Determination of trace elements in meteorites by instrumental and radiochemical neutron activation analysis and measurement of cosmogenic radionuclides by low-level gamma spectrometry

In ten meteorites the elements Na, Mg, Al, Cl, Sc, Cr, Fe, Co, Ni, Ga, As, Se, Br, Sr, Mo, Ag, Sn, Sb, Cs, Ba, La, Ce, Sm, Eu, Tb, Yb, Lu, Hf, Ta, W, Ir, Au, Th and U have been determined by instrumental neutron activation analysis. Irradiation is followed by gamma spectrometry using a 50 cc Ge(Li) detector. For improving detection limits or determination accuracy of heavy alkali metals, REE, Th and U radiochemical group separation is applied after irradiation. The samples are dissolved in a mixture of hydrofluoric and nitric acid at 440 K in an autoclave. The evaporation residue dissolved in a mixture of 0.1 M oxalic and 0.5 M hydrochloric acids is given onto an anionite KPS column. Fractions are eluated with the above mentioned mixture, with 2n HCl and 6n HNO3 containing Th- and U-group radionuclides in the first, Rb and Sr in the second and the REE in the third one. The chemical yield is controlled by 90Y, 137Cs and 238Np. In two meteorites fallen in November 1985 and March 1988 onto the territory of East Germany the cosmogenic radionuclides 22Na, 26Al, 48V and 54Mn are measured using a gamma spectrometer installed in an underground laboratory. Because of relatively high content of Rb, Cs and other volatile elements a low condensation temperature of the meteorite Hohenlangenbeck is assumed. Its low 22Na/26Al ratio may be explained by a reduced cosmic particle flux during its last five years in orbit. (author)