Characterization and genetic inferences of arsenates, sulfates and vanadates of Fe, Cu, Pb, Zn from Mount Cervandone (Western Alps, Italy).

Mount Cervandone is among the most renowned mineral deposits in the Alpine chain and type locality of several very rare REE-arsenates. The present study allowed for the characterization and description of the assemblages of a number of arsenates, sulfates and vanadates of Fe, Cu, Pb, Zn that occur with a number of rare minerals of B, Be, As, Nb, Y, REE on the Italian slope of Mount Cervandone. The mineral deposits of Cervandone mainly occur in alpine quartz fissures and pegmatitic dikes. The pegmatitic dikes are hosted by very fine grained two-mica leucocratic gneisses. Locally the pegmatite dikes are cross cut by quartz veins. The assemblages reported in this study indicate that arsenates, sulfates and vanadates of Fe, Cu, Pb, Zn are mainly hosted in quartz veins and only occur sporadically in pegmatitic dikes. In the pegmatite dikes the Be, As, Y and REE minerals occur with higher frequency than in the quartz veins. During the Alpine event we account for a "scenario" where swarms of NYF (niobium, yttrium, fluorine) granitic pegmatites intruded the leucogranitic-aplites. It is unequivocal that the pegmatites show a strong NYF geochemical signature represented by the occurrence of an unique mineralogy. Following these premises we expected that during the Alpine event As-enriched hydrothermal fluids circulating through pegmatite dikes allowed the destabilization of accessory minerals hosted in these dikes and consequently the hydrothermal fluids assimilated light elements (Be, B, F), high field strength elements (Y, Nb, Ta) and rare earth elements (La, Ce, Nd, Th, U) and allowed the crystallization of several rare and exotic minerals.