The use of instrumental neutron activation and multivariate statistic analyses in differentiation of Brazilian phosphate ores.

Phosphated rocks from three ores located in the Middle-West region of Brazil can be used as low-level radioactive reference material due to the fact that they contain significant concentrations of thorium and, in some cases, of uranium. This paper describes the procedure to characterise those samples using several analytical methods. Statistical analysis and correlations studies have shown several geochemical similarities and the results obtained suggest the possibility to produce a reference material composed of a mixture of two similar ores.