The crystal structure of laptevite-(Ce), NaFe2+(REE7Ca5Y3)(SiO4)(4)(Si3B2PO18)(BO3)F-11, a new mineral species from the Darai-Pioz alkaline massif, Northern Tajikistan

作者：Uvarova Yulia A; Sokolova Elena^*; Hawthorne Frank C; Agakhanov Atali A; Karpenko Vladimir Y; Pautov Leonid A

来源：Zeitschrift fur Kristallographie-Crystalline Materials, 2013, 228(10): 550-557.

DOI：10.1524/zkri.2013.1623

• Laptevite-(Ce)
• Crystal-structure refinement
• Electron-microprobe analysis
• Vicanite-group minerals
• Darai-Pioz, Tajikistan

Laptevite-(Ce), ideally NaFe2+(REE7Ca5Y3) center dot (SiO4)(4)(Si3B2PO18)(BO3)F-11, is a new member of the vicanite group discovered in the moraine of the Darai-Pioz glacier, Alai Mountain Range, Tien-Shan, Tajikistan. The crystal structure of laptevite-(Ce), trigonal, a = 10.804(2) angstrom, c = 27.726(6) angstrom, V= 2802.6(2) angstrom(3), sp. gr. R3m, Z = 3, D-calc. = 4.660 . 10(3) kg/m(3), has been refined to R-1 = 0.0387 for 924 unique (F-o %26gt; 4 sigma F) reflections, collected on a Bruker single-crystal P4 diffractmeter with a 4K CCD detector and MO-K-alpha X-radiation. The simplified formula is NaFe2+(REE,Ca,Y)(15)(SiO4)(4) RSi,B,P)(6)O-18](BO3)F-11. In the crystal structure of laptevite-(Ce), there are four tetrahedrally coordinated T sites. The T(1) site is occupied by Si and minor B, (T(1)-O) = 1.594 angstrom; the T(2, 3) sites are occupied by Si, (T(2,3)-O) = 1.64 angstrom; the T(4) site is occupied by B, P and minor Si, with (T(4)-O) = 1.51 angstrom. The [3]-coordinated T(5) site has composition B-0.84 square 0.16, with (T(5)-O) = 1.42 angstrom. Cations at the T(1 + 4), T(2, 3) and T(5) sites form the complex anions (Si3B2PO18), (SiO4)(4) and (BO3), respectively. The [7-10]-coordinated M(1-5) sites are occupied by REE, Ca, Y and minor Sr, with (M(1-5)-O) = 2.37-2.62 angstrom. The octahedrally coordinated M(6) site is occupied by Fe2+ %26gt; Mn %26gt; Ti, with (M(6)-O) = 2.13 angstrom. The [101-coordinated M(7) site has composition Na0.75REE0.25, with (M(7)-O) = 2.64 angstrom. The T and M polyhedra form a framework. Laptevite-(Ce) is isostuctural with other vicanite-group minerals: vicanite(Ce), okanoganite-(Y), hunclholmenite-(Y) and proshchenkoite-(Y). Vicanite-group structures differ in the dominant cation species at the T(1, 3-6) and M(3-7) sites.

• 出版日期2013
• 单位CSIRO