Determination of 18 Siderophile Elements Including All Platinum Group Elements in Chondritic Metals and Iron Meteorites by Instrumental Neutron Activation

Abstract

An instrumental neutron activation method is developed to analyze chondritic metals and iron meteorites. By changing irradiation and decay times, and selecting suitable γ-ray and X-ray photopeaks, not only all platinum group elements (Ru, Rh, Pd, Os, Ir, Pt) but also other siderophilic elements (Fe, Co, Ni, Cu, Ga, Ge, As, Mo, Sb, W, Re, Au) can be nondestructively determined in the meteoritic metal samples. To obtain analytical data as accurate as possible, interfering reactions and neutron flux gradients during irradiation are considered. Siderophile elemental abundances measured for the Odessa iron meteorite are highly consistent with the literature values. Rh abundances for bulk H, L, LL, EH, and EL chondrites, which had been scarcely reported in the literature, are derived from Rh/Ni abundance ratios in the metal separates of the corresponding chondritic groups.

Application of neutron activation analysis to micro gram scale of solid samples

“…In relative method of INAA [3], test samples and reference samples are usually prepared in the same shape and measured at the same position in gamma-ray counting for simplifying the data reduction procedure and reducing analytical uncertainty. In this study, however, both sample shape and counting position were largely different between the test samples and the reference samples.…”

“…For such a case, a few hundred μg kg -1 of Ir and a few hundred mg kg -1 of Co can be reliably determined. When an extremely small size (e.g., micro gram) of samples such as micrometeorites recovered on the Earth surface and tiny particles returned from extraterrestrial asteroids are to be analyzed by INAA, the conventional INAA procedure used for a few tens mg [3] is not suitable. For such tiny samples, neutron irradiation with high neutron flux and long irradiation time (namely, high neutron dose) is required.…”

Redistribution of elements in the heavily shocked Yanzhuang chondrite

“…The γ-spectra were collected within 2 months after irradiation using large volume Ge detectors. Details of the instrumental neutron activation analysis (INAA) procedure can be found in Kong et al (1996). Two polished sections were made for the unmelted and melted portions of Yanzhuang.…”

Analytical techniques for the determination of precious metals in geological and related materials

“…Rhodium, which has short-lived nuclides, is not determined by RNAA. Parry 97 and Artem'ev 98 in their review articles discussed in detail the various radiochemical separation procedures employed for the precious 100 Nguyen 101 and other workers 15,17,[102][103][104][105][106][107][108] have utilized the NAA technique for the precious metal analysis in different types of samples. The full details of the procedures are given in Table 10.…”