FROM STRUCTURE TOPOLOGY TO CHEMICAL COMPOSITION. IV. TITANIUM SILICATES: THE ORTHORHOMBIC POLYTYPE OF NABALAMPROPHYLLITE FROM THE LOVOZERO MASSIF, KOLA PENINSULA, RUSSIA

AbstractThe crystal structure of a murmanite-related mineral (MRM) of the murmanite group (seidozerite supergroup), ideally Na2CaTi4(Si2O7)2O4(H2O)4, from Mt. Pyalkimpor, the Lovozero alkaline massif, Kola Peninsula, Russia, was refined in space group P$ {\bar 1} $ with a = 5.363(2), b = 7.071(2), c = 12.176(5) Å, α = 92.724(3), β = 107.542(7), γ = 90.13(2)°, V = 439.7(4) Å3 and R1 = 5.72%. On the basis of electron-microprobe analysis, the empirical formula calculated on 22 (O + F), with two constraints derived from structure refinement, OH = 0.11 per formula unit (pfu) and H2O = 3.89 pfu, is (Na2.12K0.07Sr0.01)Σ2.20Ca0.85(Ti3.01Nb0.39Mn0.20Fe2+0.19Mg0.17Zr0.01Al0.01)Σ3.98(Si4.20O14)[O3.90F0.10]Σ4[(H2O)3.89(OH)0.11]Σ4{P0.03}, with Z = 1. It seems unlikely that {P0.03} belongs to MRM itself. The crystal structure of MRM is an array of TS blocks (Titanium-Silicate) connected via hydrogen bonds. The TS block consists of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the Ti-dominant MO1 site and Ca-dominant MO2 site give ideally (Ca□)Ti2 pfu. In the H sheet, the Ti-dominant MH site and Na-dominant AP site give ideally Na2Ti2 pfu. The MH and AP polyhedra and Si2O7 groups constitute the H sheet. The ideal structural formula of MRM of the form AP2MH2MO4(Si2O7)2(XOM,A)4(XOA)2(XPM,A)4 is Na2Ti2(Ca□)Ti2(Si2O7)2O4(H2O)4. MRM is a Ca-rich and Na-poor analogue of murmanite, ideally Na2Ti2Na2Ti2(Si2O7)2O4(H2O)4 and a Na-rich and (OH)-poor analogue of calciomurmanite, ideally (Ca□)Ti2(Na□)Ti2(Si2O7)2O2[O(OH)](H2O)4. MRM and (murmanite and calciomurmanite) are related by the following substitutions: O(Ca2+□)MRM ↔ O(Na+2)mur and O(Ca2+□)MRM + H(Na+2)MRM + O(O2–)MRM ↔ O(Na+□)cal + H(Ca2+□)cal + O[(OH)–]cal. MRM is a possible new mineral of the murmanite group (seidozerite supergroup) where Ti + Mn + Mg = 4 apfu.

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Pre-Pegmatite Stage in Peralkaline Magmatic Process: Insights from Poikilitic Syenites from the Lovozero Massif, Kola Peninsula, Russia

Minerals ◽

10.3390/min11090974 ◽

2021 ◽

Vol 11 (9) ◽

pp. 974

Author(s):

Julia A. Mikhailova ◽

Yakov A. Pakhomovsky ◽

Olga F. Goychuk ◽

Andrey O. Kalashnikov ◽

Ayya V. Bazai ◽

...

Keyword(s):

Chemical Composition ◽

Kola Peninsula ◽

Hydrothermal Solution ◽

Rare Metal ◽

Lovozero Massif ◽

Accessory Minerals ◽

Rare Elements ◽

Hydrothermal Stage ◽

Magmatic Stage ◽

Residual Solution

The Lovozero peralkaline massif (Kola Peninsula, Russia) is widely known for its unique mineral diversity, and most of the rare metal minerals are found in pegmatites, which are spatially associated with poikilitic rocks (approximately 5% of the massif volume). In order to determine the reasons for this relationship, we have investigated petrography and the chemical composition of poikilitic rocks as well as the chemical composition of the rock-forming and accessory minerals in these rocks. The differentiation of magmatic melt during the formation of the rocks of the Lovozero massif followed the path: lujavrite → foyaite → urtite (magmatic stage) → pegmatite (hydrothermal stage). Yet, for peralkaline systems, the transition between magmatic melt and hydrothermal solution is gradual. In the case of the initially high content of volatiles in the melt, the differentiation path was probably as follows: lujavrite → foyaite (magmatic stage) → urtitization of foyaite → pegmatite (hydrothermal stage). Poikilitic rocks were formed at the stage of urtitization, and we called them pre-pegmatites. Indeed, the poikilitic rocks have a metasomatic texture and, in terms of chemical composition, correspond to magmatic urtite. The reason for the abundance of rare metal minerals in pegmatites associated with poikilitic rocks is that almost only one nepheline is deposited during urtitization, whereas during the magmatic crystallization of urtite, rare elements form accessory minerals in the rock and are less concentrated in the residual solution.

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From structure topology to chemical composition. XXVIII. Titanium silicates: Jinshajiangite from the Oktyabr'skii Massif, Donetsk Region, Ukraine, a new occurrence

The Canadian Mineralogist ◽

10.3749/canmin.1900089 ◽

2020 ◽

Vol 58 (2) ◽

pp. 223-229 ◽

Cited By ~ 1

Author(s):

Maxwell C. Day ◽

Elena Sokolova ◽

Frank C. Hawthorne ◽

Robert T. Downs

Keyword(s):

Chemical Composition ◽

Chemical Analysis ◽

Electron Microprobe ◽

Unit Cell ◽

Crystal Data ◽

Unit Cell Parameters ◽

Cell Parameters ◽

Structure Topology ◽

Titanium Silicates ◽

Azov Sea

ABSTRACT Here we report electron-microprobe data and unit-cell parameters for jinshajiangite, ideally NaBaFe2+4Ti2(Si2O7)2O2(OH)2F, from a new locality: the Oktyabr'skii massif in the coastal area of the Azov Sea, Donetsk region, Ukraine. Chemical analysis by electron microprobe gave Nb2O5 1.59, ZrO2 0.61, TiO2 17.07, SiO2 27.60, Al2O3 0.08, Fe2O3 2.04, FeO 16.42, BaO 9.81, ZnO 0.76, MnO 12.97, CaO 1.82, MgO 0.07, K2O 2.05, Na2O 2.51, F 2.48, H2O 1.92, O = F –1.04, sum 98.76 wt.%; H2O was determined in accord with the required number of monovalent anions for the Ti-dominant perraultite-type minerals: OH + F = 3 pfu; the Fe3+/Fe2+ ratio was assigned in accord with Mössbauer-spectroscopy results for jinshajiangite from a different locality. The empirical formula calculated on the basis of 19 (O + F) is (Na0.71Ca0.28□0.01)Σ1(Ba0.56K0.38□0.06)Σ1(Fe2+1.99Mn1.59Fe3+0.22Zn0.08Mg0.02Al0.01□0.09)Σ4 (Ti1.86Nb0.10Zr0.04)Σ2(Si4.00O14)O2[(OH)1.86F0.14]Σ2F1.00, Z = 4. Unit-cell parameters from the single-crystal data were determined by least-squares refinement of 9807 reflections with I > 10σI and are as follows: a = 10.726(8), b = 13.834(10), c = 11.065(8) Å, α = 108.172(5), β = 99.251(7), γ = 90.00(1)°, V = 1537.5(3.4) Å3, space group C .

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