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GEOREF RECORD

Calciomurmanite, (Na,) (sub 2) Ca(Ti,Mg,Nb) (sub 4) [Si (sub 2) O (sub 7) ] (sub 2) O (sub 2) (OH,O) (sub 2) (H (sub 2) O) (sub 4) , a new mineral from the Lovozero and Khibiny alkaline complexes, Kola Peninsula, Russia

Inna S. Lykova, Igor V. Pekov, Nikita V. Chukanov, Dmitriy I. Belakovskiy, Vasiliy O. Yapaskurt, Natalia V. Zubkova, Sergey N. Britvin and Gerald Giester
Calciomurmanite, (Na,) (sub 2) Ca(Ti,Mg,Nb) (sub 4) [Si (sub 2) O (sub 7) ] (sub 2) O (sub 2) (OH,O) (sub 2) (H (sub 2) O) (sub 4) , a new mineral from the Lovozero and Khibiny alkaline complexes, Kola Peninsula, Russia
European Journal of Mineralogy (August 2016) 28 (4): 835-845

Abstract

The new mineral calciomurmanite, (Na,) (sub 2) Ca(Ti,Mg,Nb) (sub 4) [Si (sub 2) O (sub 7) ] (sub 2) O (sub 2) (OH,O) (sub 2) (H (sub 2) O) (sub 4) , a Na-Ca ordered analogue of murmanite, was found in three localities at Kola Peninsula, Russia: at Mt. Flora in the Lovozero alkaline complex (the holotype) and at Mts. Eveslogchorr (the cotype) and Koashva, both in the Khibiny alkaline complex. Calciomurmanite is a hydrothermal mineral formed as a result of late-stage, low-temperature alteration (hydration combined with natural cation exchange) of a high-temperature, anhydrous phosphate-bearing titanosilicate, most likely lomonosovite and/or betalomonosovite, in the peralkaline (hyperagpaitic) rocks. The holotype sample is associated with microcline, aegirine, lorenzenite and fluorapatite, whereas the cotype sample occurs with microcline, aegirine, lamprophyllite, tsepinite-Ca and tsepinite-K. The mineral occurs as lamellae up to 0.1 X 0.4 X 0.6 cm, sometimes combined in fan-shaped aggregates up to 3.5 cm. Calciomurmanite is pale brownish or purple; the streak is white. The lustre is nacreous on cleavage surface and greasy on broken surface across cleavage. The (001) cleavage is perfect, mica-like; the fracture is stepped. D (sub meas) = 2.70(3), D (sub calc) = 2.85 g cm (super -3) The mineral is optically biaxial (-), alpha = 1.680(4), beta = 1.728(4), gamma = 1.743(4), 2V (sub meas) = 58(5) degrees . The IR spectrum is reported. The chemical composition (wt%, electron-microprobe data, H (sub 2) O by the Alimarin method) is: Na (sub 2) O 5.39, K (sub 2) O 0.30, CaO 7.61, MgO 2.54, MnO 2.65, FeO 1.93, Al (sub 2) O (sub 3) 0.85, SiO (sub 2) 30.27, TiO (sub 2) 29.69, Nb (sub 2) O (sub 5) 6.14, P (sub 2) O (sub 5) 0.27, H (sub 2) O 11.59, total 99.23. The empirical formula of the holotype sample, calculated on the basis of Si + Al = 4 apfu, is: Na (sub 1.34) Ca (sub 1.04) K (sub 0.05) Mg (sub 0.49) Mn (sub 0.29) Fe (sub 0.21) Nb (sub 0.36) Ti (sub 2.85) (Si (sub 3.87) Al (sub 0.13) ) (sub Sigma 4) O (sub 16.40) (OH) (sub 1.60) (PO (sub 4) ) (sub 0.03) (H (sub 2) O) (sub 4.94) Calciomurmanite is triclinic, P-1, a = 5.3470(6), b = 7.0774(7), c = 12.146(1) A, alpha = 91.827(4), beta = 107.527(4), gamma = 90.155(4) degrees , V = 438.03(8) A (super 3) and Z = 1. The strongest reflections of the X-ray powder pattern [d,A(I)(hkl)] are: 11.69(100)(001), 5.87(68)(011, 002), 4.25(89) (-1-11, -111), 3.825(44)(-1-12, 003, -112), 2.940(100)(-1-21, -121), 2.900(79)(004, 120). The crystal structure was solved by direct methods from single-crystal low-temperature (200 K) X-ray diffraction data and refined to R = 0.0656 for the holotype and 0.0663 for the cotype. The structure is based on a three-sheet HOH block: an octahedral (O) sheet containing alternating chains of NaO (sub 6) and TiO (sub 6) octahedra and two heteropolyhedral (H) sheets consisting of Si (sub 2) O (sub 7) groups, TiO (sub 6) octahedra and CaO (sub 8) polyhedra. H (sub 2) O molecules occupy two sites in the interlayer space.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 28
Serial Issue: 4
Title: Calciomurmanite, (Na,) (sub 2) Ca(Ti,Mg,Nb) (sub 4) [Si (sub 2) O (sub 7) ] (sub 2) O (sub 2) (OH,O) (sub 2) (H (sub 2) O) (sub 4) , a new mineral from the Lovozero and Khibiny alkaline complexes, Kola Peninsula, Russia
Affiliation: Moscow State University, Faculty of Geology, Moscow, Russian Federation
Pages: 835-845
Published: 20160829
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 23
Accession Number: 2016-085272
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N67°00'00" - N68°00'00", E33°00'00" - E34°00'00"
Secondary Affiliation: Russian Academy of Sciences, Fersman Mineralogical Museum, RUS, Russian FederationSt. Petersburg State University, RUS, Russian FederationUniversity of Vienna, AUT, Austria
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201641
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