Xenotime from the Podwiśniówka mine pit, Holy Cross Mountains (South-Central Poland)

This report presents the results of petrographical and mineralogical (optical microscopy, SEM/EDS) study of xenotime derived from the Upper (Middle?) Cambrian rocks (Wiśniówka Sandstone Fm.) of the abandoned Podwiśniówka mine pit. This is the first work on this mineral from the Holy Cross Mts. The authigenic xenotime occurs primarily as overgrowths around/on zircon in siliciclastic rocks. Moreover, this mineral is characterized by the large size of the overgrowths reaching 50 μm long and 20 μm wide. The presence of pyritecoated zircon/xenotime aggregates indicates that the xenotime formed prior to hydrothermal quartz-pyrite mineralization. The apparent lack of xenotime and vein pyrite in the tuff-bearing series, compared to the other two series displaying hydrothermal signature (pyrite, hematite, nacrite, jarosite), as well as considerable variations of the xenotime overgrowths in size and morphology, and their dominant irregular patchy-zonal microtexture may provide evidence for direct precipitation of this mineral from hydrothermal fluids.