Occurrence and Origin of Alluvial Xenotime from Central Eastern Portugal (Central Iberian Zone/Ossa-Morena Zone)

Trace amounts of alluvial xenotime (YPO4) were identified in black sands from pan concentrates collected during a rare earth reconnaissance survey, carried by the Instituto Geologico e Mineiro (IGM) in Central Eastern Portugal. The xenotime occurs as sub-rounded grains with an average size of ≈ 250 μm, and its identification was confirmed through XRD methods and EPMA analysis. It is believed that xenotime is more abundant than normally recognized and therefore frequently overlooked. The largest concentrations of this mineral occur in Nisa, S.to Antonio das Areias and Marvao. The regional geology and the accompanying mineral suite suggest xenotime originates from the granitic massifs of Nisa and Penamacor as well as the Beira Baixa Arkoses and levels of Plio-Pleistocene gravels interspersed with sandy clay. Although its economic interest is presently limited, its demand may increase as a result of the potential use of yttrium in the manufacturing of superconductors that are stable at ambient temperature.