Metamict zircon from Mozambique

Metamict zircon from granite pegmatites of Zambézia, Mozambique has been studied by annealing, microprobe, X-ray diffraction, DT and TG analysis, and IR spectroscopy. The specimens are contaminated by epitaxially intergrown xenotime. It is presumed that the lanthanoides, occur in the xenotime phase and only sparsely in the zircon. Some U and Th are evenly distributed throughout the completely metamict parts of the zircon but elsewhere only in minor amounts. Around the metamict parts they build up their own uranium and thorium phases or occur as fracture fillings. Th prefers the xenotime phase and U the zircon.