Alpine monazite: further data

Monazite specimens from various localities in the Alps have been examined by electron microprobe and by single-crystal X-ray diffraction. With the exception of Sm, which is higher in general in pegmatite specimens, the average distribution of the REE is similar for fissure and pegmatite samples. The general average is similar to the value reported in the literature for the mineral; appreciable variations, however, occur in several cases. The samples from pegmatites usually contain higher amounts of actinides (U, Th) than the samples from fissures; in some cases, the REE distribution of very highly thorian and uranoan monazite is markedly different from the average, but no unique correlation between such distribution and the actinide content is found. There is evidence that the Y-REE fractionation does not depend exclusively on differences in ionic radii. Particularly interesting is the presence of sulfate ion (up to about 1% SO3) in specimens of the Devero-Formazza-Veglia area.