X-ray mapping investigations of the monazites from the Mt Weld deposit : compositional variance as an indicator of provenance

The Mt Weld lanthanide deposit in central Western Australia is considered to be one of the largest high grade deposits known in the world, first reported as a carbonate and phosphate rich ultramafic silicate intrusion that contained a resource of the Lanthanide series. It has been dated between 1.6" 2.0 billion years, where the formation of a carbonate layer in the cooling melt created a preferred environment for elevated lanthanide deposition. Mineralogical surveys of the area have outlined various primary lanthanide minerals however limited work has been undertaken on the supergene expression of the secondary lanthanide mineralogy, primarily due to the similar physical and electronic nature of the lanthanides.