.00(Fe0.69Ca0.21)0.89(Si2O8)Be2[О1.89(OH)0.11]2.00. BEI (compo) of an aggregate of natrotitanite (light grey), fluorite-(Y) (grey) and elpidite (dark grey).

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