• journal_title：Mineralogical Magazine
• Contributor：A. Guastoni ; F. Nestola ; C. Ferraris ; G. PArodi
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2012.076.3.23
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：76
• issue：3
• firstpage：761
• section：Letter

Xenotime-(Y), (Y,REE)PO₄, and thortveitite, (Sc,Y)₂Si₂O₇, in a miarolitic cavity in a niobium, yttrium, fluorine (NYF) granitic pegmatite at Baveno, Verbania, Southern Alps, Italy, were investigated by electron microprobe analysis and single-crystal X-ray diffraction. Fluorine has an important role as a complexing agent for Y and REEs in supercritical pegmatitic fluids; annite-siderophyllite and chamosite are the most likely sources of the Y and REEs. The thortveitite from Baveno contains up to 3.20 wt.% SnO₂, an unusually high Sn content. Xenotime-(Y) is enriched in Gd in comparison to other Alpine xenotimes. Quantitative chemical data and measurements of the lattice parameters show that a higher scandium content results in a smaller unit-cell volume in thortveitite. The substitution of REEs for Y up to ~20 mol.% has little effect on the unit cell of xenotime-(Y). The textures of xenotime-(Y) and thortveitite provide information about the dissolution and crystallization processes in the miarolitic cavity.