Determination of major and trace elements in some minerals by k0-instrumental neutron activation analysis

A method for the determination of major and trace elements in some minerals (orpiment, realgar, lorandite, dolomite and markasite) from the Allchar mine, Republic of Macedonia, based on k0-instrumental neutron activation analysis (k0-INAA) is presented. The concentration of U and Th in all investigated minerals was found to be <1 mg/kg. Data obtained for other trace elements (Ce, Co, Cr, Cs, Sc, Se, Tb and Te) showed that the concentrations in the investigated minerals are also low (0.6-2 mg/kg for Ce, 0.1-17 mg/kg for Co, 0.4-6.7 mg/kg for Cr, 0.04-52 mg/kg for Cs, 0.006-3.5 mg/kg for Sc, 0.4-0.9 mg/kg for Se and 2.6 mg/kg for Te). The concentration of Fe, Ca, Mg, As and Sb in these minerals was found to be relatively high (0.02-40% for Fe, 0.3-21% for Ca, 0.03-13% for Mg, 0.4-53% for As and 8-270 mg/kg for Sb). This is because of the presence of some particles of iron minerals (marcasite and pyrite), and/or calcite, dolomite, stibnite and arsenic minerals, which are the most abundant minerals in the mine. The high concentration of As (>50%), especially in realgar and orpiment, due to the high background produced by 76As activity after irradiation by thermal neutrons, makes the determination of short-lived radionuclides present at micro levels by k0-INAA impossible. To increase the accuracy of the determination and to enlarge the number of elements measured, arsenic should be separated from the samples. (author)