| Abstrakt: |
A non-metamict aeschynite-(Y) with a very high titanium content was found in a leucogranite sample at the Triolet Valley (Mont-Blanc group, Western Alps, Italy); associated minerals are anatase, manganoan ilmenite, thorianite, apatite, titanite, zircon, thorite, chlorite and calcite. Aeschynite crystals are tabular {100}, orange-brown in color, with resinous luster and irregular fracture. Unit cell parameters are: ɑ = 10.862 (2), b = 7.483 (2), c = 5.150(1)Å, V = 418.6(2) Å3, space group Pnma. Chemical analyses, performed on four crystals by electron microprobe, revealed a heterogeneous distribution of all the elements measured. The overall average on 11 analytical points leads to the following chemical formula: (Y0.60REE0.24Th0.08U0.03Ca0.02)∑ = 0.97 (Ti1.84Nb0.09Tao0.01W0.06)∑ = 2.00(O,OH)6. The presence of hydroxyl groups, required for the charge balance, is confirmed by IR spectrum. The REE pattern shows an enrichment in intermediate and heavy REE. |
