BASTNASITE-(CE) AT THE NKOMBWA HILL CARBONATITE COMPLEX, ISOKA DISTRICT, NORTHEAST ZAMBIA

Within the Nkombwa Hill carbonatite complex, bastnasite-(Ce), (Ce,La)C O3F, has been identified as an abundant mineral in xenoliths hosted by late-stage ferrocarbonatite sills and dykes. Bastnasite-(Ce) occurs a s fibrous yellow crystals, about 1 mu m in size, replacing monazite an d in association with baryte, in a matrix of dolomite. In common with bastnasite-(Ce) from other locations, the bastnasite-(Ce) of Nkombwa H ill contains up to 70% RE2O3, almost entirely as light rare-earth oxid es. However, Nkombwa Hill bastnasite-(Ce) is relatively deficient in L a and enriched in Pr and Nd.