REPRODUCIBILITY OF ELEMENTAL CONCENTRATIONS FOR JB-1, A GSJ ROCK REFERENCE SAMPLE, WITH SPECIAL REFERENCE TO MO, W AND TA

Sixteen aliquots of JB-1 with different weights were studied by instru mental neutron activation analysis. It is observed that concentrations of Na, Fe, Sc, U, Th and rare earth elements are reproducible for JB- 1 with the sample size of mg level. However, concentrations of Mo, W a nd Ta show a significant scatter even at 50 mg level. It is, therefore , suggested that chemical standards be used for Mo, W and Ta determina tion for geological samples, otherwise the rock reference sample, if u sed as a standard, be checked for the reproducibility of concentration s of these three elements.