Non-metamict betafite from Le Carcarelle (Vico volcanic complex, Italy): occurrence and crystal-structure
| Autor: | C. T. Williams, Fernando Cámara, E. Caprilli, R. Oberti, G. Della Ventura |
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| Přispěvatelé: | Camara, F., Williams, T. C., DELLA VENTURA, Giancarlo, Oberti, R., Caprilli, E., Camara, F, WILLIAMS T., C, Oberti, R |
| Jazyk: | italština |
| Rok vydání: | 2004 |
| Předmět: |
pyrochlore
crystal structure Mineral Materials science 010504 meteorology & atmospheric sciences Pyrochlore Mineralogy Electron microprobe engineering.material 010502 geochemistry & geophysics electron microprobe analysis 01 natural sciences chemistry.chemical_compound Metamictization Betafite Crystallography chemistry Geochemistry and Petrology engineering Sodalite Biotite betafite Latium 0105 earth and related environmental sciences Magnetite |
| Zdroj: | Mineralogical magazine 68 (2004): 939–950. info:cnr-pdr/source/autori:Cámara F.; Williams C.T.; Della Ventura G.; Oberti R.; Caprilli E./titolo:Non-metamict betafite from Le Carcarelle (Vico volcanic complex, Italy): occurrence and crystal structure./doi:/rivista:Mineralogical magazine (Print)/anno:2004/pagina_da:939/pagina_a:950/intervallo_pagine:939–950/volume:68 |
| ISSN: | 0026-461X |
| Popis: | Non-metamict betafite, a pyrochlore-group mineral with general formulaA2−mB2XO6Y(O,OH,F)1−n·pH2O and 2 Ti > Nb+Ta and U > 20% at theAsite, has been found at Le Carcarelle, (Latium, Italy). It occurs within miarolitic cavities of a foid-bearing syenitic ejectum enclosed within the pyroclastic formation known as “ignimbrite C”, which belongs to the main effusive phase of the Vico volcanic complex. The host rock is composed of K-feldspar, biotite, augitic clinopyroxene, magnetite and minor sodalite. Electron microprobe analyses gave the following crystal-chemical formula: (Ca1.24Na0.17U0.49REE0.03)Σ=1.93(Ti1.05Nb0.76Zr0.14Fe0.04Ta0.01)Σ=2.00O6(O,OH). Compared with other occurrences reported in the mineralogical literature, betafite from Le Carcarelle is extremely enriched in U and depleted in Th. Due to its young age of formation (∼150 k.y.), this betafite sample is highly crystalline, thus allowing structure refinement of unheated material. Betafite from Le Carcarelle is cubicFdm, witha= 10.2637(13) Å, andV= 1081.21(35) Å3, and has a smallerAsite (consistent with the higher U content), and a larger and more distortedBsite (consistent with the higher Ti content) than calciobetafite from Campi Flegrei, Italy (Mazzi and Munno, 1983). Analysis of the atomic displacement parameters provides evidence for static disorder at theXsite. |
| Databáze: | OpenAIRE |
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