Nixonite, Na2Ti6O13, a new mineral from a metasomatized mantle garnet pyroxenite from the western Rae Craton, Darby kimberlite field, Canada
| Autor: | Andrew J. Locock, Luca Peruzzo, Fabrizio Nestola, Fei Wang, D. Graham Pearson, Garrett A. Harris, Dongzhou Zhang, Chiara Anzolini, Steven D. Jacobsen |
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| Rok vydání: | 2019 |
| Předmět: |
crystal structure
geography jeppeite Rae Craton geography.geographical_feature_category kimberlite 010504 meteorology & atmospheric sciences Geochemistry 010502 geochemistry & geophysics 01 natural sciences Mantle xenoliths Mantle (geology) Craton Geophysics Geochemistry and Petrology Nixonite mantle xenolith new mineral Crystal structure Jeppeite Kimberlite New mineral Geology 0105 earth and related environmental sciences |
| Zdroj: | The American mineralogist 104 (2019): 1336–1344. doi:10.2138/am-2019-7023 info:cnr-pdr/source/autori:Anzolini C.[1], Wang F.[2], Harris G.[1], Locock A.[1], Zhang D.[3], Nestola F.[4], Peruzzo L.[5], Jacobsen S.[2], Pearson D.[1]/titolo:Nixonite, Na2Ti6O13, a new mineral from a metasomatized mantle garnet pyroxenite from the western Rae Craton, Darby kimberlite field, Canada/doi:10.2138%2Fam-2019-7023/rivista:The American mineralogist/anno:2019/pagina_da:1336/pagina_a:1344/intervallo_pagine:1336–1344/volume:104 |
| ISSN: | 1945-3027 0003-004X |
| DOI: | 10.2138/am-2019-7023 |
| Popis: | Nixonite (IMA 2018-133), ideally Na2Ti6O13, is a new mineral found within a heavily metaso-matized pyroxenite xenolith from the Darby kimberlite field, beneath the west-central Rae Craton, Canada. It occurs as microcrystalline aggregates, 15 to 40 mm in length. Nixonite is isostructural with jeppeite, K2Ti6O13, with a structure consisting of edge- and corner-shared titanium-centered octahedra that enclose alkali-metal ions. The Mohs hardness is estimated to be between 5 and 6 by comparison to jeppeite, and the calculated density is 3.51(1) g/cm(3). Electron microprobe wavelength-dispersive spectroscopic analysis (average of 6 points) yielded: Na2O 6.87, K2O 5.67, CaO 0.57, TiO2 84.99, V2O3 0.31, Cr2O3 0.04, MnO 0.01, Fe2O3 0.26, SrO 0.07, total 98.79 wt%. The empirical formula, based on 13 O atoms, is: (Na1.24K0.67Ca0.06)S-1.97(Ti5.96V0.023Fe0.018)S6.00O13 with minor amounts of Cr and Mn. Nixonite is monoclinic, space group C2/m, with unit-cell parameters a = 15.3632(26) angstrom, b = 3.7782(7) angstrom, c = 9.1266(15) angstrom, b = 99.35(15)degrees, and V = 522.72(1) angstrom(3), Z = 2. Based on the average of seven integrated multi-grain diffraction images, the strongest diffraction lines are [d(obs) in angstrom (I in %) (hkl)]: 3.02 (100) (310), 3.66 (75) (110), 7.57 (73) (200), 6.31 (68) (20 (1) over bar), 2.96 (63) (31 (1) over bar), 2.96 (63) (20 (3) over bar), and 2.71 (62) (402). The five main Raman peaks of nixonite, in order of decreasing intensity, are at 863, 280, 664, 135, and 113 cm(-1). Nixonite is named after Peter H. Nixon, a renowned scientist in the field of kimberlites and mantle xenoliths. Nixonite occurs within a pyroxenite xenolith in a kimberlite, in as-sociation with rutile, priderite, perovskite, freudenbergite, and ilmenite. This complex Na-K-Ti-rich metasomatic mineral assemblage may have been produced by a fractionated Na-rich kimberlitic melt that infiltrated a mantle-derived garnet pyroxenite and reacted with rutile during kimberlite crystallization. |
| Databáze: | OpenAIRE |
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