Waimirite-(Y), orthorhombic YF3, a new mineral from the Pitinga mine, Presidente Figueiredo, Amazonas, Brazil and from Jabal Tawlah, Saudi Arabia: description and crystal structure

Autor(es):Mostrar menos -

Atencio, Daniel ^[1] ; Bastos Neto, Artur C. ^[2] ; Pereira, Vitor P. ^[2] ; Ferron, Jose T. M. M. ^[3] ; Hoshino, M. ^[4] ; Moriyama, T. ^[4] ; Watanabe, Y. ^[4] ; Miyawaki, R. ^[5] ; Coutinho, Jose M. V. ^[1] ; Andrade, Marcelo B. ^[6] ; Domanik, Kenneth ^[7] ; Chukanov, Nikita V. ^[8] ; Momma, K. ^[5] ; Hirano, H. ^[4] ; Tsunematsu, M. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo, SP - Brazil

^[2] Univ Fed Rio Grande do Sul, Inst Geociencias, BR-91501970 Porto Alegre, RS - Brazil

^[3] Univ Fed Rio Grande do Sul, Inst Geociencias, Programa Posgrad Geociencias, BR-91501970 Porto Alegre, RS - Brazil

^[4] Natl Inst Adv Ind Sci & Technol, Inst Georesources & Environm, Tsukuba, Ibaraki 3058567 - Japan

^[5] Natl Museum Nat & Sci, Dept Geol & Paleontol, Tsukuba, Ibaraki 3050005 - Japan

^[6] Univ Sao Paulo, Sao Carlos Inst Phys, BR-13560970 Sao Carlos, SP - Brazil

^[7] Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 - USA

^[8] Russian Acad Sci, Inst Problems Chem Phys, Chernogolovka 142432, Moscow Region - Russia

• Tipo de documento: Artigo Científico
• Fonte: MINERALOGICAL MAGAZINE; v. 79, n. 3, p. 767-780, JUN 2015.
• Citações Web of Science: 5

Resumo

Waimirite-(Y) (IMA 2013-108), orthorhombic YF3, occurs associated with halloysite, in hydrothermal veins (up to 30 mm thick) cross-cutting the albite-enriched facies of the A-type Madeira granite (similar to 1820 Ma), at the Pitinga mine, Presidente Figueiredo Co., Amazonas State, Brazil. Minerals in the granite are `K-feldspar', albite, quartz, riebeckite, `biotite', muscovite, cryolite, zircon, polylithionite, cassiterite, pyrochlore-group minerals, `columbite', thorite, native lead, hematite, galena, fluorite, xenotime-(Y), gagarinite-(Y), fluocerite-(Ce), genthelvite-helvite, topaz, `illite', kaolinite and `chlorite'. The mineral occurs as massive aggregates of platy crystals up to similar to 1 mu m in size. Forms are not determined, but synthetic YF3 displays pinacoids, prisms and bipyramids. Colour: pale pink. Streak: white. Lustre: non-metallic. Transparent to translucent. Density (calc.) = 5.586 g/cm(3) using the empirical formula. Waimirite-(Y) is biaxial, mean n = 1.54-1.56. The chemical composition is (average of 24 wavelength dispersive spectroscopy mode electron microprobe analyses, O calculated for charge balance): F 29.27, Ca 0.83, Y 37.25, La 0.19, Ce 0.30, Pr 0.15, Nd 0.65, Sm 0.74, Gd 1.86, Tb 0.78, Dy 8.06, Ho 1.85, Er 6.38, Tm 1.00, Yb 5.52, Lu 0.65, O (2.05), total (97.53) wt.%. The empirical formula (based on 1 cation) is (Y0.69Dy0.08Er0.06Yb0.05Ca0.03Gd0.02Ho0.02Nd0.01Sm0.01Tb0.01Tm0.01Lu0.01 )(Sigma 1.00){[}F-2.54 square O-0.25(0.21)](Sigma 3.00). Orthorhombic, Pnma, a = 6.386(1), b = 6.877(1), c = 4.401(1) angstrom, V = 193.28(7) angstrom(3), Z = 4 (powder data). Powder X-ray diffraction (XRD) data {[}d in angstrom (I) (hkl)]: 3.707 (26) (011), 3.623 (78) (101), 3.438 (99) (020), 3.205 (100) (111), 2.894 (59) (210), 1.937 (33) (131), 1.916 (24) (301), 1.862 (27) (230). The name is for the Waimiri-Atroari Indian people of Roraima and Amazonas. A second occurrence of waimirite-(Y) is described from the hydrothermally altered quartz-rich microgranite at Jabal Tawlah, Saudi Arabia. Electron microprobe analyses gave the empirical formula (Y0.79Dy0.08Er0.05Gd0.03Ho0.02Tb0.01 Tm0.01Yb0.01)(Sigma 1.00){[}F2.85O0.08 square(0.07)](Sigma 3.00). The crystal structure was determined with a single crystal from Saudi Arabia. Unit-cell parameters refined from single-crystal XRD data are a = 6.38270(12), b = 6.86727(12), c = 4.39168(8) angstrom, V = 192.495(6) angstrom(3), Z = 4. The refinement converged to R-1 = 0.0173 and wR(2) = 0.0388 for 193 independent reflections. Waimirite-(Y) is isomorphous with synthetic SmF3, HoF3 and YbF3. The Y atom forms a 9-coordinated YF9 tricapped trigonal prism in the crystal structure. The substitution of Y for Dy, as well as for other lanthanoids, causes no notable deviations in the crystallographic values, such as unit-cell parameters and interatomic distances, from those of pure YF3. (AU)

• Processo FAPESP: 11/22407-0 - Caracterização de espécies minerais brasileiras novas e raras
• Beneficiário: Daniel Atencio
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 13/03487-8 - Centro de caracterização de novas espécies minerais: espectroscopia Raman, difração por raios X e nêutrons, e microssonda eletrônica
• Beneficiário: Marcelo Barbosa de Andrade
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores